3D sensitive volume microdosimeter with improved tissue equivalency: charge collection study and its application in 12C ion therapy

B James,M Reinhard,A Kok,D Bolst,M Povoli,S Guatelli,D Prokopovich,A Rosenfeld,M Petasecca,M Lerch,N Matsufuji,M Jackson,L T Tran

doi:10.1088/1742-6596/1154/1/012012

Abstract

This research focuses on the characterisation of a new 3D sensitive volume (SV) microdosimeter covered with polyimide – a material which closely mimics human tissue. The electrical and charge collection properties of the device were investigated and its application in 12C ion therapy were studied. Charge collection studies revealed uniform charge collection and no cross talk between adjacent SVs. To study the microdosimetric response in 12C ion therapy, the new polyimide mushroom microdosimeter were placed at various positions along the central axis of a 290 MeV/u 12C ion spread out Bragg peak (SOBP) at the Heavy Ion Medical Accelerator in Chiba (HIMAC), Japan. From these microdosimetric spectra, dose mean lineal energy and RBE10 results were obtained, with RBE10 increasing from 1.3 at the entrance to 2.7 at the end of the SOBP. The results obtained in this work show that the new generation of mushroom microdosimeters, covered with tissue equivalent polyimide material, are a useful tool for quality assurance in heavy ion therapy applications.

Highlights

Particle therapy has many advantages over conventional photon therapy, for treating deepseated solid tumours due to its greater conformal energy deposition achieved in the form of the Bragg Peak (BP)
To study the microdosimetric response in 12C ion therapy, the new polyimide mushroom microdosimeter were placed at various positions along the central axis of a 290 MeV/u 12C ion spread out Bragg peak (SOBP) at the Heavy Ion Medical Accelerator in Chiba (HIMAC), Japan
No charge collection can be seen within the connecting regions between sensitive volumes, or in the unconnected array

Summary

Introduction

Particle therapy has many advantages over conventional photon therapy, for treating deepseated solid tumours due to its greater conformal energy deposition achieved in the form of the Bragg Peak (BP). Successful treatment with heavy ions requires knowledge of the relative biological effectiveness (RBE) of the primary and secondary radiation field. Different methods and approaches are used to calculate the RBE-weighted absorbed dose in heavy ion therapy. The RBE calculated using the microdosimetric approach been reported [1] for a therapeutic 12C beam using a tissue equivalent proportional counter (TEPC). The Centre for Medical Radiation Physics (CMRP), University of Wollongong, has initiated the concept of silicon microdosimetry to address the shortcomings of the TEPC [2].

Methods

Results

Conclusion