Abstract: An exposure control circuit captures an X-ray generator exposure time for a master exposure and replicates that time for subsequent exposures in a series. In one preferred circuit an read counter bank counts down clock pulses during the master exposure time, and then this count is held and is used by a write counter bank which counts up during subsequent exposures. A control circuit controls loading an enabling functions of the read and write counters. For the subsequent exposures, an output relay circuit terminates the X-ray generator exposure when the write counter bank reaches a predetermined count. This arrangement is used favorably with digital subtractive angiography (DSA).

Abstract: A radiation therapy imager provides images of a patient while being treated while on a radiation therapy machine for purposes of verification and monitoring of position and alignment, and for shaping of the radiation field. The radiation therapy imager has a video camera mounted on the gantry of the radiation therapy machine and positioned diametrically opposite the treatment head. An elongated light box is disposed over the camera to exclude ambient light from the camera and a fluoroscopic plate is positioned at the distal end of the light box, i.e., the end remote of the camera. The plate is aligned with and facing the head to produce a fluoroscopic image in response to the treatment radiation that is applied from the head through the patient. A mirror in the light box is oriented to reflect the image to the camera to permit monitoring on a viewing screen. The light box can be retracted from under the treatment table either by telescoping the light box down or by swinging the light box to one side.

Abstract: A process for enhancing a still video image can correct digital fluoroscopy images which are under- or overexposed and have their image brightness values concentrated to one end of the gray scale. A pixel histogram is formed, but is clipped at a low value. Then, a cumulative histogram is formed from the clipped histogram. The cumulative histogram, which has a generally linear slope, is normalized and is used for mapping the brightness of luminance values of the original image. The new values form an optimal video image with the gray scale values spread over the entire range. The image shows details not only in the middle gray areas, but in the light and dark areas as well.