X-ray examination
MethodX-rays are electromagnetic waves with high permeability of the hard substances of skeletal and kinetic organs, but which are absorbed by soft tissue. The parts of the body turned toward the radioactive source receive an even, but stronger radiation intensity than those turned away. In passing through the body the rays are scattered, which is inconvenient in terms of both the radiation exposure and imaging on a photographic plate. The simplest method of reducing scattered radiation is to increase the distance between the object and the screen. However, in accordance with the central projection laws this also causes image enlargement. The size of the image also increases when the distance between the body and the radioactive source is reduced. FAn understanding of the principles underlying skeletal growth is required to assess pre-teen X-rays. Ossification of initially cartilaginous epiphysis follows certain laws and is age-dependent. It is therefore possible to determine bone maturation on the basis of a radiological examination of carpal ossification. This is carried out with a-p radiography of the left hand. By comparing this to X-ray atlases it is threfore possible to determine bone maturation and compare chronological age (actual age) and effective age (age in relation to body size). |
The process of measuring relative lengths and angles with X-rays is called radiometry. In order to identify skeletal deformity obviously divergent from the norm, measurements are compared to those of a normal group. However, it must be remembered that the range of skeletal measurements taken to date is extremely wide. They include what is known as the biological spread and are an indication of formal skeletal diversity with no pathological implication. Included in the method-related spread are also errors due to differing radiological projections. Despite the standardisation of techniques, and subject to the size and localization of the images depicted, significant projection errors have to be taken into consideration. For example, even minor rotation of the chest during radiological imaging of a scoliosis results in a noticeable change of angle. This means that varying degrees of pelvic tilt also have to be taken into account when measuring the hip socket. Radiometry is particularly significant in planning orthopaedic operations. It is impossible to specify the procedure and intention of an operation without having accurate evidence of the deformity. In preparing the operating strategy an outline sketch is usually made from the X-ray and the aim of the operation written in to it. The superposition of the skeletal sketch determines the choice of specific operating schedule. |