A triple-phase bone scan is an imaging procedure that may be used to diagnose complex regional pain syndrome (CRPS). A triple-phase bone scan may also referred to as a three-phase bone scan, triphasic bone scan, or simply bone scan. Bone scans observe the patient’s bone to detect abnormalities such as issues with regular blood flow. Due to the difficult nature of diagnosing CRPS, a bone scan is typically not the only diagnostic test used.
Bone Scan Process
Before a bone scan, patients receive an intravenous (IV) injection of a special substance. This substance is radioactive with a tendency to concentrate in the patient’s bones. When imaging is taken, the radioactive tracer creates patterns that represent blood flow within the observed area. After the injection, the patient will lay on a table. A special gamma camera circles the body, taking several images of the bodily region being observed. The gamma camera is sensitive to the radiation emitted by the injected radioactive tracer. Therefore, the image results of the bone scan will show areas where the radioactive tracer has naturally concentrated within the patient’s bones.
Bone Scan Stages
A triple-phase bone scan earns its name because the process typically involves three stages. Images are typically taken at three separate stages after the radioactive substance is injected. Depending on the condition and the doctor’s goals, the times during which the scans are taken may vary.
Stage One: Flow
During the initial “flow” phase, the first scans are taken. Scans may be taken within the first few seconds of injection with the radioactive tracer. This phase is used to evaluate blood flow in the affected region by observing how the radioactive material initially flows through the observed bone tissue.
Stage Two: Blood Pool
The “blood pool” phase involves images taken roughly five minutes after the injection is given. In some cases, phase two occurs roughly five hours after the injection. Body regions with inflammation have dilated capillaries, which causes blood to become stagnant and “pool.” Observing abnormal blood pooling in phase two is therefore an indicator of inflammation, which can be a sign of CRPS.
Stage Three: Delayed
The “delayed” phase of a bone scan typically occurs roughly two to three hours after the injection. In some cases, phase three occurs up to 25 hours later. By this time, the majority of the radioactive tracer has been metabolized by the patient’s body. Doctors can then observe bone turnover (bone metabolism), or the amount of tissue that is regularly removed and replaced within the bone.
Bone Scan Uses
Bone scans are not only helpful for diagnosing CRPS. Bone scans may be used to diagnose a number of other conditions. The main benefits of the three distinct stages are that different conditions will typically manifest during different stages in the imagine process. For example, patients who may have metastatic bone disease are typically only tested after a few hours, as results within the first few seconds do not typically indicate symptoms of metastatic bone disease. Metastatic bone disease occurs when certain types of cancer develop in a patient’s organ and spread to the bone tissue.
Other uses for bone scans may include, but are not limited to, the following:
- Other metabolic disorders, such as osteomalacia and osteoporosis
- Cancerous and non-cancerous bone tumors
- Arthritis and other degenerative bone diseases
- Fractures that cannot be seen through standard X-rays
- Bone infections, such as osteomyelitis
- Observing and diagnosing unidentified bone pain
Bone Scan for Treatment Observation
In some cases, a bone scan may be used to monitor and observe the patient’s response to CRPS treatments. Bone scans may help doctors to see increased blood flow that occurs after treatment regimens such as a sympathetic block. A sympathetic block involves injection of a special anesthetic near the patient’s spine, which acts to block sympathetic pain-receptor nerves and improve blood flow.
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Huggler, Melchior, Rudolf Kissling, and Florian Brunner. “Bone metastases mimicking Complex Regional Pain Syndrome I: a case report.” Journal of Medical Case Reports 2 (2008): 345. Academic OneFile. Web. 1 Mar. 2014.
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