X-ray diagnostics – the procedure

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In X-ray diagnostics, there are three techniques:

• conventional radiography,
• fluoroscopy,
• computed tomography (CT) and other tomographic techniques.

1. Conventional Radiography

The most frequently used technique is the conventional radiography which is associated with a comparatively low radiation exposure. The part of the body to be examined is exposed to X-rays for a fraction of a second and the radiation penetrating the body is visualised using a digital detector or – in rare cases – still a film-screen system. The representation of dense structures such as bone is light, whereas that of less dense tissues such as fatty tissue is darker. Structures of mean density such as soft tissues (e.g. muscle), are depicted in different shades of grey.

Fluoroscopy

2. Fluoroscopy

Examinations of movement processes (such as swallowing or the heartbeat), or precise assessments of overlapping structures (e.g. of the gastro-intestinal tract) sometimes require additional fluoroscopy. This technique involves soft X-radiation penetrating the body to produce a series of images that are made visible on a monitor.

Fluoroscopy also includes angiography. During this examination, a contrast medium is administered to the patient to make vessels visible which cannot otherwise be imaged. Angiography may be accompanied by so-called interventional procedures such as the widening of narrowed or blocked blood vessels.

The radiation dose of a fluoroscopy may be well above that of a conventional radiography.

Computed tomography (CT)

3. Computed tomography (CT) and other tomographic techniques

CT is an X-ray procedure where cross-sectional images of the body are created. During CT an X-ray machine, consisting of an X-ray tube and a radiation detector on the opposite site, continuously rotates around the body, following a circular or spiral path to obtain several radiographs from different angles (projections). A computer program is used to transform these projection images into cross-sectional non-overlapping images (virtual "slices") of high-contrast displaying tissues of different density in well distinguishable shades of grey.

The radiation dose to the patient caused by CT is relatively high as compared to radiography.

In recent times, dental cone beam CT and digital breast tomosynthesis (DBT) were introduced as additional tomography techniques. Dental cone beam CT is mainly used in dentistry, orthodontics, and otolaryngology to reduce the problem of superposition, e.g. for a more precise treatment planning. DBT is e.g. be used for further evaluation of a suspicious breast finding after a conventional mammogram, if alternative examination procedures were not conclusive.