Background. While neoadjuvant concurrent chemoradiotherapy has improved outcomes for esophageal cancer patients, surgical complication rates remain high. The most frequent perioperative complications after trimodality therapy were cardiopulmonary in nature. The radiation modality utilized can be a strong mitigating factor of perioperative complications given the location of the esophagus and its proximity to the heart and lungs. The purpose of this study is to make a dosimetric comparison of Intensity-Modulated Radiation Therapy (IMRT), proton and 3D conformal radiotherapy (3D-CRT) with regard to reducing perioperative cardiopulmonary complications in esophageal cancer patients. Materials. Ten patients with esophageal cancer treated between 2010 and 2013 were evaluated in this study. All patients were simulated with contrast-enhanced CT imaging. Separate treatment plans using proton radiotherapy, IMRT, and 3D-CRT modalities were created for each patient. Dose-volume histograms were calculated and analyzed to compare plans between the three modalities. The organs at risk (OAR) being evaluated in this study are the heart, lungs, and spinal cord. To determine statistical significance, ANOVA and two-tailed paired t-tests were performed for all data parameters. Results. The proton plans showed decreased dose to various volumes of the heart and lungs in comparison to both the IMRT and 3D-CRT plans. There was no difference between the IMRT and 3D-CRT plans in dose delivered to the lung or heart. This finding was seen consistently across the parameters analyzed in this study. Conclusions. In patients receiving radiation therapy for esophageal cancer, proton plans are technically feasible while achieving adequate coverage with lower doses delivered to the lungs and cardiac structures. This may result in decreased cardiopulmonary toxicity and less morbidity to esophageal cancer patients.
Purpose: Pancreatic cancer is a highly aggressive malignancy. Chemoradiation therapy (CRT) is used in many cases to improve local-regional control; however, toxicities associated with radiation can be significant given the location of the pancreas. The purpose of this study is to quantify the dosimetric changes seen when using photons or protons in patients receiving CRT for cancer of the pancreas. Patients and Methods: Ten patients with pancreatic head adenocarcinoma treated between 2010 and 2013 were evaluated in this study. All patients underwent simulation with contrast-enhanced computed tomography imaging. Separate treatment plans using proton radiation therapy, intensity-modulated radiation therapy, and 3-dimensional photon radiation therapy modalities were created for each patient. Dose-volume histograms were calculated and analyzed to compare plans between the 3 modalities. The organs at risk evaluated in this study are the kidneys, liver, small bowel, and spinal cord. To determine statistical significance, analysis of variance and 2-tailed paired t tests were performed for all data parameters. Results: The proton radiation therapy plans resulted in significantly lower doses delivered to the kidneys, liver, small bowel, and spinal cord. This finding was seen consistently across the parameters analyzed in this study. Conclusion: For patients receiving CRT, the proton plans are technically feasible and dosimetrically appealing with superior organs at risk sparing. Proton radiation therapy may improve the therapeutic ratio for patients receiving CRT for pancreatic cancer.
IntroductionThe utilization of proton therapy has increased sharply with an increasing number of proton centers opening within the United States. The challenges of accurately delivering particle therapy increase over photon based techniques due to the Bragg peak and sharp energy fall off. Thus as intrafractional motion occurs, the water-equivalent path length (WPL) can vary as organs of different density pass through the particle's path, resulting in under coverage of the planning tumor volume (PTV) and higher doses to organs at risk (1-3).The ability to deliver a planned radiation dose, robustness, of a treatment plan depends on factors which cannot be entirely accounted for by a single free breathing planning CT (4). These factors are eloquently described in the Paganetti paper and include factors independent of Original Article
calibrations were constructed for all the tube voltages. All HU images and direct ED images were imported into a treatment planning system, where all HU images were assigned the corresponding CT calibration curves while all direct ED images were assigned a linear CT calibration curve. A cylindrical planning target volume of 5 cm in diameter was planned to receive full prescription dose from 9 coplanar beams on all images. Gamma analysis was performed to demonstrate dosimetric change quantitatively. Results: The deviation of ED obtained from the direct ED images was -0.4%AE1.7% from the true values for all inserts, slightly better than that from the HU images, which was determined to be -0.7%AE1.8%. Gamma analysis on intercomparison between the direct ED images and the HU images acquired at the same tube voltage indicated negligible difference with lowest passing rate at 99.9%. Gamma analysis on cross-comparison among the direct ED images acquired at various voltages indicated negligible inherent variation with lowest passing rate at 99.1%, slightly better than the lowest passing rate of 99.0% scored on cross-comparison among the HU images acquired at various tube voltages. Conclusion: Direct ED images require no CT calibration while showing equivalent dosimetry, regardless of tube voltages, compared to that obtained from standard HU images. The ability of acquiring direct ED images simplifies the current practice at a safer level by eliminating CT calibration and HU conversion from commissioning and treatment planning, respectively. Furthermore, it unlocks a wider range of tube voltages in CT scanner for better imaging quality while maintaining similar dosimetric accuracy.Purpose/Objective(s): Traditional radiation therapy inverse planning relies on the weighting factors to subjectively balance the conflicting criteria for different structures. The resulting manual trial-and-error determination of the weighting factors has long been recognized as the most timeconsuming part of treatment planning. The purpose of this work is to develop a novel inverse planning framework that parameterizes the dosimetric tradeoff among the structures with physically more meaningful quantities to simplify the search for a clinically sensible plan.Materials/Methods: A permissible dosimetric uncertainty is introduced for each of the structures to balance their conflicting dosimetric requirements. For simplicity, the uncertainty of a structure is extracted from a library of previous cases that possess similar anatomy and prescription. The inverse planning is then formulated into a convex feasibility problem with the goal of generating plans with acceptable dosimetric uncertainties. A sequential procedure (SP) is derived to simultaneously tune and solve the model. In SP, the feasibility problem is reduced to 3 submodels to contain the uncertainty in the planning target volume (PTV), the critical structures, and all other structures to spare, respectively. The proposed technique is applied to plan a liver case and a head-and-neck case in...
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