David M Isaacs, DORotating Resident at

William Beaumont Hospital Department of Nuclear Medicine

Cardiac Anatomy utilizing CT Angiography

ObjectivesExamine the need for Coronary Anatomy

Imaging using CT Angiography (CTA)Explore the basic Technique and dose of

Coronary CT Angiography (CCTA)Examine the different reconstruction

algorithmsDetail the Coronary Anatomy utilizing CCTAExamine Cardiac CTA for imaging veins and

other heart structuresBriefly review recently published data

regarding clinical applications of CCTA

BackgroundMore than 5 million patients with acute

chest pain present to emergency departments in the United States each year

Patients who are at highest risk for adverse outcomes derive the greatest benefit from glycoprotein IIb and IIIa inhibitor therapy and early revascularization

By contrast, patients at low risk may be discharged without a long-term effect on their risk of death or myocardial infarction

BackgroundThe term acute coronary syndrome (ACS)

describes clinical manifestations of acute myocardial ischemia induced by coronary artery disease

The rate of missed diagnosis of acute coronary syndromes, which remains unacceptably high (2%–4%), is associated with a twofold increase in mortality

This factor contributes to a low threshold for hospital admission of patients with chest pain by emergency department physicians.

Consequences of a missed acute coronary syndrome, and resultant liability issues (20% of emergency department malpractice dollar losses), and more than 2 million patients with acute chest pain are unnecessarily admitted to the hospital

BackgroundShort examination times of approximately

5 minutes and robust image quality, multidetector cardiac CT constitutes a highly attractive approach for initial work-up in the emergency department setting.

Patient Selection and PreparationContraindication

history of severe allergic reaction to an iodinated contrast material

impaired renal function (creatinine level of > 1.5 mg/dL)

Ideal Patients : Have a normal sinus rhythm, Targeted heart rate of less than 65 beats per

minute during image acquisitionHeart rate should be measured during a breath-

holding test to determine whether the

administration of a ß-blocker is necessaryheart rate often decreases by 5–10 beats per minute

during the first few seconds of a postinspiration breath hold

ß-blocker (eg, 5–20 mg of metoprolol) immediately before the CT examination

A Standard CT Protocol1. Localization:

projectional anteroposterior topographic scan of the chest. The imaging volume should extend from 1–2 cm below the

carina to the bottom of the heart.2. Determination of Contrast Agent Transit Time:

15 mL of the contrast agent, immediately followed by 40 mL of saline, is injected at a flow rate of 5 mL/sec

Scanning is initiated 10 seconds after the start of the contrast medium injection

Axial images are acquired at the level of the aortic root (10-mm collimation) at intervals of 2 seconds and are instantly displayed

3. Data Acquisition: Images are acquired in helical mode during injection of 60–

100 mL of the contrast agent followed by 40 mL of saline solution, at a rate of 4–5 mL/

sec

A Standard CT Protocol The short scan duration of 12 to 15 seconds permits a

breath-hold imaging duration that can capture homogenous contrast opacification around the narrow peak of contrast enhancement

Optimal image quality usually can be achieved in diastole (starting at approximately

65% of the R-R cycle)

Images typically reconstructed with 1-mm section thickness and a 0.5-mm overlap at 16-section multidetector CT and with a 0.75-mm section thickness and 0.4-mm overlap at 64-section multidetector CT

Nearly isotropic resolution (voxel size, 0.4 x 0.4 x 0.6 mm) permits reformatting of images in any arbitrary plane without a significant loss of image information.

ECG triggering and gating ECG triggering:

the scanner acquires data only for a defined period after the signal from the R wave of the ECG trace.

