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Nuclear Cardiology and you

Nuclear Cardiology and you. Anatomy & Physiology. Four cardiac chambers left ventricle of importance in NM Coronary arteries supply myocardium with blood NM detects quality of perfusion to myocardium, an indirect assessment of the coronary arteries. CLINICAL INDICATIONS.

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Nuclear Cardiology and you

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  1. Nuclear Cardiology and you

  2. Anatomy & Physiology • Four cardiac chambers • left ventricle of importance in NM • Coronary arteries • supply myocardium with blood • NM detects quality of perfusion to myocardium, an indirect assessment of the coronary arteries

  3. CLINICAL INDICATIONS • Coronary artery disease causes myocardial ischemia and infarction. • Ischemia is reversible condition, caused by temporary deficiency of oxygen to the myocardium • Infarction is irreversible condition, that leads to death of a portion of the myocardium.

  4. Clinical indications • During a stress test (exercise) or when certain drugs are administered, the demand for blood flow (oxygen) through the coronary arteries increases. • If the increase in the demand cannot be met the myocardium becomes ischemic. • Ischemia can cause decreased tissue perfusion, and contraction in affected area.

  5. Mechanical activity • Each cardiac cycle (each beat) consists of systole (ventricular contraction) and diastole (ventricular relaxation) • Both sides of heart contract in unison • Left ventricular contraction is most important to NM.

  6. Radiopharmaceuticals • Evaluation of myocardial perfusion: • Single photon emitters, thallium-201 chloride (201-Tl), Technitium 99m sestamibi, (tc99m tetrafosmin) (tc99m teboroxime) • Positron emitting tracer, Rubidium-82 (Rb82)

  7. Radiopharmaceuticals • Evaluation of ventricular function: • Tc99m labeled red blood cells • Tc99m albumin • Detection of acute myocardial necrosis: • Tc99m pyrophospate (PYP) • Indium 111 antimyosin

  8. Types of Procedures • Gated cardiac blood pool • typically a rest study • MUGA or NVG are common names • First pass cardiac • stress or rest • Myocardial perfusion • SPECT images • stress/rest or rest only • frequently gated

  9. Gated Blood Pool (MUGA) • Gating process • Functional assessment • ventricular wall motion • ES and ED ventricular volumes • LV ejection fraction • normal = 64% +/- 12%

  10. Gated Blood Pool (MUGA) • Radiopharmaceutical • Tc-99m labeled red blood cells • in-vitro and in-vivo labeling • Images • anterior • left lateral • left anterior oblique (best LV separation)

  11. Gated blood pool (MUGA) • In-vitro labeling: withdraw 1.5-3ml of patients blood into a heparinized syringe. • Inject blood into RBC reaction vial. cold kit • Add contents of syringe I, mix, add contents of syringe II, mix. • Add 30mCi of Tc99m • 20-30 minutes reinject patient with tagged RBC’s.

  12. Gated blood pool (MUGA) • In-vivo labeling: make up “cold” (non-radioactive) kit of PYP by adding 2-3ml saline • Inject patient with 1-3ml from “cold” PYP • Wait up to 20-30 min, inject patient in opposite arm as PYP injection.

  13. Gated blood pool (MUGA) • In-vivo (modified) • Same procedure as using “cold” PYP inject • Except when reinjecting post-PYP injection • Tc99m is mixed with heparin and 3-5ml of patients blood. • Mixture is then reinjected into patient and tagging process and imaging begins.

  14. Gated blood pool (MUGA) • Imaging begins immediately post-injection (PI) • Patient is hooked up to a 3 or 5 lead ECG. • Multiple-images are attained (as per protocol) • 300-600 beats/image or set acquired time is attained 5-10 min.

  15. Gated blood pool (MUGA) • Calculate EF=(ED-ES)/EDx100 • Normal EF= 50-70% • Abnormal EF=35-45% severe impairment below 30%

  16. Gated Blood Pool (MUGA) • Exercise assessment • stress done with bicycle w/camera positioned over heart • rest EF to compare stress EF • Primary uses of test • congestive heart failure • cardiomyopathy • chemo cardiotoxicity

  17. First Pass Cardiac Study • What’s ‘first pass’? • temporal separation of chambers • Functional assessment • ventricular wall motion • ES and ED ventricular volumes • LV and RV ejection fractions • pulmonary transit time

  18. First Pass Cardiac Study • Radiopharmaceuticals via bolus • Tc-99m DTPA • Tc-99m sestamibi • Tc99m pertechnatate. • Adult doses: 8-30 mCi • Images • one anterior image for 60 seconds • acquisition is divided into many millisecond frames for resolution

