Scintigraphy: A Diagnostic Tool for Medical Imaging

Scintigraphy: A Diagnostic Tool for Medical Imaging

Which organs can be represented?

Scintigraphy is commonly used to examine the thyroid, kidneys, heart, lungs, and bones. In principle, however, it can also assess the function of almost all other organs, such as the liver, lymph, brain, parathyroid glands, spleen, stomach or oesophagus. It is also used to look for sources of inflammation if the fever is unclear.

 

Thyroid scintigraphy

Scintigraphy is very well suited to distinguish between functioning and non-functioning thyroid tissue (thyroid function disorders) and check the organ’s shape, size and position. If the injected pertechnetate builds up, this indicates benign tumours (adenomas) that produce thyroid hormones without being involved in the control loop (thyroid autonomy). A memory defect indicates (malignant) tumours or cysts.

If autonomy is suspected, suppression scintigraphy can also be performed, in which thyroid hormones are given in the form of tablets, and their effects on the thyroid gland are checked. The typical response would be choking the hormone secretion, thus reducing radiopharmaceutical accumulation.

Scintigraphy of the Kidneys

Static kidney scintigraphy (isotope nephrography ) is rarely used, usually when structural changes such as malformations cannot be determined with other imaging methods. Renal function scintigraphy is used more frequently: renal perfusion scintigraphy can evaluate the blood flow in the kidneys, and renal excretion scintigraphy can detect outflow disorders of urine from the kidneys and ureters.

A particular measuring device can determine the changes in radiation activity over time and the (side-separated) kidney function. Various molecules labelled with technetium are used as radiopharmaceuticals, filtered out of the blood in a specific way and excreted exclusively via the kidneys.

 

Scintigraphy am Herz

Myocardial perfusion scintigraphy is used when there is a suspicion of a circulatory disorder ( coronary heart disease ). The carrier is thallium, which, like potassium, is transported into the heart muscle depending on blood flow and metabolic activity. A lack of accumulation suggests narrowing or occlusion of the vessels or dead tissue. The pictures are taken at rest and during physical exertion (e.g. on a stationary bicycle).

With the  cardiac scintigraphy  (radionuclide ventriculography) the functions of the left ventricle such as contraction force, ejection capacity and filling and emptying speed can be assessed.  Red blood cells serve as carriers for the technetium , and their path through the bloodstream and the heart is recorded. At the same time, the electrical activity of the heart is recorded using an ECG. However, this examination is now mostly replaced by ultrasound or magnetic resonance imaging.

Scintigrafie der Lunge

Lung scintigraphy is usually the method of choice when there is a suspicion of a vascular blockage within the pulmonary circulation ( pulmonary embolism ). In  lung perfusion scintigraphy  , small human proteins (albumin) labelled with technetium are injected into the patient, which spread into the smallest pulmonary vessels and become stuck there.

Lung sections that are not supplied with blood appear as gaps (perfusion failures). In this case, a  lung ventilation scintigraphy must also  be performed in order to distinguish perfusion failures due to an embolism from gaps due to reflex constriction in lung diseases with poor lung ventilation (eg collapse of a lung lobe, overinflation of the bronchi). The patient must inhale radioactively labelled xenon gas (functional ventilation scintigraphy) or microparticles containing technetium (static ventilation scintigraphy) for several minutes. The distribution of these allows conclusions to be drawn about lung ventilation.

Bone scintigraphy

Skeletal scintigraphy is suitable for assessing many bone remodelling processes and diseases. It is often used to search for cancer metastases and monitor their therapy. Radioactively marked diphosphonate, built into the bone, is usually injected. Increased storage as a sign of increased metabolic activity can occur, for example, after a broken bone, in the event of inflammation, a tumour or a degenerative disease. Decreased storage is found when bone tissue is destroyed, for example, in the case of cancer.

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