A NEW METHOD FOR MEASUREMENT OF BONE MINERAL DEPOSITION PATTERN

USING DUAL ENERGY RADIOGRAPHIC DENSITOMETRY METHOD IN A SINGLE EXPOSURE

抄録

Quantitative observations of bone mineral distribution in the maxillo-mandibular bone are of great interest in the clinical field. Radiographic densitometry is the most simple method but the film density is influenced by the X-ray exposure and processing conditions and by the soft tissue layer. This fluctuation can be corrected from the image of the wedge of the reference material simultaneously projected with the object on the same film. There is no other method than the dual energy technique to correct the effect of the soft tissue layer to be applicable in the maxilla-mandibular region. Two radiograms of the object obtained by a different beam quality represent the different X-ray contrast. When the penetrated fractions of the incident X-rays through the object at different energies are obtained from the film density and the characteristic curve of the film and substituted for the first order simultaneous equation whose coefficients are the mass attenuation coefficients of the bone mineral and soft tissue to the X-rays of the respective energy, the bone mineral content is obtained as the solution of the equation in the form of the product of the mineral density and the thickness of the bone (mg/cm2). This paper shows the principle of the method and the results of the experiment which agreed closely with the data obtained by the chemical assessment.