Multiphase skeletal scintigraphy is a diagnostic procedure in nuclear medicine that represents a special imaging technique of scintigraphy that can precisely reveal functional changes in the skeletal system. The field of application of multiphase skeletal scintigraphy is primarily in the evaluation of both inflammatory processes of the skeletal system and bone tumors and, in particular, osseous metastases (bone metastases). Multiphase skeletal scintigraphy is particularly well suited as a diagnostic search method for detecting pathologic (pathological) functional changes of the skeletal system because even early stages of disease, for example, osteomyelitis (bone marrow inflammation), can be detected earlier with skeletal scintigraphy, in contrast to computed tomography or magnetic resonance imaging.
Indications (areas of application)
- Diagnosis of primary and secondary bone tumors – both malignant (malignant) and benign (benign) tumors of the skeletal system can be detected with multiphase skeletal scintigraphy with a high degree of sensitivity (sensitivity: percentage of diseased patients in whom the disease is detected by the use of the procedure, ie. i.e., a positive finding occurs) and specific (specificity: probability that actually healthy individuals who do not have the disease in question are also detected as healthy by the procedure). However, it should be noted that with the help of the procedure is not possible to adequately diagnose the type of tumors of the bones.
- Staging (determination of the degree of spread of a malignant tumor) and therapy monitoring – multiphase skeletal scintigraphy is an excellent method in the performance of a staging examination, because the procedure allows the assessment of tumors that would be impossible to visualize using conventional X-ray examination or computed tomography.For the detection of an osteolytic tumor (bone-degrading tumor) in conventional X-ray examination is necessary reduction of calcium salt content in the bone of 30-50%. Also, the volume necessary to detect the osteolytic tumor is much lower in multiphase skeletal scintigraphy than in computed tomography, and the radiation exposure is lower in scintigraphy. The skeletal system is a common target area for osseous metastases (bone metastases; daughter tumors) – breast carcinoma (breast cancer), prostate carcinoma, bronchial carcinoma (lung cancer), renal cell carcinoma, thyroid carcinoma, pancreatic carcinoma (pancreatic cancer), colorectal carcinoma (colon cancer), Gastric carcinoma, hepatocellular carcinoma, ovarian carcinoma (ovarian cancer) [listing in falling frequency] – represent, so a precise examination is necessary to assess both metastasis and therapy.
- Conventionally radiologically elusive fractures – the use of multiphase skeletal scintigraphy to evaluate fractures is indicated, for example, in fractures such as march or stress fractures. These types of fractures are so-called fatigue fractures, which can result from cyclic loading of the bone. However, the diagnostic procedure is complex, because a fatigue fracture can be shown in conventional X-ray only after several weeks.
- Inflammatory processes of the skeletal system – especially osteomyelitis (bone marrow inflammation) and osteitis (bone inflammation) represent important indications for the performance of scintigraphy. Osteomyelitis is an endogenous form of bone and bone marrow inflammation. In contrast, osteitis represents bone inflammation that is exogenous (caused by pathogens originating outside the body). Arthritides (inflammatory joint diseases) can also cause unexplained bone pain, which can be assessed by scintigraphy.
- Joint endoprostheses – to assess the position and function of implanted prostheses/endoprostheses, e.g. hip or knee joint prostheses; healing, (DD inflammatory/non-inflammatory loosening) multi-phase skeletal scintigraphy can be used.
- Avascular necrosis (AVN) and bone infarction (occlusion of the blood vessels supplying the bone with subsequent deficiency of oxygen and nutrients to the bone tissue) – by using the different phases of scintigraphy, the blood flow and metabolic function of the skeletal system can be precisely assessed.
- Bone metabolism disorders – in the context of primary hyperparathyroidism (parathyroid hyperfunction; pathological (pathological) increased release of parathyroid hormone), there is an increased degradation of bone due to an increased release of parathyroid hormone from the parathyroid gland. Through the parathyroid hormone calcium is mobilized from the bone, so that the calcium content in the blood serum can be normalized.
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)
Before the examination
- Application of the radiopharmaceutical – Radioactively labeled diphosphonates are used to perform skeletal scintigraphy. The use of 99mTechnetium-labeled hydroxy-methylene diphosphonate is particularly common. The application of the radiopharmaceutical is intravenous.
- Implementation of other diagnostic procedures – before the implementation of skeletal scintigraphy, additional nuclear medicine procedures such as sonography (ultrasound) are performed.
- Bladder emptying – after application, the patient should be encouraged to drink fluids and empty the bladder frequently so that the amount of radiopharmaceutical that has not been deposited in the bone can be quickly eliminated from the body.
The procedure
Of crucial importance for the functional principle of skeletal scintigraphy is the high affinity of the applied radiopharmaceutical to the bone matrix. In multiphase skeletal scintigraphy, in contrast to 1-phase skeletal scintigraphy, imaging of the deposited radiopharmaceutical is performed with the gamma camera at different time points. In phase 1, radionuclide angiography (method of vascular imaging) is performed in the first 60 seconds after application of the radiopharmaceutical. This phase is also referred to as the perfusion phase and is used to image arterial blood flow. In phase 2, which is also referred to as the blood pool phase and occurs 5-10 minutes after the application has been performed, a change in vascular permeability can be detected, for example, in the context of inflammatory processes. The altered permeability is detected by an increased deposition of the radioactive pharmaceutical in the interstitium (space between organs or parts of organs). Meanwhile, in phase 3, the adsorption (accumulation) of the radiopharmaceutical is complete, so that after 2-4 hours, the third phase of multiphase skeletal scintigraphy, known as late uptake, can be completed. In phase 3, bone metabolism is now assessed. Areas with increased bone metabolism are referred to here as hotspots.
After the examination
At the end of the examination, patients should continue to consume plenty of fluids to achieve adequate elimination of the radioactive pharmacon to minimize radiation exposure.
Potential complications
Intravenous administration of the radiopharmaceutical may result in local vascular and nerve lesions (injuries). Radiation exposure from the radionuclide used is considered to be rather low. Nevertheless, the theoretical risk of a radiation-induced late malignancy (leukemia or carcinoma) is increased, so that a risk-benefit assessment should be performed. Due to reduced bladder emptying, radiation exposure can be significantly higher than in normal cases. Because of this, abnormalities of bladder emptying should be addressed, especially in the medical history.
