Toward millisecond scanning beam radiography

The rapid scanning beam Rotating Aperture Wheel (RAW) device is capable of achieving about 1, 000 beam passes per second over each point in the field of view, allowing millisecond exposure times. Screen -film images of a chest phantom were obtained with exposure times of tens of milliseconds at scan speeds of a few hundred beam passes per second. These are the shortest exposure times ever achieved by a nongrid, purely scanning beam anti -scatter device. Because the scanning beam speed and exposure times were not synchronized for this study, well understood overlap artifacts appeared on the original radiograph. However, this artifactual density variation was subtracted, and the noise variation caused by the different quantum fluence in the alternating regions was imperceptible. A number of artifact correction methods are discussed. Finally, the application of various RAW device configurations to the millisecond exposure times used for cardiac cineradiography are outlined.