PET (Positron Emission Tomography) is a recognized clinical certainty with proven uses emerging in three major areas: Oncology, Neurology and Cardiology. PET can accurately determine whether a tumor is benign or malignant, show the progression of disease and accurately track the effectiveness of cancer treatment. PET can reveal dysfunctional cognitive patterns, making it a valuable tool for assessing patients with various forms of dementia. PET is an imaging modality that has helped advance the treatment of refractory seizures as a pre-surgical diagnostic tool to guide treatment options. A PET scan provides one of the highest levels of accuracy of any non-invasive test for the diagnosis of coronary artery disease and the assessment of myocardial viability. PET technology also has a potentially larger and valuable role in early diagnosis and tailoring therapies.

PET is a nuclear medicine procedure. The patient is injected with a radiopharmaceutical which concentrates at the site of metabolic activity. A sophisticated detector images the distribution of the radiopharmaceutical in the body, thus imaging tissue function. PET can detect the spread of malignant tumors and differentiate cancerous tissue from benign tumors and scar tissue. This can have a dramatic impact on patient treatment, planning and care.

HOW PET WORKS
Radiopharmaceuticals based on positron emitting isotopes, such as fluorodeoxyglucose, become signal-emitting tracers when injected into the patient. During a PET scan, patients are first injected with a radiopharmaceutical, usually FDG, a radioactive glucose compound. As the compounds are distributed throughout the body and processed by the organ being targeted for imaging, the PET scanner detects the FDG accumulated in glucose-avid organs or tissues and creates images that are displayed on a video monitor. The signals detected by the camera are processed by a computer to create images that display the distribution of metabolic activity as a tomographic slice. Because cancer cells usually have a higher metabolic rate than surrounding cells, they absorb more of the tracer and will show up more prominently on the image.

PET’S ADVANTAGES FOR PATIENT DIAGNOSIS
PET enables physicians to better determine the presence of a tumor, as well as the extent and spread of disease. With better information about the early presence or spread of cancer, physicians can select the treatment approach that's most effective for the patient.

An important benefit of PET is its high-definition imaging which can detect tissue abnormalities even in the absence of structural changes. The detection of small amounts of malignant tissue, often undetectable by conventional imaging techniques, can have a major impact on the choice of treatment for patients, which may involve drug therapy, surgery, radiation, chemotherapy or a combination of all available options.

PET AND CANCER
PET is considered particularly effective in identifying whether or not cancers are responding to treatment, if a person is cancer free, or if a cancer has recurred—and where. Cancers for which PET is considered particularly effective include: lung, lymphoma, melanoma, breast, colorectal, esophageal, head and neck, pancreatic, ovarian, cervical and thyroid. Cancer of the prostate, kidney and musculoskeletal system can be FDG avid and may be suitable for PET scanning in select cases.

• Staging of Cancer: PET is extremely sensitive in determining the full extent of disease, especially in the cancers noted above. Confirmation of metastatic disease allows the physician and patient to more accurately decide on how to proceed with the patient's management

• Checking for recurrences: PET is currently considered to be the most accurate diagnostic procedure to differentiate tumor recurrences from radiation necrosis or post-surgical changes. Such an approach allows for the development of a more rational treatment plan for the patient.

• Assessing the Effectiveness of Chemotherapy: The level of tumor metabolism is compared on PET scans taken before and after a chemotherapy cycle. A successful response seen on a PET scan frequently precedes alterations in anatomy and is considered to be an earlier indicator of tumor shrinkage than might be seen with other diagnostic modalities.

• Early Detection: Since PET images biochemical activity, it can accurately characterize a tumor as benign or malignant, thereby avoiding surgical biopsy when the PET scan is negative. Conversely, since a PET scan images the entire body, confirmation of non-local metastasis can alter treatment plans in certain cases from surgical intervention to chemotherapy.

PET IN NEUROLOGY

Epilepsy
PET has helped advance the diagnosis of refractory epilepsy leading to cures in certain cases. PET is one of the most accurate methods available to localize the areas of the brain causing epileptic seizures and to determine if surgery is a viable treatment option.

