Radionuclide imaging is a type of imaging technique that allows physicians to obtain clear images of various parts of the body, including digestive system organs. To obtain the images generated by this technique, tiny amounts of radioactive materials (called “tracers”) are introduced into the patient’s body. The tracers emit a type of energy called gamma rays, which are detected by special devices.

The amount of radiation received during radionuclide imaging is generally considered minimal and safe. For most people, the tracer used in the procedure is harmless and is flushed from the body via urination after the test. Patients are often encouraged to drink plenty of fluids and urinate frequently to help flush the tracer from the body.

Radionuclide imaging can be used to help diagnose various disorders of the digestive system. These include:

• Gallbladder disorders. A cholescintigraphy – also known as a HIDA scan – may reveal acute or chronic gallbladder inflammation and obstruction of the bile ducts.
  
  
• Gastrointestinal bleeding. A radioactive material is injected into a patient to help highlight organs and reveal abnormalities that might be a sign of gastrointestinal (GI) bleeding, particularly in the lower GI tract.
  
  
• Gastroparesis. A gastric emptying study helps the physician examine the rate of emptying from the stomach. Scintigraphic gastric emptying is a different test that allows the physician to observe whether or not poor relaxation of the stomach causes delayed stomach emptying. 

Radionuclide imaging can also be used to detect the source of unexplained pain and a number of conditions and diseases affecting the skeletal system, including bone fractures, arthritis (inflammation of the joints), infections, tumors and others.

Radionuclide imaging is not recommended for certain types of patients, including pregnant or nursing women. Patients should inform their physician of any medications they are taking and any recent testing using a contrast medium (dye) that has been injected or taken orally or rectally. Patients will receive the radioactive material either orally or by injection into a vein anywhere from a few minutes to several days before the test.

Radionuclide imaging is typically performed on an outpatient basis. However, the equipment necessary to perform the test usually requires it to take place in a hospital’s radiology or nuclear medicine department.

During the test, patients are asked to lie on a table (gantry) while a scanner moves over them. Although the test is not generally painful, some patients may become uncomfortable after lying on the table for a long period.

There are no restrictions on daily routine following the test. However, it is recommended that patients drink plenty of fluids to flush the tracer from the body. The radioactive materials in the body release their energy and decay into non-radioactive atoms within a few hours to a few days. Test results are usually available within a few days of the scan and additional tests or appropriate treatment will follow, if necessary.

Radionuclide imaging is a visual scanning technique that uses radioactive materials called tracers (radionuclides) to reveal images of internal organs, including those in the digestive tract. These tracers accumulate in certain organs and tissues and emit gamma rays, which are detected by a special camera. A computer then converts this information into clear two- and three-dimensional images of the body. In some cases, extra color is added to enhance clarity of the images.

Analysis of radionuclide images helps physicians diagnose disease. The images are usually analyzed by radiologists (physicians who specialize in the use of radiant energy for diagnostic purposes) or other nuclear medicine expert. The information is then sent to the patient’s physician, and a treatment plan is formulated.

Radionuclide imaging can help diagnose several disorders of the digestive system. For example, these scans can be used to detect abnormalities in the body’s ability to digest food or to reveal damage to organs that may be the source of gastrointestinal bleeding. These tests also are effective at revealing tumors in the digestive tract.

Other conditions detected by radionuclide imaging include:

• Abnormalities in size, shape or position of organs
  
  
• Cancer, both in its site of origin and cancer that has spread to other areas
  
  
• Coronary and vascular problems
  
  
• Thyroid disorders
  
  
• Neurological disorders
  
  
• Blood clots (embolism)
  
  
• Lung, kidney or bladder malfunction
  
  
• Sites of seizures (epilepsy) in the brain
  
  
• Parkinson’s disease (a brain disorder characterized by shaking and difficulty with walking, movement and coordination)
  
  
• Alzheimer’s disease (a degenerative brain disease affecting memory, thought and behavior)

Additionally, radionuclide imaging allows physicians to determine how well newly transplanted organs are functioning. For example, a test known as a cholescintigraphy can help determine whether there is rejection of a transplanted liver.

Radionuclide imaging is often described as being the opposite of an x-ray – instead of radioactive material being directed into the body from the outside, the radioactivity comes from the inside and is projected outward. Although some patients worry about the potentially harmful effects of radioactivity, dosage levels are so low that the risk is minimal for most patients.

Radionuclide imaging can be used to help diagnose various disorders of the digestive system. These include:

• Crohn’s disease. A form of inflammatory bowel disease that causes inflammation of the digestive tract, usually in the small intestine.  A white blood cell scan in which the cells are tagged with radioactive material can be useful in defining the location and extent of the disease.
  
  
• Gallbladder and bile duct disorders. A cholescintigraphy – also known as a HIDA scan – may reveal acute or chronic gallbladder inflammation (cholecystitis) and obstruction of the bile ducts. The patient receives an injection of a nuclear contrast material and a special camera reveals whether bile is emptied from the gallbladder at a lower-than-normal level, which may indicate improper functioning of the gallbladder. In some cases, the contrast material may not reach the gallbladder at all, which may indicate that a gallstone is blocking the opening of the gallbladder or cystic duct.
  
