The energy spectrum of X ray radiation passed through the human body contains information about the physicochemical properties of tissues. For example, the structure of tissue can be studied from spectral data obtained in different spectral ranges [2,4,5].The goal of this work was to demonstrate that multi energy (spectrozonal) roentgenography could be imple mented in digital fluorographs.Spectrozonal fluorography can be used to analyze calcinates in diagnosis of thoracic cavity diseases. Analyses of calcinates in digital images is more difficult than in film images because the image borders in the lat ter case are significantly sharper than in the former case, like the vessel image borders in ortho projection. It was shown that organic inclusions visible in X ray photo graphs made in different spectral ranges could be differ entiated by the effective atomic number Z eff and electron ic density of tissue. However, monochromatic or quasi monochromatic X ray radiation should be used in quan titative analysis [1,4,5]. A special detection method should be developed to use the polychromatic radiation of the common X ray tube.Water and calcium oxalate can be regarded as mod els of blood vessels and calcinates, respectively: Z eff = 7.9 and Z eff = 18.4. Significant difference between effective atomic numbers makes it possible to distinguish between blood vessels and calcinates even against the background of substantial error in Z eff .Conventional methods of spectrozonal X ray detec tion are based on the use of X raying at two peak values of anode voltage (kV) or spectrozonal X ray detectors.The practical implementation of the method is based on characteristic angles:(1)where I ob , I f are intensities of X ray radiation at the X ray photograph plane at inclusion and background sites, respectively, at high (h), medium (m), and low (l) anode voltage.Local radiation intensity at image sites and charac teristic angles calculated from Eq. (1) allow the resulting image to be synthesized in terms of θ or ϕ and tissues to be differentiated regardless of their structure and density. Calibration of the system using samples with standard Z eff allows the method of subtractive synthesis of spectrozon al images, which improves the signal/noise ratio [3], to be supplemented with physical characteristics of inclu sion.Experiments were performed using a scanning digital X ray apparatus with a semiconductor linear detector.The 23 × 14.5 cm X ray phantom contained filter 19 mm Al and a container with samples filled with polyurethane foam. The main components of the samples are listed in Table 1.The phantom was in the detector plane, and the fil ter was oriented toward the detector. A series of three photographs was taken at anode voltage U l = 55 kV, U m = 85 kV, and U h = 125 kV.Characteristic angles were calculated as follows.

No abstract