X-ray examination

An X-ray examination makes different parts of the body and body tissue visible using X-ray waves. The German physicist Wilhelm Konrad Röntgen inadvertently discovered X-rays during an experiment in 1895.

Method

X-rays are electromagnetic waves with high permeability through the hard substances of skeletal and locomotor organs but are absorbed by soft tissue. Parts of the body facing the radiation source receive a stronger radiation intensity than those turned away. As the rays pass through the body they are scattered, which is inconvenient both in terms of 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, according to the laws of central projection this also causes image enlargement. The size of the image also increases when the distance between the body and the radiation source is reduced.

An understanding of the principles underlying skeletal growth is required to assess pre-teen X-rays. Ossification of initially cartilaginous epiphyses 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 with X-ray atlases it is therefore possible to determine bone maturation and compare chronological age (actual age) with 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 deformities that deviate significantly from the norm, measurements are compared with those of a normal reference group. However, it must be remembered that the range of skeletal measurements recorded to date is extremely wide. They include what is known as biological variation and are an indication of formal skeletal diversity without pathological implication. The method-related variation also includes errors caused by differing radiological projections. Despite standardisation of techniques, and depending on the size and localisation of the images depicted, projection errors must be taken into consideration. For example, even minor rotation of the chest during radiological imaging of scoliosis results in a noticeable change in angle. This means that varying degrees of pelvic tilt must also be considered when measuring the hip socket.