Norm of Bone Scan (Bone Scintigraphy)
Even concentration of radioactive isotope throughout the osseous tissues.
Usage of Bone Scan (Bone Scintigraphy)
Detection, staging, and evaluation of osseous metastatic disease. Detection of pathologic conditions that cause increased uptake, including acute hematogenous osteomyelitis (AHOM), aseptic necrosis, bone fractures, bone infarction, bone infection, bone metastasis, bone necrosis, bone tumors, bone trauma, osseous metastatic disease, osteoarthritis, osteoid osteoma, osteomyelitis, Paget's disease, renal osteodystrophy, temporomandibular joint disease, transient osteoporosis, tuberculosis, and soft-tissue calcification. Differentiation of cellulitis from osteomyelitis. Monitoring of degenerative bone disorders, bone grafts, and prosthetic joint replacements. Aids in the selection of a biopsy site in the abnormal bone, in the evaluation of the effectiveness of arthritides, and in suspected abuse of a child.
Description of Bone Scan (Bone Scintigraphy)
A nuclear medicine radioactive isotope study that will show bone changes from a few weeks up to 6 months before conventional radiographs will show such changes. Diagnostic sensitivity is 95.2% and accuracy 78.7%. The radioactive isotope 99mTc-diphosphonate (technetium diphosphate) is administered intravenously. As the entire body is scanned, images from the low-level radioactive isotope in the bony tissues are recorded on paper or film, creating two-dimensional images of the skeletal outlines. The epiphyses of growing bones or new bone formation shows up as areas of high metabolism, or concentration, and are called “hot spots,” whereas areas of low concentration, associated with ischemia or tumor displacement, are referred to as “cold spots.” Increased uptake of the isotope by bone tissue indicates an abnormality in that area. There is a phenomenon called bone scan flare, which shows an increase in bone lesions with improvement while the client is receiving chemotherapy for either breast or small-cell lung or non–small-cell lung cancers. Bone scintigraphy is especially important in detecting metastatic tumors and fractures not immediately seen on radiograph, especially in the spine, ribs, face, and small bones of the hands and feet. This test is invaluable in evaluating clients with osteomyelitis. Its disadvantage is that when it shows an abnormality, it is nonspecific as to the pathologic process present.
Professional Considerations of Bone Scan (Bone Scintigraphy)
Consent form NOT required.
Hematoma at injection site.
Clients who cannot lie still for an extended period of time.
During pregnancy, risks of cumulative radiation exposure to the fetus from this and other previous or future imaging studies must be weighed against the benefits of the procedure. Although formal limits for client exposure are relative to this risk-benefit comparison, the United States Nuclear Regulatory Commission requires that the cumulative dose equivalent to an embryo/ fetus from occupational exposure not exceed 0.5 rem (5 mSv). Radiation dose to the fetus is proportional to the distance of the anatomy studied from the abdomen and decreases as pregnancy progresses. For pregnant clients, consult the radiologist/radiology department to obtain estimated fetal radiation exposure from this procedure.
- The client should not drink unnecessary fluids for 2–4 hours.
- Obtain an alcohol wipe, a tourniquet, a needle, a syringe, and a radioactive isotope.
- Remove all jewelry and metal objects.
- Sedatives are used only if the client is unable to lie still for the scan.
- The client should void before the intravenous radioisotope is administered.
- 99mTc-diphosphonate (technetium diphosphate) is administered intravenously into a vein of the arm.
- During the next 2–3 hours, the client must drink 32 ounces of water to promote renal filtering of excess tracer.
- The client should void just before the scan to remove any tracer not picked up by bone that was filtered by the kidney.
- For 1–3 hours after the injection, the client is placed in a supine position on the scanning table and instructed to lie still while the entire body is scanned and two-dimensional images of the skeleton are recorded.
- If deep sedation was used, follow institutional protocol for postsedation monitoring. Typical monitoring includes continuous ECG monitoring and pulse oximetry, with continual assessments (every 5–15 minutes) of airway, vital signs, and neurologic status until the client is lying quietly awake, is breathing independently, and responds appropriately to commands spoken in a normal tone. The client should not operate a motor vehicle for 24 hours after receiving sedation.
- Check the injection site for redness or swelling. If a hematoma is present, apply warm soaks.
- Encourage oral fluid intake.
Client and Family Teaching
- The radioisotope delivers less radiation than a regular radiograph, and the scanning machine is detecting the injected isotope, rather than exposing the client to radiation.
- Do not drink fluids for 4 hours before the scan.
- The radioisotope will be injected intravenously before the scan.
- Most of the radioactive material will be excreted from the body through urine and stool within 48 hours and is not harmful to other people nearby.
- Results are normally available within 24 hours.
- In women who are breast-feeding, formula should be substituted for breast milk for 1 or more days after the procedure.
Factors That Affect Results
- Failure to void before the test may cause an overdistended urinary bladder, which can interfere with pelvic imaging.
- Health care professionals working in a nuclear medicine area must follow federal standards set by the Nuclear Regulatory Commission. These standards include precautions for handling the radioactive material and monitoring of potential radiation exposure.
- 32% of bone scans give false-positive results for persons with T1 or T2 breast cancer.
- Routine bone scans are not warranted in clients with squamous cell carcinoma of the head and neck.