PET Scanning: The Basic FactsA Brief Overview for Referring Physician Office Staff

What is PET Scanning?PET is an acronym for Positron Emission Tomography.

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

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

How is a PET scan done? Like nuclear medicine procedures, a PET scan is usually a simple, non-invasive test that provides no side effects to most patients undergoing the procedure.

The PET Center will tell the patient about any preparation required for the procedure. Sometimes it is important that patients not exercise extensively in the 24-hours prior to the scan. Patients will generally need to arrive at their appointment NPO except for water for at least four hours. It is especially important that no sugar be ingested, because the glucose in foods (or in the case of inpatients, IVs) would compete with the uptake of the radioactive glucose. Medications should be taken as scheduled, however, only with a cracker if food is required. Diabetic patients will often be scheduled in the very early afternoon, peak control time after morning insulin.

At the PET Scan appointment, the patient will be injected intravenously with the 18FDG. There are no side effects from the injection. The patient will be asked to wait for 30 – 60 minutes for the imaging drug to distribute in the body. Movement, reading, or any other activity during that time will affect the pattern of uptake of the drug, so the patient will be asked to rest quietly. After that, the patient will be escorted to the imaging camera, which resembles a CT scanner – a large donut with a table that moves through the hole. Much like a CT, there are no loud noises or feeling during the picture-taking, which will last 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 today are performed with an imaging drug that acts like a tracer amount of a sugar when it is administered intravenously. The imaging drug most commonly used is FDG (18Fludeoxy-glucose). FDG provides a signal that the PET scanner detects—tissues that are under-using or over-using glucose can be shown on the pictures. Cancer cells, because they are dividing faster than normal cells, use more glucose than normal tissues.

The PET Scanner, with its ability to image these radionuclides is able to demonstrate the distribution of the FDG in the body. The FDA has found that FDG is indicated in positron emission tomography (PET) imaging: 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

Important information to know about referring a patient:The basic principle behind PET scanning—functional imaging—requires that information about the general health and status of the patient be gathered. Diseases, infections, or surgeries can affect the use of glucose in tissues, so it is important that the

PET physician has access to information about the patient. Progress notes and a recent history and physical is usually sufficient.

Patients with diabetes can have a PET scan—the FDG does not affect blood glucose levels. It is very important that the PET center know that the patient is a diabetic for optimal scheduling and patient preparation. Diabetic patients must have good control of their blood glucose levels at the time of the PET scan for optimal results.

Because the PET scan provides a picture of the “function” of cells and tissues in the body, it is often important that anatomic imaging studies (like CT, MR or x-rays) be available for comparison during the interpretation of the PET scan.

What PET Scans are covered by insurance? An insurance company may scrutinize PET scans for coverage. Many private insurance carriers require a pre-authorization or pre-certification be obtained before the scan to assure coverage. In some cases, the insurance company may need detailed information about the usefulness of PET in order to make a decision about its use in a specific patient. Your local PET center may be able to provide this information to you.

The Medicare program, administered by the Centers for Medicare and Medicaid Services (CMS), formerly the Health Care Financing Administration (HCFA), reimburses health care providers for a variety of PET procedures, as indicated below:

(Indications with FDG as radiopharmaceutical, except for Rubidium 82 Cardiac Perfusion) Solitary Pulmonary Nodule Lesion characterizationLung cancer Diagnosis, staging and re-stagingColorectal Cancer Diagnosis, staging and re-stagingLymphoma Diagnosis, staging and re-stagingMelanoma (but not for evaluation of regional nodes)

Diagnosis, staging and re-staging

Head and Neck Cancer (excludes central nervous system or thyroid cancers)

Diagnosis, staging and re-staging

Esophageal Cancer Diagnosis, staging and re-stagingBreast Cancer* Staging, re-staging and monitoring therapyRefractory Seizures Pre-surgical evaluationMyocardial Viability After inconclusive SPECT; Initial assessment *RB 82 Cardiac Perfusion In lieu of SPECT or following inconclusive SPECT

* Coverage effective for procedures performed on or after 10/01/02For each of these indications, Medicare imposes certain conditions and restrictions for coverage. For more complete information about Medicare’s coverage policy for PET, we urge you to review carefully the Medicare Coverage Issues Manual, Section 50-36. This document can be accessed at http://cms.hhs.gov/manuals/06_cim/ci50.asp - _50_36.

CMS continuously reviews its coverage policy for PET, based on advances in the technology, as well as evidence available on medical effectiveness for selected indications. To confirm coverage policy inclusions and restrictions, consult with your local Medicare carrier or fiscal intermediary.

Coverage and reimbursement policies of private payers will vary, depending on a variety of factors including location, payment arrangement, patient volume, etc. While some private payers may rely on Medicare reimbursement coverage as the basis for their reimbursement policies, many others may consider alternative information. Please consult with individual payers for more information on PET procedures.