Axial black blood turbo spin echo imaging of the right ventricle

Black-Blood Contrast in Cardiovascular MRI

MRI is a versatile technique that offers many different options for tissue contrast, including suppressing the blood signal, so‐called black‐blood contrast. This contrast mechanism is extremely useful to visualize the vessel wall with high conspicuity or for characterization of tissue adjacent to the blood pool. In this review we cover the physics of black‐blood contrast and different techniques to achieve blood suppression, from methods intrinsic to the imaging readout to magnetization preparation pulses that can be combined with arbitrary readouts, including flow‐dependent and flow‐independent techniques. We emphasize the technical challenges of black‐blood contrast that can depend on flow and motion conditions, additional contrast weighting mechanisms (T₁, T₂, etc.), magnetic properties of the tissue, and spatial coverage. Finally, we describe specific implementations of black‐blood contrast for different vascular beds.

Reverse double inversion-recovery: Improving motion robustness of cardiac T2 -weighted dark-blood turbo spin-echo sequence

BACKGROUND

Cardiac dark-blood turbo spin-echo (TSE) imaging is sensitive to through-plane motion, resulting in myocardial signal reduction.

PURPOSE

To propose and validate reverse double inversion-recovery (RDIR)-a dark-blood preparation with improved motion robustness for the cardiac dark-blood TSE sequence.

STUDY TYPE

Prospective.

POPULATION

Healthy volunteers (n = 10) and patients (n = 20).

FIELD STRENGTH

1.5T (healthy volunteers) and 3T (patients).

ASSESSMENT

Compared to double inversion recovery (DIR), RDIR swaps the two inversion pulses in time and places the slice-selective 180° in late-diastole of the previous cardiac cycle to minimize slice misregistration. RDIR and DIR were performed in the same left-ventricular basal short-axis slice. Healthy subjects were imaged with two preparation slice thicknesses, 110% and 200%, while patients were imaged using a 200% slice thickness only. Images were assessed quantitatively, by measuring the myocardial signal heterogeneity and the extent of dropout, and also qualitatively on a 5-point scale.

STATISTICAL TESTS

Quantitative and qualitative data were assessed with Student's t-test and Wilcoxon signed-rank test, respectively.

RESULTS

In healthy subjects, RDIR with 110% slice thickness significantly reduced signal heterogeneity in both the left ventricle (LV) and right ventricle (RV) (LV: P = 0.006, RV: P < 0.0001) and the extent of RV dropout (P < 0.0001), while RDIR with 200% slice thickness significantly reduced RV signal heterogeneity (P = 0.001) and the extent of RV dropout (P = 0.0002). In patients, RDIR significantly reduced RV myocardial signal heterogeneity (0.31 vs. 0.43; P = 0.003) and the extent of RV dropout (24% vs. 46%; P = 0.0005). LV signal heterogeneity exhibited a trend towards improvement with RDIR (0.12 vs. 0.16; P = 0.06). Qualitative evaluation showed a significant improvement of LV and RV visualization in RDIR compared to DIR (LV: P = 0.04, RV: P = 0.0007) and a significantly improved overall image quality (P = 0.03).

DATA CONCLUSION

RDIR TSE is less sensitive to through-plane motion, potentiating increased clinical utility for black-blood TSE.

LEVEL OF EVIDENCE

1 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2018;47:1498-1508.

Black-blood steady-state free precession (SSFP) coronary wall MRI for cardiac allografts: a feasibility study

PURPOSE

To assess the hypothesis that steady-state free procession (SSFP) allows for imaging of the coronary wall under the conditions of fast heart rate in heart transplantation (HTx) patients.

MATERIALS AND METHODS

With the approval of our Institutional Review Board, 28 HTx patients were scanned with a 1.5T scanner. Cross-sectional black-blood images of the proximal portions of the left main artery, left anterior descending artery, and right coronary artery were acquired with both a 2D, double inversion recovery (DIR) prepared turbo (fast) spin echo (TSE) sequence and a 2D DIR SSFP sequence. Image quality (scored 0-3), vessel wall area, thickness, signal-to-noise ratio (SNR, vessel wall), and contrast-to-noise ratio (CNR, wall-lumen) were compared between TSE and SSFP.

RESULTS

The overall image quality of SSFP was higher than TSE (1.23 ± 0.95 vs. 0.88 ± 0.69, P < 0.001). SSFP had a higher coronary wall SNR (20.1 ± 8.5 vs. 14.9 ± 4.8, P < 0.001) and wall-lumen CNR (8.2 ± 4.6 vs. 6.8 ± 3.7, P = 0.005) than TSE.

CONCLUSION

Black-blood SSFP coronary wall MRI provides higher image quality, SNR, and CNR than traditional TSE does in HTx recipients. It has the potential to become an alternative means to noninvasive imaging of cardiac allografts.

Coronary wall MR imaging in patients with rapid heart rates: a feasibility study of black-blood steady-state free precession (SSFP)

We assessed the hypothesis that black-blood steady-state free precession (SSFP) would provide coronary wall images comparable to images from TSE and have better performance than TSE under conditions of fast heart rate. With IRB approval, thirty participants without a history of coronary artery disease (19 men, 11 women, 26-83 y/o) were scanned with a 1.5 T MR scanner. Cross-sectional black-blood images of the proximal portions of coronary arteries were acquired with a two-dimensional (2D), double inversion recovery (DIR) prepared TSE sequence and a 2D DIR SSFP sequence on the same planes. Image quality (ranked with a 4-point system, scored from 0 to 3), vessel wall area and thickness, signal-to-noise ratio (SNR) of the wall and contrast-to-noise ratio (CNR, wall to lumen) were compared between SSFP and TSE with SPSS software (v 13.0). Totally 28 scans were completed. For SSFP and TSE, there was no difference in image quality. SSFP had a higher SNR (23.7 ± 10.1 vs. 14.4 ± 5.2, P < 0.001) and wall-lumen CNR (8.8 ± 4.5 vs. 6.7 ± 3.2, P = 0.001). Good agreements between measured wall area (r = 0.701, P < 0.001) and thickness (r = 0.560, P < 0.001) were found. For 10 participants with heart rate more than 80 beats/min, the image quality of SSFP was higher than TSE (P = 0.016). SSFP provided image quality and measurement accuracy that was comparable to TSE. With its higher performance under fast heart rate conditions, SSFP may break through the existing thresholds for heart rate and extend clinical applicability of coronary wall MR imaging to a larger population.

MRI of nonischemic cardiomyopathy

OBJECTIVE

The purpose of this article is to present current clinical and research issues in MRI evaluation of nonischemic cardiomyopathy, a diverse set of diseases, many of which have a genetic basis.

CONCLUSION

Cardiac cine MRI along with delayed myocardial enhancement MRI and other MRI techniques can provide information beyond echocardiography for tissue characterization. MRI is increasingly being used for evaluation of genetically positive, phenotypically negative patients as well as for risk stratification.