Gamma Evaluation with Octavius 4D Phantom for PreTreatment of Modern Radiotherapy Treatment Techniques

Srivastava Rp

doi:10.23880/ijnmrs-16000117

Abstract

Purpose: In modern radiotherapy techniques such as intensity-modulated radiation therapy (IMRT) and volume modulated arc therapy (VMAT), the quality assurance (QA) process is vital. The goal of the study was to verify the treatment planning dose delivered during delivery of complex treatment plans. The QA standard is to perform patient-specific comparisons between planned doses and doses measured in a phantom. Materials and Methods: Ninety-five complex IMRT and VMAT plans for different pathologies planned using Eclipse treatment planning system (TPS). The Octavius 4D phantom has been used to verify patient specific quality assurance of all VMAT plans calculating with different algorithms. Conclusion: Overall, good agreement was observed between measured and calculated doses in most cases with gamma values above 1 in >95% of measured points in volumetric 3D analysis and 1 in >90% in 2D analysis. The Octavius 4D phantom is an effective and efficient method for patient specific QA.

Highlights

Intensity-modulated radiation therapy (IMRT) and volumetric modulated arc therapy volume modulated arc therapy (VMAT)) can deliver optimal dose distributions delivering prescription doses to the target volumes, which are enough to control tumor cells, while reducing doses to normal tissues by modulating photon beam intensities [1,2,3]
VMAT modulating the multi-leaf collimator (MLC) positions, gantry rotation speed, and dose rates has been broadly adopted in the clinic, having benefits of delivering prescription dose to target volume while sparing normal
It has shown that VMAT can achieve a similar plan quality and monitor unit (MU) effectiveness as compared to intensity modulated radiation therapy (IMRT) resulting in shortening the treatment time in the clinic [4]

Summary

Introduction

Intensity-modulated radiation therapy (IMRT) and volumetric modulated arc therapy VMAT) can deliver optimal dose distributions delivering prescription doses to the target volumes, which are enough to control tumor cells, while reducing doses to normal tissues by modulating photon beam intensities [1,2,3]. VMAT modulating the multi-leaf collimator (MLC) positions, gantry rotation speed, and dose rates has been broadly adopted in the clinic, having benefits of delivering prescription dose to target volume while sparing normal. Intensity-modulated radiation therapy (IMRT) and VMAT can produce highly conformal radiation dose distributions and enhance treatment localization. These complex treatment techniques place higher demands on dose calculation algorithms in terms of both accuracy and computation speed [5,6]. With the increasing popularity of IMRT and VMAT techniques in clinics, accuracy in treatment planning systems (TPSs) has always been a concern in modern radiotherapy

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