Christopher J. François

Comparison of 3D Free-Breathing Coronary MR Angiography and 64-MDCT Angiography for Detection of Coronary Stenosis in Patients with High Calcium Scores

OBJECTIVEnThe objective of our study was to compare the diagnostic performance of coronary MR angiography (MRA) and 64-MDCT angiography (MDCTA) for the detection of significant stenosis (> or = 50%) in patients with high calcium scores.nnnMATERIALS AND METHODSnEighteen patients (12 men, six women; mean age, 56 y; age range, 38-77 y) who had at least one calcified plaque with a calcium score of > 100 underwent coronary MRA and conventional coronary angiography (CAG) within 2 weeks of MDCTA. Coronary MRA image quality of the calcified segments was assessed by two observers in consensus on a 4-point scale (1 = not visible, 2 = poor, 3 = good, 4 = excellent) using a 10-segment model from the modified American Heart Association classification. Three experienced radiologists, unaware of the results of conventional CAG, independently assessed for the presence of significant stenosis on MDCTA images and the corresponding MRA images. Receiver operating characteristic (ROC) curves were calculated for each reader using conventional CAG as the gold standard.nnnRESULTSnThirty-three calcified plaques with a calcium score of > 100 were detected on MDCTA in the 18 patients. The coronary segments with nodal calcification (n = 17) showed a higher mean image quality score than the segments with diffuse calcification (n = 16) (3.47 +/- 0.62 vs 2.94 +/- 0.77, respectively; p < 0.05). Of the 33 coronary segments with calcification, 12 significant stenoses were identified on conventional CAG. The sensitivity, specificity, and area under the ROC curve (AUC) for MRA and MDCTA, respectively, were as follows: reader 1, 75%, 81%, 0.82 versus 75%, 48%, 0.68; reader 2, 83%, 71%, 0.82 versus 67%, 52%, 0.63; and reader 3, 83%, 71%, 0.85 versus 83%, 43%, 0.65, respectively. The average AUC of MRA for the three readers was significantly higher than that of MDCTA (p = 0.030).nnnCONCLUSIONnCoronary MRA has higher image quality for coronary segments with nodal calcification than for coronary segments with diffuse calcification. Coronary MRA has better diagnostic performance than coronary MDCTA for the detection of significant stenosis in patients with high calcium scores.

Unenhanced MR Angiography of the Thoracic Aorta: Initial Clinical Evaluation

OBJECTIVEnIn patients with difficult i.v. access or renal insufficiency, or in those who are pregnant, we hypothesized than an unenhanced 3D segmented steady-state free precession (SSFP) MR angiography (MRA) technique would be an alternative to contrast-enhanced MR angiography (CE-MRA) for the evaluation of vasculature.nnnMATERIALS AND METHODSnMRA examinations of the thoracic aorta were retrospectively reviewed in 23 patients in whom both CE-MRA and 3D SSFP were performed. CE-MRA was performed using an ECG-gated gradient-echo FLASH sequence. Three-dimensional SSFP MRA was performed during free breathing using a motion-adaptive navigator technique. Quantitative assessment of the 3D SSFP and CE-MRA image sets was performed by comparing the aortic lumen diameter. The quality of the images of the aortic root (scale of 1-5) and the presence of cardiovascular and noncardiovascular pathology were independently determined for both techniques by two reviewers. Bland-Altman and Wilcoxons signed-rank analyses were performed.nnnRESULTSnThe difference in orthogonal measurements of the aortic diameter between those made on images from the 3D SSFP and those made from the CE-MRA sequences was -0.042 cm. The aortic root was better visualized with 3D SSFP: score of 3.78 (of 5) for CE-MRA versus score of 4.65 (of 5) for 3D SSFP (p < 0.05).nnnCONCLUSIONnIn patients in whom contrast material is contraindicated, unenhanced MRA using a 3D SSFP technique can be performed.

Pulmonary vein imaging with unenhanced three-dimensional balanced steady-state free precession MR angiography: initial clinical evaluation.

PURPOSEnTo determine whether unenhanced magnetic resonance (MR) angiography performed with a three-dimensional (3D) segmented steady-state free precession (SSFP) sequence would be an alternative to contrast material-enhanced MR angiography for evaluating pulmonary veins (PVs) prior to and following radiofrequency (RF) ablation for atrial fibrillation.nnnMATERIALS AND METHODSnMR angiographic examinations of PVs, performed in 20 patients (nine men, 11 women; mean age, 56.4 years +/- 12.7 [standard deviation]), were retrospectively reviewed according to an institutional review board-approved protocol. The number of PVs and their orthogonal measurements obtained from the 3D SSFP images were compared with those obtained from contrast-enhanced MR angiography. Signal-to-noise and contrast-to-noise ratios were also compared. Qualitative assessment of both techniques was performed by independent reviewers who scored the image quality (on a scale of 1 to 5) on the basis of PV conspicuity. The presence of cardiac and extracardiac pathologic indicators was also determined. Bland-Altman and Wilcoxon signed rank statistical analyses were performed.nnnRESULTSnThe mean difference in PV diameter measurements between contrast-enhanced MR angiography and 3D SSFP was -0.02 cm +/- 0.25. Signal-to-noise and contrast-to-noise ratios were higher for 3D SSFP images than for contrast-enhanced MR angiograms. Qualitatively, there was no significant difference in PV conspicuity between the techniques. Noncardiac pathologic indicators were detected in 10 of 20 patients on 3D SSFP images but not on contrast-enhanced MR angiograms.nnnCONCLUSIONnUnenhanced PV MR angiography performed by using a free-breathing 3D SSFP technique is as accurate as contrast-enhanced MR angiography for measuring PV diameter. This technique can be used for patients in whom contrast-enhanced computed tomographic or MR angiography is contraindicated and may be sufficient in all patients.

