During the implementation of clinical trials NCT00950001 and NCCTG/N107C/CEC.3 on post-operative stereotactic radiosurgery into clinic, it brought us some thinking of fundamental concept in science that the local cont...During the implementation of clinical trials NCT00950001 and NCCTG/N107C/CEC.3 on post-operative stereotactic radiosurgery into clinic, it brought us some thinking of fundamental concept in science that the local control rate and survival rate rely on the treatment of marginal region more than resection cavity. Marginal region might still contain residual cancer cell while the resection cavity contains only water fluid most time. Radiation treatment should focus more on the margin rather than the cavity, thus treating cancer rather than water.展开更多
In the linear accelerator-based stereotactic radio surgery (SRS) and stereotactic body radiotherapy (SBRT) programs, single isocenter-multiple metastases’ treatment has become more and more popular due to their high ...In the linear accelerator-based stereotactic radio surgery (SRS) and stereotactic body radiotherapy (SBRT) programs, single isocenter-multiple metastases’ treatment has become more and more popular due to their high efficiency in treatment time. However, the absence of a comprehensive quality assurance program is still the challenge for medical physicists. The Winston-Lutz-Gao test, which we developed two years ago, was performed for the first time on a True Beam STx (Varian Medical System) linear accelerator in this study. Beams were designed by Eclipse with gantry, collimator, and couch full rotations, and a 200-pound weight was placed on the couch to mimic real treatment. The “frameless SRS QA target pointer” from the Brainlab company, with a 3.5-mm metallic ball embedded in the center, was used as a phantom. Images were acquired by the portal imager built-in linear accelerator and analyzed directly by the Image browser in ARIA. We found that the farther the metastases were from the linac isocenter, the worse the congruence was between the beam mechanical and the radiation center. The farthest metastases should be within 6 cm from the linac isocenter per the AAPM TG-142 and American Society for Radiation Oncology (ASTRO) white paper criteria. To the best of our knowledge, this is the first off-isocenter Winston-Lutz test performed on a True Beam STx linear accelerator.展开更多
文摘During the implementation of clinical trials NCT00950001 and NCCTG/N107C/CEC.3 on post-operative stereotactic radiosurgery into clinic, it brought us some thinking of fundamental concept in science that the local control rate and survival rate rely on the treatment of marginal region more than resection cavity. Marginal region might still contain residual cancer cell while the resection cavity contains only water fluid most time. Radiation treatment should focus more on the margin rather than the cavity, thus treating cancer rather than water.
文摘In the linear accelerator-based stereotactic radio surgery (SRS) and stereotactic body radiotherapy (SBRT) programs, single isocenter-multiple metastases’ treatment has become more and more popular due to their high efficiency in treatment time. However, the absence of a comprehensive quality assurance program is still the challenge for medical physicists. The Winston-Lutz-Gao test, which we developed two years ago, was performed for the first time on a True Beam STx (Varian Medical System) linear accelerator in this study. Beams were designed by Eclipse with gantry, collimator, and couch full rotations, and a 200-pound weight was placed on the couch to mimic real treatment. The “frameless SRS QA target pointer” from the Brainlab company, with a 3.5-mm metallic ball embedded in the center, was used as a phantom. Images were acquired by the portal imager built-in linear accelerator and analyzed directly by the Image browser in ARIA. We found that the farther the metastases were from the linac isocenter, the worse the congruence was between the beam mechanical and the radiation center. The farthest metastases should be within 6 cm from the linac isocenter per the AAPM TG-142 and American Society for Radiation Oncology (ASTRO) white paper criteria. To the best of our knowledge, this is the first off-isocenter Winston-Lutz test performed on a True Beam STx linear accelerator.
