Radiation Risk of Medical Imaging for Adults and Children
What are the generally accepted indications for a medical imaging procedure? An appropriate imaging procedure is justified if it changes…Read more
Nuclear medicine bone scans are used to evaluate and localise bony pathologies. They are useful to assess the source of presumed bone pain, such as hip pain or foot pain.
Bone scans are often used as a complementary study to further investigate abnormalities found on other diagnostic images (X-ray, CT or MRI), and in the evaluation of primary bony malignancies and presumed metastatic disease.
Bone scans can be used to localise a lesion for biopsy.
Listed below are some common reasons to refer for a bone scan:
In general, nuclear medicine bone scans are not carried out on pregnant women. The patient benefit-versus-risk should be discussed with the nuclear medicine specialist. An alternative test, such as MRI, should be considered.
Breast-feeding/caring for children
Women who are breast-feeding will be asked to not breast-feed for a short duration.
Similarly, patients should avoid prolonged close contact with young children due to the small amount of radioactivity released for a while after the test. This link to the ‘What are the precautions for lactating patients who require a Nuclear Medicine procedure?’ question in the Nuclear Medicine referrers’ section contains a table that shows suggested times.
Weight limits depend on the equipment available at your local practice and the area that needs to be examined. Most scanning beds have weight limits ranging from 160 kg to 220 kg. Some imaging can be carried out with the patient sitting or standing, or on a hospital bed/trolley. Please discuss this with your local practice if necessary.
Recent nuclear medicine scan or treatment – patients requiring multiple nuclear medicine scans (for example a bone scan and a myocardial perfusion scan) need to have their procedures coordinated for the most effective schedule. Studies using technetium-based radiopharmaceuticals (the majority of bone scans) cannot be carried out within 24–48 hours of each other, as residual activity from one scan might affect the images obtained in the other.
Recent Iodine 131 (iodine therapy for thyroid disease) is a relative contraindication because of the long half-life of 131I (8 days) and high energy photons (360 keV), which obscure other pathologies; for example, cervical spine fracture. The recommended interval between 131I treatment and a bone scan depends on the dose given, and the patient’s uptake and retention pattern. It is recommended that if there is any suspicion of recent radio-iodine therapy, the patient be checked under the gamma camera for background activity BEFORE injection with 99mTc bone agent. It is difficult to predict the effect, so it is best for the referring doctor to contact the doctor supervising the radioiodine therapy for information about the likely residual activity.
There are minimal direct adverse effects.
There are infrequent reports of allergic reactions associated with bone scanning agents, and it is the pharmaceutical or preservatives that give the reaction, not the radioisotope.
Radiopharmaceuticals used in bone scans are not known to have any adverse interaction with food or medication. The patient should feel no effect from the injection of radiopharmaceutical, and can maintain normal activities between the early and delayed images.
The individual’s radiation dose is influenced by factors such as the actual dose administered, renal function and hydration levels. The effective dose is also influenced by ‘weighting’ factors assigned to patients of different ages and sex.
The ‘standard’ 70 kg patient with the recommended 740 MBq administered dose receives an estimated absorbed total body radiation dose of approximately 2–5 mSv.
See Radiation Risk of Medical Imaging for Adults and Children.
No specific post-procedural care is required.
If you have any queries, please discuss the patient with your nuclear medicine specialist. A nuclear medicine bone scan provides different information to other imaging studies, such as plain X-rays, CT or MRI scans (see Nuclear Medicine for a comparison between these procedures).
When investigating bone tumours or infections, sometimes other bone agents, such as gallium (67Ga) citrate, positron emission tomography (PET) imaging, 201Tl-thallous chloride or a white cell labelling agent, might be more useful. For example, 67Ga can provide more sensitive data than traditional bone scans in evaluating a response to the management of necrotising otitis externa.
Australian and New Zealand Society of Nuclear Medicine www.anzsnm.org.au
Society of nuclear medicine and molecular imaging www.snm.org
Page last modified on 26/7/2017.
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