3D-Mesa “Bridge” Silicon Microdosimeter: Charge Collection Study and Application to RBE Studies in $^{12}{\rm C}$ Radiation Therapy

Abstract

Microdosimetry is an extremely useful technique, used for dosimetry in unknown mixed radiation fields typical of space and aviation, as well as in hadron therapy. A new silicon microdosimeter with 3D sensitive volumes has been proposed to overcome the shortcomings of the conventional Tissue Equivalent Proportional Counter. In this article, the charge collection characteristics of a new 3D mesa microdosimeter were investigated using the ANSTO heavy ion microprobe utilizing 5.5 MeV and 2 MeV ions. Measurement of the microdosimetric characteristics allowed for the determination of the Relative Biological Effectiveness of the heavy ion therapy beam at the Heavy Ion Medical Accelerator in Chiba (HIMAC), Japan. Well-defined sensitive volumes of the 3D mesa microdosimeter have been observed and the microdosimetric RBE obtained showed good agreement with the TEPC. The new 3D mesa "bridge" microdosimeter is a step forward towards a microdosimeter with fully free-standing 3D sensitive volumes.

Characterisation of Silicon Diode Arrays for Dosimetry in External Beam Radiation Therapy

“…A DUO test structure identical to the array's central cross-shaped pixels and proximal microstrips was used to perform the charge collection efficiency (CCE) study by means of the Ion Beam Induced Charge Collection (IBICC) technique at ANSTO ion microprobe. Full description of IBICC technique can be found at [22].…”

Characterization of proton pencil beam scanning and passive beam using a high spatial resolution solid‐state microdosimeter

“…Recently, the CMRP has developed and fabricated SOI microdosimeters consisting of micron‐sized well‐defined 3D SVs known as “bridge” microdosimeters. The device was previously characterized in detail and successfully applied in 12 C ion therapy at HIMAC, Japan . Using this microdosimeter, we were able to measure the microdosimetric quantity , which was used as an input parameter for the MKM to calculate the RBE 10 corresponding to 10% of human salivary gland (HSG) cell survival.…”

Study on the RBE estimation for carbon beam scanning irradiation using a solid‐state microdosimeter

“…The even and odd rows of the sensitive volumes (SVs) are read out independently to avoid the occurrence of events in the adjacent SVs that are being read as a single event in the case of the oblique charged‐particle tracks. Figure shows a simplified section of the bridge microdosimeter that is designed to provide well‐defined 3D SVs by removing silicon surrounding the SV using plasma etching, as well as to eliminate the charge sharing between the neighboring SVs . The device is segmented into three sections that can be readout separately including each even or odd array of 3D SVs to reduce the noise through the minimization of the capacitance and the reverse current of each segment and possibility to adjust sensitive area depends on the dose rate.…”