This document discusses computed tomography angiography (CTA) and its applications in cardiology. CTA uses computed tomography to visualize blood vessels throughout the body, including coronary arteries. Coronary CTA can detect plaque buildup in coronary arteries without being invasive. Current multidetector CT systems can acquire high-resolution images of the heart within 20 seconds while the patient holds their breath. Coronary CTA provides diagnostic information but also exposes patients to radiation. It is most useful for evaluating cardiac symptoms in low-to-intermediate risk patients.

1. CT ANGIOGRAPHY IN CARDIOLOGY

2. CT ANGIOGRAPHY
• Computed tomography angiography (CTA) is a
computed tomography technique used to visualize
arterial and venous vessels throughout the body.
• Coronary computed tomography angiography
(CCTA) is a heart imaging test that helps determine if
plaque buildup has narrowed a patient's coronary
arteries, the blood vessels that supply the heart.

3. CT ANGIOGRAPHY (CONTD...)
• Noninvasive coronary imaging requires a system
capable of acquiring motion-free, high spatial
resolution images within less than 20 seconds, while
patients are holding their breath.
• Current generation 64-channel multidetector row
computed tomography (MDCT) fulfills these
requirements reasonably well.

4. • The basic principle of CT
technology harnesses
ionizing radiation within
a gantry rotating around
the patient in which x-
rays are detected on a
detector array and
converted through
reconstruction
algorithms to images.

5. • Physical limits to spatial and temporal resolution are recognized, based on
minimum detector width for detection of radiation signals and the speed
at which the gantry can physically rotate.
• Each row is a narrow channel, approximately 0.625 mm in width for
“standard” width detectors, through which x-rays are detected on
scintillation crystals.
• The number of detector rows aligned in an array has increased from one
in single-detector units to 4, 16, 64, and ultimately 256 to 320 rows in
“wide-area” detectors.
• The increase in the number of rows leads to wider coverage, with more of
the heart viewed simultaneously—up to 16 cm in a single gantry rotation
for 320 detector rows at a width of 0.625 mm each leading to shorter scan
acquisition times and consequently reduced radiation exposure and
contrast requirements.

6. Abbara S, Arbab-Zadeh A et al: J Cardiovasc Comput Tomogr 3:190, 2009.

7. RADIATION DOSE

8. • Radiation exposure : Radiation doses of cardiac CT scans vary
greatly depending on the scan parameter settings, scan range
(cranial-caudal length of the scan), gender (women receive
more radiation due to breast tissue), and patient body habitus
(obesity increases exposure).
• Chest x-ray is 0.04 to 0.10 mSv,
• Average annual background radiation 3 to 3.6 mSv.
• Invasive diagnostic coronary angiography 2.1 to 4 mSv.
• Coronary CT angiography 4 to 11 mSv.

9. • This study showed that the effective dose for cardiac MSCT scanning in
daily practice is estimated to be 6.4± 1.9 and 11.0 ±4.1 mSv with 16- and
64-slice CT, respectively.
• The increase in dose estimates with the 64-slice technology is explained by
the higher spatial and temporal resolution achieved with current CT
scanner technology.

11. • Image quality of coronary CTA is improved by
– Achieving a slow, regular heart rate, excluding very obese
patients,
– Selecting patients able to cooperate with instructions to be
motionless and to hold their breath during imaging, and
– By assessing the presence and distribution of coronary
calcification.

12. PATIENT PREPARATION AND SCANNING
SEQUENCE

13. Dewey M, Vavere AL, et al. CORE-64 Multicenter International Trial. AJR
Am J Roentgenol 2010; 194:93.

14. CT ANGIOGRAPHY PROCEDURE
• For maximum enhancement CTA should start when contrast
agent arrives in the ascending aorta ( 15-25 sec. after i.v
injection).
• A standard three-phase injection protocol consists of
administration of undiluted contrast, 40 to 60 mL, at a rate of
approximately 5 mL/sec through an antecubital 18 to 20
gauge intravenous line, followed by a smaller volume of dilute
contrast (50:50 contrast-to-saline ratio, for a total of 10 to 20
mL), and then a bolus of saline (40 mL).

15. • The intent is to maximize contrast enhancement of the left
side of the heart and arterial structures, with mild contrast
enhancement of the right side of the heart and pulmonary
artery.
• Timing of the scan in relationship to the contrast bolus is
commonly performed using the triggered bolus method, in
which contrast attenuation in the pulmonary artery or aorta is
monitored, followed by automated scan initiation once an
adequate CT attenuation value (110 to 180 Hounsfield units
[HU]) is achieved.

18. SCAN MODES
• There are two basic scan modes in cardiac CT:
• Helical (spiral) scanning : Most current MDCT scanners use
spiral, retrospectively gated acquisition techniques.
• Helical scanning involves continuous radiation exposure and
table movement (the patient is moved through the rotating x-
ray beam), during which the detector arrays receive
projection data from multiple contiguous slices of the patient.
• Axial (sequential, step & shoot) scanning : axial imaging
involves sequential scanner “snapshots,” in between which
the x-ray tube is turned off and the table is moved to a
different position for the next image to be acquired.

