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Nuclear medicine imaging uses radioactive material and a gamma camera to help diagnose a variety of conditions, such as osteomyelitis, bone cancer, rheumatoid arthritis, and more.
Bone scans and myocardial perfusion imaging (MPI) are the most common types of nuclear medicine imaging. These exams can look at the whole body or a specific area of concern using a small amount of radioactive material (called a radiopharmaceutical) injected into an arm vein that travels through your bloodstream into your bones, or to the heart in the case of MPI.
A gamma camera detects the radiation, and a computer interprets it to create images of the areas of concern. These images can indicate how much of the radiopharmaceutical is absorbed by the area of concern or how it reacts in the organ or tissue. This in turn provides information about how well the organ or tissue is functioning.
The radiopharmaceutical is excreted from the body through your urine – 24 hours after your exam 95% of the radiopharmaceutical will have decayed within the body. Keeping hydrated and voiding frequently will help eliminate it from your body.
Due to the use of radiation in these types of exams, it’s important to note the following:
Nuclear medicine imaging involves a small dose of ionizing radiation from the radiopharmaceutical injected into your vein, and also from the CT scan during a bone scan with SPECT/CT imaging. CT imaging is a form of X-ray and, depending on the area being scanned, the exposure to radiation from this scan can be slightly higher than that of standard X-rays, but the associated risk is still small. Overall, the radiation exposure from a bone scan with SPECT/CT is about the equivalent of exposure to the earth’s natural background radiation over two years. In most cases, the benefits, such as the early detection of a serious illness, outweigh the small increased risk from radiation exposure.
Mayfair Diagnostics complies with policies and has procedures in place for nuclear medicine radiation safety, including a Radiation Safety Officer who ensures we follow all policies and procedures.
All exposures of radiation are held to the standard of ALARA (as low as reasonably achievable) for all medical imaging exams that involve radiation. This means that no or low exposure is best, and the risk-benefit ratio should always be considered.
Radiation dosage is measured in millisieverts (mSv). When talking about the risks of radiation exposure, we are referring to possible side effects, such as the chance of developing cancer later in life. If medical imaging is recommended, your doctor will consider the benefits of an accurate diagnosis and compare it to the small risk of radiation exposure. We created this Radiation Dose Examples infosheet to illustrate how radiation from medical imaging compares to other sources of radiation exposure.
For bone scans or bone scans with SPECT/CT, you will have two separate appointments booked on the same day. The first appointment will take approximately 15 minutes. During this time, a small amount of radioactive material is injected, usually into an arm vein. Over the next couple of hours, the material will move from the bloodstream to the bones. A gamma camera is used to look at how the injection moves through the bloodstream into the area of concern, taking pictures in a “planar” format.
During the second part of the appointment, imaging will be performed without any additional injections, to document uptake in the bones. It will take approximately 30-45 minutes. You will be asked to hold as still as possible, while breathing normally – movement can blur the images and make them more difficult to interpret. If required, additional SPECT/CT imaging may also be performed towards the end of this appointment.
SPECT/CT (single photon emission computed tomography/computed tomography) imaging combines two imaging types to help localize the area of abnormal activity that may be present on the planar bone scan image. For the “SPECT” part, the nuclear medicine gamma camera rotates 360 degrees around the body and acquires measurements of the radiation being emitted, which the system reconstructs into a 3D image. No additional radiation is emitted for the SPECT portion. For the “CT” portion, a low-dose CT image is taken, similar to those from a classic diagnostic CT scan, but using limited radiation. In this case, they are fused electronically with the SPECT images to get the SPECT/CT image.
Watch the video: What happens during a bone scan?
Myocardial perfusion imaging (MPI) is a two-part exam, performed over two days. On the first day, you will need to fast for four hours prior to the appointment and then the radiopharmaceutical is injected into your arm vein while seated. You will rest for about 45 minutes and will even have a small snack, then you will be positioned so that the gamma camera can take images that show the blood flow to your heart while resting. The appointment takes about 1.5-2 hours, and afterwards you may return to your daily activities.
On the second day, you will again need to fast for four hours prior to the appointment. You will also need to wear exercise clothing for the exercise or stress portion of this study. Electrodes will be placed on your chest and an intravenous (IV) line is inserted into your arm. After an internal medicine physician discusses your medical history and symptoms with you, you will be asked to walk on a treadmill as it gradually increases in speed and inclination. Once your heart rate reaches a certain point (calculated according to your age) and you feel tired, the radiopharmaceutical is injected into the IV. You will continue walking for approximately one minute to circulate the radiopharmaceutical to your heart muscle before ceasing exercise.
After the injection, you will rest for about 20 minutes and then lie under the nuclear medicine gamma camera for another set of images. These images show the blood flow to your heart muscle at stress. The appointment takes 2-4 hours, and afterwards you can return to your daily activities. Please note, it you’re unable to exercise on the treadmill, you can be given a medication (through your IV) that dilates your heart’s arteries to “mimic” a stress condition.
Watch the video: What to expect during myocardial perfusion imaging
These exams are covered under your Alberta Health Care Insurance Plan and must be requested by a health care practitioner. To determine whether it’s appropriate for you, your doctor will often review your medical and family history, risk factors, how long symptoms have been present, and how they affect daily activities. If this exam is indicated as a best next course of action, your doctor will provide you with a requisition and the appointment can be booked.
Bone scans (both with and without SPECT/CT) are performed at our Castleridge, Mahogany Village, Market Mall, Mayfair Place, and Sunpark locations. MPI is only offered at our Mayfair Place location. For more information visit our services page.
REFERENCES
Centres for Disease Control and Prevention (2021) “Radiation in Healthcare: Nuclear Medicine.” www.cdc.gov. Accessed January 23, 2024.
Mount Sinai (2023) “Radiology: Frequently Asked Questions.” www.mountsinai.org. Accessed January 23, 2024.
Radiation Safety Institute of Canada (2023) “Patient Radiation Exposure in Nuclear Medicine Imaging.” radiationsafety.ca. Accessed January 23, 2024.
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