Rationale and Objectives
To compare the diagnostic value of magnetic resonance (MR) and computed tomography (CT) for the detection of coronary artery disease (CAD) with special regard to calcifications.
Materials and Methods
Twenty-seven patients with known CAD were examined with a targeted, navigator-gated, free-breathing, steady-state free precession MR angiography sequence (repetition time = 5.6 milliseconds, echo time = 2.8 milliseconds, flip angle 110°) and 16-slice coronary CT angiography. Segment-based sensitivity, specificity, and accuracy for the detection of stenoses larger than 50% were determined as defined by the gold standard catheter coronary angiography along with the subjective image quality (Grade 1–4). The degree of calcifications in each segment was quantified using a standard calcium scoring tool.
Results
Of 115 possible segments, 7% had to be excluded in MR imaging because of poor image quality. In CT, 3% were nondiagnostic because of image quality and 15% were not evaluable because of calcifications. Values for the detection of relevant coronary artery stenoses in the evaluated segments were: sensitivity: MR imaging 85% versus CT 96%; specificity: 88% versus 96%; accuracy: 87% versus. 96%. Average subjective image quality was 1.8 for MR imaging and 1.6 for CT. Of the 15% of segments that had to be excluded from CT evaluation because of calcifications, MR imaging provided the correct diagnosis segments in 67%.
Conclusions
CT provided a better image quality with superior accuracy for the detection of CAD. Despite its overall inferiority, MR imaging proved to be helpful method in interpreting coronary stenosis in severely calcified segments.
Computed tomography (CT) and magnetic resonance coronary angiography (MRA) are noninvasive imaging methods for the detection of coronary artery disease (CAD) in symptomatic and preclinical patients. Both methods have undergone clinical evaluations with comparisons to the gold standard, catheter coronary angiography (CCA). In these studies, good results with reliable diagnostic values were reported for both CT and magnetic resonance imaging (MRI) ( ). However, these studies differ in design (eg, number of evaluated segments, diameter of evaluated segments) and there are only two published studies on a direct comparison of CT and MRI ( ). One of the main disadvantages of computed tomography of the heart is the difficulty in assessing severely calcified segments ( ). Severe calcifications can impair the capability to correctly determinate stenoses due to beam hardening and partial volume artefacts. In MRI, calcifications may cause a signal loss and theoretically should not cause “blooming” artifacts. Therefore, MRI is supposed to be more consistent and not to be affected by calcifications, but this has not yet been investigated in a clinical study. The purpose of this study was to directly compare both modalities for the detection of coronary artery stenosis in an intraindividual patient study, paying special regard to calcified segments to investigate the value of alternative or additional MRI scans in the diagnosis of CAD.
Material and methods
Subjects
A total of 27 patients (21 male, mean age 59 ± 11) with suspected or known CAD were enrolled in this study. Exclusion criteria within this population were atrial fibrillation or other severe arrhythmias, claustrophobia, the presence of MRI-incompatible implants or other contraindication to MRI. Written informed consent was obtained from all participants.
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MRI
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CT
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CCA
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Data Evaluation
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Results
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Table 1
Image Quality, Diagnostic Accuracy of Coronary MRI and CT to Detect Stenoses of ≥50%
MRI CT Evaluated segments (of 115) (%) 103 (90%) 91 (79%) Not assessed 7% motion/misregistration 15% calcified 3% stent 3% motion 3% stent Image quality 1.8 ± 1.3 1.6 ± 0.6 ( P = NS) Sensitivity (%) 85 96 Specificity (%) 88 96 Accuracy (%) 87 96
MRI: magnetic resonance imaging; CT: computed tomography; NS: not significant.
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Table 2
Diagnostic Accuracy for MRI and CT in Calcified Segments
Group A Group B Group C Number of segments (of 43) 21 14 8 Diagnostic accuracy CT 13 NA 4 NA 0 NA 7 of 8 right 8 of 10 right 6 of 8 right MRI 1 NA 1 NA 0 NA 16 of 20 right 9 of 13 right 6 of 8 right
MRI: magnetic resonance imaging; CT: computed tomography; NA: not assessable.
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Discussion
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