Use of Scintigraphy

Scintigraphy is most commonly used to examine the thyroid gland, kidneys, heart, lungs, and bones. In principle, however, it can also be used to assess the function of almost any other organ, including the liver, lymph, brain, parathyroid glands, spleen, stomach, or esophagus. It is also used to look for sites of inflammation when fever is unclear.

Scintigraphy of the thyroid gland

Scintigraphy is very useful for distinguishing functioning and nonfunctioning thyroid tissue (thyroid dysfunction), including checking the shape, size, and location of the organ. If there is an increased accumulation of injected pertechneate, this indicates benign tumors (adenomas) that produce thyroid hormones without being involved in the regulatory circuit (thyroid autonomy). A storage defect indicates (malignant) tumors or cysts. If autonomy is suspected, a 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 tested. The normal response would be a throttling of hormone release and thus decreased accumulation of the radiopharmaceutical.

Scintigraphy of the kidneys

Static renal scintigraphy (isotopic nephrography) is used infrequently, usually when there are structural changes such as malformations that cannot be determined by other imaging modalities. Renal function scintigraphy is more commonly used: Renal perfusion scintigraphy can be used to determine blood flow to the kidneys, and renal excretion scintigraphy can be used to detect urinary outflow obstructions from the kidney and ureter. A special measuring device can be used to determine the changes in radiation activity over time and the (side-separated) renal function. Various technetium-labeled molecules serve as radiopharmaceuticals, which are filtered from the blood in a specific way and excreted exclusively through the kidneys.

Scintigraphy of the heart

Myocardial perfusion scintigraphy is used when a circulatory disorder (coronary artery disease) is suspected. The carrier is thallium, which, like potassium-depending on blood flow and metabolic activity-is transported to the myocardium. Lack of accumulation suggests vasoconstriction or occlusion or dead tissue. Images are obtained at rest and during physical exertion (e.g., on a stationary bicycle). Cardiac internal scintigraphy (radionuclide ventriculography) can be used to assess left ventricular functions such as contractility, ejection fraction, and filling and emptying rates. Red blood cells serve as carriers for the technetium, whose path through the bloodstream and the heart is logged. At the same time, the electrical activity of the heart is recorded by ECG. However, this examination is now predominantly replaced by ultrasound or magnetic resonance imaging.

Scintigraphy of the lung

Lung scintigraphy is usually the method of choice when vascular occlusion within the pulmonary circulation (pulmonary embolism) is suspected. During pulmonary perfusion scintigraphy, the patient is injected with small, technetium-labeled human proteins (albumin) that spread to and become lodged in the smallest pulmonary vessels. Sections of the lungs that are not perfused show up as cavities (perfusion failures). In this case, a pulmonary ventilation scintigraphy must also be performed in order to distinguish perfusion failures due to an embolism from cavities due to reflex constriction in lung diseases with poor pulmonary ventilation (e.g., collapse of a lung lobe, hyperinflation of the bronchi). The patient must inhale radioactively labeled xenon gas (functional ventilation scintigraphy) or microparticles containing technetium (static ventilation scintigraphy) for several minutes. Its distribution allows conclusions to be drawn about lung ventilation.

Bone scintigraphy

Skeletal scintigraphy is useful for evaluating many remodeling processes and diseases of the bones. It is often used to search for metastases in cancer and to monitor their therapy. Radioactively labeled diphosphonate is usually injected and incorporated into the bone. Increased storage as a sign of increased metabolic activity can occur, for example, after a bone fracture, in the case of inflammation, a tumor or a wear and tear disease.Decreased storage is found when bone tissue is destroyed, for example, in cancer.