Duration of a scintigraphy | Scintigraphy

Duration of a scintigraphy

A scintigraphy can usually be performed very quickly. Depending on the type of tissue to be examined, the examination takes between 10 minutes and one hour. However, the duration of the preparation time is important.

Since in an examination of the thyroid gland, medication for hyperthyroidism or hypothyroidism must be discontinued, these “preparations” take one day. It is also important to note that some radionucleotides take a long time to be absorbed by the corresponding tissue. Therefore, it is possible that after administration of the radioactive substances, the examination can take place after 10 minutes or even several days. It is also possible that one measurement is not sufficient and that a control measurement must be made.

Operating principle

The formation of the scintigraphic image (scintigram) is based in principle on the detection of radiating radiopharmaceuticals. This so-called tracer substance (radionuclide) is bound to a certain carrier, which is specific for the respective tissue to be imaged and preferably accumulates there (e.g. iodine for imaging the thyroid gland; bisphosphates for imaging bone). The injected radionuclide, as an unstable isotope, has the property of emitting radiation (preferably ?-radiation) when it decays, which can then be recorded by a gamma camera.

In most cases the technetium isotope 99mTc is used as radioactive nuclide. The gamma rays captured by the gamma camera will then be converted into light flashes by a so-called scintillation crystal in the camera and further on into electrical signals. These electrical signals then become visible as black color in the scintigram. The degree of blackness depends on the frequency of the radiation, i.e. on the amount of enriched radioactive substance in the respective organ/tissue. Thus, the more a tissue accumulates, the darker it appears in the image.

Forms of scintigraphy

In scintigraphy, two types can be distinguished in imaging. On the one hand, static scintigraphy can be used, in which the distribution in the respective organ/tissue is detected only at a previously defined time after the injection of the radiopharmaceutical.On the other hand, however, dynamic scintigraphy can also be performed, in which both the flooding and the outflow process of the radiopharmaceutical in the organ/tissue is depicted. This allows an exact representation of the blood flow in certain regions as well as an answer to certain questions such as the function of the kidneys or the excretory capacity of the liver. In the above-mentioned SPECT method, a combination of scintigraphy and computed tomography, static and dynamic components can be recorded in addition to three-dimensional imaging.