General and Cardiac Nuclear Medicine
About General Nuclear Medicine
What is general nuclear medicine?
A nuclear medicine scan is a non-invasive imaging system that uses very small amounts of radioactive material to detect and treat a variety of diseases, including heart disease and many types of cancers. These imaging scans use radioactive materials called radiotracers.
A nuclear medicine scan consists of three phases: radiotracer administration, taking images, and image interpretation. Depending on the type of exam you are undergoing, the radiotracer is either injected into a vein, swallowed, or inhaled as a gas. It then travels through your blood and accumulates in the area being studied, giving off energy in the form of gamma rays. A device called a gamma camera detects the rays. From there, a computer measures the amount of radiotracer absorbed by your body and produces special pictures that offer details on the examined area.
What are some common uses of the procedure?
Physicians use nuclear medicine imaging scans to:
- analyze kidney function,
- visualize heart blood flow and function (such as a myocardial perfusion scan),
- scan lungs for respiratory and blood flow problems,
- identify inflammation in the gall bladder,
- evaluate bones for fractures, infection, arthritis, and tumours,
- determine the presence or spread of cancer in various parts of the body,
- identify bleeding into the bowel,
- locate the presence of infection,
- measure thyroid function to detect an overactive or underactive thyroid,
- investigate abnormalities in the brain, such as seizures, memory loss, and blood flow abnormalities, and
- localize the lymph nodes before surgery in patients with breast cancer or melanoma.
How should I prepare for a nuclear scan?
For most scans, you can eat and drink as normal. Jewellery and other metallic accessories should be removed prior to the exam because they may interfere with the procedure. Depending on the type of scan you are undergoing, you may be asked to wear a gown during the exam.
If there is any possibility that you are pregnant or if you are breastfeeding your baby, you should inform your physician and the technologist performing your exam.
You should also inform your physician and the technologist about any prescription or over-the-counter medications you are taking, including vitamins and herbal supplements. Also tell them if you have any allergies and let them know about recent illnesses or other medical conditions.
For certain scans, some preparation is required. You will receive specific instructions in your appointment letter.
How is the procedure performed?
You will be positioned on an examination table. If necessary, a nurse or technologist will insert an intravenous (IV) line into a vein in your hand or arm to administer the radiotracer.
It can take anywhere from several seconds to several days for the radiotracer to travel through your body and accumulate in the area that will be studied. As a result, imaging may be done immediately, a few hours later, or even several days after you have received the radioactive material. When it is time for the imaging to begin, a gamma camera will be positioned over you to take a series of images. You may be asked to change positions in between the taking of images. However, once you have changed position, you will need to lie very still, as any movement can affect the quality of the scan.
The length of time for nuclear medicine procedures varies greatly, depending on the type of exam. Actual scanning time for nuclear imaging exams can take from 20 minutes to several hours, and may be conducted over several days. If you have several hours to wait between taking the medicine and receiving the scan, then you may leave the department and return at the appropriate time.
When the examination is completed, you may be asked to wait until the technologist checks the images in case additional images are needed. Occasionally, additional images are obtained for clarification or better visualization of certain areas or structures. This does not necessarily mean that something abnormal was found, and should not be a cause of concern for you.
What will I experience during and after the procedure?
Most nuclear medicine procedures are painless and are rarely associated with significant discomfort or side effects.
If the radiotracer is given intravenously, you will feel a slight pin prick when the needle is inserted into your vein for the intravenous line. When swallowed, the radiotracer has little or no taste. When inhaled, you should feel no differently than when breathing room air or holding your breath. With some procedures, a catheter may be placed into your bladder, which may cause temporary discomfort.
Unless your physician tells you otherwise, you may resume your normal activities after your nuclear medicine scan. If any special instructions are necessary, a technologist, nurse, or physician will inform you before you leave the nuclear medicine department.
Radioisotopes decay with time, and may pass out of your body through your urine or stool during the first few hours or days following the test. You may be instructed to take special precautions after urinating, to flush the toilet twice and to wash your hands thoroughly. You should also drink plenty of water to help flush the radioactive material out of your body, as instructed by the nuclear medicine personnel.
Who interprets the results and how do I get them?
A radiologist who has specialized training in nuclear medicine will interpret the images and forward a report to your referring physician.
About Cardiac Nuclear Medicine
What is cardiac nuclear medicine?
Cardiac nuclear medicine is a diagnostic imaging procedure that uses small amounts of radioactive materials to provide pictures of the structure and function of the heart.
What are some common uses of the procedure?
