Application of an in-house developed complementary metal-oxide-semiconductor-based optical computed tomography (CMOS-OCT) imaging system for stereotactic radiosurgery dosimetry using a PRESAGE® dosimeter

Abstract

PRESAGE® dosimeter can be useful for 3D verification of radiotherapy treatment delivery when careful attention is given to the dosimeter measurement technique. Ideally, a low noise and fast optical CT scanning system is required for imaging the dosimeter for verification of advanced radiotherapy treatment delivery. We have developed a complementary metal-oxide-semiconductor (CMOS)-based optical computed tomography (OCT) system (CMOS-OCT), implementing the recent advances in CMOS active pixel sensor (APS) technology that offer on-chip image processing and high-speed readout. In this study, we present the dosimetric response of irradiated PRESAGE® dosimeter measured with the CMOS-OCT system and describe a feasibility study of using the calibrated system to verify stereotactic radiosurgery (SRS) treatment. PRESAGE® dosimeters were irradiated using a 6 MV Elekta Synergy linear accelerator to investigate dosimetric and geometric properties of PRESAGE® dosimeter with CMOS-OCT imaging system, in order to verify a clinical SRS treatment plan of the brain. The tomographic projection images of the PRESAGE® dosimeter were captured by the image sensor within 100 s for a 360-degree rotation. The CMOS-OCT imaging system showed good linearity in dose-response measured by PRESAGE® dosimeter. The correlation of the optical density (OD) changes measured from the CMOS-OCT with attenuation value measured using a calibrated UV/Vis spectrophotometer was found to be better than 0.996. The tomographic reconstruction of the dose distribution from the PRESAGE® showed good agreement when compared with the calculated dose distributions from the treatment planning software. The in-house CMOS-OCT imaging system is capable of visualising and verifying the dose distribution of stereotactic radiosurgery treatment. The CMOS-OCT imaging of the PRESAGE® dosimeter provides accurate dosimetric and geometric information on radiotherapy delivery in a three-dimensional volume, which is useful in advanced radiotherapy. The introduction of CMOS technology in the OCT improves the imaging speed of the dosimeters dose readout.