PET stands for Positron Emission Tomography. Its a procedure that adds an important new dimension to a physicians ability
to diagnose and manage diseases such as cancer.
PET scans are simple, painless, and quick; offering patients and their families life-saving information that helps physicians detect
and diagnose diseases early and quickly begin treatment.
PET scanning and molecular imaging provide real life answers to better diagnose illness, guide treatment options, and give patients
ultimate control over their critical, life-saving health care decisions.
PET (or positron emission tomography) is a medical imaging tool which assists physicians in detecting disease. A PET scan produces
digital pictures that can, in many cases, identify many of the most common forms of cancer, including lung, breast, colorectal,
lymphoma and melanoma. Technically, PET is a medical imaging technology that images the biology of disorders at the molecular level
before anatomical changes are visible.
A PET scan is very different from an ultrasound, X-ray, MRI, or CT. Unlike these imaging technologies which merely confirm the
presence of a mass, a PET scan can distinguish between benign and malignant disorders. A PET scan can detect abnormalities in cellular
activity, generally before there is any anatomical change.
Once cancer is diagnosed, the PET scan is an essential next step to adequately stage the cancer, identifying the primary tumor
and the extent, if any, of the metastases.
PET can also help physicians monitor the treatment of disease. For example, chemotherapy leads to changes in cellular activity,
and that is observable by PET long before structural changes can be measured by ultrasound, X-rays, CT, or MRI. A PET scan gives
physicians another tool to evaluate treatments, perhaps even leading to a modification in treatment, before an evaluation could
be made using other imaging technologies.
PET also plays a role in identifying recurrence of cancer. Since PET is dependent on metabolic and not structural changes, malignant
processes can be separated from necrosis, edema and scarring.
In addition to cancer studies, PET is used in cardiology studies to measure damaged heart tissue and in neurology to identify brain
disorders such as Alzheimers, Parkinsons and epilepsy.
Cancer cells have a much higher metabolic rate than other cells. One characteristic is that cancer cells need higher levels of
glucose for energy. This is the biological process PET measures.
A typical oncology PET scan begins with an injection of the common radiopharmaceutical called FDG. A patient relaxes and lies still
for about 45 minutes while the FDG tracer distributes throughout the body.
The patient is then scanned. The gamma rays being emitted by FDG are recorded by the PET scanner and the images are reconstructed
and reviewed. The distribution of the FDG helps the physician identify areas of suspected malignancy.
The information is reconstructed to provide transaxial, sagittal and coronal representations of the metabolic activity of the body.
If an area is cancerous it will accumulate more FDG and the signals will be stronger there than in the surrounding tissue.
Generally PET can visualize a tumor in size from 7mm to 1cm depending on the location.