19. Abbara S, Arbab-Zadeh A et al: J Cardiovasc Comput Tomogr 3:190, 2009.

20. ECG GATING
a. PROSPECTIVE TRIGGERING: The trigger signal is derived from
the patient’s ECG based on a prospective estimation of the RR
interval.
The scan is usually triggered to begin at a defined point after
the R wave, usually allowing image acquisition to occur during
diastole.
Advantage: ● dose efficient (80% reduction in x-ray exposure)
Disadvantage : ● limited portion of cardiac cycle data set
obtained
● greatly depends on the regularity of patient’s heart rate

21. A diagram showing the division of the cardiac cycle into 10%
intervals. The two ovals cover the two regions of the cardiac cycle
where the motions are the most still. The light blue oval covers the
mid- to end-systolic phase, and the red oval covers the mid- to end-
diastolic phase.
Hurst’s The Heart

22. b. RETROSPECTIVE GATING : Collects data during the
entire cardiac cycle. Once scan is complete , data
from specific periods of the cardiac cycle are used for
image reconstruction by retrospective referencing to
the ECG signal.
Advantage : allows assessment of cardiac function
via four-dimensional reconstruction.
Disadvantage : higher radiation dose exposure.

23. TECHNICAL LIMITATIONS
• Cardiac motion artifacts.
• High spatial resolution is required to image relatively
smaller vessels e.g. Coronary arteries.
• Current MDCT scanner provide a spatial resolution
of 0.4mm compared to 0.2mm for invasive
angiography .

24. TECHNICAL LIMITATIONS
• Blooming Artifacts ： High-attenuation structures,
such as calcified plaques or stents, appear enlarged
(or bloomed) because of partial volume averaging
effects and obscure the adjacent coronary lumen,
the main cause of false-positive results in coronary
CTA because of overestimation of the degree of
stenosis.

25. CARDIAC COMPUTED TOMOGRAPHY ANATOMY

26. CARDIAC COMPUTED TOMOGRAPHY ANATOMY

29. 1. This noninvasive acquisition does not use IV contrast
materialand is performed at a relatively low
radiation dose compared with coronary CTA.
2. It is used to detect and quantify coronary artery
calcification (CAC).
3. Although CAC is a specific indicator of the presence
of coronary artery atherosclerosis, it represents only
the calcified or healed plaque, not the full burden of
plaque.
COMPUTED TOMOGRAPHY FOR DETECTING
CORONARY ARTERY CALCIUM

30. 4. CAC is estimated to represent approximately 10–20%
of the total atherosclerotic plaque burden.
5. Patients who have CAC are more likely to have
noncalcified plaque that is prone to rupture, leading
to acute thrombosis, than patients without CAC .

31. (From Burke AP, Taylor A, Farb A, et al: Coronary calcification: Insights
from sudden coronary death victims. Z Kardiol 89[suppl 2]:49, 2000.)

32. • The AGATSTON-JANOWITZ SCORE was the initial
method for calcium quantification and is the most
widelyused.
• To be included in the Agatston-Janowitz score, CAC
must reach a threshold of 130 HU and cover an area
of at least 1 mm2; calcifications that are lower in
attenuation or smaller in sizeare not included in the
score.
Agatston AS, Janowitz WR, Hildner FJ, Zusmer NR, Viamonte M, Jr.,
Detrano R. Quantification of coronary artery calcium using ultrafast
computed tomography. J Am Coll Cardiol. 1990;15:827-832

33. • The score of each calcificationis calculated by
multiplying the area of the CAC by an attenuation-
weighting factorbased on the highest HU value of
the CAC, a score ranging from1 to 4.
• 1 for 130-199 HU,
• 2 for 200-299 HU,
• 3 for 300-399 HU,
• 4 for 400 HU.

34. • The CAC score can be classified into five
groups:
• 1) zero, no coronary calcification;
• 2) 100, mild coronary calcification;
• 3) > 100 to 399, moderate calcification;
• 4) >400 to 999, severe calcification;
• 5) > 1000, extensive calcification.

36. CORONARY CALCIUM SCORING

38. A, Data from MESA for the distribution
of CAC scores among men relative to
age and ethnicity
B, Major cardiovascular outcomes
observed in MESA in association with
higher thresholds of coronary calcium
scores

39. CORONARY CALCIUM
COVERAGE SCORE
• Higher clinical risk is
associated with
multivessel CAC
• The number of calcified
lesions (the more
lesions, the worse the
prognosis)
• Diffuse spotty calcified
lesions (small foci <3
mm in size).
Distribution of coronary calcium on cardiac CT in four different patients: A, no
detectable coronary calcium; B, coronary calcium in all three epicardial coronary
arteries including (clockwise) the right coronary artery (arrow) and the left
anterior descending and left circumflex coronary arteries; C, a “spotty” or diffuse
pattern with multiple small (<3 mm) foci of coronary calcium; and D, a large
calcified lesion in the left anterior descending coronary artery.
Williams M, Shaw LJ et
al: J Am Coll Cardiol
Img 1:61, 2008.

