Validation of fluence-based 3D IMRT dose reconstruction on a heterogeneous anthropomorphic phantom using Monte Carlo simulation.

Yuji Nakaguchi,Nozomu Nagasue,Takeshi Ono,Yoshinobu Shimohigashi,Yudai Kai,Masato Maruyama

doi:10.1120/jacmp.v16i1.5199

Yuji Nakaguchi, Nozomu Nagasue + Show 4 more

Open Access

https://doi.org/10.1120/jacmp.v16i1.5199

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Abstract

In this study, we evaluated the performance of a three‐dimensional (3D) dose verification system, COMPASS version 3, which has a dedicated beam models and dose calculation engine. It was possible to reconstruct the 3D dose distributions in patient anatomy based on the measured fluence using the MatriXX 2D array. The COMPASS system was compared with Monte Carlo simulation (MC), glass rod dosimeter (GRD), and 3DVH, using an anthropomorphic phantom for intensity‐modulated radiation therapy (IMRT) dose verification in clinical neck cases. The GRD measurements agreed with the MC within 5% at most measurement points. In addition, most points for COMPASS and 3DVH also agreed with the MC within 5%. The COMPASS system showed better results than 3DVH for dose profiles due to individual adjustments, such as beam modeling for each linac. Regarding the dose‐volume histograms, there were no large differences between MC, analytical anisotropic algorithm (AAA) in Eclipse treatment planning system (TPS), 3DVH, and the COMPASS system. However, AAA underestimated the dose to the clinical target volume and Rt‐Parotid slightly. This is because AAA has some problems with dose calculation accuracy. Our results indicated that the COMPASS system offers highly accurate 3D dose calculation for clinical IMRT quality assurance. Also, the COMPASS system will be useful as a commissioning tool in routine clinical practice for TPS.PACS number: 87.55.Qr, 87.56.Fc, 87.61.Bj

Highlights

In patient-specific intensity-modulated radiation therapy (IMRT) quality assurance (QA), ion chamber measurement and film measurement have traditionally been performed in homogeneous phantoms
Most of the glass rod dosimeter (GRD) measurement points agreed with the Monte Carlo simulation (MC) within 5%
The results of treatment planning system (TPS) show good agreement with MC and confirm that this IMRT plan does not have any problems in terms of accuracy at the measurement points

Summary

Introduction

In patient-specific intensity-modulated radiation therapy (IMRT) quality assurance (QA), ion chamber measurement and film measurement have traditionally been performed in homogeneous phantoms. This method provides useful empirical evidence,(1) but suffers from the potential failure to record the dose from parts of each beam in that do not intersect the film plane. Another common method is two-dimensional (2D) arrays which measure by each beam in a homogeneous phantom. It is possible to reconstruct the 3D dose distribution in the patient based on fluence measured with the MatriXX

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