Download 1 - JACC: Cardiovascular Imaging

JACC: CARDIOVASCULAR IMAGING
VOL. 4, NO. 1, 2011
© 2011 BY THE AMERICAN COLLEGE OF CARDIOLOGY FOUNDATION
PUBLISHED BY ELSEVIER INC.
ISSN 1936-878X/$36.00
DOI:10.1016/j.jcmg.2010.10.007
A Prospective Study for Comparison of
MR and CT Imaging for Detection of
Coronary Artery Stenosis
Ashraf Hamdan, MD,*‡ Patrick Asbach, MD,† Ernst Wellnhofer, MD,*
Christoph Klein, MD,* Rolf Gebker, MD,* Sebastian Kelle, MD,* Harald Kilian, MD,*
Alexander Huppertz, MD,† Eckart Fleck, MD*
Berlin, Germany; and Tel Aviv, Israel
O B J E C T I V E S The purpose of the present study was to directly compare the diagnostic accuracy of
magnetic resonance imaging (MRI) and multislice computed tomography (CT) for the detection of
coronary artery stenosis.
B A C K G R O U N D Both imaging modalities have emerged as potential noninvasive coronary imag-
ing modalities; however, CT— unlike MRI— exposes patients to radiation and iodinated contrast agent.
M E T H O D S One hundred twenty consecutive patients with suspected or known coronary artery
disease prospectively underwent 32-channel 3.0-T MRI and 64-slice CT before elective X-ray angiography. The diagnostic accuracy of the 2 modalities for detecting significant coronary stenosis (ⱖ50%
luminal diameter stenosis) in segments ⱖ1.5 mm diameter was compared with quantitative invasive
coronary angiography as the reference standard.
R E S U L T S In the patient-based analysis MRI and CT angiography showed similar diagnostic accuracy
of 83% (95% confidence interval [CI]: 75 to 87) versus 87% (95% CI: 80 to 92), p ⫽ 0.38; sensitivity of 87%
(95% CI: 76 to 93) versus 90% (95% CI: 80 to 95), p ⫽ 0.16; and specificity of 77% (95% CI: 63 to 87) versus
83% (95% CI: 70 to 91), p ⫽ 0.06, respectively. All cases of left main or 3-vessel disease were correctly
diagnosed by MRI and CT angiography. In the patient-based analysis MRI and CT angiography were
similar in their ability to identify patients who subsequently underwent revascularization: the area under
the receiver-operator characteristic curve was 0.78 (95% CI: 0.69 to 0.87) for MRI and 0.82 (95% CI: 0.74
to 0.90) for CT angiography.
C O N C L U S I O N S Thirty-two channel 3.0-T MRI and 64-slice CT angiography similarly identify
significant coronary stenosis in patients with suspected or known coronary artery disease scheduled for
elective coronary angiography. However, CT angiography showed a favorable trend toward higher
diagnostic performance. (J Am Coll Cardiol Img 2011;4:50 – 61) © 2011 by the American College of
Cardiology Foundation
From the *Department of Internal Medicine/Cardiology, Deutsches Herzzentrum Berlin, Berlin, Germany; †Imaging Science
Institute, Charité-Universitätsmedizin Berlin, Berlin, Germany; and the ‡Heart Institute and Department of Diagnostic
Imaging, Sheba Medical Center, Tel-Hashomer, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel. The study
was supported by the Foundation Deutsches Herzzentrum Berlin. Dr. Hamdan has received a grant from the European Society
of Cardiology Working group for Cardiovascular Magnetic Resonance. All other authors report that they have no relationships
to disclose.
Manuscript received August 31, 2010; revised manuscript received September 28, 2010, accepted October 4, 2010.
JACC: CARDIOVASCULAR IMAGING, VOL. 4, NO. 1, 2011
JANUARY 2011:50 – 61
C
oronary artery disease (CAD) is the leading cause of death in the western world,
and its prevalence is still increasing (1).
The current gold standard for the diagnosis of obstructive CAD remains conventional coronary angiography; however, it is invasive and associated with risks, and a substantial number of the
procedures are for diagnostic purposes only without
the need for intervention (2). Thus, noninvasive,
See page 62
low-risk, and cost-effective coronary angiography
would represent important progress in the diagnosis
of obstructive CAD.
Magnetic resonance imaging (MRI) and multislice
computed tomography (CT) have been proposed as
noninvasive imaging modalities to determine the presence of coronary artery stenosis (3,4). Several studies
have directly compared these 2 imaging approaches
for the diagnosis of obstructive CAD (5– 8). However,
in recent years, noninvasive coronary imaging modalities have been further spectacularly developed. In the
field of MRI the recent use of 3.0-T MRI systems
(9,10) and 32-element coils (11,12) has allowed improvements in both the signal-to-noise ratio (SNR)
and parallel imaging techniques, which enable further
improvement of the spatial and temporal resolution of
the 3-dimensional (3D) free-breathing whole-heart
coronary imaging. By contrast, 64-slice CT technology has higher spatial and temporal resolution than
the older CT generations, which results in improved
image quality and great clinical reliability. In addition,
a direct comparison of the ability of MRI and CT
angiography to predict the need for revascularization
has not been made.
Therefore, we conducted a prospective 2-center
study to determine the diagnostic accuracy of MRI
and multislice CT angiography involving 32-channel
3.0-T MRI and 64-slice CT for the detection of
clinically relevant coronary artery stenosis in patients
with suspected or known CAD referred for invasive
coronary angiography. Thus, the study was designed
to determine the presence or absence of coronary
artery stenosis in patients already at substantial risk for
CAD who might require coronary revascularization.
METHODS
Study design. The study is a prospective, 2-center
study. MRI and CT angiography were performed
and evaluated at 2 different centers. The local
institutional review board and the German Federal
Hamdan et al.
MRI vs. CT for Detection of Coronary Stenosis
51
Department for Radiation Protection approved the
study, and all patients gave written informed
consent.
