Abstract: An x-ray source, whose output is collimated into a thin fan-shaped beam, and detector means spaced from the source are mounted for scanning and orbiting jointly about a body in a partial or complete revolution to provide x-ray intensity data for reconstructing an image. The detector and source combination and the body are moved relative to each other in an axial direction for scanning the body layers in sequence. In one embodiment the x-ray source is pulsed as it scans and in another the fan-shaped beam is on continuously and readout is done sequentially so in either case a large number of intensities for each layer are obtained. A high precision encoder system is used to synchronize x-ray pulses and readouts spatially and with line frequency. Means are provided for storing the cables which lead to the rotatable source, and the detectors and other moveable components. An embodiment for scanning a body part such as a breast has means for conditioning and controlling water in which the part is immersed.