40. • In comparison with a CAC score of zero, the presence of any
CAC is associated with a fourfold risk of coronary events over
3 to 5 years.
• In patients at intermediate clinical risk for coronary events
(e.g., by Framingham score), the CAC score can help to
reclassify patients to a higher or lower risk group.
• For instance, a CAC score of zero confirms low risk of events.
Conversely, a CAC score of greater than 400 is observed with a
significant cardiac event rate (greater than 2 %/year) in
patients who appear to be intermediate risk by Framingham
score.
Kronmal RA, McClelland RL, Detrano R, et al: Risk factors for the progression of
coronary artery calcification in asymptomatic subjects: Results from the Multi-Ethnic
Study of Atherosclerosis (MESA). Circulation 115:2722, 2007.

41. • However, not every atherosclerotic plaque is calcified, and
even the detection of a large amount of calcium does not
imply the presence of significant stenoses.
• Therefore, it adds only incrementally to traditional risk
assessment and should not be used in isolation.
• The test is most useful in intermediate risk populations,in
which a high or low score may reclassify individuals to a
higher or lower risk group. Unselected screening is not
recommended.

42. CT ANGIOGRAPHY : INDICATIONS
• Suspected CAD with symptoms
• Intermediate pre-test probability of CAD with
uninterpretable ECG or unable to exercise.
• Acute chest pain with intermediate pre-test probability
of CAD and no ECG changes and negative serial
enzymes.
• Chest pain syndrome with uninterpretable or equivocal
stress test (exercise, perfusion, or stress echo).

43. PRE TEST PROBABILITY FOR CAD
Modified from Gibbons RJ, Balady GJ, Bricker JT, et al: ACC/AHA 2002 guideline update for exercise
testing: Summary article. A report of the American College of Cardiology/ American Heart Association
Task Force on Practice Guidelines (Committee to Update the 1997 Exercise Testing Guidelines). J Am
Coll Cardiol 40:1531, 2002.

44. CT ANGIOGRAPHY : INDICATIONS ..)
• Evaluation of suspected aortic dissection or thoracic
aneurysm.
• Evaluation of suspected pulmonary embolism.
• Evaluation of pulmonary vein anatomy prior to
invasive radiofrequency ablation for atrial fibrillation.
• Evaluation of coronary arteries.

45. CT ANGIOGRAPHY : INDICATIONS
• Assessment of complex congenital heart diseases
including anomalies of coronary circulation, great
vessels, and cardiac chambers and valves.
• Noninvasive coronary arterial mapping, including internal
mammary artery, prior to repeat cardiac surgical
revascularization.
• Evaluation of coronary artery anomalies.
• Coronary artery bypass grafts.

46. CORONARY CT ANGIOGRAPHY
• The primary clinical application of cardiac CT is the
performance of noninvasive coronary CT angiography among
patients with symptoms suggestive of myocardial ischemia.
• The overall accuracy of 64-row CT angiography included a
sensitivity of 87% to 99% and specificity of 93% to 96%.
• Coronary CT angiography for evaluating CAD is most useful in
low- to intermediate-risk patients with angina or anginal
equivalent.
• The negative predictive value of coronary CT angiography is
uniformly high in studies, approaching 93% to 100%; in other
words, coronary CT angiography is an excellent modality for
ruling out coronary disease.

48. GRADING
• 0 Normal: Absence of plaque and no luminal stenosis
• 1 Minimal: Plaque with <25% stenosis
• 2 Mild: 23%-49% stenosis
• 3 Moderate: 50%-69% stenosis
• 4 Severe: 70%-99% stenosis
• 5 Occluded
Raff GL, Abidov A, Achenbach S, et al: SCCT guidelines for the interpretation
and reporting of coronary computed tomographic angiography. J
Cardiovasc Comput Tomogr 3:122, 2009.

49. Coronary artery lesions of differing severity and grade as depicted on cardiac CT. A, Large mixed plaque without significant
stenosis in the proximal left anterior descending coronary artery (curved multiplanar reformat), with outward arterial
remodeling (arrow), as shown in the cross-sectional image (inset). B, Large noncalcified plaque with outward arterial
remodeling in the right coronary artery with mild luminal stenosis (<25%). C, Moderate stenosis (50%) in the proximal left
circumflex coronary artery with a mixed plaque (arrow). D, High-grade (>70%) stenosis of the mid–left anterior descending
coronary artery with a noncalcified plaque (arrow). E, Total occlusion (arrow) of the distal left circumflex coronary artery.
Motoyama S, Kondo T, et al:J Am Coll Cardiol 50:319, 2007.

50. CLINICAL APPLICATIONS OF CORONARY CT
• In emergency department.
• Detection of non calcified plaque.
• Evaluation after CABG
• Imaging of coronary stents

51. ROLE IN EMERGENCY DEPARTMENT
• Because of the High negative predictive value of cardiac CT, it
has been used to exclude CAD among patients presenting
with acute chest pain.
• There was improved efficiency of clinical decision making for
triage in the emergency department, with a shorter length of
stay in the hospital and more direct discharges from the
emergency department.
• This improvement appeared to be accomplished safely,
without putting patients at greater risk for undetected acute
coronary syndromes.

