12/18/2013 03:42 PM EST
Source: American College of Radiology, Radiological Society of North America
Related MedlinePlus Page: MRI Scans
Related MedlinePlus Page: MRI Scans
Nuclear Medicine - Hepatobiliary
What is Hepatobiliary Imaging?
Hepatobiliary imaging is a type of nuclear medicine imaging that helps evaluate the liver, gallbladder and the ducts that are part of the biliary system.
Nuclear medicine is a branch of medical imaging that uses small amounts of radioactive material to diagnose and determine the severity of or treat a variety of diseases, including many types of cancers, heart disease, gastrointestinal, endocrine, neurological disorders and other abnormalities within the body. Because nuclear medicine procedures are able to pinpoint molecular activity within the body, they offer the potential to identify disease in its earliest stages as well as a patient’s immediate response to therapeutic interventions.
Nuclear medicine imaging procedures are noninvasive and, with the exception of intravenous injections, are usually painless medical tests that help physicians diagnose and evaluate medical conditions. These imaging scans use radioactive materials calledradiopharmaceuticals or radiotracers.
Depending on the type of nuclear medicine exam, the radiotracer is either injected into the body, swallowed or inhaled as a gas and eventually accumulates in the organ or area of the body being examined. Radioactive emissions from the radiotracer are detected by a special camera or imaging device that produces pictures and provides molecular information.
What are some common uses of the procedure?
Physicians perform hepatobiliary imaging to evaluate disorders that affect liver cells, the ducts of the biliary system and the gallbladder.
Hepatobiliary imaging is also used to help diagnose symptoms such as:
- abdominal pain that may be caused by a sudden inflammation of the gallbladder called cholecystitis
- pain or fever following surgery on the gallbladder or the upper gastrointestinal tract
- biliary atresia in newborns, a blockage in the ducts that carry bile from the liver to the gallbladder
How should I prepare?
You may be asked to wear a gown during the exam or you may be allowed to wear your own clothing.
Women should always inform their physician or technologist if there is any possibility that they are pregnant or if they are breastfeeding. See the Safety page for more information about pregnancy and breastfeeding related to nuclear medicine imaging.
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.
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.
You should not eat or drink for at least four hours before your exam. You should not have tests that use barium for 48 hours before hepatobiliary imaging.
What does the equipment look like?
Nuclear medicine procedures are performed using either single photon emission computed tomography (SPECT) or positron emission tomography (PET).
The gamma camera, which is encased in metal, is capable of detecting radiation and taking pictures from different angles. A gamma camera does not emit any radiation. It may be suspended over the examination table or it may be beneath the table. Often, gamma cameras are dual-headed with one camera next to the other at a 90 degree angle. In some imaging centers, the gamma camera is located beneath the exam table and out of view. The camera may be located within a large, doughnut-shaped scanner similar in appearance to a computed tomography (CT) scanner.
SPECT uses a gamma camera that rotates around the body to produce more detailed, three-dimensional images.
How does the procedure work?
With ordinary x-ray examinations, an image is made by passing x-rays through the body from an outside source. In contrast, nuclear medicine procedures use a radioactive material called a radiopharmaceutical or radiotracer, which is injected into your bloodstream, swallowed or inhaled as a gas. This radioactive material accumulates in the organ or area of your body being examined, where it gives off a small amount of energy in the form of gamma rays. A gamma camera, PET scanner, or probe detects this energy and with the help of a computer creates pictures offering details on both the structure and function of organs and tissues in your body.
How is the procedure performed?
Nuclear medicine imaging is usually performed on an outpatient basis, but is often performed on hospitalized patients as well.
You will be positioned on an examination table. If necessary, a nurse or technologist will insert an intravenous (IV) catheter into a vein in your hand or arm.
Depending on the type of nuclear medicine exam you are undergoing, the dose of radiotracer is then injected intravenously, swallowed or inhaled as a gas.
Pediatric patients are given a smaller dose of radiotracer.
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.
After the initial series of images is taken, you may be given a medication that causes your gallbladder to empty. Additional images will be taken as your gallbladder empties.
Hepatobiliary imaging is usually completed within one to four hours. Occasionally, patients may need to return for additional imaging up to 24 hours later.
If you had an intravenous line inserted for the procedure, it will usually be removed unless you are scheduled for an additional procedure that same day that requires an intravenous line.
What will I experience during and after the procedure?
Except for intravenous injections, most nuclear medicine procedures are painless and are rarely associated with significant discomfort or side effects.
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.
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.
If you receive a medication that causes your gallbladder to empty, you may experience slight abdominal discomfort or nausea, but it should pass within a few minutes. Although imaging may be performed over a period of several hours, you may not be on the imaging table the entire time.
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, nurse 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.
Who interprets the results and how do I get them?
A radiologist or other physician who has specialized training in nuclear medicine will interpret the images and forward a report to your referring physician.
What are the benefits vs. risks?
- Nuclear medicine examinations offer information that is unique—including details on both function and structure—and often unattainable using other imaging procedures.
- For many diseases, nuclear medicine scans yield the most useful information needed to make a diagnosis or to determine appropriate treatment, if any.
- Nuclear medicine is less expensive and may yield more precise information than exploratory surgery.
- Because the doses of radiotracer administered are small, diagnostic nuclear medicine procedures result in relatively low radiation exposure to the patient, acceptable for diagnostic exams. Thus, the radiation risk is very low 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.
- The risks of the treatment are always weighed against the potential benefits for nuclear medicine therapeutic procedures. You will be informed of all significant risks prior to the treatment and have an opportunity to ask questions.
- Allergic reactions to radiopharmaceuticals may occur but are extremely rare and are usually mild. Nevertheless, you should inform the nuclear medicine personnel of any allergies you may have or other problems that may have occurred during a previous nuclear medicine exam.
- Injection of the radiotracer may cause slight pain and redness which should rapidly resolve.
- Women should always inform their physician or radiology technologist if there is any possibility that they are pregnant or if they are breastfeeding. See the Safety page for more information about pregnancy, breastfeeding and nuclear medicine exams.
What are the limitations of Hepatobiliary Imaging?
Nuclear medicine procedures can be time consuming. It can take hours to days for the radiotracer to accumulate in the part of the body under study and imaging may take up to several hours to perform, though in some cases, newer equipment is available that can substantially shorten the procedure time.
The resolution of structures of the body with nuclear medicine may not be as high as with other imaging techniques, such as CT or MRI. However, nuclear medicine scans are more sensitive than other techniques for a variety of indications, and the functional information gained from nuclear medicine exams is often unobtainable by other imaging techniques.