“step and shoot” scan technique an image is acquired every second heartbeat to

allow table translation between image generation ECG gating:

the scanner acquires data in a nonstop, helical mode while an independent ECG trace is generated at the same time

Images are acquired both during systole and diastole

ECG triggering and gatingTo

summarize: TriggerTrigger GatingGating

ECG to acquire data and is prospective

ECG to reconstruct data and is retrospective

“Step and shoot”

Continuous

coronary calcification scoring

aortic root imaging

required for coronary artery CTA

Multiplanar Imaging- Key= Temporal Resolution The advent of multidetector CT (MDCT),

particularly with scanners having 64 or more detectors, has continued to improve temporal resolution (TR).

TR may be thought of as the “shutter speed” of the scanner and is the key to recent advancements in MDCT technology. Temporal resolution in the region of 100 msec is required to create relatively motionless images of the beating heart

Thus, the heart and coronary arteries are routinely imaged as a motion-free volume of data and is reconstructed in multiple formats:Multiplanar reformation (MPR), maximum intensity

projection (MIP), volume rendering (VR), curved reformation, and cine imaging

Multidetector CT Postprocessing TechniquesMultiplanar Reformation

• MPR is the basic tool used to interpret cardiac CT angiographic studies

• Data from specific phases of the cardiac cycle are retrospectively referenced to the electrocardiogram for reconstruction

• The workstation allow images of the heart and coronary arteries to be manually rotated for optimal evaluation of the cardiac anatomy

• Automatically orient data sets along the cardiac axes and into the traditionally used cardiac planes (ie, short-axis, horizontal long-axis, vertical long-axis)

Multidetector CT Postprocessing TechniquesMaximum Intensity Projection

Technique that takes the highest-attenuation voxel in a predetermined slab of data and projects it from the user toward the viewing screen, resulting in a two-dimensional image.

similar to traditional angiograms, which display intraluminal opacity values

can allow quick assessment for significant coronary artery stenosis

limitation of MIP images is that they lack depth and spatial information

Multidetector CT Postprocessing TechniquesVolume Rendering

3D technique in which the CT attenuation values for

each voxel can be assigned a specific color, thereby producing an overall image of the heart

only true 3D technique and provides the depth and spatial information that is lacking with MIP

facilitate surface evaluation of the heart and coronary arteries

useful for evaluating complex anatomy, including coronary artery anomalies, bypass grafts, and fistulas

easily understandable format for referring physiciansuseful also for surgical planning

Multidetector CT Postprocessing TechniquesCurved Reformation

Coronary arteries are often tortuous, accurate

evaluation requires assessment of the entire vessel along its center line

Curved reformatted images provide this capability

by sampling a given volume (ie, artery) along a predefined curved anatomic plane

Most useful for depicting the lumen of a coronary

artery from its ostium to its distal end.Is especially helpful in patients with bypass grafts

and highly tortuous coronary arteries

Multidetector CT Postprocessing TechniquesCine Imaging

examine the motion and physiologic features of cardiac structures such as the LV and cardiac valves

data from the heart and coronary arteries are typically reconstructed at specific points during the cardiac cycle, ie. Examine certain anatomy during systole and

diastoleparticularly useful for examining LV wall motion and wall

thickening and for assessing valve motion in multiple planes

reconstruction of the cardiac data during both systole and diastole allows determination of quantitative LV functional parameters, including end-diastolic and end-systolic ventricular volumes, stroke volume, and ejection fraction

Ventricular FunctionLeft Ventricle Normal Function

Right Ventricle Normal Function

Radiation Exposure at CT Coronary Angiography ECG-controlled dose modulation technique is used to

reduce the tube current during systole,The effective radiation dose is 6.7–7.6 mSv in men and

8.1–9.2 mSv in womenFor 64-section scanners, the radiation dose at cardiac CT

is 6.9–11.1 mSvWithout tube current modulation, the radiation dose is

estimated to be approximately 16–20 mSvBy comparison, a mean effective radiation dose of

approximately 5 mSv is incurred at selective coronary angiography RadioGraphics 2006;26:963-978

The estimated total body radiation exposure after a 16 slice MDCT coronary angiogram is 2 to 3 times the average exposure from a diagnostic catheterization but similar or lower than the exposure from a rest-stress myocardial scintigraphic study

Coronary ArteriesBy general consensus,

the coronary artery tree is divided into 17 segments, according to the AHA system of classification

Coronary Anatomy- Segments

Axial CT image (0.75-mm section thickness) at the midventricular level shows a middle segment of the right coronary artery (RCA) and distal segments of the left anterior descending and left circumflex branches.