52. • There was increased diagnostic testing and higher radiation
exposure in the CCTA group, with no overall reduction in the
cost of care.
• On the basis of the clinical trials evidence, coronary CT
angiography received a recommendation as “appropriate” for
patients at low and intermediate likelihood for having CAD.

54. DETECTION OF NON CALCIFIED PLAQUE
• Defined as any coronary arterial wall lesion with an x-ray
attenuation detectably below that for the iodine contrast
medium but higher than for surrounding tissue, noncalcified
plaque is difficult to quantify, with limited accuracy and
reproducibility for the techniques in use.
• Detection requires maximal spatial and temporal resolution
and minimized image noise through higher radiation
exposures.

55. • Among asymptomatic patients, noncalcified plaque frequently
is found along with CAC but is present in only 5% to 10% of
patients as the sole finding, and very infrequently in an
obstructive pattern.
• For this reason, screening CT angiography is not advocated in
asymptomatic patients for the purpose of detecting
noncalcified plaque.
Hausleiter J, Meyer T, Hadamitzky M, et al: Prevalence of noncalcified coronary
plaques by 64-slice computed tomography in patients with an intermediate risk for
significant coronary artery disease. J Am Coll Cardiol 48:312, 2006.

56. • Among symptomatic patients, noncalcified plaque tends to be
a common finding.
• Plaques with low attenuation values (15 to 50 HU) tend to be
morphologically classified as lipid-rich, and those with
attenuation values of approximately 100 HU tend to be
fibrous plaques.
• Plaques associated with greater risk for plaque rupture or ACS
include:
a) low-attenuation plaque (plaque with attenuation values <30
HU),
b) outward arterial remodeling (artery diameter ratio of the
involved segment to a proximal reference of 1.1 or greater)
c) and a spotty pattern (<3 mm in size) of calcification.
Motoyama S, Kondo T, et al:J Am Coll Cardiol 50:319, 2007.

57. CORONARY CT ANGIOGRAPHY OF NON-CALCIFIED
PLAQUE

58. CORONARY CT ANGIOGRAPHY OF CALCIFIED PLAQUES
A significant stenosis
of
LAD is confirmed on
coronary angiography
Extensive calcified plaques are
noticed in the proximal and
middle segments of left anterior
descending (LAD) on curved
multiplanar reformatted
Extensive calcified
plaques are
noticed in volume
rendering images

59. CORONARY CT ANGIOGRAPHY OF MIXED
PLAQUES
Coronary CT angiography of mixed plaques. Mixed plaques are observed in
the proximal segment of the left anterior descending (LAD) artery with > 50%
stenosis (a, arrow). Coronary angiography confirms the significant stenosis of
the LAD (b, arrow).

60. BYPASS GRAFT IMAGING
• 1. Graft location : MDCT can accurately characterize the
origin, course, and touchdown of prior bypass grafts
• 2. Graft patency : Patency of both arterial and venous bypass
grafts can be assessed.
• Recent studies have suggested that the sensitivities and
specificities of MDCT for detecting stenosis or occlusion of
bypass grafts, when compared with invasive angiography,
approaching 100%.
• Before reoperative CABG, cardiac CT is considered an
appropriate indication, defining the relationship of sternal
wires to cardiac and graft structures for the purpose of
planning surgical reentry techniques.

61. • High-risk findings on cardiac CT include cardiac structures
adjacent to or adherent to the sternum and coronary bypass
grafts that extend into the midline.
• CT images also guide the surgical team on optimal locations
for aortic crossclamping, to avoid regions with extensive CAC
or atheroma .
• Occasionally, artifacts related to metallic clips can interfere
with assessment of the distal anastomosis of an arterial graft
(internal mammary or radial artery graft).
Maluenda G, et al: Perioperative outcomes in reoperative cardiac surgery guided by
cardiac multidetector computed tomographic angiography. Am Heart J 159:301,
2010.

62. Cardiac CT provides high accuracy for evaluation of coronary bypass
grafts owing to their large size, often limited extent of calcified
atherosclerosis, and limited mobility, as shown in the oblique multiplanar
reformat (A) and three-dimensional volume-rendered reformat (B).

63. High-risk substernal reoperative anatomy in a patient with previous
coronary bypass surgery including a coronary bypass graft (arrow)
immediately beneath the sternum, shown in axial (A) and sagittal (B)
views. The right ventricle is immediately adjacent and adherent to the
sternal wire (C, arrow).

64. Three-dimensional rendering image shows the adhesion of the mid-portion
of the left internal mammary artery graft to the sternum.
Fuster V, Walsh RA Hurst’s The Heart

65. Noncontrast CT showing extensive aortic calcification (“porcelain aorta”).
A, In the coronal plane, calcification extends from the aortic sinotubular
junction to the aortic arch. B, C, Cross-sectional images (at levels
indicated by arrows extending from A) from the upper (B) and lower (C)
ascending aorta show the circumferential nature of the calcification

66. STENT PATENCY
• Image artifact from metallic stents limits the application in
patients with prior coronary stent procedures.
• Small stents are difficult to evaluate .
• However, 90% accuracycan be obtained in stents 3 mm or
greater in diameter with the use of sharp kernel and wide
display window.
• Quantitative assessment of within-stent contrast density may
assist in the diagnosis.
• A contrast density ratio of 0.81 between the stent (proximal,
mid-, and distal portions) and the aorta showed a sensitivity
of 90.9% and a specificity of 95.2% in-stent stenosis for stents
down to 2.5 mm in size.
Abdelkarim MJ, Ahmadi N, Gopal A, et al: J Cardiovasc Comput Tomogr 4:29, 2010

67. CORONARY CT ANGIOGRAPHY OF A PATENT STENT
A patent coronary stent is noticed in the proximal left anterior descending (LAD)
artery on a curved multiplana reformatted (MPR) image with clear demonstration of
the intrastent lumen without in-stent restenosis.

