Absolute measurement of bone mineral density in general radiography using energy-resolving photon-counting detector

• Published in: 2023 IEEE Nuclear Science Symposium, Medical Imaging Conference and International Symposium on Room-Temperature Semiconductor Detectors (NSS MIC RTSD) p. 1
• Main Authors: Kimoto, N., Hayashi, H., Lee, C., Nishigami, R., Kobayashi, D., Katsumata, A., Yamamoto, S.
• Format: Conference Proceeding
• Language: English
• Published: IEEE 04.11.2023
• Subjects: Bone density; Density measurement; Radiography; Semiconductor detectors; Semiconductor device measurement; Statistical analysis; Teeth
• ISSN: 2577-0829
• DOI: 10.1109/NSSMICRTSD49126.2023.10338573

Energy-Resolving Photon-Counting Detector (ERPCD), which can acquire X-ray energy information, has the potential for quantitative analysis of objects. In previous research, algorithms to determine the effective atomic number (Z eff ) image have been proposed. Although these methods have been found to be ideally usable for determining the properties of materials, it remains to be clarified their applicability and impact on clinical diagnosis. The aim of our study is to demonstrate the effectiveness of the functional images and to propose an absolute measurement of Bone Mineral Density (BMD). Our algorithms can realize an ideal analysis in which polychromatic X-rays measured with the ERPCD can be treated as monochromatic X-rays by using Z eff information. Then each mass thickness (ρt) can be determined by assuming that the object consists of soft tissue and bone elements. For assuming each element, the following two different systems were used: system A in which mass attenuation coefficients of Z eff = 6.5 (acrylic) and 13 (aluminum) were applied, and system B in which those of Z eff = 6 (resin) and 16 (hydroxyapatite) were used. To demonstrate our method, dental samples of the mandible and teeth and BMD calibrators (0-0.8 g/cm 2 ) were measured using a prototype ERPCD system by mimicking actual dental radiography. In the ρt images, each element can be extracted completely even in areas where bone and/or teeth overlap with acrylic (soft-tissue), which demonstrates the possibility of accurately analyzing each element itself. When analyzing these values, there is a linearity in the relationship between measured BMD and predetermined one for systems A and B, which means that BMD can be measured using the ERPCD. Furthermore, for system B, the measured BMD was in good agreement with the predetermined one. It was found that absolute BMD measurement can be performed without using a BMD calibrator.