Cardiac nuclear medicine imaging is performed:
- to visualize blood flow patterns to the heart walls (called a myocardial perfusion scan),
- to evaluate the presence and extent of suspected or known coronary artery disease,
- to determine the extent of injury to the heart following a heart attack, or myocardial infarction,
- to evaluate the results of bypass surgery or other revascularization procedures designed to restore blood supply to the heart, and
- in conjunction with an electrocardiogram (ECG), to evaluate heart wall movement and overall heart function with a technique called cardiac gating.
How does the procedure work?
Nuclear medicine procedures use a radioactive compound called a radiotracer, which is injected into your bloodstream, swallowed, or inhaled as a gas. This compound will then accumulate in the parts of your heart with good blood flow and give off gamma rays. A gamma camera detects these rays. From there, a computer will construct images of the heart based on the detected gamma rays.
Problems with blood flow to the heart are best evaluated by determining changes in blood flow. To that end, you will undergo a stress test—most commonly through physical exercise such as walking a treadmill or pedalling a stationary bicycle for a few minutes—to make your heart work harder than normal. While you exercise, your blood pressure will be frequently measured. When blood flow to the heart has reached its peak, you will be given the radiotracer through an IV leading into your arm. About a minute later, you will stop exercising and you will be positioned on the examination table.
Approximately one half-hour later, the imaging will begin. Once the technologist has positioned the gamma camera, it will move slowly in an arc over your chest.
This same heart scan will be performed at another time, when you have not been exercising (called a resting scan). Images of your heart obtained after you exercise will be compared with images of your resting heart. If you are unable to use a treadmill or stationary bicycle, you will not exercise. Instead, you will be given a drug that increases blood flow to the heart.
How long will it take?
Actual scanning time for each heart scan varies from 15 to 30 minutes, depending on the type of scanner used. Total time in the nuclear medicine department will be approximately two to four hours.
When the examination is completed, you may be asked to wait until the technologist checks the images. Occasionally, additional images are required for better visualization of certain areas or structures, but this does not necessarily mean that anything abnormal was found and should not be a concern for you.
How should I prepare?
You should avoid caffeine (coffee, tea, etc.) and smoking for 48 hours before the examination.
Also, do not eat or drink anything after midnight on the day of your procedure. You may, however, continue taking medications with small amounts of water, unless your physician says otherwise. If you take beta-blocker medication (Inderal, metoprolol, etc.) you should ask your physician about temporary discontinuation.
Let your physician know if you have any allergies or other medical conditions. Women should let their physician or technologist know if there is any possibility that they are pregnant or if they are breastfeeding their baby.
You should speak with your physician about the test if you have asthma or a chronic lung disease, problems with your knees or hips, or trouble keeping your balance; these problems may limit your ability to perform the exercise required for this procedure.
You may be asked to wear a hospital gown during the exam or you may be allowed to wear your own clothing. Jewellery and other metallic accessories should be left at home, if possible, or removed prior to the exam because they may interfere with the procedure.
What will I experience during and after the procedure?
Most nuclear medicine procedures are painless and are rarely associated with significant discomfort or side effects.
If the radiotracer is given intravenously, you will feel a slight pin prick when the needle is inserted into your vein for the intravenous line. When the radioactive material is injected into your arm, you may feel a cold sensation moving up your arm, but there are generally no other side effects.
You will be asked to exercise until you are either too tired to continue or become short of breath, or if you experience chest pain, leg pain, or other discomfort that causes you to want to stop.
If you are given a medication to increase blood flow because you are unable to exercise, the medication may induce a brief period of feeling anxious, dizzy, nauseous, shaky, or short of breath. You may also experience mild chest discomfort. Any symptoms that do develop typically resolve as soon as the infusion is complete. In rare instances, if the side effects of the medication make you too uncomfortable, other drugs can be given to stop the effects.
It is important that you remain still while the images are being recorded, otherwise the quality of the scan can be affected.
Unless your physician tells you otherwise, you may resume your normal activities after your nuclear medicine scan. If any special instructions are necessary, a technologist, nurse, or physician will inform you of them before you leave the nuclear medicine department.
Through the natural process of radioactive decay, the small amount of radiotracer in your body will lose its radioactivity over time. It may pass out of your body through your urine or stool during the first few hours or days following the test. You may be instructed to take special precautions after urinating, to flush the toilet twice and to wash your hands thoroughly. You should also drink plenty of water to help flush the radioactive material out of your body, as instructed by the nuclear medicine personnel.
Who interprets the results and how do I get them?
A radiologist who has specialized training in nuclear medicine will interpret the images and forward a report to your referring physician.
