Myocardial Perfusion ImagingMyocardial 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 80-100 ml/min/100g at rest, 3-5 fold while demand When tachycardia, absolute flow , but inner-to-outer flow ratio

1973 Zaret et al. 43K NEJM 1973;288:809

1977 Botvinick et al. 81Rb AJC 1977;39:364

1973 Lebowitz et al. 201Tl JNM 1973;14:421

Heo et al. 99mTc Cardiology 1994;12:187

1989 Najm et al. Function EHJ 1989;10:142

Cooke et al. SPECT AJCI 1993;7:152

Maddahi et al. Quantitative JACC 1989;114:1689

Myocardial perfusion Radiotracers

Mechanism, Extraction, and Linearity with flow

Comparison of MPS protocols 201Tl 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

201Tl rest-redistribution protocol Likely optimal and most cost-effective viability study

99mTc sestamibi / tetrofosmin protocols Better imaging characteristics, high resolution, least attenuation, no signific

ant redistribution Dual isotope 201Tl rest / 99mTc stress protocol

Brief with high throughput 24-hr 201Tl imaging to maximize viability assessment Difficulties in comparing 201Tl and 99mTc images

Tl-201 Myocardial imaging

Patient preparation: fasting for 4 hours. Dosage: 2-3 mCi, i.v. Stress imaging: 10 min post Tl-201 admi

nistration. 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 48-72 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 pot

entiation Pharmacologic stress

SPECT processing stepsProcess Utilization

Filtering

Timing Prereconstruction Standard

with Reconstruction Optional

Types Adaptive Optional

Conventional Standard

Reconstruction

Transverse Analytic (backprojection) Standard

Iterative Optional

Oblique angle Manual / Automatic

Display

Cine review Screen Mandatory

Study review Screen Preferred

Hard copy Optional

Methods of MPS QuantitationOperation Method Utilization

Sampling Circumferential profile

Cylindrical Standard

Cylindrical and Spherical Optional

Maximum count Standard

Average count Optional

Normalization Maximum count Standard

Average region Optional

Maximum count (%) Optional

Analysis Normal database Standard

Threshold Optional

Variables Extent, Severity, Reversibility Standard

Transient dilation, Lung washout Optional

Display 2D polar maps (Bullseye maps) Standard

Circumferential profiles Optional