Nuclear Medicine

Nuclear medicine imaging uses small amounts of radioactive materials called radiotracers that are typically injected into the bloodstream, inhaled or swallowed. The radiotracer travels through the area being examined and gives off energy in the form of gamma rays which are detected by a special camera and a computer to create images of the inside of your body.

Nuclear medicine imaging provides unique information that often cannot be obtained using other imaging procedures and offers the potential to identify disease in its earliest stages.

Tell your doctor if there's a possibility you are pregnant or if you are breastfeeding and discuss any recent illnesses, medical conditions, allergies and medications you're taking. Depending
on the type of exam, your doctor will instruct you on what you may eat or drink beforehand. Leave jewellery at home and wear loose, comfortable clothing. You may be asked to wear a gown.

WHAT IS GENERAL NUCLEAR MEDICINE?

Nuclear medicine imaging uses small amounts of radioactive material to diagnose, evaluate or treat a variety of diseases. These include many types of cancers, heart disease, gastrointestinal, endocrine or neurological disorders and other abnormalities. Because nuclear medicine exams can pinpoint molecular activity, they have the potential to identify disease in its earliest stages. They can also show whether a patient is responding to treatment.

DIAGNOSIS

Nuclear medicine imaging procedures are non-invasive. With the exception of intravenous injections, they are usually painless. These tests use radioactive materials called radiopharmaceuticals or radiotracers to help doctors diagnose and evaluate medical conditions.

Depending on the type of exam, the radiotracer is injected, swallowed or inhaled as a gas. It eventually accumulates in the area of the body under examination. A special camera or imaging device detects radioactive emissions from the radiotracer. The camera or device produces pictures and provides molecular information.

THERAPY

Nuclear medicine also offers therapeutic procedures, such as radioactive iodine (I-131) therapy that use small amounts of radioactive material to treat cancer and other medical conditions affecting the thyroid gland.

WHAT ARE SOME COMMON USES OF THE PROCEDURE?

Physicians use nuclear medicine imaging procedures to visualize the structure and function of an organ, tissue, bone or system within the body.

HEART

• Visualize heart blood flow and function (such as a myocardial perfusion scan)
• Detect coronary artery disease and the extent of coronary stenosis
• Assess damage to the heart following a heart attack
• Evaluate treatment options such as bypass heart surgery and angioplasty
• Evaluate the results of revascularization (blood flow restoration) procedures
• Evaluate heart function before and after chemotherapy (MUGA)
• Identify the presence of cardiac amyloidosis

LUNGS

• Scan lungs for pulmonary embolism
• Assess differential lung function for lung reduction or transplant surgery
• Bones
• Evaluate bones for fractures, infection and arthritis
• Evaluate for metastatic bone disease
• Evaluate painful prosthetic joints
• Evaluate bone tumours
• Identify sites for biopsy

BRAIN

• Investigate abnormalities in the brain in patients with certain symptoms or disorders, such as seizures, memory loss and suspected abnormalities in blood flow
• Detect the early onset of neurological disorders such as Alzheimer's disease
• Assist in surgical planning and identify the areas of the brain that may be causing seizures
• Evaluate for abnormalities in a chemical in the brain involved in controlling movement in patients with suspected Parkinson's disease or related movement disorders.

OTHER SYSTEMS

• Identify gallbladder disease or post-operative complications
• Measure extent of liver cirrhosis
• Identify the site of bleeding into the bowel
• Evaluate lymphedema in arms or legs
• Evaluate fever of unknown origin or cause of sepsis/infection
• Assess thyroid function to detect an overactive or underactive thyroid or characterise nodules.
• Evaluate for hyperparathyroidism (overactive parathyroid gland)
• Evaluate rate of stomach emptying for digestive issues
• Evaluate tear ducts for blockages
• Assess kidneys for obstruction, post-surgical follow-up, scarring and overall function

NUCLEAR MEDICINE IS ALSO USED FOR IMAGING CANCER

• Stage cancer by determining the presence or spread of cancer in various parts of the body
• Localize sentinel lymph nodes before surgery in patients with breast cancer or skin and soft tissue tumors
• Plan treatment
• Evaluate response to therapy
• Detect the recurrence of cancer
• Detect rare tumors

HOW SHOULD I PREPARE?

You may wear a gown during the exam or be allowed to wear your own clothing.

Women should always tell their doctor and technologist if there is any possibility that they are pregnant or they are breastfeeding. Special instructions will be given to those women who are breastfeeding and any woman who is of child-bearing age will need to confirm they are not pregnant at the time of the scan by signing a consent form and possibly having a blood test. Tell the doctor and the technologist performing your exam about any medications you are taking, including vitamins and herbal supplements. List any allergies, recent illnesses and other medical conditions.

You will receive specific instructions based on the type of your scan. It is very important to follow these instructions to ensure your test can be performed accurately.

In some instances, certain medications or procedures may interfere with the examination ordered.

WHAT DOES THE EQUIPMENT LOOK LIKE?

The special camera and imaging techniques used in nuclear medicine is called a Gamma Camera or SPECT/CT camera.

The gamma camera detects radioactive energy that is emitted from the patient's body after they have been given the radiopharmaceutical tracer and converts it into an image. Unlike X-ray and CT, the gamma camera itself does not emit any radiation. The gamma camera is composed of radiation detectors, called gamma camera heads, which are encased in metal and plastic and most often shaped like a box, attached to a round circular donut shaped gantry. The patient lies on the examination table which slides in between two parallel gamma camera heads that are positioned above the patient. Sometimes, the gamma camera heads are oriented at a 90 degree angle and placed over the patient's body.

