Abstract: A method and apparatus for determining a specified physical characteristic in an object exposes the object to at least two angularly fixed sources of electromagnetic radiation to create projected images of the object. The sources are rotationally scanned about the object so as to oscillate in an angular range about the object. The sources are relatively stationary to one another. A three dimensional reconstructed image of the object based on the projected images of the object is created and examined for a specified physical characteristic in the object.

Abstract: A pencil beam of X-rays is scanned over the surfaces of the body of a person being examined as the person walks through the scanning apparatus. Specifically, a tracking assembly is employed to rotate the scanning plane through a tracking angle and in a direction progressing from the entrance to the exit of the portal, through which the person passes, in order to substantially track the person or body as it moves with respect to the system from the entrance to the exit X-rays that are scattered or reflected from the subject's body are detected by a detector assembly. The signal produced by this scattered X-ray detector in then used to modulate an image display device to produce an image of the subject and any concealed objects carried by the subject. The detector assembly is constructed in a configuration to automatically and uniformly enhance the image edges of low atomic number (low Z) concealed objects to facilitate their detection.