Transcript CV-MRI by Ali Bayram (ppt, handout)

CARDIOVASCULAR IMAGING WITH
COMPUTED TOMOGRAPHY(CT)
Hakan SOLMAZ,
Institude of Biomedical Engineering,
Boğaziçi University
Computed Tomography of the Heart
Key Points
greater spatial and temporal resolution
 detailed anatomic information
 image reconstruction in 3-D
 estimation of calcified and noncalcified
plaque in coronary arteries
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Computed Tomography of the Heart
A Brief History of CT
Comes from the Greek word "tomos"
meaning "slice" or "section" and graphia
meaning "describing".
 The first clinical CT scanners were installed
between 1974 and 1976, were dedicated to
only head imaging.
 The first CT scanner developed by
Hounsfield.
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Computed Tomography of the Heart
How Does CT Work?
combines the use of a digital computer
together with a rotating x-ray device
 cross sectional images or "slices"
 lungs, liver, kidneys, pancreas, pelvis,
extremities, brain, spine, and blood vessels .
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Computed Tomography of the Heart
How Does CT Work?
Computed Tomography of the Heart
How Does a CT Look Like
Outside view of a CT system
showing the patient table
Inside view of a CT system
showing the X-ray tube and detector
Computed Tomography of the Heart
Why is CT Performed?
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CT has the unique ability to image a
combination of soft tissue, bone, and blood
vessels
Conventional X-Ray imaging shows the
dense bone structures,
X-ray angiography depicts the blood vessels,
MR imaging is excellent in showing soft
tissue and blood vessels
Computed Tomography of the Heart
Why is CT Performed?
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CT can provide detailed cross sectional
images and diagnostic information for nearly
every part of the body;
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the brain, vessels of the brain, eyes, inner ear,
sinuses
the neck, shoulders, cervical spine and blood
vessels of the neck
the chest, heart, aorta, lungs, mediastinum
the thoracic and lumbar spine
the upper abdomen, liver, kidney, spleen, pancreas
and other abdominal vessels
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Computed Tomography of the Heart
CT of the Heart
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Planar Imaging vs CT Imaging
Planar image processors can not show
smaller structures
They create images of the silhouette of the
contrastfilled vessels
3-D CT image can reveal complex anatomy
and spatial relationships
Computed Tomography of the Heart
CT of the Heart
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Planar Imaging vs CT Imaging
CT imaging is slower than planar imaging
planar radiograph ~ 4 to 10 ms exposure
time
tomographic image slice ~ 50 to 250 ms
each image slice must be acquired during
the late diastole
Computed Tomography of the Heart
CT of the Heart
standard chest radiograph
which is a planar projection
three-dimensional computed
tomographic image
Computed Tomography of the Heart
Two Types of CT Scanners
Electron-beam CT
 developed for cardiac imaging; 50-100 ms
per image slice
 reflecting electron beam onto a stationary
tungsten target
 Multidetector CT
 developed for body imaging
 mechanically rotating an x-ray tube
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Computed Tomography of the Heart
Two Types of CT Scanners
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new multidetector CT scanners;
high spatial and temporal resolution
Computed Tomography of the Heart
Principles of Cardiovascular CT Examination
the image data are acquired during one
breath-hold within a chosen scan protocol
 most protocols require iodinated contrast
agents to enhance cardiovascular structures
 two Acquisition modes;
 The sequential 2-D mode
 The spiral 3-D mode
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Computed Tomography of the Heart
Principles of Cardiovascular CT Examination
A smaller slice thickness allows better
resolution
 radiation exposure and scan time increase
 volume covered is reduced
 A slower heart rate allows better CT image
quality
 betablockers are desirable to slow the heart
rate
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Computed Tomography of the Heart
Clinical Cardiovascular Indications
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CT can be used for a number of
cardiovascular indications, but sometimes
with another imaging test;
Hypertension; CT + MRI
acute midsternal chest; CT + angiography
Computed Tomography of the Heart
Clinical Cardiovascular Indications
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Cardiac CT is especially
useful in evaluating the
myocardium,
coronary arteries,
pulmonary veins,
thoracic aorta,
pericardium
Computed Tomography of the Heart
Clinical Cardiovascular Indications
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Cardiomyopathy with contrast enhanced CT
ischemic cardiomyopathy, CT typically
shows;
Focal ventricular wall thinning
Fibrous or calcified replacement of
myocardium
Aneurysm formation
Computed Tomography of the Heart
Clinical Cardiovascular Indications
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non-ischemic cardiomyopathy, CT typically
shows;
global dilatation and myocardial thinning,
focal myocardial hypertrophy
Computed Tomography of the Heart
Clinical Cardiovascular Indications
two chamber view
three chamber view
Computed Tomography of the Heart
Clinical Cardiovascular Indications
four chamber view
short-axis view
Computed Tomography of the Heart
Clinical Cardiovascular Indications
Coronary artery stenosis with contrast
enhanced CT scan
 allow one to assess stenosis
 Coronary CT angiography is challenging
 the blood vessels are small, tortuous, and in
rapid motion during the cardiac cycle
 CT doesn’t have enough spatial and
temporal resolution to show all the coronary
segments
 There may be plaque calcification
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Computed Tomography of the Heart
Clinical Cardiovascular Indications
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Uses of CT angiography;
To rule out severe proximal stenosis
To assess anomalous coronary arteries and
to determine their origins and their
relationship
evaluate the severity of stenosis in venous
aortocoronary grafts
Computed Tomography of the Heart
Clinical Cardiovascular Indications
 Coronary
CT can exclude significant
obstructive disease and assess
atherosclerotic plaque
Computed Tomography of the Heart
Clinical Cardiovascular Indications
The smaller images are the views at the level of aortic valve
Computed Tomography of the Heart
Clinical Cardiovascular Indications
 Pericardial
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diseases;
Detailed anatomic information about the
pericardium
Inflammation of the pericardium can be
detected with contrast-enhanced CT
Computed Tomography of the Heart
Clinical Cardiovascular Indications
Cardiac masses can be described on CT
according to their,
 size, density, and spatial relationship to
adjacent structures
 Although CT can also detect tumors, it is
limited
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Computed Tomography of the Heart
Clinical Cardiovascular Indications
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additionaly;
valve stenosis and regurgitation,
aortic disease,
pulmonary embolism,
pulmonary veins imaging
Computed Tomography of the Heart
Frequently Asked Questions
Does the CT examination hurt?
 No, it does not, except the case of iodine
contrast injection, which is discomfortable
during the needle is placed
 Is CT Imaging Safe?
 the diagnostic benefit of a CT scan usually
outweighs the risk of x-ray radiation
exposure or injections of imaging contrast
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Computed Tomography of the Heart
Frequently Asked Questions
How long will the CT examination take?
 the actual procedure will typically be between
10 minutes and 45 minutes
 Can I Move While I am in the CT Scanner?
 You should not move when you are on the
CT table and the images are being acquired.
CT exams of the chest and abdomen require
the patient to hold their breath for a short
period of time, for example, 10 to 25 seconds
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Computed Tomography of the Heart
References
http://imaginis.com
 Physical Principles of Medical Imaging; Perry
Sprawls, Proff. Of Radiology, Emory
University School of Medicine
 http://www.radiologyinfo.org
 http://www.clevelandclinic.org/heartcenter
 http://www.ctisus.org
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