Renate Jerecic

Contrast-Enhanced Whole-Heart Coronary Magnetic Resonance Angiography at 3.0-T: A Comparative Study With X-Ray Angiography in a Single Center

OBJECTIVES The purpose of this study was to prospectively evaluate the diagnostic performance of 3.0-T contrast-enhanced whole-heart coronary magnetic resonance angiography (CMRA) in patients with suspected coronary artery disease (CAD). BACKGROUND A slow-infusion, contrast-enhanced whole-heart CMRA approach has recently been developed at 3.0-T. The accuracy of this technique has not yet been determined among patients with suspected CAD. METHODS The 3.0-T contrast-enhanced whole-heart CMRA was performed in 69 consecutive patients. An electrocardiography-triggered, navigator-gated, inversion-recovery prepared, segmented gradient-echo sequence was used to acquire isotropic whole-heart CMRA with slow infusion of 0.2 mmol/kg gadobenate dimeglumine. The diagnostic accuracy of whole-heart CMRA in detecting significant stenoses (> or =50%) was evaluated using X-ray angiography as the reference. RESULTS The CMRA examinations were successfully completed in 62 patients. Acquisition time of whole-heart CMRA procedure was 9.0 +/- 1.9 min. The 3.0-T whole-heart CMRA correctly identified significant CAD in 32 patients and correctly ruled out CAD in 23 patients. The sensitivity, specificity, and accuracy of whole-heart CMRA for detecting significant stenoses were 91.6% (87 of 95), 83.1% (570 of 686), and 84.1% (657 of 781), respectively, on a per-segment basis. These values were 94.1% (32 of 34), 82.1% (23 of 28), and 88.7% (55 of 62), respectively, on a per-patient basis. CONCLUSIONS Contrast-enhanced whole-heart CMRA with 3.0-T allows for the accurate detection of coronary artery stenosis with high sensitivity and moderate specificity.

Multiecho dixon fat and water separation method for detecting fibrofatty infiltration in the myocardium

Conventional approaches for fat and water discrimination based on chemical‐shift fat suppression have reduced ability to characterize fatty infiltration due to poor contrast of microscopic fat. The multiecho Dixon approach to water and fat separation has advantages over chemical‐shift fat suppression: 1) water and fat images can be acquired in a single breathhold, avoiding misregistration; 2) fat has positive contrast; 3) the method is compatible with precontrast and late‐enhancement imaging, 4) less susceptible to partial‐volume effects, and 5) robust in the presence of background field variation; and 6) for the bandwidth implemented, chemical‐shift artifact is decreased. The proposed technique was applied successfully in all 28 patients studied. This included 10 studies with indication of coronary artery disease (CAD), of which four cases with chronic myocardial infarction (MI) exhibited fatty infiltration; 13 studies to rule out arrhythmogenic right ventricular cardiomyopathy (ARVC), of which there were three cases with fibrofatty infiltration and two confirmed with ARVC; and five cases of cardiac masses (two lipomas). The precontrast contrast‐to‐noise ratio (CNR) of intramyocardial fat was greatly improved, by 240% relative to conventional fat suppression. For the parameters implemented, the signal‐to‐noise ratio (SNR) was decreased by 30% relative to conventional late enhancement. The multiecho Dixon method for fat and water separation provides a sensitive means of detecting intramyocardial fat with positive signal contrast. Magn Reson Med 61:215–221, 2009.

