Nuclear CardiologyNuclear CardiologyJohn N. Hamaty D.O.John N. Hamaty D.O.

Second year student moduleSecond year student module

Nuclear cardiology has been an active clinical discipline for more than two decades.

Indirect measure of coronary perfusion to the myocardium.

Utilized for the assessment of functional categories as well as prognosis and risk.

InstrumentationInstrumentation

Scintillation (gamma) cameraScintillation (gamma) camera

Collimation (focusing Lens)Collimation (focusing Lens)

Computer (principal component)-Computer (principal component)-processorprocessor

Spect ImagingSpect Imaging

Single-photon emission computed Single-photon emission computed tomographytomography

Planar images obtained over 180 degree Planar images obtained over 180 degree arcarc

Three planes-Three planes- A) short axisA) short axis B) Horizontal B) Horizontal C) VerticalC) Vertical

Myocardial perfusion imagingMyocardial perfusion imaging

Allows Allows RELATIVE RELATIVE distribution of myocardial blood flow

Absolute quantification is not feasible with spect

PET scanning is only absolute testPET scanning is only absolute test

Myocardial perfusion imagingMyocardial perfusion imaging

Most important clinical application of Most important clinical application of myocardial perfusion imaging is in myocardial perfusion imaging is in conjunction with stress testing for conjunction with stress testing for evaluation of ischemic heart diseaseevaluation of ischemic heart disease

Stress testingStress testing Objective is to “stress” the heart via Objective is to “stress” the heart via

treadmill or pharmacologic testingtreadmill or pharmacologic testing Alterations in heart rate, O2 consumption Alterations in heart rate, O2 consumption

and blood pressure effect uptake of the and blood pressure effect uptake of the nuclear agent.nuclear agent.

Goal heart rate is 85% of predicted based Goal heart rate is 85% of predicted based on age (220-age) then 85% is target.on age (220-age) then 85% is target.

Sensitivity/Specificity is 85% with Sensitivity/Specificity is 85% with nuclear/echo augmentationnuclear/echo augmentation

Myocardial perfusion imagingMyocardial perfusion imaging

Demonstrated that findings on stress Demonstrated that findings on stress images reflect the hemodynamic and images reflect the hemodynamic and functional significance of coronary artery functional significance of coronary artery stenosis and thus provide important stenosis and thus provide important prognostic information.prognostic information.

RadiopharmaceuticalsRadiopharmaceuticals

Thallium-201Thallium-201

Technetium-99Technetium-99

Thallium-201Thallium-201

Cyclotron producedCyclotron produced Doses of 3-4 mCiDoses of 3-4 mCi Initial myocardial accumulation is Initial myocardial accumulation is

proportionalproportional to myocardial blood flow. to myocardial blood flow. ContinuousContinuous exchange of Tl takes place exchange of Tl takes place

across the cell membrane.across the cell membrane.

Thallium-201Thallium-201

Energy requiring (Na-K-Atp-ase)Energy requiring (Na-K-Atp-ase) Cell re-accumulation of Tl gives effective Cell re-accumulation of Tl gives effective

half-life in heart of 7.5 hours.half-life in heart of 7.5 hours. Unique property because it allows early Unique property because it allows early

and late imaging after injectionand late imaging after injection

Thallium-201Thallium-201

Images immediately after injection reflect Images immediately after injection reflect the flow dependent initial distribution and the flow dependent initial distribution and thus regional myocardial blood flow-thus regional myocardial blood flow-IschemiaIschemia

Thallium-201Thallium-201

Images taken after a delay of 2-24 hours Images taken after a delay of 2-24 hours reflect the distribution of the potassium reflect the distribution of the potassium pool and hence allow for detection ofpool and hence allow for detection of

Myocardial ViabilityMyocardial Viability

Myocardial ViabilityMyocardial Viability

Detection of living cells despite hypo-Detection of living cells despite hypo-akinesis of ventricular contractilityakinesis of ventricular contractility

Stunned myocardiumStunned myocardium

Hibernating myocardiumHibernating myocardium

Technetium-99Technetium-99

Emmits Gamma rays at 140 kevEmmits Gamma rays at 140 kev Half-life is 6 hoursHalf-life is 6 hours Slow body clearanceSlow body clearance 30 mCi30 mCi Initial distribution is similar to Tl and is Initial distribution is similar to Tl and is

proportional to regional blood blowproportional to regional blood blow

Technetium-99MTechnetium-99M

Difference is tech extraction from the heart Difference is tech extraction from the heart is greater (65%) and is greater (65%) and redistributionredistribution is much is much less than Tl.less than Tl.

Because the intracellular retention is Because the intracellular retention is relatively fixed over time, no significant relatively fixed over time, no significant redistribution occurs.redistribution occurs.

Technetium-99MTechnetium-99M

Since no significant redistribution occurs, Since no significant redistribution occurs, the myocardial blood flow at the time of the myocardial blood flow at the time of injection is “frozen” over time and imaging injection is “frozen” over time and imaging can occur hours later.can occur hours later.

Technetium-99MTechnetium-99M

This also allows for assessment of wall This also allows for assessment of wall motion and ejection fraction. Since image motion and ejection fraction. Since image is “fixed” for a period of time, we can look is “fixed” for a period of time, we can look at systolic and diastolic function. Allows at systolic and diastolic function. Allows greater sensitivity in detection of infarcted greater sensitivity in detection of infarcted and ischemic myocardium. and ischemic myocardium.

Gated spect imagingGated spect imaging

This has increased the sensitivity and This has increased the sensitivity and specificity of interpretation due to detection specificity of interpretation due to detection of breast/diaphram artifact.of breast/diaphram artifact.

Chamber size and right ventricular Chamber size and right ventricular function can also be assessedfunction can also be assessed

Dual isotope imagingDual isotope imaging

Utilizing an “Hybrid” of imaging proticals, Utilizing an “Hybrid” of imaging proticals, two injections of rest thallium and stress two injections of rest thallium and stress tecnetiumtecnetium

Greater patient throughputGreater patient throughput Allows for viability testingAllows for viability testing Comparing apples and oranges(two Comparing apples and oranges(two

different agents)different agents)