Russell J Hamilton

Interests

Teaching

Medical Physics, Therapeutic Radiation Therapy Physics

Research

Radiation Oncology, Mathematical Modeling of Response to Radiation

Courses

Scholarly Contributions

Journals/Publications

• James, S., Al‐Basheer, A., Elder, E., Huh, C., Ackerman, C., Barrett, J., Hamilton, R., & Mostafaei, F. (2023).

  Evaluation of commercial devices for patient specific QA of stereotactic radiotherapy plans

  . Journal of Applied Clinical Medical Physics, 24(8). doi:10.1002/acm2.14009
• Kuo, P. H., Hamilton, R. J., Garland, L. L., Sawyer, T. W., Sawyer, D. M., Kuo, P. H., Hsu, C. C., Hamilton, R. J., Garland, L. L., Eshghi, N., Sawyer, T. W., Kuo, P. H., Hamilton, R. J., Sawyer, T. W., Sawyer, D. M., Kuo, P. H., Hsu, C. C., Hamilton, R. J., Garland, L. L., & Eshghi, N. (2021). Pilot Study: Texture Analysis of PET Imaging Demonstrates Changes in 18F-FDG Uptake of the Brain After Prophylactic Cranial Irradiation.. Journal of nuclear medicine technology, 49(1), 34-38. doi:10.2967/jnmt.120.248393
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  Prophylactic cranial irradiation (PCI) is used to decrease the probability of developing brain metastases in patients with small cell lung cancer and has been linked to deleterious cognitive effects. Although no well-established imaging markers for these effects exist, previous studies have shown that structural and metabolic changes in the brain can be detected with MRI and PET. This study used an image processing technique called texture analysis to explore whether global changes in brain glucose metabolism could be characterized in PET images. Methods: 18F-FDG PET images of the brain from patients with small cell lung cancer, obtained before and after the administration of PCI, were processed using texture analysis. Texture features were compared between the pre- and post-PCI images. Results: Multiple texture features demonstrated statistically significant differences before and after PCI when texture analysis was applied to the brain parenchyma as a whole. Regional differences were also seen but were not statistically significant. Conclusion: Global changes in brain glucose metabolism occur after PCI and are detectable using advanced image processing techniques. These changes may reflect radiation-induced damage and thus may provide a novel method for studying radiation-induced cognitive impairment.
• Hamilton, R. J., Stea, B., Smith, L., Locke, A., Hamilton, R. J., & Garcia, A. (2020). Robust Planning Optimization Improves Safety and Homogeneity for Craniospinal Irradiation in the Supine Position. International Journal of Radiation Oncology Biology Physics, 108(3), e346-e347. doi:10.1016/j.ijrobp.2020.07.826
• Mirzapour, M., Hadad, K., Faghihi, R., Hamilton, R. J., & Watchman, C. J. (2020). Fast Monte-Carlo Photon Transport Employing GPU-Based Parallel Computation. IEEE Transactions on Radiation and Plasma Medical Sciences, 4(4), 450-460.
• Mostafaei, F., Dougherty, S. T., & Hamilton, R. J. (2020). Preliminary Clinical Evaluation of Intrafraction Prostate Displacements for Two Immobilization Systems. Cureus, 12(9), e10206.
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  Immobilization systems and their corresponding set-up errors influence the clinical target volume to the planning target volume (CTV-PTV) margins, which is critical for hypofractionated prostate stereotactic body radiotherapy (SBRT). This preliminary study evaluates intrafraction prostate displacement for two immobilization systems (A and B). Six consecutive patients having localized prostate cancer and implanted prostate marker seeds were studied. Planar X-ray images were acquired pre- and post-treatment to find the intrafraction prostate displacement. The average absolute displacements (lateral, longitudinal, vertical) were 0.9 ± 0.4 mm, 1.7 ± 0.1 mm, 1.3 ± 0.3 mm (system A), and 0.5 ± 0.2 mm, 0.6 ± 0.1 mm, 0.8 ± 0.3 mm (system B), with average three-dimensional displacements of 2.6 ± 0.2 mm (system A) and 1.3 ± 0.2 mm (system B). The computed CTV-PTV margins (lateral, longitudinal, vertical) were 2.5 mm, 2.5 mm, 3.6 mm and 1.4 mm, 1.6 mm, 2.4 mm for systems A and B, respectively. This suggests that the immobilization system influences intrafraction prostate displacement and, therefore, the margins applied. However, the margins found for both systems are comparable to the margins used for hypofractionated prostate SBRT.
• Sawyer, D. M., Sawyer, T. W., Eshghi, N., Hsu, C., Hamilton, R. J., Garland, L. L., & Kuo, P. H. (2020). Pilot Study: Texture analysis of PET imaging demonstrates changes in F-FDG uptake of the brain after prophylactic cranial irradiation. Journal of nuclear medicine technology.
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  Prophylactic cranial irradiation (PCI) is used to decrease the probability of developing brain metastases in patients with small cell lung cancer and has been linked to deleterious cognitive effects. While no well-established imaging markers for these effects exist, previous studies have shown that structural and metabolic changes of the brain can be detected with magnetic resonance imaging and positron emission tomography (PET). This study utilized an image processing technique called texture analysis to explore whether global changes in brain glucose metabolism could be characterized in PET images. F-FDG PET images of the brain from patients with small cell lung cancer, obtained before and after the administration of PCI, were processed using texture analysis. Texture features were compared between the pre- and post-PCI images. Multiple texture features demonstrated statistically significant differences before and after PCI, when texture analysis was applied to the brain parenchyma as a whole. Regional differences were also seen but were not statistically significant. Global changes in brain glucose metabolism occur after PCI and are detectable using advanced image processing techniques. These changes may reflect radiation-induced damage and thus may provide a novel method for studying radiation-induced cognitive impairment.
• Goldbaum, D. S., Hurley, J. D., & Hamilton, R. J. (2019). A simple knowledge-based tool for stereotactic radiosurgery pre-planning. Journal of applied clinical medical physics, 20(12), 97-108.
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  We studied the dosimetry of single-isocenter treatment plans generated to treat a solitary intracranial lesion using linac-based stereotactic radiosurgery (SRS). A common metric for evaluating SRS plan quality is the volume of normal brain tissue irradiated by a dose of at least 12 Gy (V12), which is important because multiple studies have shown a strong correlation between V12 and incidence of radiation necrosis. Unrealistic expectations for values of V12 can lead to wasted planning time. We present a model that estimates V12 without having to construct a full treatment plan. This model was derived by retrospectively analyzing 50 SRS treatment plans, each clinically approved for delivery using circular collimator cone arc therapy (CAT). Each case was re-planned for delivery via dynamic conformal arc therapy (DCAT), and then scaling arguments were used to extend dosimetric data to account for different prescription dose (PD) values (15, 18, 21, or 24 Gy). We determined a phenomenological expression for the total volume receiving at least 12 Gy (TV12) as a function of both planning target volume (PTV) and PD: , where are fit parameters, and a separate set of values is determined for each plan type. In addition, we generated a sequence of plots to clarify how the relationship between conformity index (CI) and TV12 depends on plan type (CAT vs DCAT), PTV, and PD. These results can be used to suggest realistic plan parameters and planning goals before the start of treatment planning. In the absence of access to more sophisticated pre-planning tools, this model can be locally generated and implemented at relatively low cost with respect to time, money, and expertise.
• Garland, L. L., Hamilton, R. J., Kuo, P. H., Krupinski, E. A., Kuo, P. H., Krupinski, E. A., Hsu, C. C., Han, J. E., Hamilton, R. J., Garland, L. L., Eshghi, N., Eshghi, A., & Choudhary, G. (2018). Regional Changes in Brain 18F-FDG Uptake After Prophylactic Cranial Irradiation and Chemotherapy in Small Cell Lung Cancer May Reflect Functional Changes.. Journal of nuclear medicine technology, 46(4), 355-358. doi:10.2967/jnmt.118.212316
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  Chemotherapy followed by prophylactic cranial irradiation (PCI) is associated with increased survival in patients with small cell lung cancer but is associated with fatigue and cognitive impairment. This retrospective study evaluated regional differences in 18F-FDG uptake by the brain before and after PCI. The null hypothesis was that direct toxic effects on the brain from PCI and chemotherapy are symmetric; thus, asymmetric deviations may reflect functional changes due to therapy. Methods: Electronic medical records from 2013 to 2016 were reviewed for patients with small cell lung cancer, MRI of brain negative for metastasis, and 18F-FDG PET/CT scans before and after PCI. As the standard of care, patients received first-line chemotherapy or chemoradiation to the thorax followed by PCI. The 18F-FDG PET/CT scans nearest the PCI were selected. Sixteen patients met these initial criteria. Commercially available PET software was used to register and subtract the PET scans before and after PCI to obtain difference maps. Occipital and cerebellar regions were excluded from the final statistical analysis given the known high variability and misregistration. The χ2 test was used to analyze the data. Results: Two patients had 18F-FDG uptake differences only in the occipital and cerebellar regions. The software registration failed on 1 patient's scans. Therefore, 13 patients were included in the final analysis. Nine of 13 patients demonstrated significant unilateral changes in only 1 region of the brain, and 3 of 13 showed significant changes unilaterally in 2 regions. The χ2 test revealed a significant unilateral regional difference on a patient level (χ2 = 6.24, P = 0.025). The most commonly affected brain region was the frontal lobe. Conclusion: Significantly more patients had unilateral than bilateral regional differences (both increases and decreases) in 18F-FDG uptake in the brain before and after PCI. This finding suggests that differences in unilateral distribution are related to functional changes, since direct toxicity alone from PCI and chemotherapy would be symmetric. The frontal region was the most commonly affected, suggesting a potential contributing etiology for cognitive impairment and decreased executive function after therapy.
• Hamilton, R. J., Dougherty, S. T., Dougherty, S. T., Xu, Y., Watchman, C. J., Lin, S. C., Hamilton, R. J., & Dougherty, S. T. (2018). Improved Dose Distribution with 3D Printed Vaginal Cylinder Applicator for VariSource HDR Afterloader. International Journal of Radiation Oncology Biology Physics, 102(3), e480-e481. doi:10.1016/j.ijrobp.2018.07.1372
• Lee, Y. C., Kim, Y., Huynh, J. W., & Hamilton, R. J. (2017). Failure modes and effects analysis for ocular brachytherapy. Brachytherapy.
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  The aim of the study was to identify potential failure modes (FMs) having a high risk and to improve our current quality management (QM) program in Collaborative Ocular Melanoma Study (COMS) ocular brachytherapy by undertaking a failure modes and effects analysis (FMEA) and a fault tree analysis (FTA).
• Halabi, T., Lu, H., Bernard, D. A., Chu, J. C., Kirk, M. C., Hamilton, R. J., Lei, Y., & Driewer, J. (2016). Automated survey of 8000 plan checks at eight facilities. Medical physics, 43(9), 4966.
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  To identify policy and system related weaknesses in treatment planning and plan check work-flows.
• Marsteller, L., Patel, P. J., J, M. L., Drew, M. E., Vitali, J., Restori, M., Patel, P., Mcgovern, M., Marsteller, L. J., Ilginis, T., Hamilton, R. J., Drew, M., & Balaggan, K. (2015). SU‐E‐T‐16: A Comparison of Expected Dwell Times and Dose Variations for NAMD Patients Treated with An Episcleral Brachytherapy Device. Medical Physics, 42(6), 3334-3334. doi:10.1118/1.4924377
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  Purpose: To evaluate the variations in dwell times and doses expected when using an episcleral brachytherapy device for treatment of neovascular agerelated macular degeneration (n-AMD) based on accurate imaging modalities Methods: Data from 40 eyes from 40 subjects with known n- AMD acquired through the Distance of Choroid Study (DOCS) conducted at Moorfields Eye Hospital was used to determine the target depth; the distance from the outer scleral surface of the eye, through the choroid, to the apex of the choroidal neovascularization (CNV). Each subject underwent, in triplicate, enhanced-depth Spectral Domain Optical Coherence Tomography (SD-OCT), Swept Source Optical Coherence Tomography, (SS-OCT) and Ocular Ultrasound (O-US). These data are the most comprehensive and accurate measurements of the dimensions of the CNV and adjacent layers of the eye for this cohort of patients. During treatment of n-AMD, patients receive a dose of 24Gy to the apex at the target depth. Using the percentage depth dose for a Sr-90 episcleral brachytherapy device, dwell times and doses to the apex were computed to determine the expected variations. Results: The mean target depth and the 95% confidence interval (CI) determined by combining O-US with SD-OCT were 1326 (956,1696)µm and with SS-OCT were 1332 (970,1693)µm. The calculated corresponding mean dwell times and 95% (CI) were 334 (223,445)s and 335 (226,445)s for SD-OCT and SS-OCT determined depths, respectively. The corresponding mean apex dose and 95% (CI) were 24 (35.9,18.0)Gy (SD-OCT) and 24 (35.6,18.1)Gy (SS-OCT). Conclusion: For episcleral brachytherapy treatment of n-AMD, using a patient population average target depth for treatment planning is inadequate, resulting in dose variations of a factor of approximately two over the 95% CI and larger variations for a nontrivial segment of the population. Each patient should have individualized imaging studies to determine the target depth for use in the dwell time calculation. Study was sponsored by Salutaris Medical Devices, Ltd., a subsidiary of Salutaris Medical Devices, Inc. Hamilton and Marsteller are founders of Salutaris Medical Devices, Inc. Drew, McGovern and Vitali are minor equity holders in Salutaris Medical Devices, Inc.
• Nguyen, N. P., Ries, T., Vock, J., Vos, P., Chi, A., Vinh-Hung, V., Thompson, S., Desai, A., Sroka, T., Vo, R. A., Gelumbauskas, S., Hamilton, R., Karlsson, U., & Mignault, A. (2015). Effectiveness of radiotherapy for elderly patients with non-melanoma skin cancer of the head. Geriatrics & gerontology international, 15(5), 601-5. doi:10.1111
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  To assess the effectiveness of conventionally fractionated radiotherapy for local control and cosmesis in elderly patients (age 70 years or older) with non-melanoma skin cancer of the head.
• Chi, A., Desai, A., Gelumbauskas, S., Hamilton, R., Karlsson, U., Mignault, A., Nguyen, N. P., Ries, T., Sroka, T., Thompson, S., Vinh-Hung, V., Vo, R. A., Vock, J., & Vos, P. (2014).