Study population. The study group consisted of 120
consecutive patients who were referred between
September 29, 2008 and May 3, 2009 to undergo
invasive coronary angiography for suspected or
known CAD. To avoid radiation exposure in
younger patients, who have a higher lifetime attributable risk than older individuals receiving the same
dose, patients enrolled in the study were at least 50
years of age (13). The exclusion criteria were atrial
fibrillation, acute coronary syndrome, New York
Heart Association functional class III or IV heart
failure, previous coronary artery bypass graft operation, body mass index of more than 40 kg/m2,
pregnancy, and breastfeeding. Patients with contraindications to MRI (noncompatible imABBREVIATIONS
plants or severe claustrophobia) or CT
AND ACRONYMS
(impaired renal function with serum creatinine level ⬎1.4 mg/dl or known allergy
3D ⴝ 3-dimensional
to iodinated contrast agents) were also not
AUC ⴝ area under the curve
considered for inclusion in the study.
CAD ⴝ coronary artery disease
Study protocol. Patients underwent MRI
CT ⴝ computed tomography
and CT angiography in random order
ECG ⴝ electrocardiogram
before invasive coronary angiography. If
LAD ⴝ left anterior descending
no contraindications were present, each
coronary artery
patient received sublingual isosorbide diLCX ⴝ left circumflex coronary
nitrate (5 mg) immediately before MRI
artery
and CT angiography. Whenever the heart
MRI ⴝ magnetic resonance
imaging
rate was ⬎65 beats/min, the patient was
RCA ⴝ right coronary artery
given 50 mg of metoprolol orally 1 h
before MRI and CT examinations and,
ROC ⴝ receiver-operator
characteristic
additionally, intravenous metoprolol (up
SENSE ⴝ sensitivity encoding
to 3 doses of 5 mg) if the heart rate was
SNR ⴝ signal-to-noise ratio
still ⬎65 beats/min.
32-channel MRI coronary angiography.
Magnetic resonance imaging was performed on a
3.0-T system (Achieva 3 Tesla, Philips, Best, the
Netherlands) with a dedicated 32-element cardiac
coil (4 ⫻ 4 anterior elements and 4 ⫻ 4 posterior
elements) for data acquisition, as described recently
(11,12). Cardiac synchronization was performed
with vector electrocardiogram (ECG). A multislice
survey using a segmented balanced steady-state free
precession sequence allowed localization of the heart
and diaphragm in the 3 standard planes (transversal,
sagittal, and coronal). Subsequently, a reference 3D
dataset was obtained to evaluate the individual coil
sensitivities for subsequent sensitivity-encoding
(SENSE) imaging. To determine the individual cardiac rest period a cine-scan with transversal slice
orientation (balanced steady-state free precession, rep-
52
Hamdan et al.
MRI vs. CT for Detection of Coronary Stenosis
JACC: CARDIOVASCULAR IMAGING, VOL. 4, NO. 1, 2011
JANUARY 2011:50 – 61
Figure 1. Diagram Illustrating the Course of the 32-Channel MRI and 64-Slice CT Angiography
Diagram illustrating the course of free-breathing navigator gated 32-channel 3.0-T magnetic resonance imaging (MRI) and 64-slice computed tomography (CT) coronary angiography. Contrast agent was administered for CT but not for MRI angiography.
etition time/echo time/flip angle 3.7 ms/1.8 ms/45°,
acquired spatial resolution 2 ⫻ 2 ⫻ 8 mm, retrospective gating, 50 phases/cardiac cycle) was performed to
visually determine the optimal patient-specific triggerdelay time and the duration of data acquisition window per RR interval (14). For real time respiratory
gating in the subsequent MRI angiography a pencilbeam prospective navigator was placed on the dome of
the right hemidiaphragm to monitor the liver–lung
interface during free-breathing with an end expiratory
acceptance window of 5 mm and a correction factor of
0.45 in cranio-caudal direction (15).
A navigator-gated, ECG-triggered 3D wholeheart MRI angiography with 130 transversal slices
covering the whole of the heart was acquired with a
segmented turbo gradient echo sequence (repetition
time/echo time/flip angle: 4.2 ms/1.3 ms/20°) with
a T2 preparation and a fat suppression pre-pulse.
The spatial resolution of the MRI angiography was
0.5 ⫻ 0.5 ⫻ 1 mm interpolated from 1 ⫻ 1 ⫻ 2
mm. Data acquisition was accelerated by employing
2-dimensional parallel imaging with a SENSE
factor of 1.5 in the feed-head and anterior-posterior
direction. Contrast agent was not administered. A
diagram showing the MRI procedure is given in
Figure 1. For analysis, multiplanar reformatting of
the 3D dataset was carried out with a previously
described dedicated coronary analysis tool (16).
Multislice CT coronary angiography. All scans were
performed with a 64-slice CT scanner (SOMATOM
Sensation 64, Siemens Healthcare, Erlangen, Germany)
with a gantry rotation time of 330 ms, retrospective
ECG gating, 120-kV tube voltage, and 850- to 1000mAs (effective) tube load. Computed tomography data
were simultaneously acquired in 64 (32 ⫻ 2) datasets/
rotation with 32 ⫻ 0.6 mm beam collimation. Scan
direction was cranio-caudal, and scan volume ranged
from the carina to below the diaphragmatic face of the
heart. Pitch value was 0.2. In patients with a heart rate
below 65 beats/min, ECG-gated tube current modulation was used. The window of full tube current was
limited to 60% to 70% of the RR interval.
After placement of an antecubital 18-G intravenous access, contrast agent transit time (iopromide,
370 mg of iodine/ml, Ultravist, Bayer Healthcare,
Germany) was assessed by injecting a test bolus of
15 ml followed by a saline flush of 50 ml, both at a
flow rate of 5 ml/s. Contrast agent transit time was
defined as the time between the start of contrast
injection and maximum enhancement in the ascending aorta at the level of the coronary ostia. For
angiographic CT data acquisition, a delay 3 s longer
than contrast agent transit time was used. The
volume of contrast agent injected for the scan
depended on the estimated scan duration. Contrast
was injected at a flow rate of 5 ml/s for the same
duration as data acquisition. Overall quantity varied
from 75 to 100 ml. Contrast injection was followed
by a 50-ml saline chaser bolus (5 ml/s). Figure 1
also shows the CT angiogram procedure.
Half-scan reconstruction yielded a temporal resolution of 165 ms. The in-plane spatial resolution
was 0.4 ⫻ 0.4 mm with a slice thickness of 0.6 mm.
