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Cardiac PET/CT

Cardiac PET/CT. Group 2. Cardiac PET . Current clinical cardiac PET can evaluate coronary artery perfusion (at rest and/or at stress), such as to risk stratify a patient for critical coronary stenosis

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Cardiac PET/CT

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  1. Cardiac PET/CT Group 2

  2. Cardiac PET • Current clinical cardiac PET can evaluate coronary artery perfusion (at rest and/or at stress), such as to risk stratify a patient for critical coronary stenosis • It can also be used to evaluate for myocardial viability, that is, distinguish infarcted from hibernating but viable tissue • Coronary perfusion is most commonly evaluated by PET with Rb-82, and viability with FDG, (although other radiotracers can be used for either exam) • PET enables physicians to screen for coronary artery disease, to assess flow rates and flow reserve and to distinguish viable from nonviable myocardium for bypass and transplant candidates

  3. Indications PET scanning may be considered medically necessary for the following indications: • To assess myocardial perfusion and thus diagnose coronary artery disease • To assess the myocardial viability in patients with severe left ventricular dysfunction to assist in determining candidacy for revascularization.

  4. Cardiac PET/CT In Cardiology, PET has become the 'gold standard' for: (1) non-invasive evaluation of stunned (ischemic) myocardium (2) differentiation of ischemic heart muscle from infracted myocardium (3) determining the candidates most suitable for coronary bypass

  5. Myocardial Viability • By measuring both blood flow (perfusion) and metabolic rate within the heart, physicians using PET scans can pinpoint areas of decreased blood flow such as that caused by blockages and differentiate muscle damage from living muscle, which has inadequate blood flow.

  6. Why Cardiac PET? • Cardiac positron emission tomography (PET) is an accurate method for assessing myocardial perfusion and metabolism in the evaluation of coronary heart disease. • PET allows more accurate detection of myocardial ischemia than single photon emission tomography (SPECT). -In addition, PET has higher spatial resolution and allows attenuation correction and the quantification of various physiologic parameters. • PET with 2-(fluorine-18) fluoro-2-deoxy-d-glucose is considered the standard of reference for predicting improvement in regional or global left ventricular function after revascularization by identifying hibernating viable myocardium that shows diminished perfusion and preserved metabolism. • Other less commonly used clinical applications of cardiac PET include assessment of myocardial oxygen consumption and fatty acid metabolism

  7. PET – Stress/Rest Exams • PET stress tests with Rb-82 are used to check the health of the coronary arteries for functionally significant obstructions (narrowing), which can reduce blood flow to heart muscle and lead to the heart muscle becoming "starved" of oxygen. • This condition is called coronary artery disease. Symptoms can include chest pain and shortness of breath. With coronary artery disease there is an increase in the possibility of a myocardial infarction (heart attack). • PET cardiac scans with Rb-82 are more accurate than other cardiac stress tests such as Thallium-201 SPECT in the detection of heart disease and provide enhanced quantification. • Patients will receive an injection and resting images, undergo a chemical stress test, receive a second injection of the isotope, and undergo stress imaging for a short time after.

  8. Myocardial Viability • Myocardial Viability - Distinguish viable myocardium from infarcted tissue in patients with suspected hibernating or stunned myocardium. Uses for PET in evaluation of myocardial viability * Determine the extent of heart muscle metabolism * Evaluate the matching of metabolism and flow in the myocardium

  9. Myocardial Viability • How are myocardial viability PET studies performed? • PET can determine the extent of heart muscle metabolism. -The technologist will give a small, safe quantity of a radiotracer by IV injection. -Since the heart muscle or myocardium will utilize glucose, the PET study is used to locate areas of viable myocardium. -The patient is comfortably positioned on the imaging bed in the PET scanner approximately 40 minutes after injection. The scan typically takes between 30-40 minutes, to acquire, but can vary between individual patients. • What the patient should know: Nothing by mouth for 4 hours before appointment except water with medication Patient will need IV Scanning time is 1-2 hours Total time in PET Imaging Center is 2-3 hours • Thus, PET can be used in the pre-operative assessment of patients with advanced CAD and impaired left ventricle function.

  10. Reading Cardiac PET • Positron emission tomography using F-fluorodeoxyglucose (FDG) as a tracer is used to measure myocardial cell glucose metabolism. • An area of ischemic viable myocardial wall will show a mismatch between the blood flow and metabolism. • Regions showing deficits in both perfusion and FDG uptake can be considered dead regions. An area showing a defect in blood flow but with preserved FDG uptake represents a blood flow-metabolism mismatch, and is considered still viable for revascularization.

  11. Ischemic Defect • The picture to the right shows resting and post-stress images of a patient. Comparison of the two sets of images shows an ischemic defect in the inferolateral wall, consistent with reversible ischemia

  12. Ischemic Defect • PET scans performed to evaluate cardiac viability are performed with a single injection of FDG after a glucose-loading procedure. • Areas of chronic or acute reversible ischemia (hibernating or stunned myocardium) will metabolize glucose for energy, thus will uptake more of the glucose tracer. • The study at the left depicts a patient with a fixed defect in the anterior wall. There is minimal reversibility in the anterolateral wall defect. • FDG uptake is increased in both areas, indicating reversible, hibernating myocardium. • Notice that septal FDG uptake is decreased, indicating that this area is not metabolizing glucose.

  13. Gated Blood Pool PET Scan with Rb-82 of the Heart • Purpose: To determine whether the cardiac ejection fraction is abnormal and to measure how well the heart muscle pumps blood

  14. Cardiac PET Scan with Rb-82 • Purpose: To determine whether the heart muscle circulation has been affected by disease and to measure how well the heart muscle pumps blood

  15. PET vs. SPECT • Existing data supports some increased accuracy of PET over SPECT, particularly for heavier patients, where breast, chest wall, and diaphragmatic attenuation interfere with conventional SPECT. • The main advantage of PET in this scenario is its ability to correct for attenuation artifacts.

  16. References • http://www.mountsinai.org/msh/clinical_services/nuclearmedicine.htm • http://www.mobilepetimaging.com/CardiacOverview.asp

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