[Feasibility of a new initial check-up program for medical X-ray and computed radiography systems].

We investigated the feasibility of a simple, easy method that uses a digital radiography (DR) phantom for daily operational checks of the medical X-ray system and computed radiography (CR) system. First, we measured exposure indicator calibration (S value) from 12 seconds to 11 minutes after irradiation to examine the effect of fading of the photostimulable phosphor screen. We then examined the management width of the exposure indicator calibration ratio and limiting resolution of the CR system. Finally, we studied the exposure indicator calibration ratio, limiting the resolution and time necessary for the initial check-up by running the program 20 times for five weeks. Under the influence of the fading, the S value increased gradually, although the level of variation was small. From the mean and coefficient of variation of the exposure indicator calibration ratio, the management width was determined as +/-10%. The exposure indicator calibration ratio and limiting resolution were within +/-10% and +/-20%, respectively. It took three minutes to accomplish the initial check-up. The initial check-up using a DR phantom is simple and can perform the operational check of the medical X-ray system and the CR system with sufficient accuracy in only 3 minutes.

[New evaluation for osteoporosis using calcaneal computed radiographs].

Quantitative analysis of bone mass is a method mainly used for the diagnosis of osteoporosis. However, there are cases of osteoporosis that cannot be diagnosed by this method alone. This study was performed to develop a new quantitative method for the evaluation of osteoporosis using texture analysis and geometric feature analysis of trabecular bone on lateral calcaneal computed radiographs. Thirty-seven cases including 11 normal and 26 abnormal lateral calcaneal radiographs were examined. The patients' ages ranged from 24 to 89 years (average age, 58.3 years). The root mean square (RMS) variation and first moment of power spectrum of trabecular bone patterns were determined as quantitative measures for texture analysis. In addition, the total area and total length of trabecular bone were obtained from geometric feature analysis. The RMS variations in pixel values, total area, and total length of trabecular bone were decreased as bone atrophy progressed. These three quantitative measures corresponded well to radiologists' subjective evaluations of bone atrophy. Moreover, our results indicated that these three quantitative measures had strong correlations with bone mineral density of the femoral neck. Therefore, we consider the computerized method with texture analysis and geometric feature analysis of lateral calcaneal radiographs to be very useful for radiologists in evaluating osteoporosis.