  Effectiveness of radiotherapy for elderly patients with non-melanoma skin cancer of the head: Elderly and skin cancer of the head

  . Geriatrics & Gerontology International, 15(5), 601-605. doi:10.1111/ggi.12319
• Hamilton, R. J., Watchman, C. J., Vonk, D. T., Turner, A. C., Stea, B., Nguyen, V. N., Hamilton, R. J., & Cheung, M. K. (2014). Evaluate and Compare the Doses Differences between Line Source and Point Source Calculation Methods for Episcleral Plaque Brachytherapy. Brachytherapy, 13, S101. doi:10.1016/j.brachy.2014.02.384
• Hadad, K., Hamilton, R. J., Watchman, C. J., Moghadam, A., Hamilton, R. J., & Hadad, K. (2013). WE‐C‐108‐03: CT‐Based 3D Dose Calculation Method Using Artificial Neural Networks (ANN). Medical Physics, 40(6), 474-474. doi:10.1118/1.4815526
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  Purpose: In this study Artificial Neural Networks (ANN) are trained to develop a fast CT based dose calculation method. The ANN is capable of calculating the 3D dose distribution inside a voxel‐based phantom for prostate I–125 seed implants. The speed allows for accurate CT‐based calculation of the dose distributions during implantation in real time due to plan modifications. Methods: Training the ANN needs a set of accurate sample dose distributions in heterogeneous CT based phantoms. For the purpose of this study, 60000 sample cubicle phantoms were extracted from 3 patient CT studies. The dose distributions of the cubicle phantoms were calculated using MCNP5. The absorption coefficient of each voxel of the cubicle phantom was calculated by analyzing the CT scan. This information was then given to the ANN as the input. The calculated dose by MCNP5 was given to it as the sample output for the purpose of training. The dose distributions calculated by ANNs were then tested for 7000 cubicle phantoms against the MCNP5 results. Finally, the ANN was used to calculate the dose distribution in two real treatment plans. The results were compared against the MCNP5 voxel based results. Results: The regression graphs for individual ANNs show a regression of R=0.99543 for the worst ANN The regression of the best Trained ANN was equal to R=0.9997 for the 7000 cases. The maximum average absolute error of the ANN dose calculation was 3% in comparison with MCNP5. Conclusion: The results of individual ANN calculations and the complete treatment plan calculations verified the accuracy of the ANN method. Capability of the ANN method to calculate the dose distributions for 500 seed positions in less than 10 minutes suggests that this method can be used for model based dose calculation for real‐time plan modifications in the case of LDR brachytherapy.
• Nguyen, N. P., Nguyen, M. L., Vock, J., Lemanski, C., Kerr, C., Vinh-Hung, V., Chi, A., Khan, R., Woods, W., Altdorfer, G., D'Andrea, M., Karlsson, U., Hamilton, R., & Ampil, F. (2013). Potential applications of imaging and -guided radiotherapy for brain metastases and glioblastoma to improve patient quality of life.
• Marsteller, L. J., Lutz, W., Hamilton, R. J., Gordon, J., & Cetas, T. C. (2012). SU-E-T-308: Dosimetry of a New Minimally Invasive Episcleral Brachytherapy Device.. Medical physics, 39(6Part14), 3774. doi:10.1118/1.4735394
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  Describe the dosimetry of an episcleral brachytherapy device..The SMD-I device is designed to treat exudative age-related macular degeneration (AMD) and employs a Sr-90/Y-90 source encapsulated in a stainless steel cylinder. The source is welded to a flexible wire allowing it to travel from a shielded vault in the SMD-I handle to the distal end of a curved cannula to deliver a therapeutic dose of radiation through the sclera to the neovascular target in the subchoroidal space. The SMD-I handle and vault are comprised of Ultem, a lightweight radiation tolerant plastic, which shields the surgeon. Dose calculations were performed using the MCNPX radiation transport code. The absolute dose rate was determined using radiochromic film (GAFChromatic© MD-55) at a point in solid water 2.0mm from the source center perpendicular to the cannula. Dose rates at several depths were measured using Kodak EDR2 film in water equivalent phantoms to compare with the absolute dose rate measurement and MCNPX calculations. The surgeon's hand dose received while manipulating the device with the source in the vault was measured using standard TL (thermoluminescence) finger ring dosimeters, TL ChipstratesTM, and calculated with MCNPX..The absolute dose rate 2.0mm from the source center is 0.45 Gy/min/mCi. The EDR2 film results agree with the absolute dose measurement and the MCNPX calculations. The dose rate decreases rapidly with depth so that the dose at the target depth (3mm) is approximately 8 times less than at 1mm depth (sclera). The dose distribution is sensitive to the angle between the cannula and the neovascular plane. Both TL methods yield a maximum dose rate of 6 μSv/min mCi to the surgeon's fingers consistent with the MCNPX calculation..The SMD-I device permits accurate delivery of a therapeutic radiation dose for the treatment of exudative AMD. Russell J. Hamilton is a founder and currently serves on the Scientific Advisory Board of Salutaris Medical Devices, Inc. Wendell Lutz and Thomas Cetas serve on the Scientific Advisory Board of Salutaris Medical Devices, Inc. All authors have received financial support from Salutaris Medical Devices, Inc.
• Nguyen, N. P., Vos, P., Vinh-Hung, V., Ceizyk, M., Smith-Raymond, L., Stevie, M., Slane, B., Chi, A., Desai, A., Krafft, S. P., Jang, S., Hamilton, R., Karlsson, U., & Abraham, D. (2012). Feasibility of image-guided radiotherapy based on helical tomotherapy to reduce contralateral parotid dose in head and neck cancer.
• Stea, B., Senner, G., Schindler, R., Marstellar, L., Lutz, W., Joffe, L., Hamilton, R. J., Gordon, J., & Georgiev, G. (2012). Minimally Invasive Retrobulbar Episcleral Brachytherapy for Treatment of Wet Age-related Macular Degeneration: Preliminary Results of a Feasibility Study. International Journal of Radiation Oncology Biology Physics, 84(3), S625. doi:10.1016/j.ijrobp.2012.07.1669
• Gordon, J. D., Krafft, S. P., Jang, S., Smith-Raymond, L., Stevie, M. Y., & Hamilton, R. J. (2011). Confidence limit variation for a single IMRT system following the TG119 protocol.
• Hadad, K., Hamilton, R. J., Watchman, C. J., Ramzanzadeh, A., Hamilton, R. J., & Hadad, K. (2011). SU‐E‐T‐587: A CT Based Monte Carlo Dosimetry for Post Implant LDR Brachytherapy. Medical Physics, 38(6), 3624-3624. doi:10.1118/1.3612549
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  Purpose: Introducing a new CT based Monte Carlo calculation for dose evaluation following LDR brachytherapy and comparing the results with conventional TG‐43 calculation Methods: We adapted a voxel based mathematical phantom of patient's body modeling in MCNP using conventional DICOM images from post implant of prostate brachytherapy. With the aid of Image processingsoftware, the implanted seed and their position are detected and conveyed to Monte Carlo SDEF source definition. The results of MCNP dosimetry is presented to the physicists in a GUI medium. Results: The developed software could aid the physicist to browse, explore or modify patient's CT and explore the results of Monte Carlodosimetry. The software is designed to evaluate the absorbed dose(dose distribution contours) and the volumetric dose histograms. The software is used to evaluate the dose distribution of HDR seeds in a gel phantom [1] and the results are within 3% of experimental data. Conclusions: The developed image processing and mathematical voxel phantom generation software package is successful in producing accurate dosimetry data based on exact patient body information. Besides producing dose distribution in CTV and PTV, the dose distributions of adjacent sensitive organs are readily available with Monte Carlo accuracy. This is an advantage of the developed software compared with conventional TG‐43 based software which ignores patient's body heterogeneity in dose evaluation
• Hamilton, R., Stea, B., Hazard, L. J., Gonzalez, V. J., & Hamilton, R. J. (2011). The role of radiation therapy in the control of locoregional and metastatic cancer. Journal of surgical oncology, 103(6).
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  High energy X-rays have been used for cancer therapy since their discovery in 1895. Major radiobiological discoveries and technological advances in radiation physics have greatly increased the accuracy of radiation. The recent integration of radiation therapy and imaging systems provides radiation oncologists with sophisticated dose delivery capability allowing continued improvements in the control of loco-regional and metastatic disease while decreasing toxicity. Key technical aspects of current radiation therapy are described with examples extending to several clinical areas.
• Hashmi, S., Hamilton, R. J., & Gordon, J. (2011). SU‐E‐T‐463: Utilizing the TG119 Assessment to Quantify Planning System Improvements. Medical Physics, 38(6), 3595-3595. doi:10.1118/1.3612417
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  Purpose: To quantify the impact of modifications to an IMRT planning system using the TG1 19 assessment score as an indicator of improvement. Method and Materials: Evaluation of an IMRT system following the TG1 19 protocol was initially performed to establish baseline results. The TG1 19 evaluation set consisted of five IMRT test cases planned and delivered to a 30 cm × 30 cm × 15 cm solid water phantom. Per‐field measurements were collected using a diode array, and composite measurements were collected using film and an ionization chamber. Measurements were compared to calculation to determine TG1 19 confidence limits. The original plans were then modified to include table attenuation, previously omitted by the planning system. Without modifying the incident radiation fields, the plans were recalculated on the modified phantom, which includes a table model. The resultant calculations were compared to the original measurements, and new TG1 19 confidence limits were determined. Results: The baseline TG1 19 assessment resulted in confidence limits of 4.36%, 23.8% and 9.16% for diode array, composite film, and composite ion chamber measurements, respectively. The TG1 19 assessment after plan modification resulted in confidence limits of 4.36%, 19.5%, and 8.54%. The TG1 19 confidence limits were reduced by 4.30% and 0.62% in film and ion chamber, respectively, which is a relative improvement of 18.1% and 6.8%. Conclusions: Using a single set of measurements, modifications to the planning system via the addition of a table model resulted in quantifiable improvement in TG1 19 assessment results. In this system, the addition of a table model improved the agreement between calculation and measurement, as indicated by the TG1 19 confidence limit results. The improvement was only observed in confidence limits from composite comparisons using film and ion chamber, but not observed for per‐field comparisons using a diode array.
• Jang, S., Hamilton, R. J., & Georgiev, G. (2011). SU‐E‐T‐573: Monte Carlo Simulated Peripheral Doses in SRS of the Brain. Medical Physics, 38(6), 3621-3621. doi:10.1118/1.3612535
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  Purpose: In arc based brain Stereotactic Radiation Surgery (SRS), a major concern is the accuracy of the peripheral doses to organs close to the treated lesions. This concern is more pronounced when planning software utilizes Pencil Beam algorithm. To evaluate the out‐of‐target radiation doses to Organs At Risk (OAR) the predicted organdoses by BrainLab Treatment Planning System (TPS) were compared with doses acquired by a Monte Carlo simulation. Methods and Materials: An arc based brainSRStreatment plan was developed in BrainLab® TPS to be treated on the Novalis® Varian linear accelerator, using 6 MV photon arcs with a 20 mm cone. The doses to different points of interest, representing major OAR were investigated. The photon spectrum in air for 20 mm cone at 100 SSD was designed and verified for the simulation with EGSnrc Monte Carlo particle transport code (DOSRZnrc user code). The resulting Percent Depth Dose (PDD) and dose profile at 75 mm depth were confirmed with respective measurements in a water phantom. Each arc will be approximated by summing simulated discrete angled beams following the arc path and accounting for the difference of their depths to the target. The doses of both calculations will be normalized to an ion chamber measurement at the isocenter. Results: The greatest difference in the PDD was less than 1%. MC simulated profile at 75 mm depth appeared to be less than 1mm wider than the measured data in the penumbra region. Conclusions: A method for simulating peripheral doses in SRS was developed. The agreement in the measured and simulated PDD and profile provide a basis for successfully utilizing this method and comparing the calculated peripheral doses by the TPS and the simulated doses by the Monte Carlo technique.
