Measurement of myocardium at risk with cardiovascular MR: comparison of techniques for edema imaging.

PURPOSE: To determine variability and agreement for detecting myocardial edema with T2-weighted short-tau inversion recovery (STIR), acquisition for cardiac unified T2 edema (ACUT2E), T2 mapping, and early gadolinium enhancement (EGE) after successfully reperfused ST-segment-elevation myocardial infarction (STEMI) and diagnostic accuracy of each sequence to predict infarct-related artery (IRA). MATERIALS AND METHODS: Local ethics committee approved the study, with patient informed written consent. On day 2 after successful primary angioplasty for STEMI, 53 patients were prospectively enrolled; 40 patients (mean age, 60 years) completed study. Two sets of cardiac magnetic resonance (MR) images were obtained on same day 6 hours apart. Basal, midcavity, and apical sections were obtained with each sequence. Interobserver, intraobserver, and interimage variability (1 minus intraclass correlation coefficient) and agreement (Bland-Altman method) were assessed. RESULTS: Size of myocardial edema significantly differed. Mean size of myocardium at risk was similar between T2-weighted STIR (18.2 g) and T2 mapping (17.3 g) (P = .54). Mean size differed between T2-weighted STIR (18.2 g) and ACUT2E (14.0 g) (P = .01) and between T2-weighted STIR (18.2 g) and EGE (14.2 g) (P = .003). T2 mapping and EGE had best agreement (interobserver bias: T2-weighted STIR, -0.9 [mean difference] ± 9.6 [standard deviation]; ACUT2E, -2.5 ± 6.9; T2 mapping, -3.8 ± 4.7; EGE, -5.3 ± 5.9; interimage bias: T2-weighted STIR, 1.5 ± 5.8; ACUT2E, -0.8 ± 4.9; T2 mapping, 3.1 ± 4.0; EGE, 1.1 ± 4.9; intraobserver bias: T2-weighted STIR, 1.4 ± 5.8; ACUT2E, 0.6 ± 4.7; T2 mapping, 2.2 ± 3.1; EGE, 1.7 ± 2.9). Variability was lowest for T2 mapping (intraobserver, 0.05; interobserver, 0.09; interimage, 0.1) followed by EGE (intraobserver, 0.03; interobserver, 0.14; interimage, 0.14), with improved detection of territory of IRA versus ACUT2E (intraobserver, 0.11; interobserver, 0.22; interimage, 0.12) and T2-weighted STIR (intraobserver, 0.1; interobserver, 0.32; interimage, 0.1). CONCLUSION: Cardiac MR methods to detect and quantify infarct myocardial edema are not interchangeable; T2 mapping is the most reproducible method, followed by EGE, ACUT2E, and T2-weighted STIR. Clinical trial registration no. NCT01468662

Inline directionally independent peak velocity evaluation reduces error in peak antegrade velocity estimation in patients referred for cardiac valvular assessment.

OBJECTIVE: The purpose of this article is to evaluate the utility of a tool in quantifying the peak antegrade velocity when assessing patients with cardiac valvular pathology. MATERIALS AND METHODS: Directionally independent peak velocity evaluation (MaxVelocity, Siemens Healthcare) phase-contrast cardiac MRI was performed for 44 patients referred to our institution with a diagnosis or concern for aortic valvular disease or undergoing imaging for thoracic aortic aneurysm. In addition, standard through-plane phase-contrast MR angiography at the level of the aortic valve was performed. The MaxVelocity technique provides a simple tool to extract the magnitude of the peak velocity, independently of its direction, from phase-contrast imaging with velocity encoding. Recent echocardiography (within 1 month) and assessment of peak forward velocity at the level of the aortic valve were required for inclusion in the study. RESULTS: The MaxVelocity technique shows significantly lower error in estimating peak antegrade velocity at the level of the aortic valve than does standard unidirectional through-plane phase-contrast MRI, using transthoracic echocardiography as the reference noninvasive imaging method. CONCLUSION: Relative to standard through-plane imaging, MaxVelocity more closely approximates echocardiography for noninvasive assessment of peak antegrade velocity. Improved accuracy is critical for surgical decision making in patients with aortic valvular disease. Therefore, MaxVelocity provides an easy approach to quantify peak velocity as part of a routine clinical MRI protocol.

