| 摘要 |
A raster scan x-ray bone densitometer. The densitometer shown uses an x-ray tube operated at two different voltages to generate a pencil beam, the energy levels of the x-ray photons being a function of the voltage applied. An integrating detector is timed to integrate the detected signal of the patient-attenuated beam over each pulse, the signals are converted to digital values and a digital computer converts the set of values produced by the raster scan into a representation of the bone density of the patient. Multiple reference detectors with differing absorbers are used by the system to continuously correct for variation in voltage and current of the x-ray tube. Calibration is accomplished by the digital computer on the basis of known bone-representing substance being carried repeatedly through the pencil beam so that a set of detected signals affected by the calibration substance is compared by the computer with a set of detected signals unaffected by the calibration material.
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