EP-1164: A statistical study on EPID QA of VMAT

U.S. Soendergaard, M. Sjoelin, P. Andersson
2013 Radiotherapy and Oncology  
2nd ESTRO Forum 2013 S437 delivery system and treatment delivery by the linac. This work is concerned with developing an algorithm to predict the DAVID signal. Materials and Methods: The lateral response resulting from the primary and scattered radiation was characterised. Convolution of the lateral response with the leaf separations of each segment in a stepand-shoot plan, combined with additional corrections for leaf leakage and penumbral drop-off, result in anticipated signals for each wire.
more » ... nals for each wire. This simple approach was used to predict the signal for a range of clinical head and neck IMRT plans. The DAVID signal for each of the plans was collected five times and the results averaged. These were then compared to the predicted signals. The percentage difference between the maximum predicted and measured signals was calculated for the whole treatment; differences >5% resulted in a failed delivery. Providing this initial test was passed, a set value of 5% of maximum result (either predicted or measured -whichever was lower) was used to assess the difference between all the predicted and measured values for each wire, for each field -results with differences greater than this set value resulted in a failed delivery. Results: All the treatments passed. The algorithm was also able to detect artificially-induced changes in MU delivery of 5% and greater, to the extent that the treatment delivery 'failed'. Conclusions: The work has shown that a simple algorithmcalculations take <5s -can be used to accurately predict the response of the DAVID. Using the procedure discussed above, enables in-vivo verification of dose and delivery of IMRT treatments that is quick, easy and does not require separate pre-treatment time on the treatment unit.
doi:10.1016/s0167-8140(15)33470-8 fatcat:2vx2xe5qxvgplibmvpivvvgm6m