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64-Slice Cardiovascular CT Angiography: A
Clinical Accuracy Evaluation
Jeffrey J Fine, PhD, MS, Christie B Hopkins, MD, FACC, Nicol Ruff,
MA, F Carter Newton, MD, FACC.
Department of Investigator Initiated Research, South Carolina Heart Center,
Columbia, South Carolina
Correspondence/Reprints: Jeffrey Fine, PhD, MS
South Carolina Heart Center
Department of Investigator Initiated Research
2001 Laurel Street
Columbia, SC 29063
(803) 254-3278
Fax: (803) 799-1967
[email protected]
Key Words: multislice computed tomography (MSCT), coronary artery imaging
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64-Slice Cardiovascular CT Angiography: A
Clinical Accuracy Evaluation
Cardiovascular computed tomography (CVCT) via the recently released 64-slice
technology increases spatial resolution while decreasing acquisition times and
slice thickness. We investigated the accuracy of 64-slice CVCT referenced by
catheter angiography. We studied 66 sequential subjects having both 64-slice
CVCT and catheter angiography within 30 days. Accuracy results were 94%
interpretable images, sensitivity 95%, specificity 96%, positive predictive value
97%, and negative predictive value 92% for lesions >50%. We found 100%
agreement between 64-slice CVCT and catheterization among vein graft
evaluations (9/9). These metrics are vastly improved from the 16-slice generation
and support 64-slice CVCT as a reliable diagnostic tool.
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Significant improvements in non-invasive coronary imaging have been observed
during the past decade.1 Cardiovascular computed tomography (CVCT), when
performed using multi-detector CT imaging technology, has the ability to
accurately and non-invasively image the myocardial anatomy and coronary
vasculature.2 Recently, the 16-slice CT scanner increased the diagnostic
capabilities of coronary artery imaging by reducing the incidence of motion
artifacts and by improving the inplane and spatial resolution from that observed in
earlier iterations of CVCT (4 and 8 slice MSCT and electron beam tomography).38
Although the negative predictive value among normal CVCT studies is clinically
useful for reliable exclusion of atherosclerosis, the sensitivity of 16-slice CVCT
remains insufficient for routine diagnostic needs.9
The technological evolution to 64-slice CVCT has further reduced slice
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thickness and improved spatial resolution to unprecedented levels. It is
hypothesized that the latest generation of cardiac CT scanners may improve
upon 16-slice accuracy measures and needs to be referenced with direct
catheter angiography, which remains the gold standard. To date there are no
published accuracy studies evaluating 64-slice CVCT technology from the United
States. The aim of the present study was to evaluate the accuracy of 64-slice
CVCT and the frequency distribution of indications for CVCT to determine if
improved performance metrics offer a low risk and patient friendly mode of
coronary angiography, which in selected clinical situations may replace the need
for catheter angiography.
The study population consisted of 66 sequential patients (62 ±7 years of
age, range 29-83, 32 males) having recently completed 64-slice CVCT
angiography and direct catheter angiography for suspicion of obstructive
coronary artery disease. Sequential patients were selected in an effort to reduce
selection bias and the angiographic procedures were performed within 30 days of
each other. Subjects were referred to CVCT by their cardiologist or primary care
provider after the presentation of symptoms or after results of nuclear perfusion
testing supported myocardial ischemia.
CVCT was performed after informed consent was provided using the
commercially available Siemens Somatom Sensation Cardiac 64 CT. Using the
64-slice CT scanner, a volume data set was acquired (64 x 0.6-mm collimation,
gantry rotation time 33 ms, pitch .2 mm, tube voltage of 120 kV), covering the
distance from the carina to the diaphragmal face of the heart. Cross-sectional
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images were reconstructed with a slice thickness of .75 mm overlapping in 0.4
mm intervals with the use of an electrocardiogram gated half-scan reconstruction
algorithm to obtain an image acquisition window of 164 ms. Patients having
elevated resting heart rates were given oral and /or intravenous metoprolol as
needed to reduce their heart rate to 50-60 beats per minute. A heart rate of 60
beats per minute or less critically influences image quality and is considered a
threshold that is desirable to minimize motion artifacts.10
Catheter and CVCT angiography results were analyzed independently by
two expert readers, each blinded to the opinion of the other, and to the results of
the second angiographic procedure. Results were analyzed for the quality of the
imaging study, detectable lesions >50%, left ventricular ejection fraction, and vein
graft patency, when applicable. Vessels with a diameter <1.5 mm were excluded
from correlation and technical quality analysis. While the observation of
calcification is possible in vessels of smaller diameter, spatial resolution limits the
reader in assigning an absolute percentage of stenosis to these clinically
insignificant vessels. The coronary vessels and their branches evaluated were;
left main, left anterior descending, left circumflex, and right coronary artery.
Direct catheter angiography was used as the gold standard for accuracy
comparisons.
Data are expressed as frequencies, percentages and descriptive statistics
(sensitivity, specificity, positive predictive value, negative predictive value). A pvalue of <0.05 was considered statistically significant.
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Among the 66 subjects, 245 coronary arteries were observed and
evaluated. 64-slice CVCT provided images of technical quality allowing for
diagnosis among 94% (62/66) of study subjects. The indications for CVCT were
divided among 7 categories with chest pain the most prevalent indication (table
1). 64-slice CVCT identification of stenotic lesions >50% within measured
coronary vessels were: sensitivity 95%, specificity 96%, positive predictive value
97%, and negative predictive value 92%.
A vessel-by-vessel accuracy analysis was conducted to determine the
level of agreement between catheter angiography and 64-slice CVCT (table 2).
Vein grafts evaluated among post revascularization patients within this study had
100% agreement between CVCT and direct angiography (9/9). Left ventricular
ejection fraction calculations were nearly identical between 64-slice CVCT and
catheter angiography (58.7 and 58.6 respectively, p = <.0001).
The main results of our study are the improved accuracy statistics of 64slice CVCT as referenced by catheter angiography. A compilation of previous 16slice accuracy studies for comparative purposes reveals significant improvement
with the 64-slice technology (figure 1). 11-17
With improved resolution, decreased slice thickness, and reduced
acquisition times, the 64-slice CT scanner has an enhanced ability to detect
significant atherosclerotic lesions, while maintaining the ability to reliably rule out
disease among patients absent of disease. Previous citations have concurred
that CVCT is a useful diagnostic tool, capable of accurately ruling out the
presence of significant lesions based upon sufficient specificity and negative
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predictive values.2,9,11-13,15-17 The concerns and limitations of CVCT were that the
16-slice technology lacks the ability to sufficiently detect significant lesions and
positively predict disease at a high accuracy level.9 Our results indicate that the
64-slice generation of multi-slice CT has increased sensitivity and positive
predictive values, allowing CVCT to be considered for routine diagnostic
evaluations. The strong agreement between 64-slice CVCT and catheter
angiography when evaluating the patency of vein grafts, calculating left
ventricular ejection fraction, and among vessel-by-vessel comparisons supports
the strength of the latest generation of cardiac CT imaging.
64-slice CVCT angiography findings compare favorably with traditional
cardiac catheterization in this study of patients assessed for obstructive coronary
atherosclerosis. The 64-slice technology was found to be more accurate than the
16-slice generation, particularly when attempting to affirm the presence of
significant atherosclerotic lesions. The results of this study suggest that the 64slice CVCT scanner has the ability to non-invasively detect significant
atherosclerosis in a reliable and highly accurate manner.
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Mini Abstract
64-Slice Cardiovascular CT Angiography: A Clinical Accuracy Evaluation
Jeffrey J. Fine, Christie B. Hopkins, Nicol Ruff, and F. Carter Newton
The diagnostic accuracy of 64-slice cardiovascular computed tomography
(CVCT) was evaluated by referencing against traditional catheter angiography.
64-slice CT has increased sensitivity, specificity, positive and negative predictive
values when compared with 16-slice technology establishing the latest
generation of CVCT as a reliable and accurate diagnostic tool.
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Tables and Figures
Table 1 Clinical Indications for CVCT (n = 66)
Indication
Chest Pain
Previous Revascularization
Abnormal Electrocardiogram
Dyspnea
Abnormal Calcium Score
Known Coronary Disease
Abnormal Cardiovascular Study
33
9
5
7
2
3
7
50%
13%
8%
11%
3%
4%
11%
Data are presented as numbers and frequency percentages.
Table 2 Vessel x Vessel Accuracy Comparison
Coronary Vessel (and branches to 1.5mm)
Left Main
Left Anterior Descending
Circumflex
Right Coronary Artery
60/61
57/61
56/61
57/62
98%
93%
92%
92%
Data are presented as ratio of agreement between 64-slice CVCT and catheter angiography and
agreement percentages.
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Figure 1.
Percentage
Accuracy Comparison Between 16 and 64 Slice
CVCT
100
90
80
70
60
50
40
30
20
10
0
16-Slice CVCT
64-Slice CVCT
Sensitivity
11
Specificity
Positive
Predictive
Value
Negative
Predictive
Value