The effects of exposure of 3D ORAM materials to protons, alphas and I2C ions have been investigated in the energy range of 0.5 to 2.5 MeV per nucleon. A permanent change occurs in the properties of the materials due to irradiation. The exposed materials are observed to fluoresce under a confocal laser scanning microscope.The intensity and depth of the fluorescence is dependent on the type and energy of the particles to which the materials were exposed. These properties should prove useful for charged particle and neutron dosimetry/detector applications
Purpose:
Knowledge‐based planning programs have become available to assist treatment planning in radiation therapy. Such programs can be used to generate estimated DVHs and planning constraints for organs at risk (OARs), based upon a model generated from previous plans. These estimates are based upon the planning CT scan. However, for distensible OARs like the bladder and rectum, daily variations in volume may make the dose estimates invalid. The purpose of this study is to determine whether knowledge‐based DVH dose estimates may be valid for distensible OARs.
Methods:
The Varian RapidPlan™ knowledge‐based planning module was used to generate OAR dose estimates and planning objectives for 10 prostate cases previously planned with VMAT, and final plans were calculated for each. Five weekly setup CBCT scans of each patient were then downloaded and contoured (assuming no change in size and shape of the target volume), and rectum and bladder DVHs were recalculated for each scan. Dose volumes were then compared at 75, 60,and 40 Gy for the bladder and rectum between the planning scan and the CBCTs.
Results:
Plan doses and estimates matched well at all dose points., Volumes of the rectum and bladder varied widely between planning CT and the CBCTs, ranging from 0.46 to 2.42 for the bladder and 0.71 to 2.18 for the rectum, causing relative dose volumes to vary between planning CT and CBCT, but absolute dose volumes were more consistent. The overall ratio of CBCT/plan dose volumes was 1.02 ±0.27 for rectum and 0.98 ±0.20 for bladder in these patients.
Conclusion:
Knowledge‐based planning dose volume estimates for distensible OARs are still valid, in absolute volume terms, between treatment planning scans and CBCT's taken during daily treatment. Further analysis of the data is being undertaken to determine how differences depend upon rectum and bladder filling state.
This work has been supported by Varian Medical Systems.
Purpose: To present the changes we made in our department of 8 radiation oncology centers to keep pace with the industry. The changing field has been the topic of task groups, seminars and symposiums with the expectation that groups like ASTRO, AAPM and NCI would help re‐write new specifications and guidelines. As with all members of the medical physics community, we await the new guidelines but continuously adopt our own quality assurance (QA) procedures to meet the demands of our changing fields. This paper addresses how we have approached these issues and how we have changed our QA processes. Method and Materials: The ever evolving industry in Radiation Oncology has forced medical physicists to develop new quality assurance (QA) procedures. Additional QA procedures are required for electronic portal imager devices (EPID), multileaf collimators (MLC), film processors, mega‐voltage cone beam CT (MVCB‐CT) tests, and QA on functional imaging devices such as PET/CT, SPECT and MRI. Results: A listing of added quality assurance procedures and specifications is shown. It demonstrates a higher level of testing that goes beyond TG40 to assure safe, accurate and reliable beam delivery. We have identified the need to address the addition of hardware, the growing use of computers, higher levels of imaging, and the move to adaptive treatments. Conclusion: We added procedures to all of our daily, weekly and monthly QA processes. This included linear accelerators, imaging and planning devices. These procedures have assured that we maintain reasonable and effective QA assessments in line with the changing industry. We expect that these or similar standards will be organized and adapted by medical physics organizations to assure uniform standards throughout all radiation oncology operations.
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