Contemporary role of X-ray devices in medical introscopy

Abstract

Visual information accounts for at least 90% of the information received by human sensory systems. At least 65% of brain systems are involved in processing visual information. As a result, many trends in the development of medical diagnostic technologies are based on visual presentation of diagnostic information. The goal of making the patient's body "transparent" has given rise to speedy progress in medical introscopy, a branch of medicine that employs all types of physical techniques for the purpose of imaging of internal organs of the human body. Electromagnetic radiation and ultrasonic waves are most commonly used for obtaining images of nontransparent anatomical organs and systems inaccessible for direct visual inspection [4]. The extensive use of a broad range of physical methods in introscopic devices (X-ray apparatuses, ultrasonic scanners, endoscopes, ophthalmoscopes, thermal imagers, gamma chambers, and tomographs of various types) raises a number of important questions. I. Why are there so many types of imaging technologies? 2. Should any radiation diagnosis department use all these technologies? 3. What is the relative clinical value of various methods of introscopy, and X-ray introscopy, in particular? These are rather difficult questions, and there is no single conclusive answer to any of them. However, some points relevant to this issue can be clarified. Virtually all new methods of medical introscopy appear to supplement rather than to replace existing methods. As a matter of fact, different methods of imaging are based on different mechanisms of interaction between a physical field and biological tissue. Therefore, they provide information on different properties of biological structures. The main point is to distinguish visually between normal and pathological tissues. For many types of imaging, this is a problem that is presently far from being solved. It should be emphasized that different methods of imaging are mainly designed to supplement rather than replace each other. Only in individual cases are the results of imaging obtained by different methods are so closely correlated with each other that simultaneous use of the competitive methods should be avoided. For example, ultrasonic and endoscopic imaging in some cases impose limitation on X-ray examination. However, it should be clearly understood that in spite of adverse side effects of X-ray radiation, it is presently (and will probably be in the foreseeable future) indispensable in medical diagnosis. At the present time, about 80% of all medical images are obtained using X-ray radiation, and the diagnostic capacity of this radiation is far from being exhausted. An ideal X-ray converter should detect all incident quanta of information and provide accurate information on its position, energy, and time of detection. Also, the dynamic range of the ideal X-ray converter should be broad enough to provide accurate detection. No currently available commercially system of X-ray imaging meets all these requirements simultaneously. First, primary X-ray images are detected against a significant background of noise caused by radiation scattered within the object of examination. Second, some incident X-ray quanta are not detected. Third, in the absence of input signal, the system forms an image generated by internal noise. Fourth, the spatial resolution of modern X-ray imaging systems is limited by the characteristics of the device rather than by the cross-section of interaction between X-ray radiation and the object of examina-