68. Stent imaging with cardiac CT. A, A large stent with uniform contrast attenuation in the lumen, indicating
patency. B, A small stent in the left anterior descending artery with another stent in the proximal diagonal
branch. Three reconstruction/display settings are shown: a medium-soft kernel, a sharp kernel, and sharp
kernel reconstruction displayed with a wide window width. Visualization of in-stent restenosis in the
diagonal branch is optimized with the third approach (i.e., sharp kernel, wide window display width).

69. CORONARY CT ANGIOGRAPHY OF IN-STENT
RESTENOSIS
An in-stent restenosis is present at the distal part of the right coronary
artery (RCA) stent which is demonstrated as the low-attenuating area on
longitudinally straightened (a), curved multiplana reformatted (b) and
cross-sectional images (c).

70. SCAN ARTIFACTS
• High heart rate (>65 beats/min for single-source scanners) can
lead to CORONARY MOTION ARTIFACT, particularly within the
mid–right coronary artery .
• Respiratory motion artifact can be minimized by holding
breath during image acquisition.

71. • Misalignment of axial image slices arises from positional
changes of the heart with patient motion (particularly
respiratory motion), ectopic heart beats, or abrupt changes in
heart rate during scanning.
• Highly attenuating objects (metallic objects or CAC) can
produce an artifact called beam hardening, created by
alteration in the energy spectrum of the x-ray beam.
• This artifact can particularly hamper interpretation of
coronary plaques with highly dense calcified atherosclerosis.

72. Multiphase axial images of the right coronary artery showing motion artifact
throughout the cardiac cycle including systole (0 to 40% phases) and diastole (50% to
90%). The most motion-free images of the right coronary artery (arrow) are at 40%
(end-systole) and 70% (mid-diastole), when cardiac motion is minimized.

73. Cardiac motion artifact. Top left panel: Three-dimensional (3D) rendering image of a heart with significant motion
artifact affecting the interpretation of the distal right coronary artery (RCA). This patient was scanned with a dual-
source computed tomography (CT) (temporal resolution of 83 ms), and the heart rate in the time of the scan was
105 beats/min. Top right panel: Maximum-intensity projection (MIP) image of the same patient showing significant
transitional motion artifact in the proximal and mid RCA. Bottom left panel: 3D rendering image of a heart without
motion artifact showing the distal RCA. The heart rate was 75 beats/min, and the patient was scanned with a dual-
source CT. Bottom right panel: MIP image of the same patient showing only slight transitional motion artifact in the
mid RCA.

74. Common imaging artifacts or nondiagnostic imaging on cardiac CT. A, Registration error seen as horizontal
lines (arrow) in the image. B, Respiratory motion seen as discontinuity of the sternum. C, Poor contrast
opacification of the coronary artery. D, Coronary duplication artifact caused by an ectopic beat. E, Poor
signal-to-noise ratio (grainy image) caused by obesity. F, Severe coronary calcification. G, Streak artifact
from an implanted biventricular pacemaker .

75. VENTRICULAR AND VALVULAR MORPHOLOGY AND
FUNCTION
• Helical scan acquisitions, allow
reconstruction of cardiac CT data
from both systolic and diastolic
phases enabling evaluation of
ventricular systolic function.
• Myocardial morphology also can
be reliably assessed for findings
of previous MI such as wall
thinning, calcification, or fatty
myocardial replacement
(indicated by negative HU
densities within the myocardium).
van der Vleuten PA, Willems TP, Gotte MJ, et al:
Quantification of global left ventricular function:. Acta
Radiol 47:1049, 2006.

76. • Cardiac ct also provides
highly accurate detection of
LV MURAL THROMBI.
• Mural thrombi typically
have an attenuation value
ranging between 25 and 80
HU (mean, approximately
40 HU) which is below that
of surrounding myocardium
(typically 70 to 200 HU)
LaBounty TM, Glasofer S, Devereux RB, et al: Comparison of cardiac computed
tomographic angiography to transesophageal echocardiography for evaluation of
patients with native valvular heart disease. Am J Cardiol 104:1421, 2009.

77. • ANATOMIC EVALUATION OF CARDIAC VALVES and their motion also
is feasible for both native and prosthetic valves.
• Aortic stenosis is characterized by CT in terms of both the extent of valvular
calcification and orifice area by planimetry.
• Valve area planimetry is closely related to other invasive and noninvasive
determinations in aortic stenosis.

