Colloid scintigraphy (static liver scintigraphy) is a nuclear medicine diagnostic procedure used to detect (identify) certain hepatic diseases associated with destruction of the RHS (reticulo-histiocytic system) of the liver. The liver parenchyma (liver tissue) is composed of various cellular components. Hapatocytes (hepatic cells) make up the majority of approximately 65%. About 15% are Kupffer stellate cells and the remaining 20% form various cells such as endothelial cells, Ito cells (fat storage cells), bile duct epithelium. Kupffer stellate cells belong to the reticulo-hystiocytic system (RHS) of the liver. They are capable of phagocytosis (uptake and storage) of various particles such as microorganisms or other pathogens and thus serve the body’s defense function. In nuclear medicine diagnostics, this property of Kupffer stellate cells is exploited by applying a radiocolloid (radiopharmaceutical with a special particle size) intravenously and having it phagocytosed and stored by the Kupffer stellate cells. However, if the cells of the RES are damaged by, for example, space-occupying lesions, they can only absorb the radiocolloid to a reduced extent, which is ultimately visualized as a storage defect on scintigraphy.
Indications (areas of application)
The suspected diagnosis of liver disease largely determines the selection or sequence of nuclear medicine examination procedures. Nowadays, many space-occupying lesions/tumors no longer represent an indication for colloid scintigraphy because the sensitivity (percentage of diseased patients in whom the disease is detected by the use of the procedure, i.e., a positive finding occurs) or specificity (probability that actually healthy individuals who do not have the disease in question are also detected as healthy by the procedure) is insufficient compared with radiological cross-sectional imaging procedures or PET-CT. For example, sonography, computed tomography (CT), and magnetic resonance imaging (MRI) have largely replaced static liver scintigraphy in the diagnosis of hepatocellular carcinoma (HCC) or liver metastases. Benign (benign) tumors are more commonly diagnosed or differentiated with scintigraphic techniques, with the following association between tumor type and scintigraphy:
- V. a. hemangioma (hemangioma); most common benign (benign) liver tumor (0.4-20%); 60-80% of patients are between 30 and 50 years old; women are affected three times more often than men; in young women, hemangiomas cause symptoms more frequently.→ Blood pool scintigraphy
- V. a. focal nodular hyperplasia (FNH); common benign (benign) hepatocellular tumor, accounting for about 1-2% of all liver tumors; nearly 90% of cases affect women, with size growth described as a result of taking oral contraceptives (“the pill”) or during pregnancy → liver function scintigraphy
- V. a. hepatocellular adenoma; benign (benign) liver tumor that occurs more frequently in women taking oral contraceptives. Hepatocytes are atypically altered and stranded. Bile ducts, portal fields, and Kupffer stellate cells are absent, resulting in a storage defect on colloid scintigraphy. → Colloid scintigraphy
Contraindications
Relative contraindications
- Lactation phase (breastfeeding phase) – breastfeeding must be interrupted for 48 hours to prevent risk to the child.
- Repeat examination – no repeat scintigraphy should be performed within three months due to radiation exposure.
Absolute contraindications
- Gravidity (pregnancy)
The procedure
- 99mTc-labeled colloid particles are administered intravenously to the patient. The size of the particles should be 200-1,000 nm to ensure preferential storage in the RHS of the liver rather than in the spleen or bone marrow.
- Planar images of the liver are obtained 20-30 min after injection of approximately 100-200 MBq of radioactive colloid. The duration of an image is approximately 3-5 min, and the examination is completed after approximately 15 min.
- Nowadays, especially for the detection of foci located centrally in the liver, images are obtained using SPECT (single photon emission computed tomography).The high-resolution multi-head systems allow imaging of lesions as small as 0.5 cm with increased resolution.
Potential complications
- Intravenous application of radiopharmaceutical may result in local vascular and nerve lesions (injuries).
- Radiation exposure from the radionuclide used is rather low. Nevertheless, the theoretical risk of radiation-induced late malignancy (leukemia or carcinoma) is increased, so that a risk-benefit assessment should be performed.