The latter is seen in the left atrioventricular groove, in close proximity to the great cardiac vein (GCV).

Coronary Anatomy- Segments Axial MIP image (5-mm section

thickness) at the level of the bottom of the heart shows a distal segment of the RCA at the origins of the posterior descending artery (PDA) and the posterior left ventricular (PLV) artery.

The posterior descending artery is seen in the posterior longitudinal sulcus, in close proximity to the middle cardiac vein (MCV).

A distal segment of the LAD also is visible.

This case demonstrates right coronary artery dominance in blood supply to the ventricles, a common finding (85%–90% of patients).

Y’all hold on, Here we go in…

Left Main Coronary Artery (LCA)Usually the first coronary artery seen

(starting superiorly from its origin)Normally arises from the left sinus of

Valsalva near the sinotubular ridge Courses posterior to the right

ventricular outflow tract (RVOT), and bifurcates into the left anterior descending (LAD), and the left circumflex (LCX) branches.

In about 15% of patients, a separate intermediate branch, or ramus intermedius (RI), also arises from the left main coronary artery

LCA Segmental Anatomy 5 = main artery, 6 = proximal segment of the left

anterior descending (LAD) branch, 7 = middle segment of the LAD

branch, 8 = distal segment of the LAD

branch, 9 = first diagonal branch, 10 = second diagonal branch, 11 = proximal segment of the left

circumflex (LCX) artery, 12 = first obtuse marginal branch

of the LCX artery, 13 = middle segment of the LCX

artery, 14 = second obtuse marginal

branch of the LCX artery, 15 = distal segment of the LCX

artery, 17 = intermediate branch

LCA segmental Anatomy 5 = main artery, 6 = proximal segment of the left

anterior descending (LAD) branch, 7 = middle segment of the LAD

branch, 8 = distal segment of the LAD

branch, 9 = first diagonal branch, 10 = second diagonal branch, 11 = proximal segment of the left

circumflex (LCX) artery, 12 = first obtuse marginal branch of

the LCX artery, 13 = middle segment of the LCX

artery, 14 = second obtuse marginal

branch of the LCX artery, 15 = distal segment of the LCX

artery, 17 = intermediate branch

The arrowhead in indicates the mid intermediate branch

LCA

VR image shows the LCA (black arrow) arising from the aorta and bifurcating into the proximal LCx artery (arrowhead) and the proximal LAD artery (white arrow).

The LCA (black arrow) bifurcates into the left anterior descending (LAD) artery (white arrowhead) and the left circumflex (LCx) artery (black arrowhead). White arrow indicates the right coronary artery (RCA).

LCA LAD The LAD artery courses

anterolaterally in the epicardial fat of the anterior interventricular groove and supplies the majority of the LV

The LAD artery is divided into proximal, middle, and distal portions

The midportion of the LAD artery extends to the point where the artery forms an acute angle

The apical segment represents the termination of the artery. Oblique axial (top) and vertical

long-axis (bottom) MPR images show the normal LAD artery (arrows) coursing in the epicardial fat of the interventricular groove toward the LV apex

LCA LAD Diagonal Septal

The major branches of the LAD artery are the diagonal and septal perforating arteries. The diagonal branches

course laterally and predominantly supply the LV free wall.

The septal branches course medially and supply the majority of the interventricular septum, as well as the atrioventricular (AV) bundle and proximal bundle branch.