For reconstruction, slice thickness of 0.75 mm,
JACC: CARDIOVASCULAR IMAGING, VOL. 4, NO. 1, 2011
JANUARY 2011:50 – 61
Hamdan et al.
MRI vs. CT for Detection of Coronary Stenosis
Figure 2. Coronary Artery Segments According to the AHA
Minor branches, such as the conus (CB), sinus node (SN), ventricular (V), acute marginal (AM), atrioventricular node (AV), and atrial circumflex (AC) branches, are indicated in the diagram only for general orientation. In addition to the illustrated 15 coronary artery segments we used the intermediate branch artery assigned to segment number 16. AHA ⫽ American Heart Association; D1 ⫽ first diagonal
branch; D2 ⫽ second diagonal branch; LAD ⫽ left anterior descending coronary artery; LCX ⫽ left circumflex coronary artery; LM ⫽ left
main coronary artery; OM ⫽ obtuse marginal branch; PD ⫽ posterior descending branch; PL ⫽ posterolateral branch; RCA ⫽ right coronary artery; RPD ⫽ right posterior descending branch. Adapted from Austen et al. (18).
increment of 0.5 mm, and standard (B25f) and
sharp (B46f) convolution kernels were used. Initial
reconstructions were obtained at 65% of the RR
interval. If motion artifacts were present, additional
reconstructions were performed in 5% increments
and decrements and displayed on dedicated workstations (Leonardo; Siemens, Forchheim, Germany). Reviews of the axial source images, muliplanar reconstructions, and curved multiplanar
reconstructions were used to evaluate the CT dataset. The effective dose of CT angiography was
calculated with dedicated software (CT-Expo V1.6
2007, Medical University Hannover, Hannover,
Germany) (17).
Conventional coronary angiography. Selective coronary angiography was performed with the transfemoral Judkins approach with standard techniques
after right and left intracoronary administration of
150 to 200 ␮g glycerin trinitrate. Quantitative
analysis of the coronary angiograms (CAAS 5.7,
Pie Medical Imaging B.V., Maastricht, the Netherlands) was performed by an experienced reader
without knowledge of the results of MRI and CT.
At least 2 orthogonal projections were evaluated;
after catheter-based image calibration and automated vessel contour detection the measurement
was performed in the projection that showed the
highest degree of stenosis. A significant coronary
stenosis was defined as ⱖ50% luminal diameter
narrowing in segments ⱖ1.5 mm diameter.
MRI and CT data analysis. The MRI and CT datasets
were interpreted by the consensus of 2 experienced
observers in a blinded fashion at 2 different centers,
without knowledge of the results of conventional
coronary angiography or the clinical characteristics
of the patients. Image quality was assessed on a
4-point scale, where 1 ⫽ poor (nondiagnostic), 2 ⫽
moderate (diagnostic with poor visibility of the
anatomic details of the coronary arteries), 3 ⫽ good
(good visibility of the anatomic details of the
coronary arteries), and 4 ⫽ excellent (excellent
visibility and differentiation of the anatomic details
of the coronary arteries) (8). A 16-coronary-arterysegment model according to the American Heart
Association (modified 15-segment model, with segment 16 being the intermediate branch of the left
coronary artery) (Fig. 2) (18) constituted the basis
for visual assessment of significant coronary artery
stenosis in segments ⱖ1.5 mm diameter. For vessels
with multiple stenosis the most severe stenosis
determined the final vessel stenosis. Coronary arteries with at least 1 visible coronary segment were
included, and coronary segments with prior stent
implantation or segments that were not visible by
MRI or CT angiography were excluded from the
analysis. To assess the clinical relevance of the MRI
and CT data, they were additionally analyzed in
their ability to predict subsequent revascularization
on the basis of location of the stenosis and vessel
size. This was compared with the final decision of
53
54
Hamdan et al.
MRI vs. CT for Detection of Coronary Stenosis
JACC: CARDIOVASCULAR IMAGING, VOL. 4, NO. 1, 2011
JANUARY 2011:50 – 61
Figure 3. Composition of Study Population
Flow chart of the study population, coronary artery disease prevalence, and excluded coronary segments. RIM ⫽ Ramus intermediate
branch; other abbreviations as in Figures 1 and 2.
the invasive cardiologist, on the basis of clinical and
angiographic information, to revascularize or not.
To assess interobserver variability for interpretation of MRI and CT angiography, 2 independent
observers visually evaluated the datasets in a randomly selected sample of 50 studies.
Statistical analysis. The quantitative conventional
coronary angiography served as the reference standard. The sample size was calculated according to
the method proposed by Connor (19). To calculate
the sample size we assumed a difference in perpatient diagnostic accuracy of more than 10% between MRI and CT (8). We intended to give the
study 80% power for an alpha level of 0.05. We
estimated that a sample of 120 patients would be
needed, assuming 50% disease prevalence, 80%
agreement between the 2 modalities on a perpatient basis, and 10% dropout rate. The failure to
falsify the null-hypothesis based on these assumptions is equivalent with the statement that the
diagnostic accuracy of MRI and CT on a perpatient analysis differs by ⬍10% (19).
Statistical analysis was performed with a statistical software package (SPSS, version 17.0, SPSS,
Chicago, Illinois). For all continuous parameters,
data are given as mean ⫾ SD. McNemar chi-square
test was used to compare the diagnostic accuracy
between MRI and CT angiography, and the area
under the receiver-operator-characteristic (ROC)
curve (AUC) (20) and DeLong and DeLong
method (21) were used to compare the prediction of
revascularization with both imaging modalities. Diagnostic accuracy, sensitivity, and specificity were
calculated according to standard definitions. Agreement between observers was assessed with Cohen
kappa statistics (22), and Wilcoxon test was used to
compare the image quality of MRI and CT angiography. All tests were 2-sided, and a p value ⬍0.05
was considered statistically significant.
RESULTS
Five patients could not be examined with MRI,
because of claustrophobia or inadequate image
quality (irregular breathing pattern); another 5 patients either cancelled the CT examination or had
inadequate image quality, because of frequent extrasystoles or insufficient intravenous contrast.
Thus, the final study cohort included 110 patients.