• Nguyen, N. P., Abraham, D., Desai, A., Betz, M., Davis, R., Sroka, T., Chi, A., Gelumbauskas, S., Ceizyk, M., Smith-Raymond, L., Stevie, M., Jang, S., Hamilton, R., & Vinh-Hung, V. (2011). Impact of image-guided radiotherapy to reduce laryngeal edema following treatment for non-laryngeal and non-hypopharyngeal head and neck cancers.
• Nguyen, N. P., Krafft, S. P., Vinh-Hung, V., Vos, P., Almeida, F., Jang, S., Ceizyk, M., Desai, A., Davis, R., Hamilton, R., Modarresifar, H., Abraham, D., & Smith-Raymond, L. (2011). Feasibility of tomotherapy to reduce normal lung and cardiac toxicity for distal esophageal cancer compared to three-dimensional radiotherapy.
• Nguyen, N. P., Krafft, S. P., Vos, P., Vinh-Hung, V., Ceizyk, M., Jang, S., Desai, A., Abraham, D., Ewell, L., Watchman, C., Hamilton, R., Jo, B., Karlsson, U., & Smith-Raymond, L. (2011). Feasibility of tomotherapy for Graves' ophthalmopathy dosimetry comparison with conventional radiotherapy.
• Stea, B., Hazard, L. J., Gonzalez, V. J., & Hamilton, R. (2011). The role of radiation therapy in the control of locoregional and metastatic cancer.
• Young, S., Hamilton, R. J., Gordon, J., & Dukes, B. (2011). SU‐E‐T‐453: Feasibility of IMRT System Evaluations Using Pre‐Made IMRT Leaf Patterns. Medical Physics, 38(6), 3593-3593. doi:10.1118/1.3612407
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  Purpose: To assess the feasibility of utilizing pre‐made IMRT leaf patterns in IMRT system evaluation. Methods and Materials: A TG1 19 evaluation set consisting of five IMRT test cases were optimized using a pencil‐beam algorithm and delivered on a 30 cm × 30 cm × 15 cm solid water phantom. Per‐field measurements were collected using a diode array, and composite measurements were collected using film and ion chamber. Measurements were compared to calculation to determine confidence limit values per TG1 19 methodology. The phantom image set, associated contours, and leaf patterns were then transferred to a separate treatment planning system utilizing different treatment planning software previously commissioned for the same LINAC. Dose calculations utilizing a convolution‐superposition algorithm were performed on this planning system utilizing the pre‐made IMRT leaf patterns and image set. These calculations were compared to previously collected measurements, and TG1 19 confidence limits were determined. Results: The TG1 19 evaluation utilizing the pencil‐beam treatment planning system resulted in confidence limits of 1.55%, 8.06%, and 3.13% for diode array, film, and ion chamber comparisons, respectively. The TG1 19 evaluation utilizing the same leaf patterns within the convolution‐superposition treatment planning system resulted in confidence limits of 10.5%, 14.9%, and 5.46% for diode array, film, and ion chamber comparisons, respectively. The TG1 19 confidence limit values for the two planning systems differed by 8.95%, 6.84%, and 2.33%.Conclusion: This study has demonstrated the feasibility in utilizing pre‐made leaf patterns to evaluate the dose model for an IMRT system. In this case, the pencil‐beam TPS calculations were closer to measured values, as quantified by the TG119 assessment.
• Bishop, M. C., Welsh, J. S., Vincent, V. H., Nguyen, N. P., Nguyen, L. M., Hamilton, R. J., Cohen, D., Borok, T. J., & Bishop, M. C. (2010). Pattern of failure following chemoradiation for locally advanced non-small cell lung cancer: potential role for stereotactic body radiotherapy.. Anticancer research, 30(3), 953-61.
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  Standard of care for locally advanced non-small cell lung cancer has been concurrent chemoradiation. However, optimal chemotherapy regimen, radiation therapy dose and treatment volume have not been clearly defined despite 30 years of controlled clinical trials. This review analyzes survival and failure pattern reported from randomized studies of chemoradiation for non-small cell lung cancer. Despite introduction of new chemotherapy agents, survival remained poor; rates of both locoregional failures and distant metastasis remained high. The current radiation dose appears insufficient to reliably establish local control. Stereotactic body radiotherapy may allow radiation dose escalation and should be tested in future clinical trials.
• Hamilton, R. J., Watchman, C. J., Jang, S., & Hamilton, R. J. (2010). WE-E-203-05: Medical Physics Teaching Opportunites in an ITunes World. Medical Physics, 37(6), 3435-3435. doi:10.1118/1.3469421
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  Introduction: Today's students have come up in a world where online audio and video content is widely available. Through the use of television production and iTunes, increased opportunities for out of the classroom learning are available. Method and Materials: During the last three years at the University of Arizona, we have used the medical TV resources in our institution to record our medical physics courses. The class studio is equipped with computers, pad camera and video players. An integrated teaching environment is achieved where one may transfer from traditional “chalk board” (pad camera) methods to advanced computational and video presentations. In class lectures proceed as normal with the inclusion of microphones for recording. Lectures are then placed on University iTunes with in a few days of class. Recordings of past years lectures are made available to the students in addition to the current instructor's lectures. Video podcasts of advanced topics not covered in lectures can also be made available which may allow for instructors to maintain course schedules. Other laboratory podcasts may also be developed for QA, machine engineering and machine operation. These will allow for students to participate in labs independently outside of normal clinic hours. Results: Students have multiple opportunities to review the lecture and other material regardless of class time. Content that may have been missed due to illness or other absence may still be covered. Additionally, competing course schedules may now be accommodated without rescheduling class times. Use of the TV/iTunes system has allowed for students in any semester to view the same topic from multiple instructors. This has given a diversity of presentation which may allow for students to better understand topics. Conclusion: Use of video lectures and podcasts in an integrated iTunes environment allows for increased opportunities for learning for medical physics students.
• Hamilton, R. J., Watchman, C. J., Nguyen, N. P., Krafft, S. P., Jang, S., & Hamilton, R. J. (2010). SU‐GG‐T‐172: Dosimetric Comparison of Low Dose Region (V5) for Tomotherapy versus Conventional IMRT Plans of Lung Cancer. Medical Physics, 37(6), 3224-3224. doi:10.1118/1.3468562
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  Purpose: To compare clinical Tomotherapy plans for lungcancer with conventional IMRT plans in terms of mean lung/ventricle dose, heterogeneity index, V5, V10, V15, and V20 for total lung. Method: The conventional IMRT plans for 16 patients treated with clinical Tomotherapy plans were made retrospectively with Pinnacle 8.0 for Varian 6EX. We designed the conventional plans to achieve comparable target coverage as well as maximum spinal cord dose of the clinical Tomotherapy plans. To minimize any planning‐related subjective issue, nine‐beam angles aligned through anterior‐posterior directions were chosen for all cases. Multiple iterative processes were performed until the objective functions were minimized and the treatment planning goals were met. Dosimetric parameters of the two types of plans were compared in terms of avoidance of normal tissues (i.e., total lung and ventricle). Results Median differences in lung between the Tomotherapy plans and conventional IMRT plans for 16 patients were 7.4%, 4.4%, 3.0%, and 1.9% for V5, V10, V15, and V20, respectively. Median ratios of mean lung dose and mean ventricle dose between the Tomotherapy plans and conventional IMRT plans were 1.2 (range, 0.97∼1.41) and 1.6 (range, 0.86∼2.55), demonstrating that dose to normal tissues for conventional IMRT plans, especially in low dose region (V5∼V10), was considerably lower than Tomotherapy plans for lungcancer. However, median ratio of heterogeneity index defined as D5%/D95% was 0.96 (range, 0.86∼2.55) indicating better dose‐uniformity of Tomotherapy plans, which resulted from the difference in number of beam angles for the two different plans. Conclusions Median V5 of conventional IMRT plans was lower than that of Tomotherapy plans, showing that conventional IMRT plan appears to be effective in low dose region (V5) for lungcancer. However, Tomotherapy plans showed better dose‐uniformity in terms of target coverage.
• Hamilton, R. J., Watchman, C. J., Vos, P., Vinh-hung, V., Smith-raymond, L., Nguyen, N. P., Krafft, S. P., Jang, S., Hamilton, R. J., Ewell, L., Desai, A., Davis, R., Ceizyk, M., & Abraham, D. (2010). Effectiveness of image-guided radiotherapy for laryngeal sparing in head and neck cancer.. Oral oncology, 46(4), 283-6. doi:10.1016/j.oraloncology.2010.01.010
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  We would like to compare the effectiveness of image-guided (IGRT) and intensity-modulated (IMRT) radiotherapy to spare the larynx in head and neck cancer patients. A retrospective review of 48 patients undergoing radiation for non-laryngeal and non-hypopharyngeal head and neck cancers. Mean laryngeal and hypopharyngeal dose was compared between 11 patients treated with IMRT and 37 patients treated with IGRT. Mean laryngeal dose was, respectively, 41.2 Gy and 22.8 Gy for the IMRT and IGRT technique (p
• Stea, B., Sanan, A., Hamilton, R. J., Guillen, J. M., Gordon, J. D., & Desai, A. B. (2010). Frameless Stereotactic Radiosurgery (SRS): Outcomes for Trigeminal Neuralgia. International Journal of Radiation Oncology Biology Physics, 78(3), S272-S273. doi:10.1016/j.ijrobp.2010.07.650
• Stevie, M., Smith-raymond, L., Krafft, S. P., Jang, S., Hamilton, R. J., & Gordon, J. (2010). TU-E-BRB-04: Confidence Limit Variation for a Single System Following the TG119 Protocol. Medical Physics, 37(6), 3400-3400. doi:10.1118/1.3469287
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  Purpose: To evaluate the consistency of TG119‐based quality assurance metrics for an IMRT system. Methods and Materials: Four planners constructed treatment plans for the five IMRT test cases described in TG119 using iPlan RT Dose 4.1 software. All plans were delivered on a Varian 6EX to a 30×30×15cm solid water phantom in one treatment session in order to minimize session‐dependent variation from phantom setup, film quality, machine performance, etc. Composite measurements utilized EDR2 film and an Exradin A1SL ionization chamber (sensitive volume of 0.056 cm3). Each film was developed and digitized immediately after exposure. Per‐field measurements were collected using a MapCHECK device at an effective depth of 5cm. All data collected were analyzed using the TG119 specifications to determine quality assurance metrics for each planner separately and then compared. Results: The mean variance of ion chamber measurements for each planner was within 1.7% of the planned dose. Resulting confidence limits were 3.77%, 1.98%, 4.50%, and 5.99%. Confidence limit values determined by composite film analysis were 26.43%, 25.02%, 21.50%, and 56.58%. Using normalization to a film point rather than to ionization chamber, these confidence limits were reduced to 12.27%, 12.73%, 6.96%, and 15.75%. Confidence limits from per‐field measurements were 1.55%, 0.00%, 0.00%, and 2.89%. Conclusions: For a single IMRT system, the accuracy assessment provided by TG119‐based quality assurance metrics showed significant variations across all composite and per‐field evaluations. Performing the TG119 evaluation a single time may not provide an adequate estimation of IMRT system accuracy.
