PET Imaging

What is PET Scanning?

PET is an acronym for Positron Emission Tomography.

PET is a nuclear medicine test that uses different types of imaging cameras and radioactive agents. PET is different from traditional x-ray, CT and MR imaging because it shows the function and metabolism of cells in the body, rather than the anatomy of the body’s structures. PET provides information about different body functions and more detailed pictures than are possible with other Nuclear Medicine procedures.

PET scans do have some unique characteristics, as described below.

How is a PET scan done?

Like other nuclear medicine procedures, a PET scan is a simple, non-invasive test that causes no side effects to patients undergoing the procedure.

North Shore PET Imaging Center will inform the patient about any preparation required for the procedure. It is important that patients not exercise 24-hours prior to the scan. Patients will need to arrive at their appointment NPO (nothing to eat or drink - except for water) for at least six hours prior to the exam. It is especially important that no sugar be ingested, because the glucose in foods (or in the case of inpatients, IVs) will compete with the uptake of the radioactive glucose tracer. Medications should be taken as scheduled. They may be taken with a cracker if food is required. Diabetic patients will often be scheduled in the very early afternoon, the peak control time after morning insulin.

At the PET Scan appointment, the patient will be injected intravenously with the 18FDG tracer. There are no side effects from the injection. The patient will be asked to wait for 30 – 60 minutes for the tracer to distribute in the body. Movement, reading, or any other activity during that time will affect the pattern of uptake of the tracer, so the patient will be asked to rest quietly. After that, the patient will be escorted to the PET scanner, which resembles a CT scanner – a large donut with a table that moves through the hole. Much like CT, there are no loud noises or vibrations during image acquisition, which lasts approximately 30 minutes to an hour.

The images will undergo reconstruction and filming. The PET physician will review the images, often comparing the functional images by PET with any CT or MR scans the patient has had.

What does the PET scan show?

Most PET scans are performed with an imaging agent which is an analog of the glucose molecule. The imaging agent most commonly used is FDG (18Fluorodeoxy-glucose). FDG provides a signal that the PET scanner detects. The pictures show tissues that are under-using or over-using glucose. Cancer cells, because they are dividing faster than normal cells, use more glucose than normal tissues.

The PET Scan is able to demonstrate the distribution of the FDG in the body. The FDA has found that PET imaging is useful:

• to assist in the evaluation of malignancy in patients with known or suspected abnormalities found by other tests, or in patients with an existing diagnosis of cancer
• in patients with coronary artery disease and left ventricular dysfunction, when with myocardial perfusion imaging, to identify left ventricular myocardium with a reversible loss of systolic function
• for the identification of regions of abnormal glucose metabolism associated with foci of epileptic seizures
  

PET / CT Scanning

At North Shore PET Imaging, the technology of PET/CT is used. The combination of PET and CT will reveal a complete picture – providing both anatomic and metabolic information at one time in great detail. A dual-purpose imaging device, PET/CT is literally the combination of PET (positron emission tomography) and CT (computed tomography) imaging techniques within a single machine. The individual scans, which are taken simultaneously, can be presented separately or as a single, overlapping, or "fused" image. The two techniques present different types of information about the human body: PET will show metabolic or chemical activity in the body; CT will show the body's anatomical structures. The combination of PET and CT into one process will also shorten the scan time. There is no other remarkable difference in what the patient experiences during the scan.