diagnostic imaging and radiology

Nuclear Medicine

Understanding nuclear medicine

Nuclear medicine is a a medical imaging specialty that uses very small amounts of radioactive materials, or radiopharmaceuticals, to examine the body and diagnose and treat disease. Special cameras allow providers to track the path of these radioactive tracers.

Because X-rays pass through soft tissue — such as intestines, muscles and blood vessels — tissues are difficult to visualize on a standard X-ray. Using a nuclear contrast agent allows the tissue to be seen more clearly.

Nuclear imaging enables visualization of organ and tissue structure as well as function. The extent to which a radiopharmaceutical is absorbed, or "taken up," by a particular organ or tissue may indicate the level of function of the organ or tissue being studied. Thus, diagnostic X-rays are used primarily to study anatomy, whereas nuclear imaging is used to study organ and tissue function.

A tiny amount of a radioactive substance is used during the procedure to assist in the examination. The radioactive substance, called a radionuclide (radiopharmaceutical or radioactive tracer), is absorbed by body tissue. Several different types of radionuclides are available, including 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 studied.

After the radionuclide has been administered and has collected in the body tissue under study, radiation will be given off. This radiation is detected by a radiation detector. The most common type of detector is the gamma camera. Digital signals are produced and stored by a computer when the gamma camera detects the radiation.

By measuring the behavior of the radionuclide in the body during a nuclear scan, your provider can assess and diagnose various conditions, such as:

  • Tumors
  • Abscesses
  • Hematomas
  • Organ enlargement
  • Cysts

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 do not absorb the radionuclide and appear less bright on the scan image are referred to as "cold spots."

In planar imaging, the gamma camera remains stationary. The resulting images are two-dimensional. Single photon emission computed tomography, or SPECT, produces axial "slices" of the organ in question because the gamma camera rotates around the patient. These slices are similar to those performed by a CT scan. In certain instances, such as PET scans, 3D images can be performed using the SPECT data.

Scans are used to diagnose many medical conditions and diseases.

Some of the more common tests include:

  • Renal scans to examine the kidneys and detect any abnormalities, such as tumors or obstruction of the renal blood flow
  • Thyroid scans to evaluate thyroid function or to better evaluate a thyroid nodule or mass
  • Bone scans to evaluate any degenerative and/or arthritic changes in the joints, detect bone diseases and tumors, and/or determine the cause of bone pain or inflammation
  • Gallium scans to diagnose active infectious and/or inflammatory diseases, tumors and abscesses
  • Heart scans to identify abnormal blood flow to the heart, determine the extent of the damage of the heart muscle after a heart attack and/or measure heart function
  • Brain scans to investigate problems within the brain and/or in the blood circulation to the brain
  • Breast scans, which are often used in conjunction with mammograms to locate cancerous tissue in the breast

How nuclear medicine scans are performed

As stated above, nuclear medicine scans may be performed on many organs and tissues of the body. Each type of scan employs certain technology, radionuclides and procedures.

A nuclear medicine scan consists of three phases:

  • Administering the tracer (radionuclide)
  • Taking images
  • Interpreting the images

The amount of time between administration of the tracer and the taking of the images may range from a few moments to a few days, depending on the body tissue being examined and the tracer being used. Some scans are completed in minutes, while others may require the patient to return a few times over the course of several days.

In order to give an example of how nuclear medicine scans are done, the process for a resting radionuclide angiogram (RNA) scan is presented below.

Although each facility may have specific protocols in place, generally, a resting RNA follows this process:

  1. The patient will be asked to remove any jewelry or other objects that may interfere with the procedure.
  2. If the patient is asked to remove clothing, he or she will be given a gown to wear.
  3. An intravenous (IV) line will be started in the hand or arm.
  4. The patient will be connected to an electrocardiogram (ECG) machine with electrodes (leads) and a blood pressure cuff will be attached to the arm.
  5. The patient will lie flat on a table in the procedure room.
  6. The radionuclide will be injected into the vein to "tag" the red blood cells. Alternatively, a small amount of blood will be withdrawn from the vein so that it can be tagged with the radionuclide. The radionuclide will be added to the blood and will be absorbed into the red blood cells.
  7. After the tagging procedure, the blood will be returned into the vein through the IV tube. The progress of the tagged red blood cells through the heart will be traced with a scanner.
  8. During the procedure, it will be very important to lie as still as possible, as any movement can adversely affect the quality of the scan.
  9. The gamma camera will be positioned over the patient as he or she lies on the table, and will obtain images of the heart as it pumps the blood through the body.
  10. The patient may be asked to change positions during the test; however, once the position has been changed, the patient will need to lie still without talking.
  11. After the scan is complete, the IV line will be discontinued, and the patient will be allowed to leave, unless your provider gives different instructions.

Expanding diagnostic capabilities with SPECT/CT

Since mid-2006, Adventist Health Portland’s nuclear medicine department has been pleased to offer new technology and capabilities to Portland and the Northwest Region. Cutting-edge molecular technologies such as SPECT/CT (single-photon emission computed tomography/computed tomography CAT scan) help to provide improved detection, diagnosis, and therapy planning for cardiac, oncology and neurology diseases as well as many other problems.

The Symbia T SPECT/CT system is the most sophisticated of its kind in the Northwest and the first SPECT/CT scanner in Portland. This technology combines the important technologies of SPECT and CT to create an important new diagnostic imaging system.

The anatomical information from a CT scan is merged with your body’s function as recorded by a SPECT scanner to produce an image that records the shape and functional processes of your living tissues. This combination of CT and SPECT improves image clarity and detail, helping physicians make earlier and more accurate diagnoses.

Patient benefits include:

  • Earlier diagnosis
  • Accurate staging and localization
  • More precise treatment
  • Patient monitoring

With the state-of-the-art images that SPECT/CT provides, patient outcomes are enhanced and unnecessary procedures are avoided. The system also features a comfortable patient opening and is designed to be very accessible, flexible and comfortable while providing exceptional image quality and accuracy of diagnostic information.

A versatile system, the SPECT/CT scanner is used to image patients with a variety of diseases including cardiac disease, cancer and neurological disorders such as Alzheimer's disease. In fact, one of the key advantages of the SPECT/CT is the ability to use a multitude of FDA-approved tracers to target various tumors at their source and detect metastatic cancer — sometimes too small to see otherwise — that has spread to other parts of the body. By finding the exact location of cancer and infection, SPECT/CT systems help physicians tailor therapy to each patient and accurately assess how well treatment is working.

Adventist Health Portland has provided comprehensive nuclear medicine healthcare services to the Portland community for more than 40 years. Expanding our diagnostic capabilities with the addition of the Siemens Symbia T SPECT/CT ensures our ability to continue to serve the community with high-quality services and cost-effective care to our patients.