Purpose: It is clinically meaningful to generate the optimal intensity‐modulated radiation therapy (IMRT) treatment plans within the restricted time with equally good quality for different patients, which is planner‐dependent. We developed a planner‐independent method for a clinical decision of prostate IMRT plan using the rectal complication probability with the volume of rectum overlapping the PTV. Methods: Eighteen prostate IMRT plans were retrospectively analyzed. The prescription dose in the all the planning target volumes (PTVs) was normalized with 76 Gy in 2 Gy fractions. We found a correlation between the fraction of rectum overlapping the PTV and the rectal normal tissue complication probability (NTCP), which is the predictable NTCP curve, which means the lower bound of the rectal NTCP. The plans beyond the predictable NTCP criteria were generated again with seven 10 MV beams from the Varian Clinac iX linear accelerator. The beams were arranged coplanar at: 0, 50, 100, 140, 220, 260, and 310. IMRT plans were generated using direct machine parameter optimization in the Pinnacle3. Results: All the regenerated plans came to be included in the predictable NTCP criteria. In our patient data, two plans were re‐planned: the NTCP for patient 7 was changed from 10.9 to 8.8 and the other NTCP for patient 14 was from 15.6 to 12.9. The rectal NTCP is clinically more meaningful than the mean dose of rectum. Conclusion: This model can predict the rectum NTCP before IMRT planning, to control the IMRT plan quality during planning. Hence we can maintain prostate IMRT plan quality using the fraction of rectum overlapping the PTV.
Purpose:The aim of this study is to develop the abdominal compression device which could control pressure level according to the abdominal respiratory motion and evaluate its feasibility.Methods:In this study, we focused on developing the abdominal compression device which could control pressure level at any point of time so the developed device is possible to use a variety of purpose (gating technique or respiratory training system) while maintaining the merit of the existing commercial device. The compression device (air pad form) was designed to be able to compress the front and side of abdomen and the pressure level of the abdomen is controlled by air flow. Pressure level of abdomen (air flow) was determined using correlation data between external abdominal motion and respiratory volume signal measured by spirometer. In order to verify the feasibility of the device, it was necessary to confirm the correlation between the abdominal respiratory motion and respiratory volume signal and cooperation with respiratory training system also checked.Results:In the previous study, we could find that the correlation coefficient ratio between diaphragm and respiratory volume signal measured by spirometer was 0.95. In this study, we confirmed the correlation between the respiratory volume signal and the external abdominal motion measured by belt‐transducer (correlation coefficient ratio was 0.92) and used the correlated respiratory volume data as an abdominal pressure level. It was possible to control the pressure level with negligible time delay and respiratory volume data based guiding waveforms could be properly inserted into the respiratory training system.Conclusion:Through this feasibility study, we confirmed the correlation between the respiratory volume signal and the external abdominal motion. Also initial assessment of the device and its compatibility with the respiratory training system were verified. Further study on application in respiratory gated therapy and respiratory training system will be investigated.This work was supported by Radiation Technology R&D program (No. 2013M2A2A7043498)and Basic Atomic Energy Research Institute (BAERI)(No. NRF‐2009‐0078390) through the National Research Foundation of Korea funded by the Ministry of Science, ICT&Future Planning.
We have retrospectively investigated 20 nasopharyngeal carcinoma patients treated in our institution between March 2007 and August 2009 was reviewed. We used simultaneous integrated boost whole field intensity modulated radiotherapy to treat the entire planning target volume in the head and neck cancer. For comparison with the jounctioned intensity modulated radiotherapy technique, treatment plans were each replanned using jounctioned intensity modulated radiotherapy technique at 6 MV. The effect on target coverage and sparing of organs at risk, including laryngeal sparing in the optimal whole field intensity modulated radiotherapy plan was compared with that achieved using a jounctioned intensity modulated radiotherapy technique. The mean larynx dose was 25.2 Gy in the whole sis intensity modulated radiotherapy. and 19.8 ar in the jounctioned intensity modulated radiotherapy. With comparison between whole field intensity modulated radiotherapy and jounctioned intensity modulated radiotherapy technique, it demonstrated that larynx dose in the whole field intensity modulated radiotherapy technique was increased to that achieved with jounctioned intensity modulated radiotherapy and conventional anterior neck field. However, if applying strong dose constraint on larynx and using the pseudo volume to enforce a steep dose fall‐off immediately outside the target, the simultaneous integrated boost whole field intensity modulated radiotherapy technique led to larynx dose comparable to that achieved with jounctioned intensity modulated radiotherapy. Therefore, in our current practice we use the simultaneous integrated boost whole field intensity modulated radiotherapy technique which does not have the problem of setup error at match line for treatment of nasopharyngeal carcinoma.
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