78. • Cardiac CT performed before TRANSCATHETER AORTIC VALVE
REPLACEMENTprovides a more accurate assessment of the aortic
annulus area with its oblique nature, determination of optimal
angiographic angulations, and detection of potential hazards such as
severe aortic root calcification.

79. • In AORTIC REGURGITATION, malcoaptation of the valve
leaflets by greater than 0.75 cm2 is associated with severe
aortic regurgitation .
• Prosthetic valve malfunction including size mismatch, tissue
ingrowth, or valve thrombosis can be identified.
• Increasingly, cardiac CT imaging in patients with prosthetic
valve endocarditis identifies paravalvular leaks , and can
provide a preoperative coronary arteriographic assessment
when cardiac surgery is anticipated.
• The weakness of cardiac CT for evaluation of valve disorders is
the inability to assess hemodynamics, so complementary
imaging should include Doppler echocardiography.
LaBounty TM, Agarwal PP, Chughtai A, et al: Hemodynamic and functional assessment of
mechanical aortic valves using combined echocardiography and multidetector computed tomography.
J Cardiovasc Comput Tomogr 3:161, 2009.

81. CORONARY ARTERY ANOMALIES
• The diagnosis of coronary artery anomalies has previously
required invasive coronary angiography; however, in up to
50% of patients, the coronary artery anomalies may be
incorrectly classified during invasive angiography.
• This misclassification may result from the difficulty in
delineating the precise vessel path within a complex 3D
geometry using a relatively restricted two-dimensional view.
• Coronary CTA has been shown to accurately depict the
anomalous vessel origin, its subsequent course, and the
relationship to the great vessels.

82. • Two studies comparing CCTA and invasive coronary
angiography found that invasive angiography was able to
detect 80% of the anomalous origins but only 53% of the
anomalous coronary courses and resulted in a precise
anatomic diagnosis in only 55% of patients.
• In a multicenter coronary artery CT registry, CCTA was able to
unequivocally demonstrate the origin and the course of the
anomalous artery in all patients with equivocal findings on
invasive coronary angiography.
Shi H, Aschoff AJ, Brambs HJ, et al.
Multislice CT imaging of anomalous
coronary arteries. Eur Radiol.
2004;14(12):2172-2181.
Schmitt R, Froehner S, Brunn J, et al.
Congenital anomalies of the coronary
arteries: imaging with contrast-
enhanced, multidetector computed
tomography. Eur Radiol.
2005;15(6):1110-1121
Datta J, White CS, Gilkeson RC,
et al. Anomalous coronary
arteries in adults: depiction at
multi-detector row CT
angiography. Radiology.
2005;235(3):812-818.

83. Evaluation of coronary anomaly. A. Three-dimensional (3D) rendering image showing an
anomalous left circumflex arising from the right coronary sinus and coursing between the
aorta and the left atrium. B. 3D rendering image showing a coronary aneurysm involving
the LM, the proximal LAD, and a diagonal branch. LAD, left anterior descending
(coronary artery); LM, left main.

84. PERICARDIAL DISEASES
• The pericardium appears as a thin
line (1 to 2 mm) surrounding the
heart, usually visible with a small
amount of adjacent pericardiaI
fat.
• The pericardium normally
enhances with contrast
administration;
hyperenhancement of the
pericardium in the appropriate
clinical setting is characteristic of
pericarditis.
• A pericardial thickness of >4 mm
in a patient with abnormal rapid
early LV diastolic filling is
diagnostic of pericardial
constriction.
Diffuse pericardial thickening surrounding the
entire heart in a patient with pericardial
constriction.
Baim RS, MacDonald IL, Wise DJ, et al. Computed tomography of absent
left pericardium. Radiology. 1980;135(1):127-128

85. 1. By CT, congenital absence of the pericardium is easily diagnosed.
2. Findings of pericardial constriction on CT include irregular pericardiaI
thickening and calcification, conical or tubular compression of one or both
ventricles, enlargement of one or both atria, dilation of the IVC, and a
characteristic diastolic bounce of the interventricular septum.
3. Pericardial effusions can be reliably detected by CT.
4. A pericardiaI cyst will appear as a well circumscribed paracardiac mass
with characteristic water attenuation (H.U. = 0), usually in the right
costophrenic angle.
5. Both primary neoplasms and, more commonly, metastatic neoplasms can
be visualized in the pericardium.

86. CONGENITAL HEART DISEASE
• Cardiac CT and MRI have been increasingly used for the assessment of
congenital heart disease.
• Both modalities can be rendered into 3D images that are useful in
clarifying the often complex anatomic relationships in patients with
congenital heart disease.
• MRI has limited use in critically ill patients, metallic implants and often mri
requires significant sedation .
• Anomalies of the aortic arch, patent ductus arteriosus, tetralogy of Fallot,
and abnormal arteriovenous connections can all be carefully evaluated
with cardiac CCTA .
• The high spatial resolution of MDCT also permits the evaluation of the
atrioventricular valves in conditions such as Ebstein anomaly and tricuspid
and mitral valve atresia.
• MDCT can also be used to accurately quantify intracardiac shunts, as well
as cardiac masses.
Rius T, Goyenechea M, Poon M. Combined cardiac congenital anomalies assessed by multi-slice spiral
computed tomography. Eur Heart J. 2006;27(6):637.