Contrast-Enhanced Whole-Heart Coronary Magnetic Resonance Angiography at 3.0-T

OBJECTIVES The purpose of this study was to prospectively evaluate the diagnostic performance of 3.0-T contrast-enhanced whole-heart coronary magnetic resonance angiography (CMRA) in patients with suspected coronary artery disease (CAD). BACKGROUND A slow-infusion, contrast-enhanced whole-heart CMRA approach has recently been developed at 3.0-T. The accuracy of this technique has not yet been determined among patients with suspected CAD. METHODS The 3.0-T contrast-enhanced whole-heart CMRA was performed in 69 consecutive patients. An electrocardiography-triggered, navigator-gated, inversion-recovery prepared, segmented gradient-echo sequence was used to acquire isotropic whole-heart CMRA with slow infusion of 0.2 mmol/kg gadobenate dimeglumine. The diagnostic accuracy of whole-heart CMRA in detecting significant stenoses (> or =50%) was evaluated using X-ray angiography as the reference. RESULTS The CMRA examinations were successfully completed in 62 patients. Acquisition time of whole-heart CMRA procedure was 9.0 +/- 1.9 min. The 3.0-T whole-heart CMRA correctly identified significant CAD in 32 patients and correctly ruled out CAD in 23 patients. The sensitivity, specificity, and accuracy of whole-heart CMRA for detecting significant stenoses were 91.6% (87 of 95), 83.1% (570 of 686), and 84.1% (657 of 781), respectively, on a per-segment basis. These values were 94.1% (32 of 34), 82.1% (23 of 28), and 88.7% (55 of 62), respectively, on a per-patient basis. CONCLUSIONS Contrast-enhanced whole-heart CMRA with 3.0-T allows for the accurate detection of coronary artery stenosis with high sensitivity and moderate specificity.

Contrast-Enhanced Whole-Heart Coronary Magnetic Resonance Angiography at 3.0 T : Comparison With Steady-State Free Precession Technique at 1.5 T

Objectives:To compare contrast-enhanced whole-heart coronary MR angiography (MRA) at 3.0 T and noncontrast steady-state free precession coronary MRA at 1.5 T in the same volunteers. Materials and Methods:Nine healthy volunteers underwent both coronary MRA using 3D FLASH with slow infusion of MultiHance at 3.0 T and 3D TrueFISP sequence at 1.5 T. Neither β-blockers nor nitroglycerine was administered in any of the imaging sessions. The same spatial resolution and heart coverage were used at both field strengths. Acquisition time, signal-to-noise ratio of coronary blood, contrast-to-noise ratio (CNR) between coronary blood and surrounding myocardium or connecting tissue, scores of image quality, coronary artery sharpness, and coverage of coronary segments for the 2 techniques were analyzed and statistically compared. Results:There were no significant differences in heart rate (68 ± 10 vs. 63 ± 6 beats/min, P > 0.05) and navigator efficiency (34.1% ± 7.7% vs. 34.8% ± 9.2%, P > 0.05) at 3.0 T and 1.5 T coronary MRA during the data acquisition. The average acquisition time of the 3.0 T coronary MRA was significantly shorter than that of the1.5 T coronary MRA (9.7 ± 2.3 vs. 14.6 ± 3.5, P < 0.05). The mean score of image quality and vessel sharpness at 3.0 T was similar to that at 1.5 T (2.8 ± 1.0 vs. 3.0 ± 1.0 and 0.63 ± 0.15 vs. 0.61 ± 0.13, respectively. P > 0.05). There was no significant difference between the number of visible coronary segments of the major coronary arteries at 3.0 T and 1.5 T (64/81 vs. 62/81, P > 0.05). However, the number of visible main coronary branches at 3.0 T was significantly higher than that at 1.5 T (18/54 vs. 7/54, P < 0.05). The overall signal-to-noise ratio at 3.0 T was significantly lower than that at 1.5 T (40.9 ± 4.7 vs. 60.9 ± 3.4, P < 0.01), whereas the overall CNR at 3.0 T was significantly higher than that at 1.5 T (35.4 ± 3.3 vs. 28.8 ± 6.4, P < 0.05). Conclusion:Contrast-enhanced whole-heart coronary MRA at 3.0 T demonstrated less acquisition time, higher CNR, and better depiction of coronary segments compared with steady-state free precession coronary MRA at 1.5 T. Patient studies are required to evaluate the clinical value of the technique.

Unenhanced MR Angiography of the Thoracic Aorta: Initial Clinical Evaluation

OBJECTIVE In 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. MATERIALS AND METHODS MRA 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. RESULTS The 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). CONCLUSION In patients in whom contrast material is contraindicated, unenhanced MRA using a 3D SSFP technique can be performed.

A Dual-Projection Respiratory Self-Gating Technique for Whole- heart Coronary MRA

To investigate the accuracy of a dual‐projection respiratory self‐gating (DP‐RSG) technique in dynamic heart position measurement and its feasibility for free‐breathing whole‐heart coronary MR angiography (MRA).

