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In recent years there has been a trend toward an increase in the number of X-ray examinations. This is due to introduction into medical practice of some special X-ray procedures and computer tomography of some organs. Also, digital systems of conversion and processing of images find progressively increasing application in medicine.However, there is a trend toward a continuous increase in the number of patients with tuberculosis all over the world. In most developed countries in the last quarter of the XXth century, the number of patients with tuberculosis increased approximately twofold; in Russia and countries of the CIS, threefold and more. This is the reason why interest is aroused in special-purpose X-ray equipment for examination of lungs, namely, scanning photoroentgenographs for mass-scale prophylactic examination of lungs [2].Ultrasonic or infrared examinations are inefficient for studying lung tissue. Endoscopy of bronchi is also a very difficult procedure. Thus, X-ray examination remains almost the only way of obtaining diagnostic information about lungs, except for laboratory biochemical analyses and tests.It should be noted that medical X-ray examinations and treatment are the second most probable cause of undesirable aftereffects after traffic accidents. However, it is still impossible to abandon X-ray examinations, in particular, of lungs. Therefore, development of low-dose X-ray equipment for mass-scale prophylactic examInations is an urgent problem. Also, an efficient system of control and documentation of individual radiation doses received by people is necessary. According to the Russian Federation Law on the Radiation Safety of People adopted in 1996, the radiation load on patients during X-ray examinations should be recorded in terms of effective dose [5].In 1996, all leading manufacturers of X-ray equipment put on the market of medical equipment various low-dose digital X-ray systems for examination of lungs. These systems differ from each other in the principles of conversion of images.There are image converters based on selenium drum (Philips), stimulated luminophore (Fuji), and large-diameter electronic image intensifiers (Siemens). The IMIX image converter (Medira) is based on the principle of optical transmission of images from the screen to a TV charge coupled device matrix. The main advantage of all these converters is that they allow acquisition of significantly more information during examination, whereas the dose received by patient is somewhat decreased as compared to film photoroentgenography. However, these devices are rather expensive, which makes it virtually impossible for these devices to replace the photoroentgenographs currently used in domestic medical institutions.The main task of the designers of conventional film photoroentgenographs is to increase sensitivity without deteriorating image quality. For example, a modification of the KF-400 photoroentgenographic camera (Russia) with improved optics and a gadolinium hydroxysulfide screen instead of the ZnS (Ag) screen has s...

Adoption in 2004 of the VNIIIMT Standard 01 22 04 provided a legal basis for evaluation of such parameters of digital X ray detectors as signal/noise ratio, detective quantum efficiency, and uniformity of brightness distri bution over the detector plane using experimental and computational methods [2]. The goal of this work was to describe the results of the use of specialized software developed at the Scientific Practical Center for Medical Radiology, Health Service Department (Moscow) for experimental and computational evaluation of the char acteristics of digital X ray detectors.In accordance with the VNIIIMT Standard, a soft ware package was developed at the Scientific Practical Center for Medical Radiology designed to assess major quality characteristics of digital X ray image formation directly at the site of use. The interface of the software provides for data processing, experimental data storage, and data transmission using the DICOM 3.0 protocol [1].The main window of the program is shown in Fig. 1. It specifies parameters of digital X ray detector, experi mental settings, and some parameters of data processing.The data and parameters include: -path to file with open field; -path to file with image for determining dark cur rents (if present) or calculated level of dark currents; -pixel size; -dose in detector plane; -coefficient of radiation quality; -position of region of interest in image; -size of region of interest along the two coordinates; -size of subarea of modified brightness. Signal/noise ratio at detector output and detective quantum efficiency at zero spatial frequency were calcu lated with due regard to the VNIIIMT Standard 01 22 04.The detective quantum efficiency was calculated from:where ψ 2 out is squared signal/noise ratio at the detector output; D det is dose in the input detector plane, µGy; A chan is the image element area (pixel) reduced to input field size (area of input channel surface), mm 2 .Coefficient 29,400 characterizes squared signal/ noise ratio at the detector input at a given radiation qual ity (reduced to dose 1 µGy and area 1 mm 2 ). The effective energy of the radiation quality in our experiments corre sponded to half attenuation Al layer of 7 mm (anode volt age, 70 kV; additional filter, 20 mm Al).The output signal/noise ratio is calculated from: ψ out = B mean (σ mean n 1/2 ),where B mean is mean brightness of the area of interest in open field; σ mean is the square root of the variance of mean Fig. 1. Main window of the program.

615.471.03:616-073.75 X-Ray diagnostic systems with digital image processing are presently extensively developed and manufactured worldwide.The physical principles underlying digital X-ray imaging may differ in different X-ray diagnostic systems available from different manufacturers [1][2][3]. However, in any of these systems information is displayed on a video monitor screen and can be processed if necessary. The sites of interest can be selected, and linear dimensions can be measured. Both images and corresponding text information can be stored, archived, and printed. The goal of this work was to describe methodological approaches to rational selection of electronic equipment for digital X-ray imaging and data processing, archiving, storage, display, printing, etc. The study was focused mainly on scanning X-ray system for prophylactic examination of lungs, because these systems could provide the opportunity for solving an urgent problem of diagnosis of tuberculosis.The solution of this problem should be based not only on purely technological but also on economic factors (availability of certain equipment for health service organizations). However, technical aspects (performance of monitors, printers, memory units, etc.) should be of primary concern.Spatial resolution is one of the most important characteristics of X-ray diagnostic devices. The limiting value of spatial resolution is determined by the following equation: