Multi-phase coronary magnetic resonance angiography improves delineation of coronary arteries

Feasibility study of the multishot gradient-echo planar imaging sequence in non-enhanced and free-breathing whole-heart magnetic resonance coronary angiography

AIM

To investigate the feasibility of non-enhanced and free-breathing whole-heart magnetic resonance coronary angiography (MRCA) using multishot gradient-echo planar imaging (MSG-EPI).

MATERIALS AND METHODS

In total, 29 healthy volunteers were recruited for free-breathing whole-heart MRCA acquisition using the MSG-EPI sequence and fast gradient echo (GRE) sequence. After the examination, the actual scanning times, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) of the left main (LM) coronary artery, subjective quality scores for each segment, and evaluable length of the coronary artery were recorded and statistically analysed.

RESULTS

There was no significant difference between the SNRLM of the MSG-EPI sequence and fast GRE sequence (p=0.130), but the CNRLM of the MSG-EPI sequence was higher (p=0.001). The subjective quality score of the mid- and distal left anterior descending branch as well as the distal circumflex branch of the coronary artery in the MSG-EPI sequence was higher than that in the fast GRE sequence (p=0.003, 0.001, and 0.003, respectively). The evaluable length of the left anterior descending branch and the circumflex branch was better using the MSG-EPI sequence than that of the fast GRE sequence (p=0.015 and < 0.001, respectively). Moreover, the scanning time of the MSG-EPI sequence was 54.5% less than that of the fast GRE sequence (p<0.001).

CONCLUSION

The MSG-EPI sequence improves the subjective and objective image quality of MRCA as well as reduces the scanning time.

Addition of gadolinium contrast to three-dimensional SSFP MR sequences improves the visibility of coronary artery anatomy in young children

Objective

This study aims to compare the value of a gadolinium contrast-enhanced 1.5-T three-dimensional (3D) steady-state free precession (SSFP) sequence with that of a noncontrast 3D SSFP sequence for magnetic resonance coronary angiography in a pediatric population.

Materials and methods

Seventy-nine patients from 1 month to 18 years old participated in this study. A 3D SSFP coronary MRA at 1.5-T was applied before and after gadolinium-diethylenetriaminepentaaceticacid (DTPA) injection. The detection rates of coronary arteries and side branches were assessed by McNemar's χ² test. The image quality, vessel length, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) of the coronary arteries were analyzed by the Wilcoxon signed-rank test. The intra- and interobserver agreements were evaluated with a weighted kappa test or an intraclass correlation efficient test.

Results

A contrast-enhanced scan detected more coronary arteries than a noncontrast-enhanced scan in patients under 2 years old (P < 0.05). The SSFP sequence with contrast media detected more coronary artery side branches in patients younger than 5 years (P < 0.05). The image quality of all the coronary arteries was better after the injection of gadolinium-DTPA in children younger than 2 years (P < 0.05) but not significantly improved in children older than 2 years (P > 0.05). The contrast-enhanced 3D SSFP protocol detected longer lengths for the left anterior descending coronary artery in children younger than 2 years and the left circumflex coronary artery (LCX) in children younger than 5 years (P < 0.05). SNR and CNR of all the coronary arteries in children younger than 5 years and the LCX and right coronary artery in children older than 5 years enhanced after the injection of gadolinium-DTPA (P < 0.05). The intra- and interobserver agreements were high (0.803-0.998) for image quality, length, SNR, and CNR of the coronary arteries in both pre- and postcontrast groups.

Conclusion

The use of gadolinium contrast in combination with the 3D SSFP sequence is necessary for coronary imaging in children under 2 years of age and may be helpful in children between 2 and 5 years. Coronary artery visualization is not significantly improved in children older than 5 years.

Velocity encoded mitral valve inflow cine: A novel and more reproducible method to determine cardiac rest periods during coronary magnetic resonance angiography

A high temporal resolution, 4-chamber (4CH) cine is the standard method for determining cardiac rest periods during whole heart coronary magnetic resonance angiography (CMRA). We evaluated the image quality and reproducibility between the 4CH cine method and a novel approach using a velocity encoded mitral valve inflow cine (MVI). The goal of this study was to compare the quality of CMRAs utilizing MVI versus 4CH methods. Sharpness and vessel length for the LCA and RCA using each method were determined using Soap Bubble and two blinded observers independently assessed coronary image quality. Offline analysis on a separate, retrospective cohort (n = 25) was used to compare MVI and 4CH reproducibility. In the prospectively evaluated cohort there was no difference in overall vessel sharpness (4CH vs MVI mean ± SD) (31.0 ± 5.5% vs 30.5 ± 5.7%, p = .63), LCA vessel sharpness (30.0 ± 5.4% vs 31.1 ± 8.2%, p = .44), LCA length (4.7 ± 1.4 cm vs 4.6 ± 1.6 cm, p = .66), RCA vessel sharpness (32.1 ± 6.9% vs 31.1 ± 7.7%, p = .55), RCA length (5.51 ± 2.6 cm vs 5.95 ± 2.4 cm, p = .38), or image quality rating (2.66 vs 2.62, p = .80) between methods. In the retrospective cohort, the MVI method had 5.4% lower inter-observer variability (95% CI 3.7,7.2%, p < .0001) and 3.9% lower intra-observer variability (95% CI 2.4,5.4%, p < .0001) than the 4CH method.

MVI is a technically feasible and more reproducible method to determine cardiac rest periods compared to 4CH while preserving vessel sharpness, vessel length & image quality.

Cardiovascular magnetic resonance imaging for structural heart disease

Cardiovascular magnetic resonance (CMR) has increasingly become a powerful imaging technique over the past few decades due to increasing knowledge about clinical applications, operator experience and technological advances, including the introduction of high field strength magnets, leading to improved signal-to-noise ratio. Its success is attributed to the free choice of imaging planes, the wide variety of imaging techniques, and the lack of harmful radiation. Developments in CMR have led to the accurate evaluation of cardiac structure, function and tissues characterisation, so this non-invasive technique has become a powerful tool for a broad range of cardiac pathologies. This review will provide an introduction of magnetic resonance imaging (MRI) physics, an overview of the current techniques and clinical application of CMR in structural heart disease, and illustrated examples of its use in clinical practice.