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Nuclear Cardiology: Myocardial Perfusion Studies and Ventriculography

Nuclear Cardiology: Myocardial Perfusion Studies and Ventriculography . Croft Stone Nuclear Medicine. Basics of MPI. Radionuclide injected at rest and/or stress Radionuclide taken up by myocardium and gamma rays emitted Rest images compared with stress images

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Nuclear Cardiology: Myocardial Perfusion Studies and Ventriculography

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  1. Nuclear Cardiology:Myocardial Perfusion Studies and Ventriculography Croft Stone Nuclear Medicine

  2. Basics of MPI • Radionuclide injected at rest and/or stress • Radionuclide taken up by myocardium and gamma rays emitted • Rest images compared with stress images • Decreased perfusion stress and rest – MI • Decreased perfusion at stress, normal with rest – ischemia • Area indicates the coronary artery, size correlates with severity of CAD

  3. Basics • Two conditions necessary for blood flow deficit measurement: • 1) coronary flow must be elevated to near maximal levels • 2) radiotracer whose myocardial extraction is proportional to coronary artery blood flow must be used

  4. Stress • Exercise and pharmacologic agents are used to achieve maximal coronary dilation and flow. • Exercise stress gives additional information: • Degree of exercise tolerance • Time to maximal heart rate • Blood pressure response

  5. Pharmacologic stress • Agents: • Dipyridamole (persantine) • Dobutamine • Adenosine

  6. Indications for Pharmacologic Stress Imaging • Inability to perform adequate exercise • Left bundle branch block • Ventricular pacemaker • CCB’s or Beta blockers • Evaluation of patients very early after acute MI (<3 days) or very early after stenting (<2 weeks)

  7. Physics • Radioactive decay • Alpha particles (ionized helium nuclei) • Beta particles (high energy electrons or positrons) • Gamma rays (photons) • Electron capture (x-rays)

  8. Gamma Camera

  9. Camera • Multiple images taken at different rotation angles to obtain 3-D information • Lead collimator excludes photons not traveling in direction of holes in the collimator • 3-D picture can be reconstructed using a mathematical model • Projection system modeled as system of simultaneous linear equations; matrix is then inverted to reveal the source distribution.

  10. Protocols

  11. Radionuclide Properties

  12. Comparison of 201Tl and 99mTc for Myocardial Perfusion Imaging

  13. Tc-99m • Technetium chelated to to a molecule that will be absorbed by the myocardium • Tc-99m-methoxyisobutyl (setamibi) • Tc-99m 1,2bis[bis (2-ethoxyethyl)phosphinoethane (tetrofosmin) • During stress, metabolism changes polarization of cell membrane, driving agent into cell • Also readily absorbed by liver and bowel

  14. Tc-99m preparation

  15. Tc-99m

  16. Quality control • 1.Motion -- There is no evidence of patient motion.2.Alignment --The alignment is very good.3.Count Increase --The myocardial max counts increases in the stress study as expected.4.Normalization --Both studies are normalized to the portion within the myocardium with the highest uptake.5.Extra-Cardiac Activity --There is no significant extra cardiac activity.6.Soft tissue attenuation– minimized • 7. Protocol consistency

  17. Simultaneous assessment of perfusion and function in a single injection, single acquisition sequence. Tc-99m permits evaluation of regional myocardial wall motion and wall thickening throughout the cardiac cycle Quantitates LV volume and EF ECG Gated SPECT imaging(MUGA: multi gated acquisition)

  18. Technique • Stannous pyrophosphate injected • Tc-sodium pertechnetate injected • Pertechnetate enters RBC’s, becomes reduced by the intracellular stannous ion, and is bound to hemoglobin • RBC’s now “tagged” with radioisotope: hence “blood pool” image

  19. Technique • Images of heart are triggered (gated) on the R wave of the ECG • 32 or more frames taken per cardiac cycle • Many cardiac cycles imaged and stored for statistical significance • Total amount of activity stored in frames at each gated time point plotted vs. total time cycle

  20. Technique • Heart rate variations can result in temporal blurring (mixing of counts in adjacent frames). • Beat rejection window usually set at 20%

  21. Sources • Cerqueira, Manuel D. Nuclear Cardiology, 1994, pp 93 – 100, 103-109. • Crean, Andrew and Coulden, Richard. Cardiac Imaging using nuclear medicine and positron emission tomography. Radiologic Clinics of North America, 42 (2004) 619-634 • Heller,Gary V. and Hendel, Robert C. Nuclear Cardiology: Practical Applications, 2004. pp 1-312. • Kowalsky, Richard J. and Falen, Steven W. Radiopharmaceuticals in Nuclear Medicine and Nuclear Pharmacy, 2004: pp 515 – 555.

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