Silicon Photomultipliers for Deep Tissue Cerenkov Emission Detection During External Beam Radiotherapy.

Manuel Suarez,Robin Pearce,Samuel DeBruin,Charles Taylor,Issam El Naqa,Ibrahim Oraiqat,John Way,Christopher Como,Roy Clarke,Alnawaz Rehemtulla,Justin Mikell

doi:10.1109/jphot.2019.2931845

Abstract

Cerenkov Emission (CE) during external beam radiation therapy (EBRT) from a linear accelerator (Linac) has been demonstrated as a useful tool for radiotherapy quality assurance and potentially other applications for online tracking of tumors during treatment delivery. However, some of the current challenges that are impacting the potential of CE are related to the limited detection sensitivity and the lack of flexible tools to fit into an already complex treatment delivery environment. Silicon photomultiplier (SiPM) solid-state devices are new promising tools for low light detection due to their extreme sensitivity that mirrors photomultiplier tubes and yet have a form factor that is similar to silicon photodiodes, allowing for improved flexibility in device design that may help in the process of wider clinical applicability. In this work, we assess the feasibility of using SiPMs to detect CE during EBRT from a Linac and contrast their performance with commercially available silicon photodiodes (PDs). We demonstrate the feasibility of the SiPM based probes for standard dosimetry measurements. We also demonstrate that CE optical signals can be detected from tissue depths about five times greater than that for standard probes based on PDs, making our SiPM probe an enabling technology of CE measurements, particularly for deep tissue applications.

Highlights

Radiotherapy is widely used in the treatment of malignant tumors with more than 60% of all cancer patients receiving ionizing radiation as a main part of their treatment [1]
We demonstrate that Cerenkov Emission (CE) optical signals can be detected from tissue depths about five times greater than that for standard probes based on PDs, making our Silicon photomultiplier (SiPM) probe an enabling technology of CE measurements, for deep tissue applications
We propose to use a flexible and effective approach based upon a novel design of on-body optical probes incorporating extremely sensitive Silicon Photomultipliers (SiPMs) to map the delivered dose by radiotherapy in real time

Summary

Introduction

Radiotherapy is widely used in the treatment of malignant tumors with more than 60% of all cancer patients receiving ionizing radiation as a main part of their treatment [1]. It is recognized that the efficacy of radiation treatment is highly dependent on the accurate delivery of radiation dose up to the lesion boundary. Evaluating the efficacy of radiation treatment is generally an offline process where radiation technologists use added margins during the planning process and make setup adjustments based on cone beam computed tomography (CBCT), just prior to delivery of high levels of ionizing radiation. The use of added margins is to account for inaccuracies in patient placement on the treatment table and internal organ motion uncertainties, exposing both. Heterogeneous cancerous and non-cancerous tissues in parallel to high energy ionizing radiation. This inadvertently results in inefficient tumor cell kill and increased exposure of surrounding vital normal tissue causing inflammatory reactions and other detrimental radiation-related side effects. Methods for detecting radiation during delivery (i.e., in vivo dosimetry) are needed to improve targeting accuracy and reduce radiation-induced side effects

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Results

Conclusion