Progress was rapid, and clinical trials of the CT scanner were under way by late 1970. To capture the image of multiple slices of the brain, the scanner went through a translate-rotate sequence, as illustrated in Figure B. The X-ray source and detector, located on opposite sides of the patient's head, were mounted on a gantry. After each scan, or "translation," had generated an X-ray image comprising 160 data points, the gantry would rotate 1° and another scan would be made. This procedure would continue through 180 translations and rotations, storing a total of almost 30,000 data points. Since the detected intensity of an X-ray varies with the material through which it passes, the data could be reconstructed by the computer into a three-dimensional image of the object that distinguished bone, tissue, water, fat, and so on.