Skeletal scintigraphy allows you to simultaneously determine in which joints inflammatory phenomena caused by rheumatic disease are observed. 2-3 hours before the start of the study, a radiopharmaceutical is injected into the patient’s vein. The drug is distributed throughout the body and accumulates in the places where the greatest number of young bone cells are concentrated (where the body is trying to restore areas destroyed as a result of inflammation). Special preparation for the examination is not required. Before starting the study, the bladder should be emptied.
Skeletal scintigraphy is a radionuclide technique based on the introduction and subsequent assessment of the accumulation of osteotropic radiopharmaceutical (RP) in bone structures. Skeleton scintigraphy is performed using a gamma camera, the device of which allows you to capture the radiation of an isotope and convert it into a graphic image. Skeletal scintigraphy is the most popular and sensitive method of nuclear medicine, capable of detecting functional disorders.
Phosphate complexes labeled with 99mTc (pirfotech, MDP, phosphotech, technefor, etc.) are used to perform skeleton scintigraphy. The cost of skeleton scintigraphy using various RP is variable. The method of skeletal scintigraphy is based on the capture of phosphate complexes of radioisope by hydroxyopatite crystals, the number of which increases in areas with increased osteogenic activity.
Symmetrical accumulation of osteotropic RP occurs in unchanged skeletal bones during scintigraphy. Skeletal scintigraphy is used to examine joints, long tubular bones, sternum, skull bones, shoulder blades, pelvic bones, spine. Skeletal scintigraphy is indispensable for identifying new areas of growth (with the spread of metastases) and bone splitting (with infection, trauma, degenerative changes).
The advantage of skeletal scintigraphy is the ability to detect bone damage earlier than radiography. Limitations of the widespread use of skeletal scintigraphy in diagnostic practice are its high cost and special requirements for radiation safety. Skeletal scintigraphy does not replace CT or MRI of bones.
A change in the accumulation of radioisotopes in bones occurs during osteoblastic processes, an increase in vascular permeability or blood flow. Skeletal scintigraphy is prescribed to detect metastatic bone damage in myeloma, melanoma, kidney, thyroid, lung, breast, prostate cancer. Most often (up to 80%) metastases are detected in the spine, pelvic bones, ribs and sternum. About 20% of metastatic lesions occur in the bones of the limbs and skull, which is why it is so important to conduct scintigraphy of the entire skeleton.
With skeletal scintigraphy, osteomyelitis and other bone inflammations are well determined. Scintigraphic criteria for osteomyelitis are a local increase in blood flow and an increase in the intensity of radioisotope accumulation in the pathological zone. Skeletal scintigraphy is indicated for the detection of Paget cancer, microcracks, hidden fractures, bone bruises and other injuries. With the help of skeletal scintigraphy, pathological changes in joints are detected early in arthropathies and arthritis.
Skeletal scintigraphy is excluded during pregnancy, a known allergy to a radioisotope drug, a recent (less than 4 days ago) X-ray of the stomach, intestines, esophagus with barium contrast, or taking bismuth preparations, because bismuth and barium can distort scintigrams. During lactation, skeletal scintigraphy is allowed with a break in feeding for at least a day after the study.
Methodology of conducting
The procedure of skeletal scintigraphy is carried out in a room equipped with a gamma camera, and usually consists of 3-4 phases. After intravenous administration of the radioactive indicator, a scan is performed at the first and fifth minutes, which makes it possible to assess the blood flow and the volume of blood supply to the pathological focus. While waiting for the next stage of the study, the patient is released, recommending drinking several glasses of water and urinating.
Then, after 2-4 hours, a repeated gamma scan is performed, aimed at assessing the distribution of RP in bone structures. It is possible to perform additional scintigrams after 24 hours. Before starting scintigraphy, it is necessary to release the bladder for a clearer and better image of the pelvic bones. During skeletal scintigraphy, the patient lies on the desktop of the gamma camera connected to the scanner. The gamma camera does not emit radiation, but only perceives the signals of the RP injected into the body.
Scanning is carried out by poly-projection and polypositional, which is facilitated by the movement of the scanner and the change of the patient’s body position. During the scintigraphy of the skeleton, one should remain motionless and calm breathing. Difficulties during skeletal scintigraphy may arise due to severe pain in the spine, bones or joints and the inability of the patient to maintain a stationary position.
Interpretation of results
Normally, scintigraphy determines the symmetrical and uniform distribution of the radioactive indicator in the bones. The areas with the highest and lowest accumulation of RP are not detected on scintigrams. The detection of an increased accumulation of RP in some areas of the bones (“hot” foci) may indicate a fracture, infection, bone cancer, arthritis, Paget’s disease. Insufficient accumulation of radioisotope occurs in some types of cancer (multiple myeloma) or with a lack of blood supply.
Skeletal scintigraphy data are interpreted in conjunction with clinical symptoms, suspected diagnosis, and radiographs. In the future, computed tomography, MRI, biopsy and other studies may be required.
Risks of scintigraphy
After the end of the examination, copious drinking, moderate activity and frequent urination are recommended for the speedy removal of the radio indicator during the day. After emptying the bladder and intestines, wash your hands thoroughly with soap. In general, the radiation dose of the radioisotope used in scintigraphy is safe for the patient. After the introduction of RP, injectable complications may develop in the form of local soreness and compaction, as well as general allergic reactions.