Cardiac image modeling tool for quantitative analysis of global and regional cardiac wall motion

Objective:To evaluate the Cardiac Image Modeling (CIM 4.6; University of Auckland, Auckland, New Zealand) tool’s ability to assess cardiac function via quantitative calculations of global and regional ejection fraction (EF) from magnetic resonance imaging in comparison with a current method of global analysis with Argus (Siemens Medical Solutions) and regional analysis with visual analysis. Background:Global cardiac function is commonly assessed quantitatively by post processing tools that calculate global EF. Currently, regional cardiac function is assessed by subjective visual analysis of wall motion, which can have significant interobserver variability. CIM is a tool that may reduce variability by generating a semi-automated 3-dimensional heart model to calculate quantitative global and regional EF. Materials and Methods:Thirty-one patients (22 men, 9 women; mean age 55.1 ± 17.5 years) were selected based on global EFs calculated at the time of the clinical visit with the Argus postprocessing tool (Siemens Medical Solutions). Patients were then placed into 2 predetermined categories of normal: EF ≥50% and abnormal: EF <50%. Regional EF was calculated for each segment of a 16-segment cardiac model. Three blinded reviewers used the standard of care assessment of regional function, which was a qualitative grading of the 16 segments into categories of normal or abnormal regional wall motion by visual analysis. CIM quantitatively analyzed global EF and regional EF for each segment. These segments were then sorted into the predetermined categories of normal (EF ≥50%) and abnormal (EF <50%). Level of agreement was conducted via Pearson correlation coefficient and Bland-Altman analysis for global EF analysis and observed proportion of agreement (pa), sensitivity, and specificity for regional EF analysis. Results:Global EF analysis showed a high correlation (r2 = 0.85; y = 0.94x + 4.85, P < 0.001) between the Argus and CIM analyses. Sixteen-segment regional EF analysis showed pa averages >0.60. Regional wall motion by short axis slices showed pa averages >0.75, and combined analyses of all 3 reviewers’ 16-segment regional data showed an overall total pa = 0.79 (sensitivity = 72%, specificity = 88%). Interobserver and intraobserver variability were low (pa > 0.65) in this study. Conclusions:Global EF analysis of cardiac magnetic resonance imaging by CIM showed high agreement with the commonly used Argus postprocessing tool. Furthermore, CIM is capable of evaluating regional EF with good agreement in comparison with the current visual method. In addition to determining abnormal versus normal cardiac wall motion, CIM is able to add to the analysis a quantitative regional EF for each given segment. As a semi-automated tool, CIM has the potential to reduce reviewer variability and decrease the time required for analysis. In the future, CIM can potentially quantitatively track global and regional changes in patients with heart disease and aid the clinical management throughout the course of the disease.

MRI of the Thoracic Aorta

Diseases of the thoracic aorta cause significant morbidity and mortality and can result in potentially catastrophic consequences. Conventional digital subtraction angiography (DSA) has been the gold standard for imaging for many years; however, this is associated with adverse effects and provides only limited information about vessel morphology. DSA is used primarily as a first-line investigation in the setting of trauma. Several other techniques also have been used in recent years, including CT and MRI. This article focuses primarily on the latter.

CT and MR Imaging of Primary, Metastatic, and Nonneoplastic Cardiac Masses

The initial evaluation of cardiac masses usually is done with echocardiography, which is limited by small fields of view and occasionally by a suboptimal acoustic window. Computed tomography and MR imaging do not have these limitations, and use of these modalities for further characterization of cardiac masses is increasing. Both CT and MR imaging can demonstrate the characteristics and extent of a cardiac mass, detailed cardiac anatomy, and its effect on cardiac function—information that can assist in preoperative planning as well as diagnosis. A cardiac mass also may be discovered incidentally in a patient undergoing CT or MR imaging for other reasons. It often is difficult to distinguish benign from malignant cardiac neoplasms, and it also is important to be aware of the features that differentiate a true cardiac neoplasm from nonneoplastic masses, which are much more common. This article presents the salient clinical, pathologic, and imaging characteristics of primary cardiac neoplasms, cardiac metastases, and nonneoplastic cardiac processes. The correct diagnosis can be made—or at least the differential diagnosis can be narrowed—when the radiologist is familiar with both the clinical presentation and the imaging characteristics of patients with cardiac masses.

126 Comparison of coronary MR and CT angiography in detection of coronary stenosis with coronary calcification

Introduction Coronary CT angiography (CTA) with 64-slice CT has become a routine clinical test for patients with suspected coronary artery disease. However, the interpretation of CTA images is still limited by moderate and severe coronary artery calcification. Coronary MR angiography (MRA), on the other hand, does not suffer from beam hardening artifact by high density calcification and can potentially visualize the lumen of calcified coronary arteries.