| Popis: |
At present, osteoporosis has become a common disease among the elderly. With the advent of an aging society, the impact of osteoporosis on the health of the population should not be underestimated. The commonly used diagnostic method of osteoporosis is bone mineral density measurement. At present, dual-energy X-ray bone densitometer (DEXA) is usually used for measurement. However, DEXA usually uses a pencil-beam X-ray for measurement. The coverage of the pencil-beam X-ray is small, so the measurement time of DEXA is long. In order to improve the speed of bone mineral density measurement, in this study, a method of rapid measurement of bone mineral density using cone-beam X-ray photography was proposed. Specifically, the GE OPTIMA XR646 HD digital radiography (DR) system was selected as the experimental equipment, and 60 kVp and 140 kVp was selected as the tube voltage for producing low-energy and high-energy X-ray. In view of the large amount of scattering information in cone-beam X-ray radiography, the point spread function of soft tissue and bone equivalent materials with a thickness of 2 to 8 cm under different photon energy spectra is simulated by using the Monte Carlo particle transport program GEANT4 for different tube voltages of the X-ray tube, and the scattering signal in cone-beam X-ray radiography is removed by the point spread function. Polymethyl methacrylate (PMMA) was used to replace soft tissue, and aluminum blocks with thickness ranging from 4 to 12 mm were used to replace bone, forming an equivalent phantom of bone mineral density. The calibration experiment of bone mineral density measurement curve was carried out, and the quadratic/cubic measurement curve of bone mineral density measurement using cone beam X-ray radiography was obtained when the X-ray tube voltage was 60 kVp and 140 kVp. Based on the point spread function and the measurement curve, a fast bone mineral density measurement method based on cone beam X-ray radiography was proposed. The validation experiment conducted on PMMA and aluminum block shows that the method proposed in this study can achieve relatively accurate measurement within the common range of bone mineral density of 0.5-1.5 g/cm2, and the relative deviation between the measured value and the nominal value is less than 7%. This study preliminarily verifies the feasibility of the method of measuring bone mineral density using cone-beam X-ray photography, which can achieve the measurement of bone mineral density while taking the X-ray image of the femur, and expand the application scope of DR machine in clinical practice. The research results can provide reference for the rapid measurement of clinical bone mineral density and the wide application of DR. |
