Myocardial Perfusion Imaging SPECT Basics

Imaging and Protocol Basics

Indications of MPI Detection of CAD Assessing functional significance of coronary

stenosis Evaluating prognosis and risk stratification Assessing medical therapy of CAD Assessing cardiac viability

Coronary Artery Disease Cardiovascular disease is the leading cause of

death in the United States Accounts for nearly 1 million deaths, half of which

are the result of CAD CAD is a condition in which the heart does not

receive enough blood Caused by accumulation of plaques in the

coronary arteries Causes stenosis of the lumen of the vessels Decreases ability of the walls of the affected

vessels to contract which inhibits cardiac function Occlusion of the vessels can also be caused by

thrombus or embolus in a coronary artery or an artery spasm

Risk Factors CAD High cholesterol High blood pressure Cigarette smoking Obesity Diabetes Sedentary lifestyle Family history of CAD Gender (more prevalent in males)

Symptoms of CAD Angina pectoris

Transient pain or discomfort resulting from a temporary lack of oxygen and nutrients to the heart muscle

Myocardial Infarction A portion of the heart muscle dies resulting from inadequate

blood flow Changes the electrical activity of the heart Decreases contractility of heart in fibrous area

Difficulty breathing Weakness Dizziness Perspiration CAD progresses over time and a person may be

asymptomatic in the early stages of the disease

Manifestations of CAD Before reaching > 70-80% vessel occlusion CAD may

have little or no effect on resting heart function When demands of the heart muscle are increased

diseased vessels cannot produce adequate blood flow

Coronary reserve: the ability to increase coronary blood flow when needed Decreases in CAD due to increased metabolic demands of

the diseased vessels Patients with severe CAD will usually have

homogeneous resting regional myocardial blood flow Diminished blood flow at stress because of the

inability to increase blood flow when needed

Treatment of CAD Drug therapy

Nitroglycerin Relaxes smooth muscle causing blood vessels to dilate

Beta blockers Depress cardiac function and decrease cardiac output

Cholesterol-lowering drugs Clot-dissolving agents

Low-fat diet Exercise

Treatment of CAD CABG (coronary artery bypass graft)

Blood vessels from one part of the body are used to bypass a blocked region of a coronary artery to improve blood supply to the affected area of the heart muscle

PTCA (percutaneous transluminal coronary angioplasty) Lumen of a stenotic vessel is dilated

Atherectomy Obstructive plaque or thrombus is removed sing

lasers or mechanical devices Intracoronary stents

Patient Prep MPI Stress Test NPO 4 hours prior to test No caffeine within 24 hours Restrict cardiac medication if possible Consent for stress Pregnancy consent Skin prep/lead placement 12 lead EKG IV placement

Contraindications Pregnancy Food within 4 hours of stress study Caffeine within 24 hours (for pharmaceutical

stress) Bronchospasm or severe obstructive lung

disease (for pharmaceutical stress) Hypotension (BP < 90) Xanthine-containing drugs

Protocols One-day

Rest Thallium 3-5mCi/Stress Sestamibi or Tetrofosmin 20-40mCi

Rest Sestamibi or Tetrofosmin 10-15mCi/Stress Sestamibi or Tetrofosmin 30-45mCi

Two-day Stress Day 1

25-45mCi Sestamibi or Tetrofosmin Rest Day 2 (if needed)

25-45mCi Sestamibi or Tetrofosmin

Imaging Protocols maiCAM180 Rest 30-40 seconds/step Stress 20-30 seconds a step 16/32 steps 32/64 projections 64x64 matrix Non-circular orbit Limiting patient motion is essential during

acquisition for quality images Movement can appear differently on upright

imaging systems than supine

Processing

Set reconstruction limits on both Rest and Stress cine data

Segami Mirage 5.715b is used for demonstration purposes

Processing Reorient slices to appropriate angles

Processing Apply mask and post filtering if necessary

Reconstruction and Review Basics: Slice Display

Planes of the heart that are reconstructed in MPI are:Horizontal Long Axis (HLA)Short Axis (SA)Vertical Long Axis (VLA)

Reconstructed data is viewed at rest and stress, and the corresponding planes and slices are compared.

Intensity/color changes between the two can represent ischemic changes.

Count deficient areas that are shared between the two can represent fixed defects.

Reconstruction and Review Basics: Slice Display

Reconstruction and Review Basics: Volume Data 3-D view of the heart that can be viewed from

all angles Gated data can be viewed as cine volume

data to assess wall motion Surface of the heart can be viewed separately

or simultaneously in both systole and diastole

Reconstruction and Review Basics: Volume Data

Reconstruction and Review Basics: Quantification Largely developed by Cedars Sinai Medical

Center (Los Angeles, CA) and Emory University (Atlanta, GA)

Polar Map or Bull's-eye of the left ventricle of the heart

Left ventricle is sliced from apex to base and displayed in concentric ring; this allows the visualization of the left ventricle in a comprehensive image, rather than multiple images as with slice displays

Reconstruction and Review Basics: Quantification

References Nuclear Cardiac Imaging: Terminology and

Technical Aspects; Crawford and Husain; 2003; SNM

Diagrams taken from Nuclear Cardiac Imaging: Terminology and Technical Aspects; Crawford and Husain; 2003; SNM

Nuclear Cardiac images taken from MAI Demo database using Cedars Sinai and Segami Mirage processing applications