A new compact gamma camera with super resolution capability and high sensitivity for monitoring sparse radioactive sources in large area

A new compact gamma camera was developed to detect and image gamma-emitting radioactive sources in large area. The gamma camera consists of a tungsten coded-aperture collimator, a pixellated NaI(Tl) scintillator, a multi-anode photo multiplier tube(PMT) and dedicated electronics for gamma photon detection and data acquisition. Two statistical iterative image reconstruction algorithms were implemented to improve the spatial resolution and sensitivity for gamma imaging. The gamma camera is a core module of RLS-1000A, a commercially available device also including a video camera and other supporting modules. RLS-1000A is capable of simultaneous gamma and visible-light imaging of a field of view (FOV) up to 30° in a two dimensional angular plane. In this case, the gamma and visible-light images are spatially and temporally registered by software. The fused images are displayed for real-time visualization of radiation intensity field and further localization of radioactive sources in the FOV. Experiments for evaluating the performances of RLS-1000A demonstrated that the angular resolution of gamma imaging achieved 1° for 60Co point sources. A 99mTc point source inducing a dose rate of 40nGy/h at the front face of gamma camera was imaged and localized correctly. Experiments also showed that RLS-1000A has the capability of real-time detecting, identifying and tracking pedestrians taking medical radioisotopes of as low as ~5-10 mCi in a carry-on bag.