Scintigraphy: Information & Scintigraphy Specialists

A prerequisite for a scintigraphic scan is the administration of a substance known as a radiodiagnostic agent. This is a weakly radioactive marker that is usually used in combination with a tracer. Substances such as radioactive thallium, iodine, or xenon are used for this purpose.

The radiodiagnostic agent is administered by injection, and sometimes by inhalation or ingestion.

The radioactive radiation emitted by the marker inside the body can be detected using a gamma camera. The resulting data is processed by a computer to create a two- or three-dimensional image.

Generally, the radioactive tracer bound to the marker is distributed throughout the body via the blood vessels. Distribution via the respiratory stream in the lungs is also possible. This allows for the visualization of blood flow to specific body regions (or lung ventilation).

For most target organs, specialized tracers are used that are preferentially taken up by these organs. For example,

• phosphate and phosphonate compounds in skeletal examinations
• so-called colloidal particles derived from the serum protein albumin for examinations of the liver, bone marrow, and spleen
• the substance MIBI (methoxyisobutyl isonitrile) for examinations of the heart and parathyroid glands

Pure radioactive iodine accumulates in the thyroid gland after some time.

Target organs for scintigraphy include, for example,

• the thyroid gland,
• the lungs,
• the myocardium (heart muscle),
• the bones,
• the kidneys,
• the liver,
• the lymph nodes,
• the salivary glands,
• the stomach,
• the intestines, or
• the brain.

The scintigraphy performed is named according to the target organ. Depending on the procedure and the tracer used, it may also be referred to as

• perfusion or inhalation scintigraphy, as well as
• colloid scintigraphy

. Unlike X-rays, which primarily depict static structures, scintigraphic images can provide information about dynamic processes in the body. For example:

• Which regions or tissues have particularly high or conspicuously low blood flow?
• Which regions show increased cellular metabolic activity (as indicated by enhanced uptake of the radioactively labeled tracer)?

In this way,

• tumors,
• organ and tissue dysfunction,
• circulatory disorders, or
• internal injuries

can be diagnosed.

Whole-body scintigraphy of a patient (lesion in the skull)

A scintigraphy can usually provide insightful answers to many diagnostic questions when used in conjunction with other imaging modalities. The applications of this procedure are correspondingly diverse. In cases of abnormal ultrasound findings, palpation findings, or thyroid hormone test results, the thyroid gland can be tested for

• hyperthyroidism
• Hypothyroidism
• Inflammation
• benign or malignant tissue changes (nodules)

If there is reasonable suspicion, a bone or skeletal scintigraphy can

• can detect tumors.
• reveal typical, subtle patterns of bone injury resulting from child abuse (“battered child syndrome”).

A lung scintigraphy can confirm or rule out a suspected pulmonary embolism. This is a combined examination consisting of ventilation scintigraphy and standard perfusion scintigraphy. This allows both lung ventilation and blood flow to be visualized equally.

A renal scintigraphy can

• visualize functional kidney tissue. It allows for an assessment of the anatomy and condition of the kidney in cases of congenital or acquired anomalies.
• dynamically visualize the excretory function of the kidney through a series of images, for example, in cases of kidney failure or following a transplant.

Myocardial scintigraphy can assess blood flow to the heart and the health of the heart muscle. It is performed

• when coronary heart disease is suspected.
• to assess the success of interventions (bypass surgery, angioplasty).

In the digestive tract, scintigraphy can

• visualize the function of the esophagus and stomach when symptoms are present. For this purpose, the radiopharmaceutical is swallowed.
• to locate bleeding from the stomach or intestinal lining.

In cases of unexplained cognitive deficits, perceptual, or motor disorders, a brain scintigraphy can

• to localize circulatory disorders in the brain.
• classify Parkinson’s disease and dementia more accurately.

In tumor diagnostics, scintigraphy is used

• to detect tumors and for staging (assessment of size and metastasis).
• to monitor the success of treatment.

A scintigraphy is usually performed on an outpatient basis. Depending on the organ to be imaged, you will receive instructions in advance regarding any dietary restrictions you may need to follow. Your doctor will also inform you if you need to stop taking any medications for a few days.

On the day of the examination, the radiopharmaceutical is usually injected into a vein in your arm. This is similar to receiving a vaccination. For a lung ventilation or inhalation scintigraphy, you will inhale a gaseous radiopharmaceutical. For an esophageal or gastric scintigraphy, you will swallow a liquid or a type of paste.

You will most likely not feel the radiotracer spreading through your body. Very rarely (in about one out of 100,000 cases), hypersensitivity reactions to one of the tracers used may occur. This can lead to circulatory problems.

For most scintigraphic examinations, you will lie down or sit still for 30 to 60 minutes while the gamma camera takes the actual images. A myocardial scintigraphy usually includes a stress test, during which you will need to pedal on an exercise bike.

In addition to using the correct tracer, the timing of the imaging is crucial for scintigraphic diagnosis: After injection of the radiopharmaceutical, the tracer is expected to appear in specific organs at specific times. The tracer first appears in the blood, then in the liver, and finally in the gallbladder.

As a result, scintigraphic examinations often involve a fairly long wait before imaging begins. You’ll spend this time at the radiology practice or clinic engaging in an activity of your choice.

Once the examination is complete, you can usually go home right away. Your ability to drive and your general well-being are usually not affected by the procedure.

Thyroid Scintigraphy

Scintigraphy is a well-established diagnostic procedure. Nevertheless, the associated radiation exposure should not be overlooked. Therefore, scintigraphy is generally not performed on pregnant or breastfeeding women. In children, the benefits and risks must be carefully weighed. In adults, scintigraphy is generally considered to be low-risk.

However, physicians report significant cumulative doses in certain patient groups. The radiation doses from multiple scintigraphy procedures, as well as X-rays and CT scans, add up. Heart patients and kidney transplant recipients, in particular, undergo many such examinations. Some patients undergo so many examinations over the course of a few years that their cumulative radiation exposure exceeds 100 millisieverts. This is a level that indisputably increases the risk of cancer.

Here, too, however, the risks and benefits must be weighed: The failure of a kidney transplant is immediately life-threatening. Furthermore, cancers usually develop very slowly. Therefore, the cancer risk associated with radiological cardiac diagnostics plays a lesser role, especially in older patients. Its immediate benefits, on the other hand, can be significant.

The radioactive substances used in scintigraphy are low-level emitters with a half-life of about six hours. After this time, their radioactivity is reduced by half. Thus, after one day, it has dropped to one-sixteenth of the original value and is therefore barely detectable.

The radiation dose to which patients are exposed during a typical scintigraphy examination is

• about ten times higher than in conventional X-rays and
• about ten times lower than that of a CT scan.