Purpose: The VariSeed 9.0 brachytherapy TPS is recently available and has new features such as ability to rotate a brachytherapy source away from normal to the imaging plane. Consequently, a dosimetric analysis was performed for a directional brachytherapy source (CivaSheet) with tests of this functionality and experiences from clinical treatment planning were documented. These observations contribute to safe, practical, and accurate use of such new software features. Methods: Several tests were established to evaluate the new rotational feature, specific to the CivaSheet for the first patients treated using this new brachytherapy device. These included suitability of imaging slice‐thickness and in‐plane resolution, window/level adjustments for brachytherapy source visualization, commissioning the source physical length for performing rotations, and using different planar and 3D window views to identify source orientation. Additional CivaSheet‐specific tests were performed to determine the dosimetric influence on target coverage: changing the source tilt angle, source positioning in the treatment plan based on the CivaSheet rectangular array of CivaDots, and influence of prescription depth on the necessary treatment margin for adequate target coverage. Results: Higher imaging‐resolution produced better accuracy for source orientation and positioning, with sub‐millimeter CT slice‐thickness and in‐plane resolution preferred. Source rotation was possible only in sagittal or coronal views. The process for validating source orientation required iteratively altering rotations then checking them in the 3D view, which was cumbersome given the absence of quantitative plan documentation to indicate orientation. Given the small Pd‐103 source size, influence of source tilt within 30° was negligible for <1.0 cm. Influence of source position was important when the source was positioned in/out of the adjacent source plane, causing changes of 15%, 7%, and 3% at depths of 0.5, 0.7, and 1.0 cm. Conclusion: The new TPS rotational feature worked well, but several issues were identified to improve the treatment planning process. Research supported in part by CivaTech Oncology, Inc. for Dr. Rivard.

Purpose: To analyze and evaluate treatment delivery time, total number of MU, and number of control points with similar IMRT plans delivered both on Varian 21EX and Elekta Synergy accelerators. Comparison of maximum dose based on a minimum volume of 2ccs was also reviewed. Method and Materials: Prostate and breast plans with similar +/−5% angles and using the same step and shoot technique were chosen for this study. These plans were created with the Pinnacle v7.4 DMPO planning system. The total MU, time (normalized for minor differences in dose rate delivery) and number of control points needed to execute these IMRT plans was compared. Maximum dose was evaluated utilizing the treatment planning software statistics and DVH. Results: The Synergy took slightly more time to deliver a similar IMRT plan than the 21EX. The 80 Elekta leaves moved more slowly than the 120 Varian leaves but the most time consuming element was the fact that the Elekta diaphragms moved for each segment. Although the carriage shifts laterally for Varian 120 leaf MLC delivery for very large fields necessitating more time, this was not needed for any of the cases studied. Conclusion: The advantage of the diagraphm movement is that larger field sizes may be delivered with the Elekta MLC without splitting beams. The movement is necessary to block the inherent leaf gaps due to the MLC limitation. Because of the slightly longer treatment time with the Elekta, patient selection and patient movement must be considered. The study did not account for time for any imaging including port films or CBCT for localization. Both accelerators produced clinically acceptable treatment plans for delivery.

Purpose: To create a routine QA procedure that would effectively test the accuracy of a Varian Millenium MLC System that was used heavily for step and shoot IMRT. Method and Materials: We researched the literature to compare published QA procedures and extracted various tests to use at our centers. The procedure that we created consisted of 4 simple monthly tests, 5 additional quarterly tests, and 8 additional annual tests. The monthly tests were evaluated visually and took a minimal amount of time to perform. The quarterly and annual tests involved irradiating more films and analyzing most of them with the RIT113 version 4.1software. The annual tests were those provided by Varian in the “QA Tests Patterns and Procedures” manual and the RIT113 software included specific options for evaluation. Results: The machine parameters and MLC shapes were input to the Impac R&V System. Therefore the tests were simple and fairly quick to run. The analysis however was time consuming because all films must be scanned with a Vidar scanner and evaluated with the RIT113 software. The advantage of using RIT113 was that the QA documentation became organized and efficient. Conclusion: The literature contains many different MLC QA tests for a variety of equipment configurations. Furthermore we found that the AAPM Task Group ♯50 Report gives guidelines for MLC testing but does not list detailed tests. By combining several references and importing the tests in Impac, our MLC QA procedure has proven to be successful with minimal time expense. Within a very busy center performing IMRT treatments, the physicist is usually consumed with patient specific QA. This type of QA isn't usually precise enough to pick up small MLC inaccuracies and additional QA tests are necessary.

Purpose: To select a reference point in a low dose gradient region of an IMRT treatment plan to enhance the MU and point dose agreement between Pinnacle and RadCalc. Method and Materials: After generating an IMRT plan within Pinnacle, we export it to RadCalc for a second check of the MU's. Frequently, the MU difference is significant for a plan with split beams or isocenter out of the field. In contrast to Pinnacle, RadCalc displays a coordinate grid over its BEV fluence. By utilizing this feature for the problematic beams, we selected reference points in low gradient regions of each beam's fluence map. In RadCalc's BEV, we identified the coordinate shifts relative to isocenter of the preferred points. We generated an Excel spreadsheet to calculate the updated coordinates in Pinnacle's 3‐D CT‐based coordinate system to reflect the desired point shift in RadCalc. These new coordinates were then entered in Pinnacle for the patient plan and re‐exported to RadCalc. The modified MU and dose comparisons within RadCalc generally fell within 5% per beam. Results: While this method adds a few extra steps to the planning process, it provides a way to choose reference points whereby the MU's and point doses between Pinnacle and RadCalc are likely to agree within a few percent, and it makes determining the coordinates of such points a reasonably efficient process. Conclusion: RadCalc is a useful program for verifying IMRT MU's and point doses generated by Pinnacle. However because Pinnacle exports the user selected reference point (typically isocenter), there are common conditions in which RadCalc understandably determines large percent differences in calculations. Our method uses RadCalc's fluence map along with a spreadsheet to determine the Pinnacle coordinates of a preferred calculation point, rather than “guessing” where to place a POI to bring about better calculation agreement.