  
• Liver disease. When the radioactive imaging material is injected and filters to the liver, it can help evaluate abnormalities such as cysts or tumors and damage caused by diseases such as cirrhosis and hepatitis.
  
  
• Gastrointestinal bleeding. A radioactive material is injected into a patient to help highlight organs and reveal abnormalities that might be a sign of GI bleeding, particularly in the lower GI tract.
  
  
• Gastroparesis. A condition in which the stomach does not contract normally, which prevents food from being digested.  A couple of radionuclide tests can be used to diagnose this condition. In a gastric emptying study, the patient consumes a meal of egg or oatmeal that contains a small bit of radioactive material. This material is revealed during digestion via a scanning technique that helps the physician examine the rate of emptying from the stomach. Scintigraphic gastric emptying involves the use of radioactive material that is taken up by the stomach lining and used to measure the volume of the stomach. Images are taken both before and after the patient  consumes a nutrient drink. The physician observes whether or not poor relaxation of the stomach causes delayed stomach emptying.
  
  
• Gastroesophageal reflux disease (GERD). A condition in which food and fluids from the stomach back up (reflux) into the esophagus. Radionuclide imaging may be used to measure the rate at which the esophagus empties in patients who experience regurgitation and heartburn that exceeds one month in duration.
  
  
• Zollinger-Ellison syndrome (ZES). This rare condition involves the formation of tumors in the pancreas or upper part of the small intestine, known as the duodenum. Radioactive substances injected into the patient can reveal tumors when the body is imaged by a gamma camera.

Radionuclide imaging is not recommended for certain types of patients, including pregnant or nursing women. Fetuses and infants are still undergoing organ development, which makes them more sensitive to the effects of radiation.

Patients should inform their physician of any medications they are taking that may interfere with the radionuclides used in the scan. Patients should also report any recent testing using a contrast medium (dye) that has been injected or taken orally or rectally.

The preparation necessary before radionuclide imaging will vary depending on the type of test to be used and the tissue to be studied. For example, patients preparing to undergo gallbladder, liver or thyroid scans are typically instructed to refrain from eating or drinking for two to 12 hours before testing. Other patients may be asked to take a laxative or have an enema (a colon cleansing procedure) prior to testing, or to avoid taking certain medications beforehand. Patients should consult their physician about necessary preparatory steps.

Patients will receive the radioactive material either orally (in food or beverage form) or by injection into a vein anywhere from a few minutes to several days before the test. In some cases (e.g., to detect the origin of rectal bleeding), a blood sample may be drawn and mixed with the radionuclide before being injected into the patient. Just prior to testing, patients should remove jewelry, dentures and any other metal that can block gamma rays. Patients may also be asked to remove articles of clothing and change into a hospital gown for the test.

Radionuclide imaging is typically performed on an outpatient basis. However, the equipment necessary to perform the test usually requires it to take place in a hospital’s radiology or nuclear medicine department.

During the test, patients are asked to lie on a table (gantry) while a scanner moves over them. Occasionally, patients may be required to shift positions so that images can be taken from different views. Although the test is not generally painful, some patients may become uncomfortable after lying on the table for a long period.

The process of testing will vary depending on the type of test being administered. A typical example involves the process known as cholescintigraphy. During this procedure, a tracer is injected into a patient's vein. The tracer travels through the body to the liver and then into the bile ducts. A special scanner known as a gamma scintillation camera is placed over the patient’s abdomen so the physician can watch the movement of the tracer through the biliary tract as it creates images of the liver, gallbladder and bile ducts. If the tracer fails to move into the gallbladder, a shot of morphine can be administered to help facilitate the process.

Depending on the part of the body being studied, radionuclide imaging may involve two sets of scans, with the first scans taken as the radioactive material moves through the body and a second set taken hours later, when the material has settled into its target areas.

After the test, patients can get up from the examination table and change back into their clothes. There are no restrictions on daily routine, but it is recommended that patients drink plenty of fluids to flush the tracer from the body. The radioactive materials in the body release their energy and decay into non-radioactive atoms within a few hours to a few days after the test. The day after the scan, patients should immediately flush the toilet after using it to limit exposure to potentially radioactive material. Patients should also talk to their physician about whether or not they should limit time around children or refrain from sexual activity for a period of time.

A radiologist or other nuclear medicine expert will examine the images and send a report to the patient’s physician. Results are usually available within a few days of the scan. Depending on the results of this test, additional tests or treatment may be recommended.

Preparing questions in advance can help patients to have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions related to radionuclide imaging:

1. Why is this test more appropriate for me than other imaging tests?
   
   
2. Which type of radionuclide imaging can best diagnose my digestive condition?
   
   
3. If I am pregnant or nursing, should I delay the test?
   
   
4. Are there any steps I need to take to prepare for the test?
   
   
5. How long will the radioactive material stay in my body?
   
   
6. Is it okay for me to have sex soon after taking the test?
   
   
7. How long will it take to get the results of my radionuclide scan?
   
   
8. Who will interpret the results of my test?
   
   
9. Are there any potential risks or dangers associated with radionuclide scans?
   
   
10. What are the next steps after I get my test results?