Feasibility of a large area x-ray sensitive vidicon for medical fluoroscopy: resolution and lag factors.

A large area x-ray-sensitive vidicon utilizing amorphous selenium (a-Se) is being investigated as an alternative to the x-ray image intensifier and television camera combination (XRII/TV) for medical fluoroscopy. The x-ray vidicon is, to a first approximation, a scaled up version of the 1" (2.54 cm) light-sensitive vidicon. The modulation transfer function (MTF) of an x-ray vidicon is mainly determined by the number of lines used, the beam spot profile, and the electronic bandwidth. The x-ray vidicon is expected to have roughly the same MTF as the 1" vidicon from a XRII/TV system referenced to the x-ray input and as such will be superior to the MTF of the complete XRII/TV system especially in high resolution applications such as cardiac cine. Beam discharge lag is expected to be approximately the same as in the 1" vidicon since they have comparable photoconductor layer capacitance. Photoconductive lag is also expected to be low since a-Se is known to have a low trap density.