Septal branches (black arrowheads)

diagonal branches (white arrowheads) of the LAD artery

LCA LCxDivided into proximal and distal segments,

based on the origin of the (usually large) obtuse marginal branches

Courses in the left AV groove, giving rise to obtuse marginal branches --

sometimes referred to as lateral branchesSupply the LV free wall and a variable portion

of the anterolateral papillary muscle Variably gives rise to posterolateral and

posterior descending artery (PDA) branches supplying the diaphragmatic portion of the LV

LCA LCx Obtuse MarginalsOblique axial MPR

(top) and VR (bottom) images show the LCx artery (black arrow) and obtuse marginal branches (white arrows).

LCA Ramus Intermedius In approximately 15% of

patients, a third branch, the ramus intermedius (RI) branch, arises at the division of the LCA, resulting in a trifurcation

When present, the RI branch courses toward the LV free wall, similar to that of a diagonal branch of the LAD artery.

RI branch (arrow) arising between the LAD artery (black arrowhead) and the LCx artery (white arrowhead), resulting in a trifurcation of the LCA

Right Coronary Artery (RCA) Normally arises from the right

coronary sinus (CS) and courses in the right AV groove toward the crux of the heart

The proximal RCA extends from the ostium to a point halfway to the acute margin of the heart

Approximately 50%–60% of patients, the first branch of the RCA is a conus artery conus artery supplies the RV

outflow tract (conus arteriosis) and forms the circle of Vieussens, an anastomosis with the LAD arterial circulation

RCA Segmental Anatomy 1 = proximal segment of the

main artery, 2 = middle segment of the main

artery, 3 = distal segment of the main

artery, 4 = posterior descending

branch, 16 = posterior left ventricular

branch, CB = conal branch, SN = sinonodal branch

RCA Segmental Anatomy 1 = proximal segment of the

main artery, 2 = middle segment of the main

artery, 3 = distal segment of the main

artery, 4 = posterior descending

branch, 16 = posterior left ventricular

branch, CB = conal branch, SN = sinonodal branch AM = acute marginal branch

RCA Branches Sinoatrial nodal artery

arises from the RCA in 58%; in the remaining patients (42%), it arises from the LCx artery

Multiple ventricular branches arise from the RCA, the largest of which is called the acute marginal branch

MPR images (top,left) and VR image (right) show the RCA (black arrow) and its branches. In this case, the conus artery (long arrow) arises from the aorta.

White arrow in top and arrow in left indicate the acute marginal branch, arrowhead in right indicates the sinoatrial nodal branch

 DominanceThe coronary artery that gives rise to the PDA

and posterolateral branch is referred to as the "dominant" arteryRCA is dominant in about 70% of casesLCA in 10% of cases, supplying the entire LVRemaining cases (20%), the RCA and LCA are

codominant; that is, portions of the LV diaphragmatic wall are supplied by both the RCA and the LCx artery

The length of the distal RCA is inversely proportional to the length of the LCA along the inferior aspect of the heart

Dominance

A right-dominant system:PDA (white arrowhead) arising from the RCA (black arrowhead). A posterolateral branch (arrow) is also seen.

A codominant system, with the inferior myocardial surface supplied equally by the RCA and the LCx artery

Normal Coronary Artery DiameterThe average size varies with gender

(approximately 3 mm in females and 4 mm in males)

each coronary artery also vary, ranging from 5 mm (LCA in males) to 2 mm (PDA in females)CCTA guidelines have not been published, and

the above are based on angiographic data.Focal abnormal dilatation to more than 1.5

times the diameter of an adjacent normal coronary artery is defined as an aneurysm

Normal Coronary Artery DiameterIf the process is

diffuse, it is known as ectasia .

Either process is easily identified with cardiac CT angiography

VR images obtained in an adolescent with Kawasaki disease show a focal RCA aneurysm (arrowhead).

