A Compton X-ray backscatter imaging (CBI) system using a single detector and a mechanically rastered "flying spot" X-ray beam has been designed, built, and tested. While retaining the essential noninvasive imaging capability of previous multiple detector CBI devices, this single detector system incorporates several advances over earlier CBI devices: more efficient detection of scattered X-rays, reduced X-ray exposure, and a simplified scan protocol more suitable for use with humans. This new CBI system also has specific design features to permit automating data acquisition from multiple two-dimensional image planes for integration into a 3D dynamic surface image. A simulated multislice scan study of a human thorax phantom provided X-ray dosimetry data verifying a very low X-ray dose (~50 mrem) delivered by this imaging device. Validation experiments with mechanical models show that surface displacement at typical heart beat frequencies can be measured to the nearest 0.1 mm (SD).