ESTRO 2022 - Abstract Book

S1317

Abstract book

ESTRO 2022

PO-1537 Evaluation of an independent dose calculation software based on AAPM Task Group 219

J. Dias 1 , S. Avelino 1 , T. Peron 1 , J. Nakashima 1

1 Vitta - Centro de Radioterapia, Radiotherapy, Brasília, Brazil

Purpose or Objective Independent Dose Calculation Software (IDCS) is an important safety tool in quality assurance programs. Considering that AAPM TG 219 report was recently published to standardize the acceptance and commissioning of IDCS, the present study applied this report to evaluate a commercial IDCS, and to validate the method and action levels suggested. Materials and Methods We assessed DoseCHECK (Sun Nuclear, FL, USA) as an IDCS for our clinical Eclipse TPS, v15.5 (Varian Medical Systems, CA, USA). The Eclipse was commissioned using the Analytical Anisotropic Algorithm (AAA) for 6 and 10 MV of a Varian TrueBeam . Based on AAPM TG 219, we evaluated 71 dose points per energy in order to verify: PDP, profiles, dynamic wedges, field edges, surface region, simple IMRT pattern (pyramid shape), and AAPM TG 119 IMRT plans. To evaluate high modulated VMAT plans, we used a home-made heterogeneous phantom. The 19 irregular static fields suggested by AAPM TG 219 were included in our analysis. We created verification dose points at positions that considered the intent of each evaluation plan. The dose range of the points tested varied from 200 to 600 cGy. We exported all plans to the IDCS. We compared the doses calculated at all verifications points by DoseCHECK (collapsed cone convolution algorithm), with Eclipse and with ionization chamber and diode measurements (diode was used for 3x3 cm 2 or smaller fields). We considered an action level of 5% for: single beam/low gradient/homogeneous phantom; or composite beams/high gradient/ homogeneous phantom. In addition, we used an action level of 7% for: single beam/high gradient/homogeneous phantom; or composite beams/high gradient/heterogeneous phantom. Results The Table 1 shows the results of case tests performed based on AAPM TG 219. The Table 2 shows the results of the 19 specific case tests suggested by AAPM TG 219. For 6 MV beam, the IDCS deviated from TPS in 2 dose points and from measurements in 8 dose points. For 10 MV beam, the IDCS deviated from TPS in 1 dose point and from measurements in 3 dose points. In both sets of tests, the situations that did not respected the action levels suggested in AAPM TG 219 were at superficial points located 5 mm from the surface, at points located 20 cm depth, and in a 6 MV high modulated AAPM TG 119 plan. The tests with poor results slightly diverge from action levels considered or they are related to not clinically relevant points.