An Introduction to Nuclear Cardiology

1
An IntroductiontoNuclear Cardiology
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.

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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

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Gated Blood Pool

• Gating process
• Functional assessment
• ventricular wall motion
• ES and ED ventricular volumes
• LV ejection fraction
• normal 64 /- 12

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Gated Blood Pool

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

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Gated Blood Pool

• Exercise assessment
• stress done with bicycle
• rest EF to compare stress EF
• Primary uses of test
• congestive heart failure
• cardiomyopathy
• chemo cardiotoxicity

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First Pass Cardiac Study

• Whats first pass?
• temporal separation of chambers
• Functional assessment
• ventricular wall motion
• ES and ED ventricular volumes
• LV and RV ejection fractions
• pulmonary transit time

13
First Pass Cardiac Study

• Radiopharmaceuticals via bolus
• Tc-99m DTPA
• Tc-99m sestamibi
• Images
• one anterior image for 60 seconds
• acquisition is divided into many millisecond
  frames for temporal resolution

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First Pass Cardiac Study

• Can be performed with exercise
• stress done with bicycle
• 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

15
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.

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Myocardial Perfusion Study

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

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Myocardial Perfusion

• Radiopharmaceuticals
• Thallium-201 chloride
• Tc-99m sestamibi
• SPECT acquisition
• provides cross-sectional images of the myocardium
  in the short axis, horizontal long axis and
  vertical long axis planes

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Myocardial Perfusion

• Performed at rest stress
• Stress study options
• treadmill exercise
• pharmacologic stress agents
• adenosine
• persantine (dipyridamole)
• dobutamine

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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 MIs

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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

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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

22
Exam Results

• Myocardial Infarction
• perfusion defect on rest stress
• Myocardial Ischemia
• perfusion defect on stress only

23
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