Realtime intraoperative imaging system combining annihilation γ-ray detectors and video projectors

Abstract

Realtime near-infrared (NIR) fluorescence imaging system could be exploited for intraoperative imaging guidance. However, the NIR fluorescence imaging technique attains only small penetration depths (a few centimeters) due to the absorption and scattering of light. The purpose of this study was to develop a realtime intraoperative imaging system using annihilation gamma-ray detectors for localization and laser projectors for visualization of surgical region embedded deep in tissue. The proof-of-principle gamma-ray detectors consisted of two front detector blocks and one backside detector block. The front detector block consisted of 8 detector modules arranged in a blank square shape and the backside detector block was composed of 4 × 8 detector modules. Each detector module was composed of a 4 × 4 array LYSO coupled to a 4 × 4 GAPD array. Front and backside detectors were located at opposite sides of each other. Commercial portable LED laser projector with a luminous flux of 500 ANSI lumens was used for the intra-operative system. Two laser projectors were positioned behind each front detector. The design parameters of the gamma-ray imaging system were adjusted and optimized using a Monte Carlo simulation tool, GATE. The performance of the system spatial resolution and count rate were estimated by simulation and by experiment using 450 kBq Na-22 point source. Experimentally measured spatial resolution and count rate were 4.1 mm and 300 counts per second which were similar to those estimated by the simulation. The beam projected by laser projectors was accurately localized the position of radiation source. Experimental results indicate that realtime intraoperative imaging system combining annihilation gamma-ray detectors and laser projectors proposed in this study would be useful to localize and to visualize surgical region embedded deep in tissue.