Cardiac and Pulmonary VeinsExcellent for imaging the Coronary Sinus

(CS) and cardiac veinsThe most constant structure is the CS itself,

which runs along the inferior aspect of the heart in the AV groove before emptying into the RA1st branch of the CS is the middle cardiac vein,

which courses in the posterior interventricular

groove from base to apexNext two branches are the posterior vein of the

LV and the left marginal veinThe CS becomes the great cardiac vein

Cardiac Veins

CS (arrowheads) coursing along the inferior surface of the heart and emptying into the RA. In this case, the posterior vein of the LV (white arrow) is prominent and the left marginal vein is absent. Black arrow indicates the posterior interventricular vein

VR image shows the great cardiac vein (arrowheads) coursing in the left AV groove.

Cardiac VeinsVariability in the cardiac veins is usually due to

absence of either the left marginal vein or the posterior vein of the LV.

Whys is this relevant?Patients treated with cardiac resynchronization

therapy typically undergo implantation of an automatic cardioverter-defibrillator for the treatment of heart failure, ideally with a transvenous approach.

If no suitable vein is present in which to place the LV pacer lead with a transvenous approach, surgical placement may be necessary

Pulmonary Veins

The PVs also receive significant attention because of ablation therapy.

LA muscle can extend into the venous ostia, and ectopic electrical foci originating at this site may be the cause of atrial fibrillation in a significant number of patients

If additional PVs are present, it is important that they be described prior to ablation. They are typically single and occur more commonly on

the right sideMiddle PVs arising on the right side have a stronger

association with atrial fibrillation

Atrial AppendagesPatients with atrial fibrillation may develop

thrombus in the LA appendage, a condition that can be evaluated with multidetector CT prior to PV ablation>97%, the LA appendages have pectinate

muscles measuring greater than 1 mmLA appendage arises from the superolateral

aspect of the LA and projects anteriorly over the proximal LCx artery

Atrial Appendage normal RA

appendage (arrow) and pectinate muscles

Vertical long-axis MPR image shows the normal LA appendage (arrow). The linear filling defects in the appendage represent normal pectinate muscles

Cardiac Valves The four cardiac valves are routinely imaged during

cardiac CT angiography, and their motion and morphologic characteristics also assessed at all cardiac CT angiographic examinations with reconstructed and cine images.

The MV is composed of two leaflets, the anterior and posterior leaflets; the other valves normally have three leafletsCalcification of the MV annulus is a common abnormality

that makes identification of the annulus possibleThe papillary muscles with their chordae tendineae are also a

component of the MV apparatus The tricuspid valve separates the RA from the RV and is

connected to the RV

Cardiac Valves

•The aortic valve separates the LV outflow tract from the ascending aorta.

• It is composed of an annulus, cusps, and commissures.

• No papillary muscles or chordae tendineae are associated with the aortic valve

AO valve: Cusps are the right coronary cusp (white *), the left coronary cusp (black *), and the noncoronary cusp (box)

Pericardium Normally paper thin, measuring

2 mm or less It is composed of two layers, the

parietal layer and the serous layer

The pericardium lining the surface of the heart is known as the visceral pericardium, or epicardium.

It is important to be aware of the more common recesses and

sinuses to distinguish them from lymphadenopathy or abnormal

soft tissue

Not too much more.. Now some practical stuff.

Cardiac CT Angiography

A Brief Look at Practical Applications

Relevant Findings at Cardiac CT Data from clinical trials in patients with ACS indicate that

the detection of a significant stenosis may help improve risk stratification.

Most patients with unstable angina or non–ST-segment-elevation myocardial infarction (80%–94%) – show a significant coronary stenosis at coronary angiography

Several studies with intravascular ultrasonography (US) demonstrated that many coronary atherosclerotic lesions that cause acute events have a distinct morphology that includes a thrombus, a small residual vessel lumen, a greater plaque burden, and more pronounced positive remodeling

So what does all this mean to CCTA?