Among the 330 arteries (right, left main–left anterior descending [LAD], and intermediate branch–
left circumflex [LCX]), 5 arteries could not be
evaluated by MRI, and another 3 could not be
evaluated by CT, resulting in 322 vessels for the
final analysis. Among the 1,561 coronary segments,
82 could not be evaluated by MRI, and another 50
JACC: CARDIOVASCULAR IMAGING, VOL. 4, NO. 1, 2011
JANUARY 2011:50 – 61
could not be evaluated by CT; 60 further segments
were stented, and 270 segments had a diameter
⬍1.5 mm (Fig. 3). Representative examples of
normal coronary angiogram and coronary stenosis
that was detected by MRI and CT are shown in
Figures 4 and 5.
Demographic and clinical characteristics of the
patients are shown in Table 1. The median time
interval between the noninvasive tests and X-ray
angiography was 1 day (mean, 0.8 day [range 0 to 3
days]), and MRI and CT were performed as sameday examinations in 85 patients (77%; mean interval, 0.1 day [range 0 to 3 days]). Mean heart rates
during MRI and CT examination did not significantly differ (62.7 ⫾ 8.3 beats/min vs. 62.4 ⫾ 8.7
beats/min, respectively; p ⫽ 0.73). The MRI angiography was acquired during diastole in 100
patients (average heart rate, 62 ⫾ 7 beats/min;
trigger delay, 675 ⫾ 75 ms; acquisition duration,
96 ⫾ 58 ms) and during systole in 10 patients
(average heart rate, 75 ⫾ 11 beats/min; trigger
delay, 377 ⫾ 103 ms; acquisition duration, 82 ⫾ 12
ms). The mean effective scan time for magnetic
resonance angiography was 17 ⫾ 4.7 min. The
optimal reconstruction window for the left coronary
system (left main–LAD, and LCX) in CT was
found at 60% to 70% and 30% to 40% of the cardiac
cycle in 105 and 5 patients, respectively, and for the
right coronary artery (RCA) at 60% to 70% and
30% to 40% of the cardiac cycle in 101 and 9
patients, respectively. The mean time spent by the
patient in the MRI and CT laboratories (including patient preparation) was 26.9 ⫾ 5.8 min and
21.2 ⫾ 4.3 min (p ⬍ 0.001). Within 1 month after
invasive coronary angiography, 53 patients underwent percutaneous revascularization (40 patients) or
surgical revascularization (13 patients). Effective
radiation dose for CT was 15.1 ⫾ 3.4 mSv for men
and 21.9 ⫾ 5.1 mSv for women. Three patients had
minor allergic reactions to contrast dye after CT
angiography.
Image quality. The image quality of the left main–
LAD was similar with MRI and CT angiography
(3.5 ⫾ 0.67 vs. 3.6 ⫾ 0.75, respectively; p ⫽ 0.89);
for the RCA, MRI demonstrated higher image
quality (3.6 ⫾ 0.56 vs. 3.3 ⫾ 0.88, respectively; p ⬍
0.001); however, for the LCX, CT showed higher
image quality (3.0 ⫾ 0.9 vs. 3.6 ⫾ 0.67, respectively; p ⬍ 0.001). The number of segments that
could not be assessed was significantly (p ⫽ 0.011)
higher for MRI than for CT (Fig. 3); however,
most of the coronary segments (48 of 82 [or 59%])
that could not be visualized by MRI were side
Hamdan et al.
MRI vs. CT for Detection of Coronary Stenosis
Figure 4. Representative Example of Normal MRI, CT, and X-Ray Angiography
Representative example of magnetic resonance imaging (MRI) and computed tomography (CT) volume rendering and corresponding invasive coronary angiography images,
showing normal angiogram of left and right coronary artery systems.
branch vessels (diagonal, marginal, or posterolateral). In contrast, only 19 of 50 (38%) segments that
could not be visualized by CT were side branch
vessels (Table 2).
Patient-based analysis. The diagnostic performance
of MRI and CT angiography on a per-patient basis
is shown in Table 3 and Figure 6A. All cases of left
main or 3-vessel disease (2 and 11 patients, respectively) were correctly diagnosed by MRI and CT
angiography.
Vessel-based analysis. Tables 3 and 4 provide direct
comparisons of MRI and CT angiography with conventional coronary angiography for the analysis of
coronary arteries. The diagnostic accuracy of MRI and
CT angiography on a per-vessel basis was similar
(Fig. 6C), with no significant differences among the
right and left main–LAD arteries. However, CT
showed significantly higher diagnostic accuracy for
the intermediate branch–LCX than MRI.
Prediction of revascularization. Table 5 and Figures
6B and 6D show similar ability of MRI and CT
55
56
Hamdan et al.
MRI vs. CT for Detection of Coronary Stenosis
JACC: CARDIOVASCULAR IMAGING, VOL. 4, NO. 1, 2011
JANUARY 2011:50 – 61
Figure 5. MRI and CT in a Patient With 2-Vessel Coronary Artery Disease
Typical examples of volume rendering (left panels), and reformatted images (center panels) of magnetic resonance imaging (MRI) and
computed tomography (CT) angiography and corresponding invasive coronary angiography images (right panels) of the left and right
coronary artery systems. (Top panels) Two-vessel disease involving the distal LAD (pink arrows) and the distal LCX (yellow arrows).
(Bottom panels) Normal distal right coronary arteries by MRI, CT, and invasive coronary angiography. Note the excellent visualization of
the coronary artery including distal segments and side branches.
angiography to predict coronary intervention at 1
month, on the patient- and vessel-based analysis. On
the basis of quantitative coronary angiography, 10 of
Table 1. Baseline Characteristics of Study Population
Characteristic
Age, yrs
Age range, yrs
Sex, male
Value
65.1 ⫾ 8.2
50–81
77 (70)
BMI, kg/m2
27 ⫾ 3.9
BMI ⬎30 kg/m2
32 (29)
Risk factors
Hypertension
78 (70.9)
Diabetes
28 (25.4)
Hypercholesterolemia
67 (60.9)
Current cigarette smoking
22 (20)
Family history of CAD ⬍55 yrs
55 (50)
Known CAD
33 (30)
Previous myocardial infarction
18 (16.3)
Prior percutaneous coronary intervention
22 (20)
Beta-blocker premedication
58 (53)
Clinical presentation
Typical angina
35 (31.8)
Atypical angina
34 (30.9)
Nonspecific chest pain
20 (18.2)
No chest pain
21 (19.1)
Distribution of disease by conventional
coronary angiography
None
48 (44)
1-vessel
34 (31)
2-vessel
17 (15)
3-vessel
11 (10)
Data are n (%) unless otherwise indicated, mean ⫾ SD when appropriate.
