BACKGROUND:
The minimum field requirement for spot-film devices is stated in 21 CFR 1020.31(g)(3): "It shall be possible to adjust the x-ray field size in the plane of the film to a size smaller than the selected portion of the film. The minimum field size, at the greatest SID, shall be equal to or less than 5 by 5 centimeters."
The minimum field requirement for image-intensified fluoroscopy is given in 21 CFR 1020.32(b)(2)(iv). That regulation allows for a minimum field size of 125 square centimeters or less for devices not equipped with stepless adjustment collimation.
FDA believes that it is not appropriate to have different minimum field size requirements for fluoroscopic and spot-film modes of operation of fixed SID fluoroscopic systems, and plans to revise 21 CFR 1020.31(g)(3) to make it compare with 21 CFR 1020.32(b)(2)(iv).
POLICY:
Fixed-SID fluoroscopic systems which are not required to, and do not provide stepless adjustment of the x-ray field during fluoroscopy must provide a minimum x-ray field size of 125 square centimeters or less during fluoroscopy and spot-film radiography. For those systems, the Food and Drug Administration will not enforce the 5 by 5 centimeter minimum field size for spot-film collimation.
Issued: 10/1/80