Online

ESTRO 2020

Session Item

Physics track: Dose measurement and dose calculation
9319
Poster
Physics
00:00 - 00:00
Clinical implementation of RayStation for Accuray Radixact tomotherapy platform
Marco Fusella, Italy
PO-1368

Abstract

Clinical implementation of RayStation for Accuray Radixact tomotherapy platform
Authors: Marco Fusella.(Istituto Oncologico Veneto, Medical Physics, Padova, Italy), Marta Paiusco.(Istituto Oncologico Veneto, Medical Physics, Padova, Italy), Nicola Pivato.(Istituto Oncologico Veneto, Medical Physics, Padova, Italy), Antonella Roggio.(Istituto Oncologico Veneto, Medical Physics, Padova, Italy), Marco Andrea Rossato.(Istituto Oncologico Veneto, Medical Physics, Padova, Italy), Alessandro Scaggion.(Istituto Oncologico Veneto, Medical Physics, Padova, Italy), Roberto Zandona.(Istituto Oncologico Veneto, Medical Physics, Padova, Italy)
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Purpose or Objective

The helical tomotherapy platform (Accuray Radixact )has been recently installed at our Institute. Alternatively to Precision TPS, we acquired RaySearch TPS (RayStation) for tomotherapy planning. The commissioning and testing of the new TPS is here presented. At the time of the submission this was the first application of the RayStation TPS for tomotherapy planning.

Material and Methods

First step: tuning the absolute dose normalization of the model. As suggested by AAPM''s TG-148, a tomotherapy plan has been optimized and calculated for two cylindrical targets and one OAR inside the Virtual Water phantom (VW) provided with the machine. A total of five plans have been generated, one for each jaws opening (static and dynamic mode). Multiple point dose measurements (up to six points for each plan) has been performed to check whether the calculated dose respects the actual output of the linac. The dose normalization of the model has been tuned by iteratively generating the machine model and recalculating the plan in VW Phantom. 

Second step: the model was further refined correcting to transverse profiles.

Third step: analysis of the model. All the profile and PDD curves was analyzed with an in-house developed routine for  1-D gamma index calculation with 1%/1mm local criterion. The second validation step of the model consisted of a volumetric measurement of the 5 plans calculated for the VW to control the helical output constancy. As third validation step  a total of 150 patient-specific QA measurements were taken with the 3D diode array ArcCHECK (Sun Nuclear Corporation), calibrated in absolute dose. Various gamma index (GI) were calculated: 3%/3mm, 3%/2mm and 2%/2mm, both local (L) and global (G) normalization, with 10% dose threshold. The disease sites of the calculated and measured plans are: prostate, Head and neck (SIB treatments), mesothelioma, pelvis, uterus and rectum. All the plans were calculated with a uniform grid of 2.5 mm.

Results

The mean GI for all profile and PDD curves resulted 98%(±1.2). The GI 3%G/2mm for the VW plans is 100%. Evaluating the plans with a tighter GI like 2%L/2mm, the average (±SD) results is 97% (±1)The average (±Standard Deviation) GP% values obtained for ArcCHECK measures are reported in table 1

GI 2%/2mm LocalGI 2%/2mm GlobalGI 3%/2mm LocalGI 3%/2mm GlobalGI 3%/3mm LocalGI 3%/3mm Global
Mean92.597.49699.298.299.6
SD6.644.9231.5
Conclusion

RayStation can be used for the creation of clinical tomotherapy treatment plans. The optimized model produces high values for pre-treatment patient specific QA, also using tighter GI than the ones suggested by TG-218.  If compared with data reported in TG-218, the collected GI 3%G/2mm outperforms previous published results. Based on the presented results the implementation in clinical routine can be considered feasible and safe.