BMI ⫽ body mass index; CAD ⫽ coronary artery disease.
the 62 patients with stenosis ⬎50% were not revascularized due to small vessels (n ⫽ 4) or because the
lesion was not regarded as hemodynamically relevant
(n ⫽ 6). On the vessel-based analysis of the 103
vessels, 29 were not revascularized. This was because
the lesion was not regarded as hemodynamically
relevant in 15 cases, the lesion was located in a small
vessel or in distal segments in 7 cases, intervention was
performed in a second session more than 1 month
after the first intervention in 3 cases, the lesions were
regarded as not suitable for intervention in 2 cases, the
patient received bypass surgery and the distal LCX
was not graftable in 1 case, and chronic total occlusion
in 1 patient.
Interobserver agreement. In 50 randomly selected
patients, the patient-based interobserver agreement
was kappa ⫽ 0.80 (95% confidence interval [CI]:
0.64 to 0.96) for MRI and kappa ⫽ 0.84 (95% CI:
0.69 to 0.99) for CT. On the vessel basis the
interobserver agreement was kappa ⫽ 0.78 (95%
CI: 0.67 to 0.89) for MRI and kappa ⫽ 0.82 (95%
CI: 0.70 to 0.94) for CT.
DISCUSSION
The present study demonstrates similar diagnostic
accuracy of MRI and CT angiography with 32channel 3.0-T MRI and 64-slice CT for the detection of significant coronary artery stenosis in patients with suspected or known CAD scheduled for
elective coronary angiography. However, CT angiography showed a favorable but nonsignificant
Hamdan et al.
MRI vs. CT for Detection of Coronary Stenosis
JACC: CARDIOVASCULAR IMAGING, VOL. 4, NO. 1, 2011
JANUARY 2011:50 – 61
Table 2. Evaluation of Segments by Invasive Angiography, 32-Channel MRI, and 64-Slice CT Angiography
32-Channel MRI
64-Slice CT
Not Evaluable
False Positive
False Negative
Not Evaluable
False Positive
False Negative
0
1
0
0
3
0
Proximal
0
5
4
1
9
4
Mid-
7
9
4
3
8
0
Distal
6
6
5
3
2
7
15
3
8
6
6
7
3
LM
LAD
Diagonal branches
LCX
Proximal
5
11
6
3
7
Distal
12
2
3
2
1
2
Marginal branches
19
3
1
3
1
1
0
1
2
1
1
0
Proximal
0
5
3
5
8
3
Mid-
0
6
1
7
2
2
Distal
4
4
0
6
2
2
14
3
2
10
4
2
82
59
39
50
54
33
Intermediate branch
RCA
RPD/PL
Total
CT ⫽ computed tomography; LAD ⫽ left anterior descending artery; LCX ⫽ left circumflex; LM ⫽ left main; MRI ⫽ magnetic resonance imaging; RCA ⫽ right coronary
artery; RPD/PL ⫽ right posterior descending branch/posterolateral branch.
trend toward higher diagnostic performance and
better prediction of subsequent revascularization.
Previous studies comparing MRI and CT angiography have yielded variable results with 1.5-T
MRI and different generations of multislice CT
(5– 8). The relatively new CT generations have
been demonstrated to outperform MRI angiography (7,8). However, in recent years MRI angiography has also shown substantial progress, and the
3.0-T MRI system (9,10) and 32-element coil
(11,12) have been introduced for coronary imaging.
Our results (Table 3) are in close agreement with
those of a recently published meta-analysis (23) that
directly compares MRI and CT angiography in 5
studies (325 patients) and shows similar sensitivity
(87% vs. 87%) but higher specificity (77% vs. 70%).
The differences might be related to the use of the
32-channel coil and 3.0-T MRI, both resulting in
higher SNR. The only study that used 3.0-T MRI
for coronary angiography resulted in slightly higher
sensitivity (94% vs. 87%), specificity (82% vs. 77%),
and diagnostic accuracy (88% vs. 83%) (10), compared with our results. The use of contrast agent,
younger patient age, lower body mass index, and
Table 3. Diagnostic Accuracy of 32-Channel MRI and 64-Slice CT Angiography for Patient- and Vessel-Based Detection of Coronary
Stenosis >50%
32-Channel MRI
64-Slice CT
p Value
Patient-based analysis
Sensitivity
54/62 (87 [76–93])
56/62 (90 [80–95])
0.16
Specificity
37/48 (77 [63–87])
40/48 (83 [70–91])
0.06
Positive predictive value
54/65 (83 [72–90])
56/64 (88 [77–93])
0.62
Negative predictive value
37/45 (82 [69–91])
40/46 (87 [74–94])
0.57
91/110 (83 [75–87])
96/110 (87 [80–92])
0.38
Diagnostic accuracy
Vessel-based analysis
Sensitivity
83/103 (81 [72–87])
87/103 (85 [76–90])
0.52
Specificity
183/219 (84 [78–88])
191/219 (87 [82–91])
0.2
Positive predictive value
83/119 (70 [61–67])
87/115 (76 [67–83])
0.38
Negative predictive value
183/203 (90 [85–93])
191/207 (92 [87–95])
0.48
Diagnostic accuracy
266/322 (83 [78–86])
278/322 (86 [82–90])
0.09
Values are n/n (% [95% confidence interval]).
CT ⫽ computed tomography; MRI ⫽ magnetic resonance imaging.
57
58
Hamdan et al.
