The reason why PET is so successful is that no other imaging technique shows the internal chemistry of the body so well. Conventional imaging techniques such as X-ray, CAT scans, and Magnetic Imaging Resonance shows anatomy. PET detects chemical and metabolic changes in disease states, such as cancer, before anatomic and structural changes (detected by conventional imaging) have time to develop. Therefore PET can detect diseases when anatomic imaging studies are still normal, and may be informative in differentiating benign from malignant process. PET evaluation of tissue metabolism can indicate the probable presence or absence of malignancy based on differences of biological activity, where as anatomic imaging depends on size and radiographic characteristics of lesions to determine the likelihood of malignancy. In addition, whole body imaging with PET provides a means to examine all the organ systems in the entire body for both primary and metastatic disease in one procedure.

Medicare, as well as many third party payers have begun to reimburse for PET because it has been shown that in certain specific disease states PET procedures are cost effective, that is, in certain situations PET is superior to conventional imaging without increasing the cost of the management of these clinical situations. PET has been shown to decrease the cost of diagnostic work-up in the situations listed below by avoiding unnecessary invasive diagnostic and surgical procedures in patients for whom these procedures will have little or no benefit. Given the importance of clinical decisions being made by PET, HCFA recognizes that the quality of image production is a significant concern. Medicare limits coverage of FDG PET to use by high-end full ring dedicated PET scanners such as our PET scanner at Boca Raton Community Hospital. (Alternative Hybrid PET cameras, such as dual head Gamma Cameras equipped with molecular coincidence detection or Gamma Cameras equipped with 511 KEV collimators have been shown to be vastly inferior in sensitivity and exams performed by these hybrid devices are not approved by Medicare for reimbursement purposes.)

1) Primary or initial diagnostic study for assessing myocardial viability prior to vascularization

2) ****Covered following inconclusive SPECT

* When PET is used for the above oncologic clinical diagnosis, PET is covered by Medicare when the PET diagnosis may assist in avoiding an invasive diagnostic procedure, or when PET results may assist in determining the optimal location for performing an invasive diagnostic procedure.

- PET is not covered for other diagnostic uses and is not covered for screening (testing of patients without specific symptoms)

**When PET is used for staging and re-staging, PET coverage is subject to the following 2 conditions:
(i) The stage of the cancer remains in doubt after the completion of a standard diagnostic work up, including conventional imaging
(ii) Clinical management of a patient would differ depending on the stage of the cancer identified on PET. The use of PET would also be considered reasonable and necessary if it could potentially replace one or more conventional imaging studies.

*** Medicare considers re-staging to include both re-staging in the setting of recurrence and re-staging following completion of a therapeutic regimen when it is important to assess whether a complete response has/has not been achieved which would obviate or necessitate the need for additional treatment respectively.
- Use of PET to monitor tumor response during the planned course of therapy (i.e. when no change of therapy is being contemplated) is not covered.

Prior to obtaining an FDG PET study, the physician ordering the procedure is required to document in the patients' chart the specific clinical question that will be answered by the imaging study. The ordering physician will thereby certify the medical necessity of the study according to the conditions described above.

The clinical utility of PET is largely derived from the clinical content in which a physician needs to decide whether to provide or withhold a potentially effective but clearly toxic or risky therapeutic intervention.

****Myocardial Viability: The use of FDG PET is supported when SPECT is positive and clinical correlation casts doubt on this finding to further predict myocardium amenable to re-vascularization.

Myocardial Viability (Thallium)

Fixed defects anterior wall, inferior wall, inferolateral wall & apex & diffuse thinning of septum without SPECT evidence of ischemia.

Myocardial Viability (PET)

Increased uptake at inferolateral wall indicating hibernating, metabolically active myocardium which is still amenable to cardiovascular revasculartization (with stenting or surgical bypass)