Accelerated two- and three-dimensional cine MR imaging of the heart by using a 32-channel coil.

PURPOSE: To compare accelerated real-time two-dimensional (2D) and segmented three-dimensional (3D) cine steady-state free precession magnetic resonance (MR) imaging techniques by using a 32-channel coil with a conventional 2D cine imaging approach for imaging the heart and to evaluate any difference caused by free breathing and breath holding for real-time imaging. MATERIALS AND METHODS: In this institutional review board-approved HIPAA-compliant study, 10 healthy volunteers and 22 consecutive patients who were suspected of having or were known to have heart disease underwent cardiac MR imaging by using a 32-channel coil. A conventional multisection 2D real-time cine sequence was used as the reference standard, and three additional accelerated cine sequences were implemented. Volumetric parameters, including ejection fraction (EF), end-diastolic volume (EDV), end-systolic volume (ESV), stroke volume(SV), and myocardial mass, were derived. Wall motion and image quality were assessed by two radiologists. In addition, image time was registered. An additional set of images was acquired by using real-time sequences with free breathing, and quantitative measurements were compared with measurements on images obtained with breath holding. For quantitative analysis, repeated-measures analysis of variance, paired t test, and Bland-Altman analysis were used; for qualitative analysis, nonparametric Wilcoxon signed-rank test was used. RESULTS: All volumetric measurements were significantly correlated with those of the standard sequence (r > 0.80, P < .01). No significant difference among protocols was observed in terms of mean levels for EF or ESV (P > .05). However, a significant difference was indicated for EDV and SV (P < .01).The accelerated protocols had significantly shorter image times (P < .001). Wall motion scores were concordant with the standard sequence in 43-44 (93%-96%) segments for the accelerated protocols, with a strong interreader agreement (intraclass correlation coefficient, > or =0.93). No significant difference was identified between real-time protocols with free breathing and those with breath holding for measurement of volumetric parameters. CONCLUSION: Accelerated real-time 2D and segmented 3D cine techniques are comparable to the standard clinical protocol in assessment of left ventricular global and regional parameters in substantially shorter image times.

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.

Optimization and comparison of myocardial T1 techniques at 3T in patients with aortic stenosis.

AIMS: To determine the optimal T1 mapping approach to assess myocardial fibrosis at 3T. METHODS AND RESULTS: T1 mapping was performed at 3T using the modified look-locker-inversion sequence in 20 healthy volunteers and 20 patients with aortic stenosis (AS). Pre- and post-contrast myocardial T1, the partition coefficient (λ; ΔRmyocardium/ΔRblood, where ΔR = 1/post-contrast T1 - 1/pre-contrast T1), and extracellular volume fraction [ECV; λ (1 - haematocrit)] were assessed. After establishing the optimal time point and myocardial region for analysis, we compared the reproducibility of these T1 measures and their ability to differentiate asymptomatic patients with AS from healthy volunteers. There was no segmental variation across the ventricle in any of the T1 measures evaluated. λ and ECV did not vary with time, while post-contrast T1 was relatively constant between 15 and 30 min. Thus, mid-cavity myocardium at 20 min was used for subsequent analyses. ECV displayed excellent intra-, inter-observer, and scan-rescan reproducibility [intra-class correlation coefficients (ICC) 1.00, 0.97, and 0.96, respectively], as did λ (ICC 0.99, 0.94, 0.93, respectively). Moreover, ECV and λ were both higher in patients with AS compared with controls (ECV 28.3 ± 1.7 vs. 26.0 ± 1.6%, P < 0.001; λ 0.46 ± 0.03 vs. 0.44 ± 0.03, P = 0.02), with the former offering improved differentiation. In comparison, scan-rescan reproducibilities for pre- and post-contrast myocardial T1 were only modest (ICC 0.72 and 0.56) with no differences in values observed between cases and controls (both P> 0.05). CONCLUSIONS: ECV appears to be the most promising measure of diffuse myocardial fibrosis at 3T based upon its superior reproducibility and ability to differentiate disease from health.