Scintigraphy

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  • scintigraphy
  • Use of scintigraphy
  • Scintigraphies at a glance

Radioactive isotope, gamma camera, technetium - terms that do not necessarily produce positive associations. Wrongful: They are important components of nuclear medicine procedures and open up numerous diagnostic and therapeutic possibilities. Scintigraphy is one of them.

Principle of scintigraphy

Scintigraphy is an examination method in which images are generated by radioactive substances, usually technetium (99mTc), which are incorporated into the body. This allows the metabolism and organ functions to be assessed and certain tissue changes to be recognized.

  • radionuclides (Radioisotopes) are unstable atomic nuclei of chemical elements that break down easily and thereby release radioactive radiation.
  • If such substances are bound to carriers ("radioactive labeling"), this results in a radiopharmaceuticalwhich can be injected into the organism as an injection, tablet or respiratory gas. It spreads throughout the body and then sends - depending on the degree of accumulation - temporarily different levels of radiation. This can be done with the help of a so-called Gamma Camera register and convert into pictures (scintigrams) via computer.
  • When support materials Chemical compounds are used that are known to be incorporated into specific organs so that they can be specifically studied. Thus, for example, Pertechneate for the diagnosis of the thyroid gland, since it is absorbed by it like iodine.

Very rapidly disintegrating radionuclides and readily precipitable carriers are used, so that the duration of action of the radioactivity is limited to minutes to hours and thus the radiation exposure to the patient is very low (usually not higher than the conventional X-ray images). Nevertheless, the examination should be carried out during pregnancy and lactation only in exceptional cases. The excretion of the radioactive degradation products via the kidneys can be accelerated with increased fluid intake following the examination.

Shapes of scintigraphy

Scintigraphy is great for testing tissues for their ability to function, even before visible changes occur. In principle one differentiates the static and the dynamic scintigraphy. The first is to assess the location, shape, size and mass of tissues and to detect abnormalities such as inflammation or tumors. The actual organ function can be assessed by means of dynamic scintigraphy. Sequential and functional scintigraphy are used as techniques for this:

  • Static scintigraphy: Here, similar to a normal x-ray examination, one or more images are taken at one time, in some cases also in two planes, in order to better visualize the three-dimensional distribution of the radiopharmaceutical. For functional analysis, this form is used when the state of the activity distribution is stable and lasts for a relatively long time. Regionally either a normal, a reduced or missing activity enrichment (memory defect, "cold spots") or an increased storage ("hot spots") can be recognized.
  • SequenzszintigrafieIf the distribution of radionuclides changes quite rapidly and over and over again (for example, urinary urinary urinary excretion), multiple exposures are taken at fixed intervals (e.g., every minute) to assess the course of the process.
  • FunktionsszintigrafieCombining sequence scintigraphy with a computer-aided calculation of radiation activity allows conclusions to be drawn about the functioning of whole organs or their subareas. This may be particularly helpful for side-by-side comparison of blood flow or organ function (e.g., kidneys, brain halves).

Emission computer tomography (ECT) is based on a similar principle to scintigraphy. Again, a radiopharmaceutical (usually fluorodeoxyglucose) is injected. The emitted radiation is then recorded using rotating cameras or ring detectors and - this is the main difference - converted by the computer into sectional images (computed tomography). In single-photon emission computed tomography (SPECT), gamma emitters are also used, while positron emission tomography (PET) uses short-lived positron emitters. The latter are extremely expensive, so the study is only carried out in large centers.

Expiration of a scintigraphy

Whether the preparation of the patient is necessary depends on the examined organ and the examination method. Sometimes the patient needs to stay sober, stop taking certain medications or drink more.

The examination is carried out lying or sitting. The most unpleasant is the most necessary spraying the radiopharmaceutical. The gamma camera is mounted on a motorized tripod, bypasses the patient and takes pictures at intervals of seconds or minutes. For this, the patient - depending on the question and the device - must hold for 10 to 30 minutes. Scintigraphy can take anywhere from a quarter of an hour (one shot) to several hours.

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