Room: AAPM ePoster Library
Purpose: To study the usefulness of new commercial software, RTappTM (SegAna LLC, Orlando, FL), developed for fast evaluation of daily treatment delivery by SBRT of the lung.
Methods: We retrospectively analyzed 20 lung cancer patient treatments by a stereotactic body radiation therapy (SBRT) technique with 10 fields and 6MV photons on Varian Truebeam. The prescriptions were 45, 50, or 54 Gy to an isodose level (80 – 90%) in 3 fractions (6 cases) or 5 fractions (14 cases). The Elekta stereotactic body frame with chest compression and Civco Vac-Lok cushions were used for patient immobilization. Daily cone-beam-computed tomography (CBCT) -based position adjustments were made for each treatment. RTapp automatically performs a bidirectional deformable registration between the CBCT and the planning CT and then uses the registration to deform the dose distribution and contours, identifying when the plan exceeds dose constraints. Dose-volume histograms for all contoured structures were calculated. RTapp enabled a comparison between the delivered and planned doses for all fractions, as well as the predicted cumulative dose after the treatment course.
Results: Among 20 patient treatments, the cumulative V90 of PTV and V100 of ITV estimated for the complete treatment by RTapp decreased more than 5% in five and one patient, respectively. Hence, these cases indicated a need for early intervention by either a further thorough study of the cause of the discrepancy or replanning before the treatment of the next fraction.
Conclusion: We confirmed the value of the RTapp software as a quick and simple tool for daily evaluation of treatment delivery accuracy before proceeding with dose delivery for lung SBRT patients as well as identifying the need for a replan.