This chapter reports characterization results from a 64 \(\times \) 64 perimeter-gated SPAD Imager imager fabricated in a 0.35- \(\mu \) m CMOS process. We demonstrate that the imager can achieve vanishing room temperature dark count probabilities at relatively long exposure times and across the entire pixel array. Furthermore, we show that perimeter gating allows the reduction of the Dark signal non-uniformity (DSNU) dark signal nonuniformity (DSNU), which is a component of the fixed-pattern noise arising from the spatial variation in nominal pixel Dark count rate (DCR) dark count rates in the native diodes. We also characterize the imager in a passive imaging mode, and we demonstrate that image quality improves with perimeter gating. We discussed several methods for compensating the residual fixed pattern noise resulting from Photo-response non-uniformity (PRNU) photoresponse nonuniformity (PRNU). The measured data illustrate the potential of perimeter gating in the development of SPAD imagers that can operate at or near the quantum limit at room temperature.