87. A patient with tetralogy of Fallot with large ventricular septal defect (black
arrows), overriding aorta (Ao), and thickened right ventricle (RV).

88. • Three-dimensional rendering (B) and corresponding maximum-intensity projection
(C) images of a patent ductus arteriosus

89. DISEASES OF AORTA
Contrast-enhanced MDCT is nearly 100% sensitive and specific for
evaluating acute aortic syndromes.
1. Acute aortic dissection is characterized by visualization of a dissection flap
(i.e., separation of the intima from the media) that forms true and false
lumens. The CT study can characterize the origin and extent of the
dissection, classify it as Type A or B, assess for concomitant aneurysmal
aortic dilatation, and identify branch vessels involvement.
2. Aortic intramural hematomas are believed to be caused by spontaneous
hemorrhage of the vaso vasorum into the medial layer. They appear as
crescent-shaped areas of increased attenuation with eccentric aortic wall
thickening. Unlike dissections, hematomas do not spiral around the aorta.
3. Aortic aneurysm is a permanent dilation of the normal aortic caliber
(usually greater than 5 cm in the thoracic aorta and greater than 3 cm in the
abdominal aorta).
Litmanovich D, Bankier AA, Cantin L, et al. CT and MRI in diseases of the aorta. AJR Am J
Roentgenol. 2009;193(4):928-940.

90. An aortic dissection starting
in the descending thoracic
aorta
A, Dissection of the descending aorta (white arrow) in a patient with
previous ascending aorta dissection repair (black arrow). Graft material
surrounds the aortic root. First-pass contrast attenuation is seen in the true
lumen of the descending aorta. B, Aortic intramural hematoma, seen as
low-attenuation material in the wall of the ascending and descending
segments of the aorta (upper and lower arrows).

91. PULMONARY EMBOLISM
• MDCT can diagnose acute and chronic pulmonary
thromboembolism.
• It has replaced nuclear ventilation/perfusion scans as the
primary imaging study in the diagnosis of acute pulmonary
embolism.
• The cross-sectional view of the main and proximal right and
left pulmonary arteries provides clear delineation of the
proximal extent of the thrombi, which is essential for
successful surgical treatment.
• Accuracy for the diagnosis of pulmonary embolism using
multidetector CT is high, with a negative predictive value of
99% among patients with low to moderate pretest likelihood,
although accuracy for the detection of subsegmental
pulmonary emboli may be limited.
Quiroz R, Kucher N, Zou KH, et al: Clinical validity of a negative computed tomography scan in patients
with suspected pulmonary embolism: A systematic review. JAMA 293:2012, 2005.

92. Patient with both an aortic dissection evidenced in a dilated aorta and a small
pulmonary embolism (black arrow) in the left pulmonary artery (PA).

93. TRIPLE RULE OUT(TRO) CTA
• Triple rule-out (TRO) CTA can evaluate the coronary arteries,
pulmonary arteries, aorta, and intrathoracic structures in
selected patients presenting with acute chest pain of unclear
etiology.
• The new 64-slice MDCT scanners can provide high-quality TRO
CTA studies by tailoring the injection of iodinated contrast to
provide simultaneous high levels of arterial enhancement in
the coronary arteries and aorta (>300 HU) and in the
pulmonary arteries (>200 HU).
Halpern EJ. Triple-rule-out CT angiography for evaluation of acute chest pain and
possible acute coronary syndrome. Radiology. 2009;252(2):332-345

94. • Radiation exposure is minimized by limiting the imaging
window to include from the aortic arch down through the
heart, rather than encompassing the entire chest.
• In addition, the same imaging parameters, such as
prospective gating and current modulation, used in CCTA are
incorporated into the TRO CTA to limit ionizing radiation doses
to between 5 and 9 mSv.
• When used in the emergency department on appropriately
selected patients, TRO CTA can eliminate the need for further
diagnostic testing in >75% of patients.

95. EVALUATION OF PULMONARY VEINS
• In the context of electrophysiology interventions such as
pulmonary vein isolation (PVI), preprocedural MDCT can be
used to define pulmonary venous anatomy and identify
supernumerary veins, and postprocedural MDCT can be used
to evaluate for pulmonary vein stenosis.
• Additionally, in the setting of congenital heart disease, CT can
be used to identify anomalous pulmonary venous return.
Taylor AJ, Cequeira M, Hodgson J, et al. ACCF/SCCT/ACR/AHA/ASE/ASNC/SCAI/SCMR 2010
appropriate use criteria for cardiac computed tomography. J Am Coll Cardiol. 2010;55

96. VIABILITY AND PERFUSION IMAGING WITH CT
• Myocardial attenuation reflects relative coronary blood flow
on first-pass imaging .
• First-pass CT stress perfusion imaging includes contrast-
enhanced CT angiography both at rest and during the
administration of adenosine agonists.
• The sensitivity for the detection of significant coronary
stenosis ranges from 72% to 98%, with specificity ranging
from 71% to 92%, with radiation doses as low as 2.5 mSv using
high-pitch helical CT.
• A meta-analysis found an overall pooled sensitivity of 81%
and specificity of 93% for this method.
Tashakkor AY, Nicolaou S, Leipsic J, et al: The emerging role of cardiac computed tomography for
the assessment of coronary perfusion: A systematic review and meta-analysis. Can J Cardiol
28:413, 2012.