Show me the Money $$ The detection and detection and

characterization of characterization of coronary atheroscleroticcoronary atherosclerotic

plaque plaque may aid in the identification of patients at risk for an acute coronary syndrome

The primary use for coronary multidetector CT may be in patients with an intermediate likelihood of experiencing an acute coronary syndrome

Coronary PlaquesThe sensitivity of CCT is greater for

calcified (94%) than for mixed (78%) or soft (53%) plaques and is mostly limited to large-caliber vessels

Compared with intravascular ultrasound, CCT tends to underestimate the noncalcified plaque volume but to overestimate the calcified plaque volume

Stenosis of the Widow Maker Significant stenosis of the left

anterior descending artery in a 67-year-old patient with unstable angina and multiple risk factors (history of premature coronary artery disease, hypercholesterolemia, hypertension) but negative results at testing for biochemical markers and no acute ECG changes.

(top) Axial thin-section (5-mm) MIP image from a 64 MDCT shows a significant luminal narrowing (arrowhead) in the middle segment of the artery.

(bottom) Selective coronary angiogram demonstrates an eccentric high-grade (94%) stenosis (arrowhead).

CABGIt is of proven value in

evaluating the patency of bypass grafts

But, limited in evaluating the anastamosis and small-vessel disease beyond the anastamosis

Recent Data The results a large multicenter study published in JAMA in 2006

(n=238)demonstrated a higher number of false-positive and nonevaluable segments using a 16 MDCT

Of 1629 nonstented segments larger than 2 mm in diameter, there were 89 (5.5%) in 59 (32%) of 187 patients with stenosis of more than 50% by conventional angiography. Of the 1629 segments, 71% were evaluable on MDCT

sensitivity for detecting more than 50% luminal stenoses was 89%; specificity, 65%; positive predictive value, 13%; and negative predictive value, 99%

They concluded that this may be useful in excluding coronary disease in selected patients in whom a false-positive or inconclusive stress test result is suspected.

Garcia M. et al. Accuracy of 16-Row Multidetector Computed Tomography for the Assessment of Coronary Artery Stenosis. JAMA. 2006;296:403-411

More Recent Data Using a 64 MDCT Sensitivity for the detection of stenosis <50%,

stenosis >50%, and stenosis >75% was 79%, 73%, and 80%, respectively, and specificity was 97% Leber A. et al. Quantification of Obstructive and Nonobstructive Coronary

Lesions by 64-Slice Computed Tomography. J Am Coll Cardiol, 2005; 46:147-154

A large Meta-analysis of the literature included 38 studies demonstrated overall that 64 spiral CT has significantly higher specificity and PPV on a per-patient basis compared with 16-section CT for the detection of greater than 50% stenosis of coronary arteries. Hamon M. et al. Coronary Arteries: Diagnostic Performance of 16- versus 64-Section Spiral

CT Compared with Invasive Coronary Angiography—Meta-Analysis (Radiology 2007;245:720-731.)

SPECT MPI As a comparisonFindings of multiple studies have shown

sensitivity ranging from 90% to 100%, specificity from 60% to 78%, and negative predictive value from 97% to 100% at radionuclide perfusion imaging for ACS if single photon emission computed tomography (SPECT) imaging is used

White C, Kuo D. Chest Pain in the Emergency Department: Role of Multidetector CT. Radiology 2007;245:672-681.

Example Case CT and radionuclide perfusion images

in a 67-year-old man who presented to the ED with atypical chest pain.

(a) Two-dimensional map of the coronary arteries from a CT triple rule-out protocol shows substantial calcification with areas of stenosis in the left anterior descending (LAD) and right coronary arteries (RCA). AcuteMarg = acute marginal, D1 = first diagonal, D2 = second diagonal, LCX = left circumflex artery.

(b) Curved planar reconstructed view of right coronary artery demonstrates substantial calcified and noncalcified plaque causing luminal narrowing (arrows).