MRI vs. CT for Detection of Coronary Stenosis
JACC: CARDIOVASCULAR IMAGING, VOL. 4, NO. 1, 2011
JANUARY 2011:50 – 61
Figure 6. MRI and CT Diagnostic Performance and Prediction of Revascularization
(A) The receiver-operator characteristic (ROC) curve describing the patient-based diagnostic performance of magnetic resonance imaging
(MRI) and computed tomography (CT) angiography. The area under the curve (AUC) was 0.82 (95% confidence interval [CI]: 0.73 to 0.90)
for MRI and 0.87 (95% CI: 0.79 to 0.94) for CT; p ⫽ 0.27. (B) The ROC curves for MRI (AUC 0.78; 95% CI: 0.69 to 0.87), CT (AUC 0.82; 95%
CI: 0.74 to 0.90), and invasive angiography (AUC 0.91; 95% CI: 0.85 to 0.97) for prediction of coronary revascularization. Both curves were
compared with the reference standard: patients who underwent subsequent revascularization and those who did not. On the patient
basis, prediction of revascularization with MRI and CT was similar p ⫽ 0.27; however, invasive angiography predicted coronary revascularization significantly better than MRI, p ⫽ 0.005, and CT, p ⫽ 0.0003. (C) The ROC curve on the vessel basis for MRI and CT diagnostic
performance. The AUC was 0.82 (95% CI: 0.77 to 0.87) for MRI and 0.86 (95% CI: 0.81 to 0.90) for CT; p ⫽ 0.23. (D) The ROC curves on
the vessel basis for prediction of revascularization: MRI (AUC 0.80; 95% CI: 0.74 to 0.86), CT (AUC 0.83; 95% CI: 0.79 to 0.89), and invasive
angiography (AUC 0.94; 95% CI: 0.92 to 0.97). Prediction of revascularization with MRI and CT was similar, p ⫽ 0.15; however, invasive
angiography predicted coronary revascularization significantly better than MRI, p ⬍ 0.001, and CT, p ⬍ 0.001.
exclusion of patients with previous angioplasty
might account for these differences.
For 64-slice CT angiography the per-patient sensitivity and specificity ranged from 91% to 99% and
74% to 96%, respectively, among single-center studies
(24) and from 85% to 99% and 64% to 90%, respectively, among multicenter studies (4,25), which is in
agreement with our data. Compared with the data in
the recently published meta-analysis (23) the sensitivity and specificity of our CT data are comparable but
slightly lower: 90% versus 97% and 83% versus 87%,
respectively. The differences might be because previous studies were often made in selected patients after
elimination or imputation of lesions in a substantial
number of segments that could not be evaluated.
Moreover, previous studies were often performed in
patients with suspected CAD or in populations with a
low prevalence of CAD.
Three-dimensional, free-breathing MRI angiography is a valuable noninvasive tool for the evaluation of
CAD (3,26,27), without the use of radiation and
potentially nephrotoxic contrast agents. However, the
diagnostic performance of this technique at 1.5-T has
not reached that of CT angiography (7,8). This is
probably attributable to the lower SNR, resulting in
inferior spatial and temporal resolution than in CT.
The 3.0-T MRI systems, however, might overcome
these shortcomings due to improved SNR as a result
of increased strength of the static magnetic field (9).
Further progress in the field of MRI angiography is
the use of 32-element coils, which alleviate noise
amplification to some extent and therefore potentially
increase the SNR and enable the use of parallel
imaging in the form of 2-dimensional SENSE
(11,12). The advantage of using 32-channel 3.0-T
MRI angiography was translated in the present study
into high image quality of the coronary arteries as
shown by visual assessment and high diagnostic performance, which was comparable to that of CT
angiography. However, the LCX had lower image
Hamdan et al.
MRI vs. CT for Detection of Coronary Stenosis
JACC: CARDIOVASCULAR IMAGING, VOL. 4, NO. 1, 2011
JANUARY 2011:50 – 61
Table 4. Diagnostic Accuracy of 32-Channel MRI and 64-Slice CT Angiography for Detection of Coronary Stenosis >50%
in Different Vessels
32-Channel MRI
64-Slice CT
p Value
Sensitivity
28/32 (88 [72–95])
25/32 (78 [61–89])
0.20
Specificity
63/75 (84 [74–91])
65/75 (87 [77–93])
0.77
Positive predictive value
28/40 (70 [55–82])
25/35 (71 [55–84])
1.0
RCA
Negative predictive value
63/67 (94 [86–98])
65/72 (90 [81–95])
0.53
89/107 (83 [75–89])
90/107 (84 [76–90])
1.0
Sensitivity
35/42 (83 [69–92])
37/42 (88 [75–95])
0.19
Specificity
56/68 (82 [72–90])
57/68 (84 [73–91])
1.0
Positive predictive value
35/47 (75 [60–85])
37/48 (77 [63–87])
0.81
Diagnostic accuracy
LM-LAD
Negative predictive value
56/63 (89 [79–95])
57/62 (92 [82–97])
0.76
91/110 (83 [75–89])
94/110 (85 [78–91])
0.48
Sensitivity
20/29 (69 [51–82])
25/29 (86 [69–95])
0.07
Specificity
64/76 (84 [74–90])
69/76 (91 [82–95])
0.001
Positive predictive value
20/32 (63 [45–77])
25/32 (78 [61–89])
0.27
64/73 (88 [78–93])
69/73 (95 [87–98])
0.24
84/105 (80 [71–86])
94/105 (90 [82–94])
0.001
Diagnostic accuracy
LCX-intermediate branch
Negative predictive value
Diagnostic accuracy
Values are n/n (% [95% confidence interval]).
Abbreviations as in Table 2.
quality and lower diagnostic accuracy as assessed by
MRI compared with CT. This might be due to the
relatively small caliber and posterior location of the
LCX, which results in a lower SNR because of the
increased distance from the artery to the receiver coils.
By contrast, MRI provides higher image quality for
the RCA. This is possibly related to the higher
temporal resolution (acquisition duration), because the
rest period of the RCA during the cardiac cycle is
shorter than that of the left coronary artery system
(28). This, however, did not result in a statistically
relevant diagnostic advantage compared with CT.
