| 摘要 |
<p>In an x-ray bone densitometer, a rotating device (12) carries a calibration material through the beam. The densitometer uses an x-ray tube (1) operated at two different voltages to generate a pencil beam (8). An integrating detector (5) is timed to integrate the detector signal of the patient-attenuated beam over each pulse, the signals are converted to digital values and a digital computer (13) converts the set of values produced by the raster scan into a representation of the bone density of the patient. Multiple reference detectors (7, 8) with differing absorbers (9, 10) are used by the system to continuously correct for variation in x-ray tube voltage and current. Calibration is accomplished by the digital computer on the basis of passing the pencil beam through known bone-representing substance as the densitometer scans portions of the patient (4) having bone and adjacent portions having only flesh.</p> |