  19. First pass study • Arrhythmia may hamper acquisition • Acquire a ECG (electrocardiogram) to verify status of rhythm.

  20. First Pass Cardiac Study • Can be performed with exercise • stress done with bicycle w/camera positioned over heart. • rest EF to compare to stress EF • Primary uses of test • same as gated cardiac study • better than gated at right ventricle assessment and cardiac shunts

  21. First Pass Cardiac Study • Primary limitation:This procedure requires a special nuclear imaging camera that cannot be used to perform any other type of nuclear procedures. Many clinics cannot justify the cost, so a gated study is used instead.

  22. Myocardial Perfusion Study • Assess coronary blood flow • Demonstrate blood perfusing the LV myocardium • Software allows gating for EF • 3D reconstruction of heart

  23. Myocardial Perfusion • Radiopharmaceuticals • Thallium-201 chloride • Tc-99m sestamibi Tc-99m tetrofosmin • SPECT acquisition • provides cross-sectional images of the myocardium in the short axis, horizontallong axis and vertical long axis planes

  24. Myocardial perfusion localization • Tc-99m sestamibi passive transport into myocardial mitochondria in proportion to blood flow. • Tc-99m tetrofosmin same as sestamibi binds to myocytes. • Tl-201chloride (similar to potassium) distributes with Na/K pump within 20 mins. of injection, leaves myocardium slowly and redistributes.

  25. Myocardial perfusion localization • Tl-201 chloride redistributes 3-4 hours after injection. • Tl-201chloride good for myocardium viability. • Second reinjection of Tl-201 may be needed.

  26. Myocardial resting dose • Tc-99m sestamibi Tc-99m tetrofosmin adult doses 8-30 mCi • Tl-201 chloride adult doses 2-5 mCi • Iv administration

  27. Indications • Detection and evaluation of CAD (coronary artery disease) • Coronary bypass surgery or angioplasty • Detection of viable tissue (Tl-201) • Evaluation of MI, chest pain, SOB, family history of heart disease. • Evaluation of blood work indicators ie: elevated creatine phosphokinase, troponin etc.

  28. Contraindications • Patient should be NPO 4-12 hrs prior to study. • Patient should be off all chemical stressors: -caffeine -dipyridamole -nitroglycerin drips and patches - as per Dr. all cardiac meds.

  29. Myocardial stress dose • Tc-99m sestamibi Tc99m tetrofosmin = 20-30 mci • Tl-201 chloride 3-5 mci • IV administration. Must have patent line. • Myocardial localization same as resting.

  30. Indications • Same as resting protocals. • Contraindications : -chest pain - discontinue chemical stressors: -caffeine -persantine -viagra

  31. Contraindications • High blood pressure • Not comfortable weaned from nitroglycerin • Allergies to chemicals (stress pharmaceuticals) • Lung conditions (asthmatic reaction to persantine or adenosine) dobutamine used in these cases.

  32. Myocardial Perfusion • Performed at rest & stress • Stress study options • treadmill exercise • pharmacologic stress agents • adenosine • persantine (dipyridamole) • dobutamine

  33. Myocardial Perfusion • Percentage of LV myocardium receiving decreased perfusion • Differentiate ischemia from MI • 24 hour delayed images demonstrate myocardial viability (hibernating) • Rest-only studies can provide information on acute MI’s

  34. Patient Prep • Any stress procedure • NPO midnight • off beta-blocker medications • Chemical stress procedure • off caffeine and asthma medications for adenosine/persantine chemical stress • Any rest procedure • requires no patient prep

  35. Acquisition • Inject first dose and acquire resting SPECT study • Prepare patient for stress • At maximal stress inject radio-pharmaceutical • Acquire stress SPECT study (gated) *variations in procedure sequence may occur

  36. Exam Results • Myocardial Infarction • perfusion defect on rest & stress • Myocardial Ischemia • perfusion defect on stress only

  37. Time Comparison • Gated study • rest 40 minutes • First pass study • rest 15 minutes • stress 60 minutes • Myocardial perfusion study • 60 minutes stress & 30 minutes rest

  38. Myocardial Infarction • Tc99m pyrophosphate (PYP) “Hot PYP” • PYP deposits in mitchondria and necrotic myocardial tissue

  39. Myocardial Infarction • Maximum PYP deposition occurs usually occurs at 48-72 hrs post infarction. • 15-30 mCi adult dose. • IV administration.

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