Multichannel semiconductor detectors for X-ray transmission computed tomography (XCT) have been developed using surface-barrier diodes fabricated from high-purity n-type silicon. X-rays are detected directly by the semiconductor detectors in the operational mode, non-biasing in conjunction with current to voltage converters (I/V converters). In addition to the image reconstruction test, the fundamental properties of the detector have been studied theoretically as well as experimentally.