Evaluation of the signal quality of an inexpensive CMOS camera towards imaging a high-resolution plastic scintillation detector array

Abstract

Several promising scintillation dosimetry systems have recently emerged that extend measurements of absorbed dose distributions to three dimensions.We have investigated the use of a small-sized, low-cost, shielded camera for fibre-less detection of scintillated light within the treatment room. An optimised shielding enclosure combined with a periscopic mirror arrangement is presented that minimizes the impact of transient radiation-induced noise on the camera chip without excessive weight or the need for strong image filtration. We demonstrate that this allows satisfactory signal quality to be achieved without the need for the expensive, high-sensitivity scientific cameras employed in other systems. The various components of camera noise are individually studied and quantified. A simple plastic scintillator array with small elements extending in three dimensions is constructed to study signal-to-noise ratios for a future, real-time scintillator array dosimetry system. SNRs are determined for a range of image integration times of 20e500 ms. The combined uncertainty from camera-specific noise sources for an inexpensive, bunker-located, shielded camera imaging 5 x 5 x 5 mm(3) scintillator elements is <0.4% for images taken under clinically relevant exposure conditions. This opens up the possibility for future realtime analysis of radiation beams with a high-resolution 3D array of plastic scintillators.