The application and limitation of the use of X-rays in medical diagnosis

Abstract

X-rays in medical diagnosis are normally used to obtain a visual image of the subject radiographed. The image results from the differential attenuation of the radiation which depends on the thickness, density and configuration of the organ irradiated and on the proportion and nature of the different chemical elements present. The nature of biological material is such that the contrast differentiation between organs or parts of an organ is frequently poor and despite methods to increase the contrast this remains one of the principal limitations. Other limitations are similar in many respects to those found when using X-rays for non-destructive testing but additional limitations are imposed since when living subjects are examined, movement of the subject can seldom be eliminated and, because radiation may be harmful, the dose must always be kept as low as reasonably practical. Further constraints are imposed by the high cost of some equipment and the shortage of qualified manpower to operate the equipment and interpret the findings. The number and type of examinations carried out may have to be limited in some very sick patients because they reach their limits of endurance. Practically every procedure therefore has to be a compromise between the advantages and the limitations imposed.