Validation and clinical implementation of commercial secondary check software with heterogeneity corrections

Abstract

Aim

To validate and implement PTW diamond secondary check software (SCS) in a routine clinical use.

Background

The secondary independent monitor unit or dose calculation verifications have led to a significant increase in the workflow associated with QA treatments. Modelling, validation and commissioning are necessary steps thereby making it a useful tool for QA.

Materials and methods

PTW Diamond SCS is capable of calculating VMAT fields, based on modified Clarkson integration, accounting for multi-leaf collimators (MLC) transmission and measured collimator scatter factors. Validation for heterogeneity corrections is made using circular phantom with inserts of various density materials. 150 VMAT plans were compared using (i) plans calculated in homogeneous cylindrical phantom and (ii) VMAT plans calculated with heterogeneity corrections using electron density values for each organ.

Results

Diamond SCS calculated dose for homogeneous cylindrical phantom resulted in average deviation of (0.1[[ce:hsp sp="0.25"/]]±[[ce:hsp sp="0.25"/]]2.14%) with Eclipse TPS calculated dose and (−2.0[[ce:hsp sp="0.25"/]]±[[ce:hsp sp="0.25"/]]1.66%) with absolute measured dose. PTW's OCTAVIUS-4D phantom with 729 ion chamber detector array measurements agreed well with Eclipse TPS calculated dose showing an average deviation of (−1.69[[ce:hsp sp="0.25"/]]±[[ce:hsp sp="0.25"/]]1.56%). Diamond SCS dose calculations were performed with heterogeneity corrections for 124 VMAT plans with isocentre at a region above −350[[ce:hsp sp="0.25"/]]HU. The overall MU variations between Diamond SCS and TPS Acuros-XB algorithms were within ±5%.

Conclusion

Hence, the Diamond SCS can be used as an additional tool along with phantom measurements for patient specific quality assurance of VMAT plans with heterogeneity corrections having isocentre at a region above −350[[ce:hsp sp="0.25"/]]HU.