Conversely, compared with MRI, CT has higher
spatial resolution, most probably resulting in a significantly higher number of segments that could not be
assessed by MRI. However, the most common false
positive CT results are found in the proximal segments (Table 2), which might be because calcified
obstructions—which might cause blooming effects
and therefore might result in obscured visualization of
the underlying coronary lumen—are more often located in the proximal segments. This can be regarded
Table 5. Diagnostic Accuracy of 32-Channel MRI and 64-Slice CT Angiography for Patient- and Vessel-Based Prediction
of Coronary Revascularization
32-Channel MRI
64-Slice CT
Invasive Angiography
p Value*
Patient-based analysis
Sensitivity
46/52 (89 [77–95])
48/52 (92 [82–97])
52/52 (100 [93–100])
Specificity
39/58 (67 [54–78])
42/58 (72 [59–82])
48/58 (83 [71–90])
0.58
Positive predictive value
46/65 (71 [58–80])
48/64 (75 [63–84])
52/62 (84 [72–91])
0.69
Negative predictive value
Diagnostic accuracy
39/45 (87 [74–93])
42/46 (91 [79–97])
85/110 (77 [69–84])
90/110 (82 [73–88])
48/48 (100 [92–100])
100/110 (91 [84–95])
0.39
0.52
0.38
Vessel-based analysis
Sensitivity
62/74 (84 [73–91])
65/74 (88 [78–94])
Specificity
191/248 (77 [71–82])
198/248 (80 [74–84])
74/74 (100 [95–100])
219/248 (88 [83–92])
0.15
0.32
Positive predictive value
62/119 (52 [43–61])
65/115 (57 [47–65])
74/103 (72 [62–80])
0.51
Negative predictive value
191/203 (94 [89–97])
198/207 (96 [91–98])
219/219 (100 [98–100])
0.50
Diagnostic accuracy
253/322 (79 [73–83])
263/322 (82 [77–86])
293/322 (91 [87–94])
0.21
Values are n/n (%); values in brackets are 95% confidence intervals. *Comparison between computed tomography (CT) and magnetic resonance imaging (MRI)
angiography.
59
60
Hamdan et al.
MRI vs. CT for Detection of Coronary Stenosis
JACC: CARDIOVASCULAR IMAGING, VOL. 4, NO. 1, 2011
JANUARY 2011:50 – 61
as a drawback of the technique, and data on prognosis
needs to clarify its clinical relevance.
Because the coronary anatomy of the patient—
besides symptoms and functional tests, as determined by conventional coronary angiography—is
crucial for deciding on the indication for revascularization procedure (29), we additionally compared
the ability of MRI and CT angiography to predict
the need for percutaneous or surgical coronary
revascularization. The 2 imaging modalities had
similar ability to identify patients who underwent
coronary revascularization on the basis of clinical
and angiographic information; however, invasive
angiography predicted coronary revascularization
significantly better than MRI and CT (Fig. 6).
Because luminal narrowing alone did not provide
the physiological effects of stenosis and functional
imaging offers different and complementary information, the combined use of noninvasive coronary
angiography and functional imaging in the same
study protocol might be necessary to adequately
predict the need for revascularization and might
improve the relatively low specificity of both modalities (Table 5). Because MRI stress testing has
been intensely researched in recent years and its
high diagnostic value—in the absence of radiation
and potentially nephrotoxic contrast agents— has
been demonstrated (30), a combined use of MRI
stress testing and coronary angiography in the same
imaging session would provide incremental and
crucial benefit for the evaluation of CAD. In
addition, MRI is a major aid in diagnosing heart
disease, particularly when examining ventricular
function and myocardial viability.
Study limitations. We used contrast medium for CT
angiography only, but gadolinium-based contrast
agent might further improve the results of MRI
angiography (10); however, the use of contrast
medium might also enhance coronary veins and
impair the depiction of coronary arteries. In addition, gadolinium-based contrast agent results in
additional study cost and has potential side effects,
particularly for patients with impaired renal function. It is also difficult to repeat the scan in the same
imaging session if the acquisition is aborted for
REFERENCES
1. Lloyd-Jones D, Adams R, Carnethon
M, et al. Heart disease and stroke
statistics—2009 update: a report from
the American Heart Association Statistics Committee and Stroke Statis-
some reason. We excluded segments with coronary
stents from our analysis, because they cause artifacts
mainly in MRI but also in CT angiography and
make a reliable analysis impossible. In symptomatic
patients after stent implantation, in-stent restenosis
cannot be excluded, and a functional test might be
more suitable in this patient population. In the
present study we used a high-end research MRI
system and compared it with a clinically available
64-slice CT machine. More recently, 320- or 256slice CT has been introduced. This new generation
of CT scanners, which were not available at the
participating centers, might have better diagnostic
accuracy for the detection of CAD. Finally, the
present study was performed in patients with clinical indications for cardiac catheterization and a
high prevalence of CAD. The study findings might
not necessarily be extrapolated to patients with less
severe CAD.
CONCLUSIONS
In this study we have demonstrated that 32-channel
3.0-T MRI and 64-slice CT angiography similarly
identify clinically relevant coronary stenosis and
similarly predict subsequent revascularization in
patients with suspected or known CAD scheduled
for elective coronary angiography. However, CT
angiography shows a trend toward higher diagnostic performance.
Acknowledgments
The authors thank Dr. Matthias Stuber from the
Johns Hopkins University School of Medicine,
Baltimore, Maryland, and Dr. Bernhard Schnackenburg from Philips Clinical Science, Hamburg,
Germany, for optimization of the magnetic resonance angiography sequence. They also thank the
technicians of the 3 laboratories for assistance in
performing the study and Anne Gale (ELS) for
editorial support.
Reprint requests and correspondence: Dr. Ashraf Ham-
dan, Department of Internal Medicine/Cardiology, German Heart Institute Berlin, Augustenburger Platz 1,
13353 Berlin, Germany. Email: [email protected].
tics Subcommittee. Circulation 2009;
119:e21–181.
2. Dissmann W, de Ridder M. The soft
science of German cardiology. Lancet
2002;359:2027–9.
3. Kim WY, Danias PG, Stuber M, et al.
Coronary magnetic resonance angiog-
raphy for the detection of coronary
stenoses. N Engl J Med 2001;345:
1863–9.
4. Miller JM, Rochitte CE, Dewey M,
et al. Diagnostic performance of coronary angiography by 64-row CT.
N Engl J Med 2008;359:2324 –36.