Dementia
The brain is highly dependent on glucose metabolism. PET can reveal abnormal patterns of uptake in the brain and is, therefore, a valuable tool for assessing patients with various forms of dementia. It is particularly useful in diagnosing Alzheimer’s disease and in distinguishing Alzheimer's disease from other dementia disorders, such as vascular dementia, Parkinson's disease, Pick’s disease and Huntington's disease.

Alzheimer's Disease: Although the only definitive test for Alzheimer's disease (AD) is autopsy, PET can supply important diagnostic information. When comparing a normal brain vs. an AD-affected brain on a PET scan, a distinctive image appears in the AD-affected brain. This pattern may be seen very early in the course of Alzheimer's disease, when other imaging is normal. The confirmation of AD is a long process of elimination that averages between two and three years of diagnostic and cognitive testing. PET can help to shorten this process by identifying distinctive pattern earlier in the course of the disease. Since currently available medical treatments seem to be more effective if started early, a correct and early diagnosis may have important patient ramifications.

PET IN CARDIOLOGY

PET has a number of important uses in cardiology. PET can be particularly helpful in the diagnosis of CAD if conventional perfusion (nuclear cardiac stress test) or echocardographic stress tests are equivocal.

Myocardial viability offers the most important role for PET in cardiology. PET flow/metabolism studies are generally regarded as the “gold standard” in identifying hibernating myocardium, a critical element in determining successful functional recovery after revascularization.

PET and CT or MRI

PET measures metabolism, unlike MR or CT, which “see” structure. It therefore complements these modalities, as it can often detect active tumor before it can be seen on MR or CT. PET can also often differentiate malignant from non-malignant masses such as scar tissue formed from surgery or radiation therapy. PET is often used in conjunction with an MR or CT through “fusion” to provide a full three-dimensional view of an organ and the location of cancer within that organ, by superimposing the functional and structural information for PET onto CT or MR.

Dedicated PET and PET/CT Scanners

PET scans are generally provided today on one of three different types of camera: Modified Gamma or Coincidence Cameras; Full-ring or partial ring dedicated PET Scanners, and combination PET/CT scanners.

Dedicated PET scanners have become the primary type of scanner used for diagnostic imaging today. CMS, the government agency that regulates reimbursement for PET, recently limited the reimbursements it approves for coincidence, or modified Gamma Camera PET. Dedicated PET scanners offer physicians a number of advantages, which include superior image resolution and a wider range of applications.

An effective alternative to a combination machine is electronic image fusion via a workstation which can combine CT and PET scans taken on different instruments at different times. This approach also allows fusion of MR and PET data which is important when soft tissue detail is required. This electronic fusion capability is also incorporated in some radiotherapy planning systems allowing the fused data to be used in preparation and optimization of the radiotherapy treatment plan – an application where a thorough understanding of both the functional and structural information are very important.

Cost & Reimbursement:

Many private insurance companies reimburse for PET scans. Medicare reimburses for PET for the following cancers: breast, colorectal, lung, lymphoma, melanoma, head and neck and esophageal. Medicare also reimburses for myocardial viability and for refractory seizures (epilepsy). For the most accurate information, please contact your patient’s insurance carrier directly

HOW TO PREPARE YOUR PATIENTS FOR A PET SCAN

For most patients, the PET scan takes about two hours to complete, depending on whether the whole body, or a particular part of the body is scanned.

Patients should bring:
• All previous studies, including CT and/or MR films and reports
• Their chemotherapy history, including date of most recent treatment.
• Insurance information.

Preparing for the Test
• Patients should not eat or drink (other than water) 4-6 hours prior to the exam.
• Patients are encouraged to drink plenty of water prior to the exam
• Patients should refrain from strenuous excise for 3 days prior to the exam.
• Diabetic patients require special preparation and should call the PET Center for instructions.

PET REFERRAL FORM
Click on the form below to open.  The form is a PDF and requires Adobe Acrobat Reader to open.  You may download the free program using the link at the bottom of this page.