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
PET scans do have some unique characteristics, as described below.
How is a PET scan done?
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.
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
- 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.