Renal Transplant: Nonenhanced Renal MR Angiography with Magnetization-prepared Steady-State Free Precession

The institutional review board approved this HIPAA-compliant study and waived informed consent. The purpose was to investigate nonenhanced magnetic resonance (MR) angiography with steady-state free precession (SSFP) with inversion recovery for assessing renal arteries in patients with renal transplants. Thirteen recipients of renal transplants underwent SSFP MR angiography before contrast material-enhanced MR angiography. Three stenoses (two mild, one severe) were identified at SSFP MR angiography in agreement with findings at contrast-enhanced MR angiography. There was no significant difference in image quality between the two methods. Results suggest SSFP MR angiography permits image quality of renal transplant arteries and detection of arterial stenosis comparable with those at contrast-enhanced MR angiography.

A respiratory self-gating technique with 3D-translation compensation for free-breathing whole-heart coronary MRA

Respiratory motion remains a major challenge for robust coronary MR angiography (MRA). Diaphragmatic navigator (NAV) suffers from indirect measurement of heart position. Respiratory self‐gating (RSG) approaches improve motion detection only in the head–feet direction, leaving motion in the other two dimensions unaccounted for. The purpose of this study was to extend conventional RSG (1D RSG) to RSG capable of 3D motion detection (3D RSG) by acquiring additional RSG projections with transverse‐motion‐encoding gradients. Simulation and volunteer studies were conducted to validate the effectiveness of this new method. Preliminary comparison was performed between coronary artery images reconstructed from the same datasets using different motion correction methods. Our simulation illustrates that a proper motion‐encoding gradient and derivation method enable accurate 3D motion detection. Results from whole‐heart coronary MRA show that 3D RSG can further reduce motion artifacts as compared to NAV and 1D RSG and enables use of larger gating windows for faster coronary imaging. Magn Reson Med, 2009.

Non-contrast-enhanced four-dimensional (4D) intracranial MR angiography: A feasibility study

T1‐shortening contrast agents have been widely used in time‐resolved magnetic resonance angiography. To match imaging data acquisition with the short time period of the first pass of contrast agent, temporal resolution and/or spatial resolution have to be compromised in many cases. In this study, a novel non‐contrast‐enhanced technique was developed for time‐resolved magnetic resonance angiography. Alternating magnetization preparation was applied in two consecutive acquisitions of each measurement to eliminate the need for contrast media. Without the constraint of contrast media kinetics, temporal resolution is drastically improved from the order of a second as in conventional contrast‐enhanced approach to tens of milliseconds (50.9 msec) in this study, without compromising spatial resolution. Initial results from volunteer studies demonstrate the feasibility of this method to depict anatomic structure and dynamic filling of main vessels in the head. Magn Reson Med 63:835–841, 2010.

Three-Dimensional Phase-Sensitive Inversion-Recovery Turbo FLASH Sequence for the Evaluation of Left Ventricular Myocardial Scar

OBJECTIVE The purpose of this study was to evaluate a new free-breathing 3D phase-sensitive inversion-recovery (PSIR) turbo FLASH pulse sequence for the detection of left ventricular myocardial scar. SUBJECTS AND METHODS Patients with suspected myocardial scar were examined on a 1.5-T MR scanner for myocardial late enhancement after the administration of gadopentetate dimeglumine using a segmented 2D PSIR turbo FLASH sequence followed by a navigator-gated 3D PSIR turbo FLASH sequence. Image quality was scored by two independent readers using a 4-point Likert scale (0 = poor, nondiagnostic; 1 = fair, diagnostics may be impaired; 2 = good, some artifacts but not interfering in diagnostics; 3 = excellent, no artifacts). Scars were compared quantitatively in volume and graded qualitatively on the basis of size (area) and location. RESULTS Thirty-three patients were scanned using both techniques. In 25 patients, the quality of the 3D PSIR images was acceptable. Scars were detected in 12 patients. Hyperenhanced scar volumes (p = 0.43), qualitative analysis of scar area (p = 0.78), and scar location (p = 0.68) were similar for both techniques. More small hyperenhanced scars, corresponding mostly to nonischemic distribution patterns, were detected using 3D PSIR than 2D PSIR. Although 2D and 3D results were found to be highly correlated for scar volume, Bland-Altman analysis indicated a systematic smaller infarct volume on the 2D PSIR scans (R(2) = 0.84). CONCLUSION Free-breathing 3D PSIR turbo FLASH imaging is a promising technique for the assessment of left ventricular scar particularly for scar quantification and the detection of small nonischemic scars in the myocardium.