(c) Radionuclide perfusion image shows a defect (arrow) in the inferior myocardial wall.

Calcium ScoringMost widely used measure of calcium burden is the

calcium score (often known as the Agatston score), which is based on the radiographic density–weighted volume of plaques with attenuation values of greater than 130 Hus

Several studies have indicated that the calcium score provides prognostic information independent of conventional risk factorsgreater than 300 was associated with a significant

increase in cardiac events Radiology 2005;235:415-422.)

© RSNA, 2005Cardiac Imaging

Coronary Artery Stenoses: Detection with Calcium Scoring, CT Angiography, and Both Methods Combined1

George T. Lau

Diagnostic Value of Coronary Calcification Findings

Results of these studies demonstrate a high negative predictive value of the absence of coronary calcifications for acute coronary syndrome

The characteristics of coronary calcification in patients with stable angina were found to differ from those in patients with unstable angina

Electron-beam CT was used to evaluate coronary arteries in all patients in the three studies listed1999-2000.

•However, the diagnostic value of a finding of coronary calcification is controversial.

• In a study by Greenland 2004, 14% of events (myocardial infarction and death) were observed in patients in whom no evidence of

coronary calcification was found at CT

Bottom Line Appropriate indications for CCT are as follows:

chest pain: intermediate pretest probability for CAD (ECG cannot be interpreted or patient is unable to exercise), persistent chest pain after equivocal stress test, or suggestion of coronary anomalies;

acute chest pain in emergency department: intermediate pretest probability for CAD (no changes in ECG and negative enzyme test results);

pulmonary vein isolation, biventricular pacemaker implantation, or coronary arterial mapping in repeat cardiac surgery;

cardiac masses or pericardial disease with technically limited images from echocardiogram, MRI, or transesophageal echocardiography;

complex congenital heart disease: assess anatomy.

Gonzalez SP, Sanz J, Garcia M. Cardiac CT: Indications and Limitations. Journal of Nuclear Medicine Technology. Vol 36, Num 1, 2008 18-24.

Bottom Line Uncertain indications for CCT are as follows:

chest pain: intermediate pretest probability for CAD (ECG can be interpreted and patient is able to exercise) or low or high pretest probability for CAD (no changes in ECG and negative

enzyme test results);

acute chest pain: rule out obstructive CAD, aortic dissection, and pulmonary embolism if the pretest probability for one of them is intermediate;

high risk of CAD in asymptomatic patients;

chest pain after revascularization (percutaneous intervention or coronary artery bypass grafts): evaluate bypass grafts or history of revascularization with stents;

intermediate perioperative risk of cardiac events in patients undergoing intermediate- or high-risk noncardiac surgery;

valvular disease (native or prosthetic valves) with technically limited images from ECG, MRI, or transesophageal echocardiogram.

Gonzalez SP, Sanz J, Garcia M. Cardiac CT: Indications and Limitations. Journal of Nuclear Medicine Technology. Vol 36, Num 1, 2008 18-24.

References: O’ Brien J, Srichai M, Hecht E. Anatomy of the Heart at

Multidetector CT: What the Radiologist Needs to Know.

RadioGraphics 2007;27:1569-1582 Lawler L. CT scanning of the coronary arteries: How to do it and how to

interpret it. Applied Radiology. Volume: 34 Number: 10 October 2005. Hoffman U, Pena A, Cury R. Cardiac CT in Emergency Department Patients

with Acute Chest Pain1 RadioGraphics 2006;26:963-978. Lau G. Et al. Coronary Artery Stenoses: Detection with Calcium Scoring, CT

Angiography, and Both Methods Combined1 Radiology 2005;235:415-422. Mollet N, Cademartiri F, Van Meighem C. et al. High-Resolution Spiral

Computed Tomography Coronary Angiography in Patients Referred for Diagnostic Conventional Coronary Angiography Circulation. 2005;112:2318-2323.

Thank YOU for your Attention !!!