• Xu, Q., Xing, L., Ma, C. M., He, Z., Hamilton, R. J., Fan, J., & Chen, Y. (2010). Registration of on-board X-ray images with 4DCT: a proposed method of phase and setup verification for gated radiotherapy.. Physica medica : PM : an international journal devoted to the applications of physics to medicine and biology : official journal of the Italian Association of Biomedical Physics (AIFB), 26(3), 117-25. doi:10.1016/j.ejmp.2009.09.001
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  Current gated radiation therapy starts with simulation 4DCT images of a patient with lung cancer. We propose a method to confirm the phase of 4DCT for planning and setup position at the time of treatment. An intensity-based rigid algorithm was developed in this work to register an orthogonal set of on-board projection X-ray images with each phase of the 4DCT. Multiple DRRs for one of ten 4DCT phases are first generated and the correlation coefficient (CC) between the projection X-ray image and each DRR is computed. The maximum value of CC for the phase is found via a simulated annealing optimization process. The whole process repeats for all ten phases. The 4DCT phase that has the highest CC is identified as the breathing phase of the X-ray. The phase verification process is validated by a moving phantom study. Thus, the method may be used to independently confirm the correspondence between the gating phase at the times of 4DCT simulation and radiotherapy delivery. When the intended X-ray phase and actual gating phase are consistent, the registration of the DRRs and the projection images may also yield the values of patient shifts for treatment setup. This method could serve as the 4D analog of the conventional setup film as it provides both verification of the specific phase at the time of treatment and isocenter positioning shifts for treatment delivery.
• Hadad, K., Ganapol, B. D., Hamilton, R. J., Hamilton, R. J., Watchman, C. J., Xu, Y., Watchman, C. J., Hamilton, R. J., Hadad, K., & Ganapol, B. D. (2009). Dose Assessment to Heart and Lungs in HDR Breast Brachytherapy. Transactions of the American Nuclear Society, 101, 1097-1099.
• Hamilton, R. J., Ganapol, B. D., Xu, Y., Watchman, C. J., Krafft, S. P., Jang, S., Hamilton, R. J., Haddad, K., & Ganapol, B. D. (2009). SU‐FF‐T‐14: Skin Dose Evaluation for HDR Accelerated Partial Breast Irradiation. Medical Physics, 36(6), 2521-2521. doi:10.1118/1.3181485
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  Purpose: Although the physical consideration of minimum skin distance has been well established for partial breast irradiation HDR treatment, there are uncertainties about the actual calculated skin dose. Usually the calculated dose is based on infinite homogenous media. Thus, the actual skin dose will be less than calculated dose due to lack of backscattering. This study confirms this conclusion by using MOSFET dosimeters and Monte Carlo 3D simulation. Materials & Methods: The MOSFET detector was first calibrated as a function of distance from HDR source. The calibration factors were obtained by recording the voltage variation after delivering exactly 1 Gy. A Contura balloon filled with water was embedded off center in a cylindrical tissue equivalent gel phantom. Four locations along the surface were selected for MOSFET placement. Two plans, one with single dwell position and the other with three dwells, were delivered with the MOSFET at different positions, with and without extra bolus for backscattering.Monte Carlo simulation was validated by simple plans with single source dwell in different catheters of the Contura balloon. Results: The measurements with bolus matched well with the TPS calculated dose, while the data acquired without bolus had dose discrepancies from 12% to 27%, corresponding to the source to detector distance ranging from 2.8cm to 3.9cm. Conclusion:MOSFETmeasurements have proved that the actual skin dose is much less than the calculated dose, which indicates that the minimum skin distance used as selecting criteria may be less than currently established standard.
• Hamilton, R. J., Watchman, C. J., Krafft, S. P., Jang, S., & Hamilton, R. J. (2009). SU‐FF‐T‐139: Dosimetric Accuracy of Low Dose Region (V5‐V10) in TomoTherapy Planning of Lung IMRT. Medical Physics, 36(6), 2552-2552. doi:10.1118/1.3181613
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  Purpose: To quantify the dosimetric accuracy of a TomoTherapy treatment planning system in areas of low dose (V5 to V10 regions) and in the presence of tissue heterogeneities in lungIMRT.Materials and Methods: CIRS anthropomorphic heterogeneous thorax phantom was used to generate clinical treatment plans using TomoTherapy's treatment planning system (TPS). Three plans were developed for treatment delivery using three different field widths (1.0, 2.5 and 5.0 cm) with standard planning parameters used in our clinic. A designated tumor volume was contoured in the phantom lung volume and was planned to receive 200 cGy fractions to a total prescription dose of 7000 cGy. Point measurements with a PTW Farmer chamber were conducted at two locations in the contralateral lung which fell with in the V5 to V10 region of low dose. Comparison of the experimental findings to the TPS results was performed to assess the dosimetric accuracy of TomoTherapy's convolution/superposition algorithm in low dose regions. Results: Comparison of the ion chamber measurements to the TPS dose calculation demonstrated an average difference of +4.5% and −3.0% at the medial and posterior points of measurement in the contralateral lung of the same axial slice. Variation as a function of field width was found to be 1–2% for chamber measurements. Over the total course of treatment of 35 fractions, differences between the TPS and measurement were 35 cGy regardless of field width or point of measurement. Conclusions: At low dose levels (V5 to V10 regions), dosimetric accuracy of conventional TPS systems is often underestimated, but our experimental results suggest the TomoTherapy TPS is reasonably accurate under the given conditions. Tomotherapy's TPS provides acceptable dosimetric accuracy in lung region areas of low dose.
• Hamilton, R. J., Watchman, C. J., Maurizo, A., Jang, S., & Hamilton, R. J. (2009). SU‐FF‐T‐127: Perhipheral Dose of Tungsten Powder Compensator (WPC) Based IMRT. Medical Physics, 36(6), 2549-2549. doi:10.1118/1.3181601
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  Purpose: To characterize the peripheral dose (PD) of the newly developed compensator system based on tungstenpowder (WPC) and to compare with MLC‐based IMRT.Method and Materials:. WPCs molded with different thicknesses of tungstenpowder for comparison with MLC‐based plans were loaded into Elekta‐SLi block‐tray. Absorbed doses along the CAX and 2cm outside the field edge were measured for thickness of 1–7 cm at 1cm‐increments, at depths of dmax, 5cm and 10cm for photon energies of 6 and 15MV. Equivalent‐MLC thicknesses were calculated by constraining the total CAX dose and total MU for each compensator thickness. Absorbed doses along the CAX and 2cm outside the field edge were measured for the MLC‐equivalent thickness using Farmer chamber. In addition, PD for a WPC‐based clinical IMRT plan was compared to the equivalent MLC plan. Results: PD with tungsten thickness of 4cm, normalized to 10Gy along the CAX, was found to increase from 35 to 142cGy with increasing field size(5×5cm2 to 20×20cm2 at dmax) and from 74 to 85cGy with depth(dmax to 10cm with 10×10cm2 field). PD at dmax increased 204% by varying tungsten thickness from 1cm to 7cm. PD increased linearly with field size and was energy‐dependant only for the deeper depths where the PD became greater for 6MV than for 15MV. With increasing depth and decreasing field size, WPC‐based PD values became nearer to those of MLC‐based PD in trend. However, at the smallest field (5×5cm2), WPC showed lower PD than MLC. WPC‐based PD of a clinical plan measured 2cm outside the field edge, were ∼60% higher than that of MLC‐based plan. Conclusion: Mean WPC‐based PD was 60% higher than MLC‐based PD, however it was equivalent to 1.5% of the prescription dose of 2Gy/fraction. Conflict of Interest: Research sponsored by Axellis Ltd.
• Hamilton, R. J., Garland, L. L., Welsh, J., Vinh-hung, V., Nguyen, N. P., Hamilton, R. J., Garland, L. L., & Cohen, D. (2008). Can stereotactic fractionated radiation therapy become the standard of care for early stage non-small cell lung carcinoma.. Cancer treatment reviews, 34(8), 719-27. doi:10.1016/j.ctrv.2008.06.001
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  Management of early stages non-small cell lung carcinoma has traditionally been surgery with radiation selected for medically inoperable patients. Recent emergence of stereotactic body radiation therapy allows for delivery of high radiation dose to the tumor while sparing normal lungs. This reviews compares loco-regional control, survival and complications rates between these two treatment modalities. Literature search identifies studies with stereotactic body radiation therapy and surgery for early stages non-small cell lung cancer. Effectiveness and toxicity of these two modalities was assessed. Stereotactic body radiation therapy is associated with minimal morbidity and provides comparable local control and survival in patients with multiple co-morbidities factors. Stereotactic body radiation therapy may become standard of care for operable early stages non-small cell lung cancer.
• Hamilton, R. J., Watchman, C. J., Stea, B., Mignault, A. J., & Hamilton, R. J. (2008). Patient positioning using implanted gold markers with the Novalis Body system in the thoracic spine.. Neurosurgery, 62(5 Suppl), A62-8; discussion A68. doi:10.1227/01.neu.0000325938.08605.eb
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  To evaluate the effectiveness of implanted gold marker registration compared with bony fusion alignment for patient positioning using the Novalis Body system..Eighteen treatment fractions of stereotactic spinal radiotherapy were analyzed for three patients who each had three implanted gold seeds placed near their spinal lesions before radiotherapy. At each treatment session, the registration was first performed using bony fusion and then verified by another bony fusion, followed by registration with implanted markers. The software reported the calculated shifts for both methods. In addition, the actual three-dimensional coordinate positions of the markers were read using PTDReader software. Implanted marker positions were analyzed for variations in individual maker coordinate displacement, interseed distances, and area transcribed by them. Measured positional differences between the two fusion methods were applied to actual treatment plans to assess the resulting dosimetric differences in the treatment plans..Both fusion algorithms were shown to localize the patient well, within 1.5 mm, but the implanted marker fusion consistently related less deviation from the planned isocenter, by approximately 0.5 mm, than did the bony fusion. Exceptions to this localization occurred when the average interseed distances were less than 3.0 cm and resulted in the two registration methods being equivalent. Implanted spine markers were also shown to have less than 0.7 mm deviation from the planned marker coordinates, indicating no migration of the seeds. Dose distributions were found to be highly dependant on differences in fusion method, with spinal cord doses up to 350% greater with bony fusion than with implanted markers..Implanted markers used with the Novalis Body system have been shown to be more effective in patient positioning than the bony fusion method in the thoracic spine.
• Hamilton, R. J., Watchman, C. J., Stea, B., Mignault, A. J., Hamilton, R. J., Gerszten, P. C., Gerszten, K., & Chang, S. D. (2008). PATIENT POSITIONING USING IMPLANTED GOLD MARKERS WITH THE NOVALIS BODY SYSTEM IN THE THORACIC SPINE. Commentaries. Neurosurgery, 62(5).
