title: Performance evaluation of phototimers.
abstract: Phototimers detect x rays impinging on or emerging from an x-ray film cassette and terminate the exposure after a predetermined amount of radiation has been received by the film. A phototimer must provide reproducible film exposures over a wide range of target-to-film distances, patient thicknesses, and technique variables. A method is needed which verifies that the phototimer is functioning properly and identifies exposure techniques and practices which are compatible with its use. Several techniques are presented for evaluating phototimer performance, and data accumulated during application of these techniques to the use of three spot-film phototimers are presented.
mesh_terms: D013679:Technology, Radiologic; D013997:Time Factors; D014965:X-Rays