Development of a radiological method for the measurement of bone mineral content in bone disease

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1. High speed image processing system using a digital image scanner Using a digital image scanner (Sharp JX450) interfaced throygh GPIB to an personal computer (Fijitsu FM11), an X-ray image could be read within 2 minutes. The characteristics of this image input system was estimated as follows. 1) Effective pixel size was 0.143mm. 2) To measure the film density, the logalithm of the output gray level should be taken. 3) The maximum measurable film density was 1.5. 4) The efective precission of the quiantamized gray level was 64. The crude performance of this system was, therefore, insufficient for the input device for the quantitative analysis. To compensate them, the soft ware system was modified and the beam quallty of the x-rays was hardened. Then the dynamic range to the object thickness became comparable to that of the michro-denditometer system. In order to improve the image processing speed, a floating point processior boad was added. The driving soft ware is on the development. 2. Observation of the growing process of new bone arround of the implanted hydroxyapatite The growing process of new bone arround of the implanted hydroxyapatite was observed from one month to one year by the hisological method and the present method. The new bone began to be calcified at one month after the implant, and grew to surround the apatite rod at three months after the operation. At one year after, the new bone grew thick and be replaced by matured lamelar bone. The observation by the present method gave the similar result to the histological observation. The bone mineral was not detected after one month. 0.3g/cm2 bone mineral was measured at three months after the operation. The mineral content did not varied to one year after the implant. 3 Summary The present mathod enable the indistructive observation of the change in the bone mineral content. In the present, only the thin object could be observed. We are planning to improve the system to observe the thicker objects.