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  OBJECTIVE: To evaluate the effectiveness of implanted gold marker registration compared with bony fusion alignment for patient positioning using the Novalis Body system. METHODS: Eighteen treatment fractions of stereotactic spinal radiotherapy were analyzed for three patients who each had three implanted gold seeds placed near their spinal lesions before radiotherapy. At each treatment session, the registration was first performed using bony fusion and then verified by another bony fusion, followed by registration with implanted markers. The software reported the calculated shifts for both methods. In addition, the actual three-dimensional coordinate positions of the markers were read using PTDReader software. Implanted marker positions were analyzed for variations in individual maker coordinate displacement, interseed distances, and area transcribed by them. Measured positional differences between the two fusion methods were applied to actual treatment plans to assess the resulting dosimetric differences in the treatment plans. RESULTS: Both fusion algorithms were shown to localize the patient well, within 1.5 mm, but the implanted marker fusion consistently related less deviation from the planned isocenter, by approximately 0.5 mm, than did the bony fusion. Exceptions to this localization occurred when the average interseed distances were less than 3.0 cm and resulted in the two registration methods being equivalent. Implanted spine markers were also shown to have less than 0.7 mm deviation from the planned marker coordinates, indicating no migration of the seeds. Dose distributions were found to be highly dependant on differences in fusion method, with spinal cord doses up to 350% greater with bony fusion than with implanted markers. CONCLUSION: Implanted markers used with the Novalis Body system have been shown to be more effective in patient positioning than the bony fusion method in the thoracic spine.
• Welsh, J., Vos, P., Vinh-hung, V., Nguyen, N., Nguyen, N. P., Nguyen, L. M., Martinez, T., Lee, H., Karlsson, U., Hamilton, R. J., Cohen, D., & Borok, T. L. (2008). Impact of tumor board recommendations on treatment outcome for locally advanced head and neck cancer.. Oncology, 75(3-4), 186-91. doi:10.1159/000163058
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  To identify physician selection factors in the treatment of locally advanced head and neck cancer and how treatment outcome is affected by Tumor Board recommendations..A retrospective analysis of 213 patients treated for locally advanced head and neck cancer in a single institution was performed. All treatments followed Tumor Board recommendations: 115 patients had chemotherapy and radiation, and 98 patients received postoperative radiation. Patient characteristics, treatment toxicity, locoregional control and survival between these two treatment groups were compared. Patient survival was compared with survival data reported in randomized studies of locally advanced head and neck cancer..There were no differences in comorbidity factors, and T or N stages between the two groups. A statistically significant number of patients with oropharyngeal and oral cavity tumors had chemoradiation and postoperative radiation, respectively (p < 0.0001). Grade 3-4 toxicities during treatment were 48 and 87% for the postoperative radiation and chemoradiation groups, respectively (p = 0.0001). There were no differences in survival, locoregional recurrences and distant metastases between the two groups. Patient survival was comparable to survival rates reported by randomized studies of locally advanced head and neck cancer..Disease sites remained the key determining factor for treatment selection. Multidisciplinary approaches provided optimal treatment outcome for locally advanced head and neck cancer, with overall survival in these patients being comparable to that reported in randomized clinical trials.
• Xu, Q., Schowengerdt, R. A., Jiang, S. B., Hamilton, R. J., & Alexander, B. M. (2008). Lung tumor tracking in fluoroscopic video based on optical flow.. Medical physics, 35(12), 5351-9. doi:10.1118/1.3002323
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  Respiratory gating and tumor tracking for dynamic multileaf collimator delivery require accurate and real-time localization of the lung tumor position during treatment. Deriving tumor position from external surrogates such as abdominal surface motion may have large uncertainties due to the intra- and interfraction variations of the correlation between the external surrogates and internal tumor motion. Implanted fiducial markers can be used to track tumors fluoroscopically in real time with sufficient accuracy. However, it may not be a practical procedure when implanting fiducials bronchoscopically. In this work, a method is presented to track the lung tumor mass or relevant anatomic features projected in fluoroscopic images without implanted fiducial markers based on an optical flow algorithm. The algorithm generates the centroid position of the tracked target and ignores shape changes of the tumor mass shadow. The tracking starts with a segmented tumor projection in an initial image frame. Then, the optical flow between this and all incoming frames acquired during treatment delivery is computed as initial estimations of tumor centroid displacements. The tumor contour in the initial frame is transferred to the incoming frames based on the average of the motion vectors, and its positions in the incoming frames are determined by fine-tuning the contour positions using a template matching algorithm with a small search range. The tracking results were validated by comparing with clinician determined contours on each frame. The position difference in 95% of the frames was found to be less than 1.4 pixels (approximately 0.7 mm) in the best case and 2.8 pixels (approximately 1.4 mm) in the worst case for the five patients studied.
• Hamilton, R. J., Watchman, C. J., & Hamilton, R. J. (2007). Dosimetric Consequences Resulting From Prostate Volume Changes During Radiotherapy. International Journal of Radiation Oncology Biology Physics, 69(3), S739-S740. doi:10.1016/j.ijrobp.2007.07.2293
• Xu, Q., Schowengerdt, R. A., Jiang, S. B., & Hamilton, R. J. (2007). A deformable lung tumor tracking method in fluoroscopic video using active shape models: a feasibility study.. Physics in medicine and biology, 52(17), 5277-93. doi:10.1088/0031-9155/52/17/012
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  A dynamic multi-leaf collimator (DMLC) can be used to track a moving target during radiotherapy. One of the major benefits for DMLC tumor tracking is that, in addition to the compensation for tumor translational motion, DMLC can also change the aperture shape to conform to a deforming tumor projection in the beam's eye view. This paper presents a method that can track a deforming lung tumor in fluoroscopic video using active shape models (ASM) (Cootes et al 1995 Comput. Vis. Image Underst. 61 38-59). The method was evaluated by comparing tracking results against tumor projection contours manually edited by an expert observer. The evaluation shows the feasibility of using this method for precise tracking of lung tumors with deformation, which is important for DMLC-based real-time tumor tracking.
• Xu, Q., Xu, Q., Schowengerdt, R. A., Jiang, S. B., & Hamilton, R. J. (2007). TH‐C‐M100F‐04: A Deformable Lung Tumor Tracking Method in Fluoroscopic Video Using Active Shape Models. Medical Physics, 34(6), 2631-2631. doi:10.1118/1.2761682
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  Purpose: Elastic tumor deformation and different intra‐ and inter‐fractional tumor paths between inhalation and exhalation were observed for some lung patients. For high accuracy and possibly 100% duty cycle dose delivery, we propose and evaluate a noninvasive method to fluoroscopically track location and shape variations of lungtumors with different types of deformations. Method and Materials: During a fluoroscopic simulation, lungtumor contours in one complete respiratory period are manually drawn by an expert. Each contour is described by 65 landmarks. The respiratory period is divided into 9 phases and a Point Distribution Models (PDM) statistically describing typical tumor shape variations are built for each phase. When tracking starts, the breathing phase for an incoming frame is first determined by the respiratory signal generated simultaneously from diaphragm motion and the PDM for this frame is also found. Starting from an initial estimate of the tumor contour, the Active Shape Models algorithm searches the area near each landmark and finds a better location. Based on the shifts found for these landmarks, the initial estimate is deformed within a certain range of typical shape variations found in PDM and also rigidly transformed to match the shifts. The new generated contour iteratively updates the previous contour estimate until no significant difference appears between two consecutive iterations or a user defined number of iterations is reached. Results:Tumors demonstrating distinct types of deformations in fluoroscopic videos were well tracked. All the landmarks of the tracked objects were manually revised by an expert using a GUI tool. The average magnitude of the deviation between the tracked and revised results was within 2 mm for 95% the landmarks and within 3mm for all landmarks. Conclusion: This method affords precise tracking of lungtumor location and deformation and may be used for real‐time tracking or DMLC radiotherapy.
• Hamilton, R. J., Watchman, C. J., Turner, A. C., & Hamilton, R. J. (2006). 2813 : Probabilistic Analysis of Radiation Induced Pneumonitis as a Function of Tumor and Margin Size. International Journal of Radiation Oncology Biology Physics, 66(3), S666-S667. doi:10.1016/j.ijrobp.2006.07.1231
• Hamilton, R. J., Welsh, J., Watchman, C. J., & Hamilton, R. J. (2006). SU‐FF‐J‐78: Implanted Marker Movements During Prostate IMRT. Medical Physics, 33(6), 2038-2038. doi:10.1118/1.2240855
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  Purpose: To quantify positional variations of implanted markers for prostate localization using the ExacTrac system. Method and Materials: Eleven patients were identified as having undergone IMRT boost for prostate cancer. The ExacTrac system was used to obtain implanted marker positions in the patient by means of two stereoscopic X‐ray tubes and DRRs from CT simulation. Marker positions were recorded by the ExacTrac software and subsequently read using the PTDreader software. Implanted marker positions were analyzed for variations in individual maker coordinate displacement, inter‐seed distances and area transcribed by the three markers. Comparisons of patient data was done for the initial boost phase (1980 cGy/11 fractions) and final boost phase (1080 cGy/6 fractions). Results: Implanted markers had maximum deviations of 3.3 mm (LAT) 6.4 mm (AP) and 3.4 mm (SI). In cases where the maximum deviation was observed for one coordinate the other coordinates were also approaching their maximums. No correlation between individual marker positions was observed. Inter‐seed distances were found to vary by +/− 2 mm over the treatment period. The area of a triangle contained by the three markers was shown to vary daily over the treatment period. In the 6 patients who were observed over both boost phases a trend was observed that indicated a progressive decrease in the area for the 4 patients not on hormone therapy and stable area size for the two on hormone therapy. Of the 11 patients followed over the final boost phase 8 were found to demonstrate a similar decrease but no correlation with hormone status was observed. Conclusions: Implanted markers in the prostate demonstrate daily variations in their positions. The observed variations exceeded the precision of the ExacTrac system. Further work is needed to address the movement of implanted markers in the prostate in positioning algorithms and correlation with prostate volume.
• Hamilton, R., Xu, Q., & Hamilton, R. J. (2006). A novel respiratory detection method based on automated analysis of ultrasound diaphragm video. Medical physics, 33(4).
