X-ray tomography

Technical principle of conventional X-ray tomography. During the exposure (from point in time to point in time ) the X-ray source (X) and detector (D) move simultaneously in opposite directions. Only image elements (purple, red) from one layer (S) are shown in sharp focus, details (yellow, green) from all other layers are blurred out of focus.

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The X-ray tomography (also blurring tomography , tomosynthesis ) is an imaging method for the representation of a layer within the examined object.

Nowadays one usually speaks of the “conventional tomography” in order to distinguish the procedure from the more modern X - ray computed tomography.

During the exposure, the X-ray film and the radiation source are moved in opposite directions. This results in a sharp image only of the structures that are in the focal plane. Structures outside the focal plane are blurred.

The movement of the recording apparatus (deflection, path) is programmable so that layers of different thicknesses can be recorded depending on the setting.

With a deflection angle of less than ± 10 ° in only one pivoting direction (usually head-to-foot direction), thick layers are obtained and this is called zonography . In the past, indications for this were suspected kidney stones , bronchial carcinoma or a spinal column injury .

Conventional X-ray tomography of the midface. The gray haze is created by the blurred structures outside the focal plane.

Compared to the aforementioned linear blurring, deflections can be made in several directions; this procedure is sometimes referred to as polytomography . This results in very thin layers with a high radiation dose. Previously, the indications for this were examinations of the inner ear.

In the form of orthopantomography , an overview of the jawbones, tomography is used in dentistry. Today, other body regions are examined almost exclusively by means of computed tomography or magnetic resonance imaging . Also in the mammography can tomosynthesis be applied.

literature

Josef Lissner (ed.): Radiology I . 3. Edition. Ferdinand-Enke-Verlag, Stuttgart 1986, ISBN 3-432-88353-6 , p. 54 .
Günter Goretzki, Arno Maurer: Physics, chemistry and radiation science for nursing professions . 6th edition. Urban & Fischer-Verlag, Munich Jena 2003, ISBN 3-437-26830-9 , p. 76 .
Stefanie Becht, Roland C. Bittner , Anke Ohmstede, Andreas Pfeiffer, Reinhard Roßdeutscher (Hrsg.): Textbook of X-ray diagnostic setting technology . 6th edition. Springer-Verlag, Berlin Heidelberg 2008, ISBN 978-3-540-31708-1 , p. 498-502 , doi : 10.1007 / 978-3-540-31709-8 .

Web links

Patient information> X-ray / fluoroscopy: conventional tomography. In: uni-bonn-radiologie.de. Radiological University Clinic Bonn, accessed on April 13, 2018 .