JACC: CARDIOVASCULAR IMAGING, VOL. 4, NO. 1, 2011
JANUARY 2011:50 – 61
5. Gerber BL, Coche E, Pasquet A, et al.
Coronary artery stenosis: direct comparison of four-section multi-detector
row CT and 3D navigator MR imaging for detection—initial results. Radiology 2005;234:98 –108.
6. Kefer J, Coche E, Pasquet A, et al.
Head to head comparison of multislice coronary CT and 3D navigator
MRI for the detection of coronary
artery stenosis. J Am Coll Cardiol
2005;46:92–100.
7. Dewey M, Teige F, Schnapauff D,
et al. Noninvasive detection of coronary artery stenoses with multislice
computed tomography or magnetic
resonance imaging. Ann Intern Med
2006;145:407–15.
8. Pouleur AC, le Polain de Waroux JB,
Keefer J, Pasquet A, Vanoverschelde
JL, Gerber BL. Direct comparison of
whole-heart navigator-gated magnetic
resonance coronary angiography and
40- and 64-slice multidetector row
computed tomography to detect the
coronary artery stenosis in patients
scheduled for conventional coronary
angiography. Circ Cardiovasc Imaging 2008;1:114 –21.
9. Stuber M, Botnar RM, Fischer SE,
et al. Preliminary report on in vivo
coronary MRA at 3 Tesla in humans.
Magn Reson Med 2002;48:425–9.
10. Yang Q, Li K, Liu X, et al. Contrastenhanced whole-heart coronary magnetic resonance angiography at 3.0-T.
A comparative study with X-ray angiography in a single center. J Am
Coll Cardiol 2009;54:69 –76.
11. Nehrke K, Börnert P, Mazurkewitz P,
Winkelmann R, Grässlin I. Freebreathing whole-heart coronary MR
angiography on a clinical scanner in
four minutes. J Magn Reson Imaging
2006;23:752– 6.
12. Niendorf T, Hardy CJ, Giaquinto
RO, et al. Toward single breath-hold
whole-heart coverage coronary MRA
using highly accelerated parallel imaging with a 32-channel MR system.
Magn Reson Med 2006;56:167–76.
13. Einstein AJ, Henzlova MJ, Rajagopalan S. Estimating risk of cancer associated with radiation exposure from 64-
slice computed tomography coronary
angiography. JAMA 2007;298:317–23.
14. Weber OM, Martin AJ, Higgins CB.
Whole-heart steady-state free precession coronary artery magnetic resonance angiography. Magn Reson Med
2003;50:1223– 8.
15. Jahnke C, Nehrke K, Paetsch I, et al.
Improved bulk myocardial motion suppression for navigator-gated coronary
magnetic resonance imaging. J Magn
Reson Imaging 2007;26:780 – 6.
16. Etienne A, Botnar RM, van Muiswinkel
AM, Boesiger P, Manning WJ, Stuber
M. ‘Soap-bubble’ visualization and quantitative analysis of 3D coronary magnetic
resonance angiograms. Magn Reson Med
2002;48:658–66.
17. Stamm G, Nagel HD. [CT-expo—a
novel program for dose evaluation in
CT]. Rofo 2002;174:1570 – 6.
18. Austen WG, Edwards JE, Frye RL,
et al. A reporting system on patients evaluated for coronary artery disease. Report
of the Ad Hoc Committee for Grading of
Coronary Artery Disease, Council on
Cardiovascular Surgery, American Heart
Association. Circulation 1975;51:5–40.
19. Connor RJ. Sample size for testing
differences in proportions for the
paired sample design. Biometrics
1987;43:207–11.
20. Zou KH, O’Malley AJ, Mauri L. Receiver operating characteristic analysis
for evaluating diagnostic tests and predictive models. Circulation 2007;115:
654 –7.
21. DeLong ER, DeLong DM, ClarkePearson DL. Comparing the areas
under two or more correlated receiver
operating characteristic curves: a nonparametric approach. Biometrics
1988;44:837– 45.
22. Cohen J. A coefficient of agreement
for nominal scales. Educ Psychol
Meas 1960;20:37– 46.
23. Schuetz GM, Zacharopoulou NM,
Schlattmann P, Dewey M. Metaanalysis: noninvasive coronary angiography using computed tomography versus magnetic resonance
imaging. Ann Intern Med 2010;152:
167–77.
Hamdan et al.
MRI vs. CT for Detection of Coronary Stenosis
24. Min JK, Shaw LJ, Berman DS. The
present state of coronary computed
tomography angiography a process in
evolution. J Am Coll Cardiol 2010;55:
957– 65.
25. Meijboom WB, Meijs MF, Schuijf
JD, et al. Diagnostic accuracy of 64slice computed tomography coronary
angiography: a prospective, multicenter, multivendor study. J Am Coll
Cardiol 2008;52:2135– 44.
26. Jahnke C, Paetsch I, Nehrke K, et al.
Rapid and complete coronary arterial
tree visualization with magnetic resonance imaging: feasibility and diagnostic performance. Eur Heart J 2005;
26:2313–9.
27. Sakuma H, Ichikawa Y, Chino S,
Hirano T, Makino K, Takeda K. Detection of coronary artery stenosis
with whole-heart coronary magnetic
resonance angiography. J Am Coll
Cardiol 2006;48:1946 –50.
28. Jahnke C, Paetsch I, Achenbach S,
et al. Coronary MR imaging: breathhold capability and patterns, coronary
artery rest periods, and beta-blocker
use. Radiology 2006;239:71– 8.
29. Smith SC Jr., Feldman TE, Hirshfeld
JW Jr., et al. ACC/AHA/SCAI 2005
guideline update for percutaneous coronary intervention—summary article:
a report of the American College of
Cardiology/American Heart Association Task Force on Practice Guidelines (ACC/AHA/SCAI Writing
Committee to Update the 2001
Guidelines for Percutaneous Coronary
Intervention). J Am Coll Cardiol
2006;47:216 –35.
30. Gebker R, Jahnke C, Manka R, Hamdan A, Schnackenburg B, Fleck E,
Paetsch I. Additional value of myocardial perfusion imaging during dobutamine stress magnetic resonance for
the assessment of coronary artery disease. Circ Cardiovasc Imaging 2008;
1:122–30.
Key Words: 3.0-T MRI y
coronary angiography y CT.
61