Myocardial Perfusion Imaging

Physiological Alteration vs. Stress Rest Stress Perfusion abnormality Molecular alteration Diastolic dysfunction Regional dysfunction ECG changes Chest pain

Myocardial perfusion scintigraphy Overview Myocardial blood flow  ml/min/100g at rest, 3-5 fold while demand   When tachycardia, absolute flow , but inner-to-outer flow ratio  1973Zaret et al. 43 KNEJM 1973;288: Botvinick et al. 81 RbAJC 1977;39: Lebowitz et al. 201 TlJNM 1973;14:421 Heo et al. 99m TcCardiology 1994;12: Najm et al.FunctionEHJ 1989;10:142 Cooke et al.SPECTAJCI 1993;7:152 Maddahi et al.QuantitativeJACC 1989;114:1689

Myocardial perfusion Radiotracers Mechanism, Extraction, and Linearity with flow

Comparison of MPS protocols 201 Tl stress-rest protocol  Long half-life, low dose, low count, poor spatial resolution, low energy, not well gated images, high scatter, attenuation  Stress always first  Probably optimal viability agent 201 Tl rest-redistribution protocol  Likely optimal and most cost-effective viability study 99m Tc sestamibi / tetrofosmin protocols  Better imaging characteristics, high resolution, least attenuation, no significant redistribution Dual isotope 201 Tl rest / 99m Tc stress protocol  Brief with high throughput  24-hr 201 Tl imaging to maximize viability assessment  Difficulties in comparing 201 Tl and 99m Tc images

Tl-201 Myocardial imaging Patient preparation: fasting for 4 hours. Dosage: 2-3 mCi, i.v. Stress imaging: 10 min post Tl-201 administration. Rest imaging: 3-4 hr later.

Cardiac drugs that may interfere with stress testing and recommended withdrawal interval Beta blockers 72 hr Ca ++ channel blockers hr Nitrates (long acting) 12 hr

Alternatives to leg exercise in cardiac stress testing Isometric (handgrip) exercise Atrial pacing Esophageal pacing Cold pressor testing Ventricular stimulation; postextrasystolic potentiation Pharmacologic stress

SPECT processing steps ProcessUtilization Filtering TimingPrereconstructionStandard with ReconstructionOptional TypesAdaptiveOptional ConventionalStandard Reconstruction TransverseAnalytic (backprojection)Standard IterativeOptional Oblique angleManual / Automatic Display Cine reviewScreenMandatory Study reviewScreenPreferred Hard copyOptional

Methods of MPS Quantitation OperationMethodUtilization SamplingCircumferential profile CylindricalStandard Cylindrical and SphericalOptional Maximum countStandard Average countOptional NormalizationMaximum countStandard Average regionOptional Maximum count (%)Optional AnalysisNormal databaseStandard ThresholdOptional VariablesExtent, Severity, ReversibilityStandard Transient dilation, Lung washoutOptional Display2D polar maps (Bullseye maps)Standard Circumferential profilesOptional