A low noise fluoroscopic radiation imager includes a large area photosensor array having a plurality of photosensors arranged in a pattern so as to have a predetermined pitch, and a low noise addressable thin film transistor (TFT) array electrically coupled to the photosensors. The TFT array includes a plurality of low charge retention TFTs, each of which have a switched silicon region that has an area in microns not greater than the value of the pitch of the imager array expressed in microns. The portion of the switched silicon region underlying the source and drain electrodes of the TFT is not greater than about 150% of the portion of the switched silicon region in the channel area of the TFT. The ratio of the TFT channel width to channel length (the distance between the source and drain electrodes across the channel) is less than 20:1, and commonly less than 10:1, with the channel length in the range of between about 1 .mu.m and 4 .mu.m. The photosensor array also includes crossover regions between address lines that have substantially no silicon therebetween so that no switched silicon region exists at the crossovers.