Nuclear medicine is a specialized area of radiology. It uses very small amounts of a radioactive substance (radionuclide) to look at organs and their function as well as other areas of your body. Nuclear medicine imaging is a mix of many different disciplines. These include chemistry, physics, mathematics, computer technology, and medicine. This branch of radiology is often used to help diagnose and treat diseases such as thyroid cancer.
Soft tissue, such as intestines, muscles, and blood vessels, is hard to see on a standard X-ray, unless a contrast agent is used. This agent allows the tissue to be seen more clearly. But nuclear imaging shows organ and tissue structure as well as function. The extent to which a radionuclide is absorbed, or "taken up," by a certain organ or tissue may even show how well the organ or tissue is working. So diagnostic X-rays are used mainly to study anatomy. Nuclear imaging is used to study organ and tissue function.
A tiny amount of the radionuclide is used during the procedure. The radionuclide is also known as a radiopharmaceutical or radioactive tracer. It's absorbed by body tissue. There are several different types of radionuclides. These include forms of the elements technetium, thallium, gallium, iodine, and xenon. The type of radionuclide used will depend on the type of study and the body part being checked.
After the radionuclide has been given and has collected in the body tissue under study, radiation will be given off. A radiation detector can pick up this radiation. The most common type of detector is the gamma camera. Digital signals are made and stored by a computer when the gamma camera detects the radiation.
With a nuclear scan, the healthcare provider can assess and diagnose many conditions, such as tumors, infections, or organ enlargement. A nuclear scan may also be used to check organ function and blood circulation.
The areas where the radionuclide collects in greater amounts are called "hot spots." The areas that don't absorb the radionuclide are called "cold spots." These look less bright on the scan image.
In planar imaging, the gamma camera stays still. The resulting images are 2-D. Single photon emission computed tomography (SPECT) makes detailed images of an organ as the gamma camera moves around you. These images are like those done by a CT scan. In certain cases, such as PET scans, 3-D images can be done using the SPECT data.
Nuclear scans are used to diagnose many health problems. Some of the more common tests are:
Nuclear medicine scans may be done on many organs and tissues of the body. Each type of scan uses certain technology, radionuclides, and procedures.
A nuclear medicine scan has 3 phases:
The amount of time from giving the tracer and then taking the images may range from a few moments to a few days. The time depends on the body tissue being looked at and the tracer being used. Some scans are done in minutes. For others, you may come back a few times over several days.
To give an example of how a nuclear medicine scan is done, here is the process for a resting radionuclide angiogram (RNA) scan. This is a type of heart scan.
Each facility may have certain protocols in place. But a resting RNA often follows this process: