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Training presentation for nuclear medicine technologists on myocardial perfusion imaging basics
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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