OA190] Novel inorganic scintillation detector system for real-time treatment verification during brachytherapy

Abstract

Purpose Afterloaded brachytherapy administers a sealed radioisotope that is guided inside pre-inserted catheters in the tumor volume. The goal with the treatment modality is to deliver high doses to the tumor with steep dose gradients to spare adjacent organs and normal tissue. Real-time treatment verification could have an important role during brachytherapy treatments to detect errors that can lead to harmful consequences for the patient. However, real-time treatment verification is presently not performed during brachytherapy, partially because commercial technology does not exhibit adequate signal intensities over the entire range of absorbed dose rates. The limited use of treatment verification is problematic because errors can occur unnoticed. The purpose of this study was to develop scintillation-based point detectors that could have an important role for real-time verification during brachytherapy to detect and prevent treatment errors. Methods A real-time treatment verification system based on miniature inorganic scintillation detectors (ISDs) was developed. The ISDs consisted of a 1 mm-size scintillator that was optically coupled to a 1 mm-diameter and 15 m-long fiber-optic cable. The ISDs were based on the scintillation materials Al2O3:Cr, Y2O3:Eu, YVO4:Eu, ZnSe:O or CsI:Tl. The fiber-optic cable transmitted the scintillation to the photodetector system which consisted of a charge-coupled device camera or a spectrometer spectrograph. We tested the ISDs under brachytherapy treatment irradiation conditions using an Ir-192 source, and compared their performance with organic scintillators BCF-12 and BCF-60 which are the current standard for scintillation detectors in radiotherapy. Results The ISDs exhibited scintillation intensities that were up to 3 orders of magnitude greater than the detectors based on the organic scintillators. The large intensities of the ZnSe:O and CsI:Tl materials made it possible to develop an in vivo dosimetry system based on low-cost photodetector and data acquisition components. The prototype in vivo dosimetry system measured dose rates with Conclusions High-intensity ISD materials make it possible to develop low-cost in vivo dosimetry systems that precisely can monitor brachytherapy treatments. Miniature ISDs can therefore facilitate dissemination of real-time treatment verification technology for brachytherapy.