Mineral content of bone: measurement by energy subtraction digital chest radiography

Abstract

Several methods are presently available for measuring the mineral content of bone. Those in widespread use include dual-photon absorptiometry and quantitative CT. The feasibilIty of using dual-energy digital chest radiography for determination of the mineral content of posterior ribs on digital chest images was studied by using a prototype unit The resufts showed a significant difference in the mineral density of the posterior ribs of control subjects and those of patients who had osteoporosis (251.1 ± 36 mg Ca2 / cm2 of rib vs 158.8 ± 48 mg Ca2 /cm2, p .01) and a close correlation with values obtained by dual-photon absorptiometry of the lumbar spine (r = .77). The results suggest that this technique Materials and MethodsImages of the chest were obtained in posteroantenor projection with the second-generation Picker scanning-slit dual-energy chest unit (Picker International, Cleveland, OH). The charactenstics of this unit have been described in detail elsewhere [1 -5]. Briefly, an X-ray fan beam is created by a 0.5-mm slit collimator placed between the patient and the focal spot of the Xray tube; the beam is aligned with a 1 .0-mm collimator placed between the patient and the detector array (consisting of 1 024 vertical pixels). The collimators and the detector array are linked mechanically and pivot about the focal spot as the beam scans horizontally across the patient (Fig. 1). A key feature of this device is its linear detector array of 1024 elements. Each element is a low/high atomic sandwich:The first section consists of a low-atomic-number phosphor (optically coupled to a photodiode) that preferentially absorbs the lower-energy photons emerging from the patient; the higher-energy photons penetrate the first section and strike the rear section, which is composed of a high-atomic-number phosphor (also optically coupled to a photodiode) (Fig. 2). In this way, low-and high-energy images are acquired simultaneously. These in turn are summed to obtain a standard digital image (comparable to a conventional radiograph) (Fig. 3) and are processed to obtain soft-tissue (bone cancelled, Fig. 4A) and bone (soft-tissue cancelled, Fig. 4B The posterior ribs were selected as the first site of measurement;they are easily accessible and provide a reproducible location for the parallelogram technique. The efficacy of using the nbs in screening for osteoporosis is suggested by dual-photon absorptiometry studies that have noted a parallel reduction in the mineral content of the ribs and spine in patients who have osteoporosis and in elderly persons [6,7].

Low Exposure X-ray Transmission Measurements for Contrast Media Detection with Filtered X-rays

“…2 are the results of calculations using Eqs. 1and (2). The experimental and theoretical results agree fairly well.…”

“…The energy subtraction method in off-line measurements was carried out by two photographic films with an absorber between them for bone minerals and chest radiography. [1][2][3][4] The first film had information for all of the incident X-rays passing through the subject. The second film was sensitive only to those X-rays with sufficient energy to pass through the absorber between the two photographic films.…”

Incorporación de aloinjertos óseos intercalares corticales: Estudio experimental en conejos

“…La radiografía simple ofrece una orientación eficaz en el seguimiento del proceso de incorporación de los injertos óseos, aunque no es capaz de distinguir entre una unión fibrosa o cartilaginosa ni de valorar objetivamente la densidad mineral ósea de un injerto. Coincidimos con otros trabajos al afirmar que, la densitometría ósea es un método útil en la valoración de la mineralización del injerto y del callo óseo 6, 16,25,26 . La congelación del injerto no influye en los fenómenos de incorporación del injerto óseo puesto que no hemos observado diferencias entre el autoinjerto fresco y el congelado.…”

“…La congelación del injerto no influye en los fenómenos de incorporación del injerto óseo puesto que no hemos observado diferencias entre el autoinjerto fresco y el congelado. La densitometría ósea no es útil para determinar el momento de la consolidación, ni de la incorporación, pero puede determinar la solidez del injerto durante su evolución 26 . El hecho de no haber encontrado diferencias de densidad mineral ósea entre los injertos indica que el método es poco sensible o bien que el proceso de mineralización no estaría influenciado por la respuesta inmunológica ni por el proceso de congelación.…”

Energy Measurement of X-rays in Computed Tomography for Detecting Contrast Media

“…1,2) In the comparison between the current measurement and FIX-ES in transmission radiography, FIX-ES was found to have a sensitivity that was two times better than that of the current measurement. 3) Other energy subtraction (ES) methods have been proposed; however, most measured x-rays as current, [4][5][6][7][8] with the exception of bone mineral measurements in which two energy windows were employed with the ES method. 9,10) No ES method, however, has been dedicated to the reduction of dose exposure.…”