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  This paper proposes a novel respiratory detection method based on diaphragm motion measurements using a 2D ultrasound unit. The proposed method extracts a respiratory signal from an automated analysis of the internal diaphragm motion during breathing. The respiratory signal may be used for gating. Ultrasound studies of diaphragm breathing motion were performed on four volunteers. The ultrasound video stream was captured and transferred to a personal computer and decomposed into individual image frames. After straightforward image analysis, region of interest selection, and filtering, the mutual information (MI) and correlation coefficients (CCs) between a selected reference frame and all other frames were computed. The resulting MI and CC values were discovered to produce a signal corresponding to the respiratory cycle in both phase and magnitude. We also studied the diaphragm motion of two volunteers during repeated deep inspiration breath holds (DIBH) and found a slight relaxation motion of the diaphragm during the DIBH, suggesting that the residual motion may be important for treatments delivered at this breathing phase. Applying the proposed respiratory detection method to these ultrasound studies, we found that the MI and CC values demonstrate the relaxation behavior, indicatingthat our method may be used to determine the radiation triggering time for a DIBH technique.
• Koong, A. C., Xu, Q., Xing, L., Schreibmann, E., Li, T., Koong, A., & Hamilton, R. J. (2006). Abstract2710: Verification of Gated Radiation Therapy Using Pre-Treatment Four-Dimenstional Cone-Beam CT. International Journal of Radiation Oncology Biology Physics, 66(3), S604. doi:10.1016/j.ijrobp.2006.07.1126
• Spelbring, D. R., Su, A., Spelbring, D., Jani, A. B., Hamilton, R. J., & Blend, M. J. (2006). Postprostatectomy target-normal structure overlap volume differences using computed tomography and radioimmunoscintigraphy images for radiotherapy treatment planning.. Clinical nuclear medicine, 31(3), 139-44. doi:10.1097/01.rlu.0000200461.93250.a5
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  The purpose of this study was to analyze regions of uptake in normal structures on postprostatectomy radioimmunoscintigraphy (RIS) images by evaluating differences in the overlap volumes of prostate fossa clinical target volume (CTV) and planning target volume (PTV) using correlative computed tomography (CT) images..The electronic records of 13 patients who received external beam radiotherapy postprostatectomy and who underwent a vessel-based RIS/CT registration were reviewed. For each patient, the RIS-defined CTV (CTV(RIS)) was compared (in terms of the overlap volume with the surrounding bladder, rectum, pubic symphysis, and penile bulb) with the CT-defined CTV(pre) before this registration and also with CTV(post) (the final target volume used for treatment). Similar analyses were done for PTV(RIS), PTV(pre), and PTV(post) defined in each case to be the corresponding CTV + 1-cm margin..CTV(RIS) overlapped significantly more with the bladder, rectum, and symphysis, but not with the penile bulb, than did either the CTV(pre) or CTV(post). However, the corresponding PTV analyses revealed no significant differences between any of the overlap volumes of any of the PTVs with the bladder, rectum, and penile bulb, but did reveal a significant difference between the PTV(RIS) and PTV(post) overlap volumes with the symphysis compared with PTV(pre) overlap volumes with the symphysis..On RIS images, there appear to be areas of uptake in the bladder, rectum, and pubic symphysis but not the penile bulb; however, the dosimetric consequences of this uptake for radiation treatment planning are minimal on the bladder, rectum, and penile bulb, but require segmentation for dose reduction to the pubic symphysis.
• Xu, Q., Xu, Q., Jiang, S. B., & Hamilton, R. J. (2006). SU‐FF‐J‐24: An Optical Flow Based Motion Tracking Method Using Fluoroscopic Video. Medical Physics, 33(6), 2025-2025. doi:10.1118/1.2240803
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  Purpose: To present an optical flow‐based method for tracking tumor motion and propose a noninvasive respiratory detection method using fluoroscopic video. Method and Materials: Fluoroscopic video of a patient is acquired. Only one frame is selected as the reference frame and objects in this frame are manually segmented. The motion of a segmented object is found by computing the average optical flow of pixels within the object. Optical flow provides a two‐dimensional motion vector for the displacement of pixels between two frames. The object is moved between frames by moving all pixels by the average velocity vector. Then the position of the object in the new frame is adjusted by applying a template matching algorithm. The algorithm moves the object over a search range of +/− 2 pixels. The object is placed at the position having the maximum correlation coefficient (CC) between the pixels in the original and new frames. This procedure is repeated to advance the object from frame to frame. Results:The outlines of tracked objects are viewed superimposed on the fluoroscopic videos. The outlines follow the general motion of the objects without drifting away for the approximately 30 seconds (300 images) and 8 respiratory cycles of a typical video. Objects that do not significantly deform are well tracked. The boundaries of objects that deform are not well described by the tracked outlines, however, the centroid motion of the objects is. The analysis yields the mean displacement of objects. As the distance an object moves away from the reference position increases, the CC decreases. A plot of the CC vs frame shows a sinusoidal curve with the breathing period as does the displacement plot, but with reversed phase. Conclusion: The mean motions of objects in fluoroscopic video are well tracked. The displacement and respiratory signal are also obtained.
• Xu, Q., Xu, Q., Xing, L., He, Z., & Hamilton, R. J. (2006). SU‐FF‐J‐116: Registration of X‐Ray Portal Images with 4DCT DRRs for Patient Setup Verification. Medical Physics, 33(6), 2047-2047. doi:10.1118/1.2240892
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  Purpose: To provide a noninvasive method for both setup verification of 4DCT treatment planning and isocenter positioning shifts for treatment delivery. Method and Materials: A ten phase 4DCT treatment planning study of the patient was acquired using a respiratory gating system. When the patient was on the treatment couch, multiple on board x‐ray images were taken in the anterior‐posterior (AP) and lateral directions. An intensity based rigid registration algorithm was applied to obtain optimal shifts in the x, y and z directions. First, a digitally reconstructed radiograph(DRR) using ray‐casting algorithm was computed from one of the ten phases of the 4DCT. The correlation coefficient (CC) between the DRR and the x‐ray image was then calculated. The 4DCT volume was shifted and new DRRs were generated until the maximum CC value was reached through an optimization process. This procedure was repeated for all ten 4DCT phases. Results: Registration of each phase of the 4DCT with the x‐ray image provided ten maximum CC values. These values exhibited a single maximum at the phase corresponding to the breathing phase when the x‐ray image was taken. The corresponding isocenter positioning shifts for treatment delivery were also obtained. The robustness of our algorithm was demonstrated by registering x‐ray images taken at five random phases to 4DCT. The resulting isocenter shifts were consistent between all phases. The standard deviations of the shifts determined for the AP x‐rays were 2 mm (lateral), 5 mm (anterior‐posterior), and 2 mm (superior‐inferior). Conclusion: Using only the RPM system, one cannot be certain that the internal anatomy is consistent between 4DCT acquisition and any particular treatment day. Our noninvasive method accounts for internal organ motion and may be used for daily 4DCT treatment setup verification and isocenter positioning.
• Su, A., Su, A., Spelbring, D. R., Jani, A. B., Hamilton, R. J., & Blend, M. J. (2005). Post-Prostatectomy Target-Normal Structure Overlap Volumes using Computed Tomography and Radioimmunoscintigraphy Images for Radiotherapy Treatment Planning. International Journal of Radiation Oncology Biology Physics, 63, S513-S514. doi:10.1016/j.ijrobp.2005.07.869
• Xu, Q., Xu, Q., & Hamilton, R. J. (2005). WE‐C‐J‐6C‐03: A Novel Respiratory Gating Method Based On Automated Analysis of Ultrasonic Diaphragm Motion. Medical Physics, 32(6), 2124-2124. doi:10.1118/1.1998508
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  Purpose: Most of the current respiratory gating systems monitor the abdominal wall movement for lungcancerradiotherapy. These systems make the assumption that this motion and that of the lungtumor are correlated. Diaphragm motion is also correlated with lungtumor motion. Research shows there is a phase shift between the abdominal wall and diaphragm motions. Previous studies used fluoroscopy to evaluate diaphragm motion. We developed a method to extract a respiratory gating signal by automatically analyzing ultrasonic diaphragm video. Method and Materials: Volunteers were examined in a supine position and their right diaphragms were imaged with B‐mode ultrasonography using a standard unit (Siemens Sonaline Prima). The analog video signal was captured with a standard pc video card (RADEON 9600XT, ATI Technologies Inc.) at a rate of 30 frames per second to decompose the video stream into frames. To reduce computation time and complexity, the region encompassing the diaphragm motion was segmented from all frames. The mutual information and correlation coefficient between a selected reference frame and all others were calculated and normalized. Diaphragm motion information was extracted for use as a respiratory gating signal. Results: Plots of either the mutual information or correlation coefficient vs time (frame number) are periodic and match the respiratory cycle. The periodicity is independent of the selected reference frame and the shape shows only minor variations. Thus, this method provides a robust signal of respiratory motion that could be used to trigger the radiation beam. Conclusion: A novel respiratory gating system is proposed for lungcancer therapy based on ultrasound imaging. The method is noninvasive, nonionizing, and specific, thus has the potential to be a useful respiratory gating system.
• Kuehl, A. K., Hamilton, R. J., & Armbruster, B. (2004). Spectrum reconstruction from dose measurements as a linear inverse problem.. Physics in medicine and biology, 49(22), 5087-99. doi:10.1088/0031-9155/49/22/005
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  There are three ways to determine the spectrum of a clinical photon beam: direct measurement, modelling the source and reconstruction from ion-chamber measurements. We focus on reconstruction because the necessary equipment is readily available and it provides independent confirmation of source models for a given machine. Reconstruction methods involve measuring the dose in an ion chamber after the beam passes through an attenuator. We gain information about the spectrum from measurements using attenuators of differing compositions and thicknesses since materials have energy dependent attenuation. Unlike the procedures used in other papers, we do not discretize or parametrize the spectrum. With either of these two approximations, reconstruction is a least squares problem. The forward problem of going from a spectrum to a series of dose measurements is a linear operator, with the composition and thickness of the attenuators as parameters. Hence the singular value decomposition (SVD) characterizes this operator. The right singular vectors form a basis for the spectrum, and, at first approximation, only those corresponding to singular values above a threshold are measurable. A more rigorous error analysis shows with what confidence different components of the spectrum can be measured. We illustrate this theory with simulations and an example utilizing six sets of dose measurements with water and lead as attenuators.
• Levin, D., & Hamilton, R. J. (2004). Optimization of tumor control probability in space and time for heterogeneous tumors in fractionated radiotherapy. International Journal of Radiation Oncology Biology Physics, 60(1), S361-S362. doi:10.1016/j.ijrobp.2004.07.203
• Levin-plotnik, D., & Hamilton, R. J. (2004). Optimization of tumour control probability for heterogeneous tumours in fractionated radiotherapy treatment protocols.. Physics in medicine and biology, 49(3), 407-24. doi:10.1088/0031-9155/49/3/005