SPECT involves the rotation of the gamma camera heads around the patient's body to produce more detailed, three-dimensional images.

HOW DOES THE PROCDURE WORK?

Ordinary x-ray exams create an image by passing x-rays through the body. Nuclear medicine exams use a radioactive material called a radiopharmaceutical which is injected into the bloodstream, swallowed or inhaled as a gas. The material accumulates in the area of your body under examination, where it gives off a small amount of energy in the form of gamma rays. Special cameras detect this energy and, with the help of a computer, create pictures that offer details on the structure and function of organs and tissues.

Unlike other imaging techniques, nuclear medicine exams focus on processes within the body, such as rates of metabolism or levels of various other chemical activity. Areas of greater intensity, called "hot spots," indicate where large amounts of the radiotracer have accumulated and where there is a high level of chemical or metabolic activity. Less intense areas, or "cold spots," indicate a smaller concentration of radiotracer and less activity.

In radioactive iodine (I-131) therapy for thyroid disease, radioactive iodine (I-131) is swallowed as a capsule, absorbed into the bloodstream and accumulates in thyroid gland where it destroys cells within that organ as well as any other site of thyroid tissue in the body.

HOW IS THE PROCEDURE PERFORMED?

Nuclear medicine imaging is performed on outpatients and hospitalized patients.

Prior to the scan, a nurse or technologist will insert an intravenous (IV) catheter into a vein in your hand or arm and you will receive a small injection of the radiopharmaceutical. Some scan requires the patient to eat/drink or inhale the radiopharmaceutical, but the technologist will explain this to you.

Different types of radiopharmaceuticals travel at different speeds in your body so imaging can begin immediately, after several hours or several days depending on your test. The length of your test will be determined by the type of scan you are having in nuclear medicine.

When it is time for the imaging to begin, the camera or scanner will take a series of images. The camera may rotate around you or it may stay in one position and you may be asked to change positions in between images. While the camera is taking pictures, you will need to remain still for brief periods of time. In some cases, the camera may move very close to your body. This is necessary to obtain the best quality images. If you are claustrophobic, you should inform the technologist before your exam begins. You can always breathe and swallow normally while having your NM procedure as long as you remain still in position.

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.

When the examination is complete, you may be asked to wait until the technologist checks the images in case more images are needed. Sometimes, more images are obtained to clarify or better visualize certain areas or structures. The need for more images does not necessarily mean there was a problem with the exam or that something abnormal was found. It should not cause you concern.

If you had an intravenous (IV) line inserted for the procedure, it will usually be removed unless you are scheduled for another procedure that same day that requires an IV line.

For patients with thyroid disease who undergo radioactive iodine (I-131) therapy, which is most often an outpatient procedure, the radioactive iodine is swallowed, either in capsule or liquid form. Specific instructions are shared with the patient prior to their procedure.

WHAT WILL I EXPERIENCE DURING AND AFTER THE PROCEDURE?

Nuclear medicine injections are generally not associated with allergic or adverse reactions and the likelihood of you having a reaction to the radiopharmaceutical is extremely low.

When the radiotracer is given intravenously, you will feel a slight pin prick when the needle is inserted into your vein for the intravenous line. You may feel a cold sensation moving up your arm when the saline is injected. Generally, there are no other side effects.

When swallowed, the radiotracer has little or no taste. When inhaled, you should feel no differently than when breathing the air around you or holding your breath.

It is important to remain still during the exam. Nuclear imaging itself causes no pain. However, having to remain still or to stay in one particular position during imaging may cause discomfort. Unless your doctor tells you otherwise, you may resume your normal activities after your exam. A technologist, nurse or doctor will provide you with any necessary special instructions before you leave.

The small amount of radiotracer in your body will lose its radioactivity over time through the natural process of radioactive decay. It may also pass out of your body through your urine or stool during the first few hours or days following the test. Drink plenty of water to help flush the radioactive material out of your body.

WHO INTERPRETS THE RESULTS AND HOW DO I GET THEM?

A Nuclear Medicine physician will interpret the images and send a report to your referring physician.

WHAT ARE THE BENEFITS VS. RISKS?

BENEFITS

• Nuclear medicine examinations provide unique information—including details on the function and anatomy of body structures—that is often unattainable using other imaging procedures.
• Nuclear medicine scans provide the most useful diagnostic or treatment information for many diseases.
• A nuclear medicine scan is less expensive and may yield more precise information than exploratory surgery.
• Nuclear medicine offers the potential to identify disease in its earliest stage, often before symptoms occur or abnormalities can be detected with other diagnostic tests.

RISKS

• Because only a small dose of radiotracer is used, nuclear medicine exams have a relatively low radiation exposure. This is acceptable for diagnostic exams. Thus, the radiation risk is very low when compared with the potential benefits.
• Nuclear medicine diagnostic procedures have been used for more than five decades, and there are no known long-term adverse effects from such low-dose exposure.
• Allergic reactions to radiotracers are extremely rare and usually mild. Always tell the nuclear medicine personnel of any allergies you may have or other problems that may have occurred during a previous nuclear medicine exam.
• Women should always tell their doctor and radiology technologist if there is any possibility that they are pregnant or they are breastfeeding.

WHAT ARE THE LIMITATIONS OF GENERAL NUCLEAR MEDICINE?

Nuclear medicine procedures can be time consuming. It can take several hours for the radiotracer to accumulate in the area of interest, and imaging may take up to several hours to perform.

The image resolution of nuclear medicine images may not be as high as that of CT or MRI. However, nuclear medicine scans are more sensitive for a variety of indications, and the functional information they yield is often unobtainable by other imaging techniques.