Nuclear medicine is a medical specialty involving the application of radioactive substances in the diagnosis and treatment of disease. Nuclear medicine determines the cause of a medical problem based on the function of the organ, tissue or bone. This is how nuclear medicine differs from an x-ray, ultrasound or any other diagnostic test that determines the presence of disease based on structural appearance. In some diseases, nuclear medicine studies can identify medical problems at an earlier stage than other diagnostic tests.
Although we don’t think much about it, everyone is continually exposed to radiation from natural and manmade sources. For most people, natural background radiation from space, rocks, soil, and even carbon and potassium atoms in his or her own body, accounts for 85 percent of their annual exposure. Additional exposure is received from consumer products such as household smoke detectors, color television sets, and luminous dial clocks. The remainder is from x-rays and radioactive materials used for medical diagnosis and therapy. With most nuclear medicine procedures, the patient receives about the same amount of radiation as that acquired in a few months of normal living.
Because of their special training, the nuclear medicine physician is able to select the most appropriate examination for the patient’s particular medical problem, thereby avoiding any unnecessary radiation exposure.
- visualize hear 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 procedures
- detect heart transplant rejection
- evaluate heart function before and after chemotherapy (MUGA)
- scan lungs for respiratory and blood flow problems
- assess differential lung function for lung reduction or transplant surgery
- detect lung transplant rejection
- evaluate bones for fractures, infection and arthritis
- evaluate for metastatic bone disease
- evaluate painful prosthetic joints
- evaluate bone tumors
- identify sites for biopsy
- identify inflammation or abnormal function of the gallbladder
- identify bleeding into the bowel
- assess post-operative complications of gallbladder surgery
- evaluate lymphedema
- evaluate fever of unknown origin
- locate the presence of infection
- measure thyroid function to detect an overactive or underactive thyroid
- help diagnose hyperthyroidism and blood cell disorders
- evaluate for hyperparathyroidism
- evaluate stomach emptying
- evaluate spinal fluid flow and potential spinal fluid leaks
In adults and children, nuclear medicine is also used to:
- 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 of the pancreas and adrenal glands
- analyze native and transplant kidney function
- detect urinary tract obstruction
- evaluate for hypertension related to the kidney arteries
- evaluate kidneys for infection versus scar
- detect and follow-up urinary reflux
In children, nuclear medicine is also used to:
- investigate abnormalities in the esophagus, such as esophageal reflux or motility disorders
In most cases you will be lying on your back, but in some cases you might be seated or placed in a specific position. The machine is not noisy and the detectors do not totally cover your body, so you will not have a feeling of confinement. The person in charge of the examination will be around and available to help you at any time. You will have the opportunity to communicate with this person during the entire examination. Certain examinations require successive images to be taken at various times following the injection.
Women should always inform their physician or technologist if there is any possibility that they are pregnant or if they are breastfeeding. You should inform your physician and the technologist performing your exam of any medications you are taking, including vitamins and herbal supplements. You should also inform them if you have any allergies and about recent illnesses or other medical conditions.
You may be asked to wear a gown during the exam or you may be allowed to wear your own clothing. Jewelry and other metallic accessories should be left at home if possible, or removed prior to the exam because they may interfere with the procedure.
It can take anywhere from several seconds to several days for the radiotracer to travel through your body and accumulate in the organ or area being 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, 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 will 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. If a probe is used, this small hand-held device will be passed over the area of the body being studied to measure levels of radioactivity. Other nuclear medicine tests measure radioactivity levels in blood, urine or breath.
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.
When the examination is completed, you may be asked to wait until the technologist checks the images in case additional images are needed. Occasionally, more images are obtained for clarification or better visualization of certain areas or structures. The need for additional images does not necessarily mean there was a problem with the exam or that something abnormal was found, and should not be a cause of concern for you.
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. 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.
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.
It is important that you remain still while the images are being recorded. Though nuclear imaging itself causes no pain, there may be some discomfort from having to remain still or to stay in one particular position during imaging. Unless your physician tells you otherwise, you may resume your normal activities after your nuclear medicine scan. If any special instructions are necessary, you will be informed by a technologist or physician 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 also pass out of your body through your urine or stool during the first few hours or days following the test. You should also drink plenty of water to help flush the radioactive material out of your body as instructed by the nuclear medicine personnel.
You will be informed as to how often and when you will need to return to the nuclear medicine department for further procedures.