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  We find the dose distribution that maximizes the tumour control probability (TCP) for a fixed mean tumour dose per fraction. We consider a heterogeneous tumour volume having a radiation response characterized by the linear quadratic model with heterogeneous radiosensitivity and repopulation rate that may vary in time. Using variational calculus methods a general solution is obtained. We demonstrate the spatial dependence of the optimal dose distribution by explicitly evaluating the solution for different functional forms of the tumour properties. For homogeneous radiosensitivity and growth rate, we find that the dose distribution that maximizes TCP is homogeneous when the clonogen cell density is homogeneous, while for a heterogeneous initial tumour density we find that the first dose fraction is inhomogeneous, which homogenizes the clonogen cell density, and subsequent dose fractions are homogeneous. When the tumour properties have explicit spatial dependence, we show that the spatial variation of the optimized dose distribution is insensitive to the functional form. However, the dose distribution and tumour clonogen density are sensitive to the value of the repopulation rate. The optimized dose distribution yields a higher TCP than a typical clinical dose distribution or a homogeneous dose distribution.
• Weichselbaum, R. R., Vijayakumar, S., Sapra, B., Pelizzari, C. A., Krauz, L., Jani, A. B., Hamilton, R. J., Brendler, C. B., Blend, M. J., & Awan, A. (2004). Influence of radioimmunoscintigraphy on postprostatectomy radiotherapy treatment decision making.. Journal of nuclear medicine : official publication, Society of Nuclear Medicine, 45(4), 571-8.
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  The aim of this study was to evaluate the role of radioimmunoscintigraphy (RIS) directed against prostate-specific membrane antigen (PSMA) in influencing postradical retropubic prostatectomy (RRP) radiotherapy (RT) decision making..The records of consecutive patients who underwent RRP, who were referred for consideration of RT, and for whom an RIS scan was obtained were reviewed. The RT decisions, with regard to (a) the decision to offer RT and (b) the general volume to be treated [prostate fossa (PF) only versus PF + pelvis (P)] before knowledge of the RIS findings were charted. The RIS findings, with regard to uptake in the PF, uptake in the P, or extrapelvic (EP) uptake were tabulated. Then, the RT treatment decisions based on the RIS knowledge were evaluated and compared with the pre-RIS RT treatment decisions..Of the 54 patients originally referred for post-RRP RT, the initial decision was to recommend RT to the PF only in 52 cases and to PF+P in 2 cases. The RIS findings were as follows: PF only, 43 patients; PF+P, 8 patients; PF+EP, 2 patients; PF+P+EP, 1 patient. After knowledge of these RIS results, the decision to offer RT was withdrawn in 4 of 54 patients (7.4%; P = 0.046). Furthermore, RIS changed the general treatment volume (PF only to PF+P) in 6 of 54 patients (11.1%; P = 0.015). In total, RIS altered the RT decision in 10 of 54 patients (18.5%; P = 0.0067). Three-year biochemical failure-free survival (with failure defined as 2 consecutive prostate-specific antigen [PSA] rises above 0.2 ng/mL after PSA nadir) was 78%; no patient, disease, or treatment factor reached statistical significance on univariate or multivariate analysis..RIS was found to influence post-RRP RT decision making for the identification of patients not likely to benefit from RT and for guiding general target volume definition.
• Weichselbaum, R. R., Vijayakumar, S., Sapra, B., Pelizzari, C. A., Krauz, L., Jani, A. B., Hamilton, R. J., Brendler, C. B., Blend, M. J., & Awan, A. (2004). Radioimmunoscintigraphy for postprostatectomy radiotherapy: analysis of toxicity and biochemical control.. Journal of nuclear medicine : official publication, Society of Nuclear Medicine, 45(8), 1315-22.
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  Our goal was to evaluate the role of radioimmunoscintigraphy (RIS) directed against prostate-specific membrane antigen (PSMA) in influencing postprostatectomy radiotherapy (RT) toxicity and biochemical control..The records of 107 postprostatectomy RT patients were reviewed. The group for whom no RIS scan was obtained (group A, n = 54) was identified as was the group for whom a RIS scan was obtained (group B, n = 53). Group B was further subdivided into those who had a RIS and CT-scan correlation to aid in treatment planning (subgroup B1, n = 40) versus those who did not (subgroup B2, n = 13). Gastrointestinal (GI) and genitourinary (GU) toxicities were reviewed for each of these groups and subgroups and compared. Biochemical failures (defined as 2 successive PSA rises after a nadir of >or=0.2 ng/mL) were identified to generate biochemical failure-free survival (BFFS) curves for each of the groups and subgroups..No significant differences in late toxicity were observed between any group or subgroup. However, acute GI toxicity was higher in group B versus group A (P = 0.026), and acute GU toxicity was higher in subgroup B2 versus subgroup B1 (P = 0.050). Overall, most toxicity was grade 1 or 2; only one case of grade 3 toxicity and no cases of grade 4 or 5 toxicity were observed. Three-year BFFS was higher for group B versus group A (80.7% vs. 75.5%) and for subgroup B1 versus subgroup B2 (84.5% vs. 71.6%). On multivariate analysis of pretreatment (age, race), surgical/staging (stage, grade, margin status, extracapsular extension, lymph node status, seminal vesicle invasion, post-radical retropubic prostatectomy [RRP] prostate-specific antigen [PSA] nadir, maximum post-RRP PSA, and RRP-to-RT interval), and treatment (hormone therapy, RT dose, RT technique, RIS scan, and RIS/CT correlation) factors on BFFS, the only covariate reaching significance was RIS/CT correlation (P = 0.042)..A small BFFS advantage was observed in patients for whom RIS was used to guide RT decision making and treatment planning; however, this advantage only reached significance in this study for those for whom the RIS/CT correlation was used to guide target definition. The improved PSA control using RIS was achieved with a small increase in acute toxicity but with no observed change in late toxicity. These findings can serve as the basis for prospective studies in this area of investigation.
• Weichselbaum, R. R., Vijayakumar, S., Spelbring, D. R., Sapra, B., Pelizzari, C. A., Krauz, L., Jani, A. B., Hamilton, R. J., Brendler, C. B., & Blend, M. J. (2004). Impact of radioimmunoscintigraphy on definition of clinical target volume for radiotherapy after prostatectomy.. Journal of nuclear medicine : official publication, Society of Nuclear Medicine, 45(2), 238-46.
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  The goal of this study was to evaluate the role of radioimmunoscintigraphy (RIS) directed against prostate-specific membrane antigen in modifying postprostatectomy prostate fossa clinical target volume (CTV) definition..The records of 25 postprostatectomy patients who received external-beam radiotherapy after prostatectomy and who underwent vessel-based RIS/planning CT registration were reviewed. For each patient, the CTV that would have been treated (CTV(pre)) before this registration was compared with that defined after the registration (CTV(post)). In addition, using a standard dose of 66 Gy in 2-Gy fractions, the corresponding bladder and rectum dose volume histograms were compared using 2 endpoints: volume receiving > or =60 Gy (V60) and area under the curve (AUC)..The mean CTV(pre) vs. CTV(post) volumes were 24.4 vs. 35.0 cm(3), respectively (P = 0.032). The V60 results for CTV(pre) and CTV(post) were 32.7 vs. 41.0 cm(3), respectively, for the rectum (P = 0.168) and 33.9 vs. 46.6 cm(3), respectively, for the bladder (P = 0.015). The AUC results for CTV(pre) and CTV(post) were 4,027 vs. 4,516 Gy x cm(3), respectively, for the rectum (P = 0.396) and 4,782 vs. 5,561, respectively, for the bladder (P = 0.119). No Radiation Therapy Oncology Group grade 3, 4, or 5 (acute or late, gastrointestinal, or genitourinary) toxicity was observed. Two-year biochemical failure-free survival (with failure defined as 2 consecutive prostate-specific antigen rises above 0.2ng/mL) was 87% for the cohort..Incorporating RIS uptake resulted in significant modifications in CTV definition. The consequences of these modifications on the rectum V60 or AUC or on the bladder AUC were not significant, although the bladder V60 did increase. However, observed toxicity was low, with acceptable short-term biochemical control, suggesting that treatment to the modified CTV was tolerable.
• Sweeney, P. J., Roeske, J. C., Pelizzari, C. A., Macdonald, L., Jani, A. B., Hamilton, R. J., Chen, G. T., & Bova, F. J. (1998). Volume rendering segmentation algorithm (VRSA) for systematic comparison of visualization techniques for cerebral arteriovenous malformations. International Journal of Radiation Oncology Biology Physics, 42(1), 364. doi:10.1016/s0360-3016(98)80580-4
• Sweeney, P. J., Rubin, S. J., Pelizzari, C. A., Hamilton, R. J., & Chen, G. T. (1995). 21 Functional spect imaging in treatment planning of brain lesions. International Journal of Radiation Oncology Biology Physics, 32, 151. doi:10.1016/0360-3016(95)97684-s
• Hamilton, R. J., Lamb, F. K., & Miller, M. C. (1994). Disk-accreting magnetic neutron stars as high-energy particle accelerators.
• Miller, M. C., Lamb, F. K., & Hamilton, R. J. (1994). Electrodynamics of disk-accreting magnetic neutron stars.
• Coleman, M. M., & Hamilton, R. J. (1993). Reliability of magnetic inclination angle determinations for pulsars.
• Lu, E. T., Hamilton, R. J., Mctiernan, J. M., & Bromund, K. R. (1993). Solar flares and avalanches in driven dissipative systems.
• Gruber, A. D., & Hamilton, R. J. (1992). Improvements in a simply constructed prism spectrometer.
• Hamilton, R. J., & Petrosian, V. (1992). Stochastic acceleration of electrons. I. Effects of collisions in solar flares.
• Lu, E. T., & Hamilton, R. J. (1991). Avalanches and the distribution of solar flares.
• Matthews, S. M., Hamilton, R. J., Gruber, R. P., & Gruber, A. D. (1991). Space curvature and the ``heavy banana `paradox' ''. The Physics Teacher, 29(3), 147-149. doi:10.1119/1.2343254
• Hamilton, R. J., & Petrosian, V. (1990). Effects of Coulomb collisions on cyclotron maser and plasma wave growth in magnetic loops.
• Hamilton, R. J., Lu, E. T., & Petrosian, V. (1990). Numerical solution of the time-dependent kinetic equation for electrons in magnetized plasma.
• Hamilton, R. J., Petrosian, V., & Benz, A. O. (1990). Statistical study of the correlation of hard X-ray and type III radio bursts in solar flares.
• Petrosian, V., & Hamilton, R. J. (1989). Statistical Study of the Correlation of Hard X-Ray and Type III Radio Bursts in Solar Flares. Bulletin of the American Astronomical Society, 21.
• Petrosian, V., & Hamilton, R. J. (1987). Generation of plasma waves by thick-target electron beams, and the expected radiation signature. The Astrophysical Journal, 321, 721. doi:10.1086/165665
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  The production of plasma waves by a nonthermal beam of high-energy electrons injected into a background thermal plasma was investigated. The coupled kinetic equations for nonthermal electrons were solved, and the level of the plasma waves produced by the bump-on-tail instability arising as a result of the Coulomb collisions of nonthermal electrons with background plasma was estimated. In addition, the radiation signatures of these waves were examined. It is shown that the wave-particle interactions have a significant effect on the overall distribution of the electrons and that it is unlikely that such effects can be discerned in the observed bremsstrahlung or synchrotron radiation of the nonthermal electrons. However, a significant fraction of the energy lost by the beam is transferred to plasma waves and is then dissipated by the thermal plasma. 14 references.
• Petrosian, V., & Hamilton, R. J. (1986). Generation of plasma waves by thick-target electron beams.. Bulletin of the American Astronomical Society, 18(3).
• Restle, P. J., Hamilton, R. J., Weissman, M. B., & Love, M. S. (1985). Non-Gaussian effects in 1/f noise in small silicon-on-sapphire resistors.