97. • Late myocardial enhancement imaging with infusion of
additional contrast medium and a delay of approximately 10
minutes can be done.
• The kinetics of iodinated contrast material is similar to that of
gadolinium, with accumulation within the interstitial space of
myocardial fibrosis.
• Under delayed imaging, contrast preferentially accumulates
within areas of scarring and can be detected on delayed
imaging.
• Delayed enhancement on cardiac CT indicates regions of
myocardium with reduced likelihood of functional recovery
and patients whose ejection fraction will remain lower after
myocardial infarction, particularly when a transmural pattern
of delayed enhancement is present.
Sato A, Hiroe M, Nozato T, et al: Early validation study of 64-slice multidetector computed tomography for the
assessment of myocardial viability and the prediction of left ventricular remodelling after acute myocardial
infarction. Eur Heart J 29:490, 2008.

99. • MDCT has the ability to differentiate prior and recent MI
based on the tissue density expressed in HU.
Prior infarctions have lower CT densities, or more
hypoenhancement, compared with recently infarcted areas
(44 ± 17 HU vs 63 ± 19 HU).
• As a result of the high spatial resolution of MDCT, it is also
possible to distinguish subendocardial from transmural MIs,
which provides additional prognostic information.
Wada H, Kobayashi Y, Yasu T, et al. Multi-detector computed tomography for imaging of
subendocardial infarction: prediction of wall motion recovery after reperfused anterior myocardial
infarction. Circ J. 2004;68(5):512-514.

102. • Another newer technique is the
application of COMPUTATIONAL FFR
from resting coronary CT
angiographic images.
• Measured from standard first-pass
coronary CT angiography its accuracy
has been compared with that for
invasive measurement of FFR of 0.80
or less.
• In a multicenter trial in 252 patients,
overall accuracy was limited at 73%,
with sensitivity of 90% and specificity
of 54%.
• The technique, still in development,
currently requires off-site analysis but
has the potential advantage of
assessment from routine coronary CT
angiograms acquired with the patient
at rest. CT fractional flow reserve (FFR) using computational fluid
dynamics. From the invasive coronary angiogram (A),
coronary lesions assessed by invasive FFR (B) are
correlated with CT-derived FFR (C).
the DeFACTO study. Circ Cardiovasc
Imaging 6:881, 2013.

103. CONTRAINDICATIONS
Absolute Contraindications
• Pregnancy
• Hypersensitivity to
iodinated contrast agent
Relative Contraindications
• H/o allergy to medicines
• Hyperthyroidism
• Renal function impairment
• Congestive heart failure
• H/O thromboembolism
• Atrial Fibrillation
 Cardiac arrhythmias, coronary artery stents
and tachycardia may result in a reduced image quality

104. CTA LIMITATIONS
• Rapid (>80 bpm) and irregular HR
• High calcium scores (>800-1000)
• Contrast requirements (Cr > 1.6 mg/dl)
• Small vessels (<1.5 mm) and collaterals
• Obese and uncooperative patients
• Radiation Exposure

105. WHAT ARE THE BENEFITS VS. RISKS?
• Benefits
– CCTA is not invasive.
– Able to view bone, soft tissue and blood vessels all
at the same time.
– Provides detailed images of many types of tissue.
– Fast and simple.

106. BENEFITS VS. RISKS (CONTD..)
– Less sensitive to patient movement than MRI.
– CT can be performed if patient has an implanted
medical device of any kind, unlike MRI.
– No radiation remains in a patient's body after a CT
examination.
– X-rays used in CT scans doesnot have no
immediate side effects.

107. • Risks
– In patients with abnormal kidney function, the dye
used in CT scanning may worsen kidney function.
– Skin damage or damage to blood vessels and
nerves if leaked out from injected vessels.
– Slight chance of cancer from excessive exposure to
radiation.
– Not recommended for pregnant women unless
medically necessary because of potential risk to
the baby in the womb.
BENEFITS VS. RISKS (CONTD..)

108. – Mothers should not breastfeed their babies for
24-48 hours after contrast medium is given.
– The risk of serious allergic reaction to contrast
materials that contain iodine is extremely rare.
BENEFITS VS. RISKS (CONTD..)

109. CAG VS MDCT

111. GUIDELINE RECOMMENDATIONS
ACCF/SCCT/ACR/AHA/ASE/ASNC/NASCI/SCAI/SCMR
2010 Appropriate Use Criteria
for Cardiac Computed Tomography. JACC Vol. 56, No. 22, 2010

120. SUMMARY AND CONCLUSION
• Coronary CT angiography represents the most rapidly
developed imaging modality in cardiac imaging.
• Demonstrates high diagnostic accuracy.
• Utilization of coronary CT angiography must be
defined in terms of whether it leads to the greatest
benefit and whether the radiation risk may be
greater than the benefit expected from the CT
examinations.