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

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.

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 .

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 Inside view of a CT systemshowing the patient table showing the X-ray tube and detector

Computed Tomography of the Heart

Why is CT Performed?

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?

CT can provide detailed cross sectional images and diagnostic information for nearly every part of the body;

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

Computed Tomography of the Heart

CT of the Heart

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

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 radiographwhich 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

Computed Tomography of the Heart

Two Types of CT Scanners

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

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

Computed Tomography of the Heart

Clinical Cardiovascular Indications

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

Cardiac CT is especially useful in evaluating the

myocardium, coronary arteries, pulmonary veins, thoracic aorta, pericardium

Computed Tomography of the Heart

Clinical Cardiovascular Indications

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

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

Computed Tomography of the Heart

Clinical Cardiovascular Indications

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 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

Computed Tomography of the Heart

Clinical Cardiovascular Indications

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

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

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