Proceedings Publications

• Lee, Y. S., Huynh, J. W., Hamilton, R. J., & Kim, Y. (2017, June). Failure modes and effects analysis (FMEA) and fault tree analysis (FTA) for eye plaque brachytherapy. In AAPM, 44, 3163.
• Miller, M. C., Lamb, F. K., & Hamilton, R. J. (1993). Acceleration of particles in the magnetospheres of accreting neutron stars. In AIP Conference Proceedings, 280, 438-442.
• Miller, M. C., Lamb, F. K., & Hamilton, R. J. (1993). Electrodynamics of neutron stars accreting from a disk. In AIP Conference Proceedings, 280, 443-447.
• Miller, M. C., Lamb, F. K., & Hamilton, R. J. (1993). Gamma‐ray production by neutron stars accreting from a disk. In AIP Conference Proceedings, 280, 433-437.

Presentations

• Hamilton, R. J. (2015, 04-04-2015). Episcleral Device for the Treatment of Neovascular Age-Related Macular Degneration. 3rd Annual Arizona Chapter Meeting of the AAPM. Gilbert, AZ: Annual Arizona Chapter of the AAPM.

Poster Presentations

• Garcia, A., Locke, A., Smith-Raymond, L., Hamilton, R. J., & Stea, B. (2020, October). Robust Planning Optimization Improves Safety and Homogeneity for Craniospinal Irradiation in the Supine Position. 2020 ASTRO Annual Meeting. Virtual: American Society for Radiation Oncology.
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  Garcia A, Locke A, Smith L, Hamilton RJ, Stea B. Robust Planning Optimization Improves Safety and Homogeneity for Craniospinal Irradiation in the Supine Position. International Journal of Radiation Oncology, Biology, Physics, Volume 108, Issue 3, e346 - e347, 2020 (ASTRO 2020)
• Hadad, K., Mirzapour, M., Faghihi, R., & Hamilton, R. J. (2020, July). GPU Based Parallel Computation for Fast Monte-Carlo Photon Transport. 2020 AAPM Annual Meeting. Virtual: American Association of Physicists in Medicine.
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  Hadad K, Mirzapour M, Faghihi R, Hamilton R GPU Based Parallel Computation for Fast Monte-Carlo Photon Transport, Med Phys, 47 (6), e788 June 2020 (AAPM 2020).
• Hamilton, R. J., Smith-Raymond, L., Locke, A., & Stea, B. (2020, July). RayStation Planning for Single Isocenter Multiple Metastases Radiosurgery Treatments. 2020 AAPM Annual Meeting. Virtual: American Association of Physicists in Medicine.
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  Hamilton R, Smith-Raymond L, Locke A, Stea B RayStation Planning for Single Isocenter Multiple Metastases Radiosurgery Treatments, Med Phys, 47 (6), e841 June 2020 (AAPM 2020).
• Mostafaei, F., Dougherty, S., & Hamilton, R. J. (2020, July). A Comparison of Two Immobilization Systems for Prostate Radiotherapy. 2020 AAPM Annual Meeting. Virtual: American Association of Physicists in Medicine.
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  Mostafaei F, Dougherty S, Hamilton R A Comparison of Two Immobilization Systems for Prostate Radiotherapy, Med Phys, 47 (6), e677 June 2020 (AAPM 2020)
• Farshad, M., Lin, S., Joshua, S., Alexis, W., Lee, Y. S., Hamilton, R. J., & Yongbok, K. (2019, July). Dosimetric Evaluation of An SRS MapCHECK for SBRT QA. Annual Meeting of the American Association of Physicists in Medicine. San Antonio, TX: American Association of Physicists in Medicine.
• Hamilton, R. J. (2018, October). Improved Dose Distribution with 3D Printed Vaginal Cylinder Applicator for VariSource HDR Afterloader Y. Xu,1 S.C. Lin,1 R.J. Hamilton,2 C.J. Watchman,2 and S.T. Dougherty3 ;. ASTRO 2018. San Antonio, TX: ASTRO.