Comparison of 3D segmented gradient-echo and steady-state free precession coronary MRI sequences in patients with coronary artery disease

Cardiac magnetic resonance imaging in the evaluation and management of mitral valve prolapse - a comprehensive review

Mitral valve prolapse is a common valve disorder that usually has a benign prognosis unless there is significant regurgitation or LV impairment. However, a subset of patients are at an increased risk of ventricular arrhythmias and sudden cardiac death, which has led to the recognition of "arrhythmic mitral valve prolapse" as a clinical entity. Emerging risk factors include mitral annular disjunction and myocardial fibrosis. While echocardiography remains the primary method of evaluation, cardiac magnetic resonance has become crucial in managing this condition. Cine magnetic resonance sequences provide accurate characterization of prolapse and annular disjunction, assessment of ventricular volumes and function, identification of early dysfunction and remodeling, and quantitative assessment of mitral regurgitation when integrated with flow imaging. However, the unique strength of magnetic resonance lies in its ability to identify tissue changes. T1 mapping sequences identify diffuse fibrosis, in turn related to early ventricular dysfunction and remodeling. Late gadolinium enhancement sequences detect replacement fibrosis, an independent risk factor for ventricular arrhythmias and sudden cardiac death. There are consensus documents and reviews on the use of cardiac magnetic resonance specifically in arrhythmic mitral valve prolapse. However, in this article, we propose an algorithm for the broader use of cardiac magnetic resonance in managing this condition in various scenarios. Future advancements may involve implementing techniques for tissue characterization and flow analysis, such as 4D flow imaging, to identify patients with ventricular dysfunction and remodeling, increased arrhythmic risk, and more accurate grading of mitral regurgitation, ultimately benefiting patient selection for surgical therapy.

Contribution of cardiovascular magnetic resonance in the evaluation of coronary arteries

Cardiovascular magnetic resonance (CMR) allows the nonradiating assessment of coronary arteries; to achieve better image quality cardiorespiratory artefacts should be corrected. Coronary MRA (CMRA) at the moment is indicated only for the detection of abnormal coronary origin, coronary artery ectasia and/or aneurysms (class I indication) and coronary bypass grafts (class II indication). CMRA utilisation for coronary artery disease is not yet part of clinical routine. However, the lack of radiation is of special value for the coronary artery evaluation in children and women. CMRA can assess the proximal part of coronary arteries in almost all cases. The best results have been observed in the evaluation of the left anterior descending and the right coronary artery, while the left circumflex, which is located far away from the coil elements, is frequently imaged with reduced quality, compared to the other two. Different studies detected an increase in wall thickness of the coronaries in patients with type I diabetes and abnormal renal function. Additionally, the non-contrast enhanced T1-weighed images detected the presence of thrombus in acute myocardial infarction. New techniques using delayed gadolinium enhanced imaging promise the direct visualization of inflamed plaques in the coronary arteries. The major advantage of CMR is the potential of an integrated protocol offering assessment of coronary artery anatomy, cardiac function, inflammation and stress perfusion-fibrosis in the same study, providing an individualized clinical profile of patients with heart disease.

Magnetic resonance coronary angiography: where are we today?

Although cardiovascular magnetic resonance allows the non-invasive and radiation free visualization of both the coronary arteries and veins, coronary vessel wall imaging is still undergoing technical development to improve diagnostic quality. Assessment of the coronary vessels is a valuable addition to the analysis of cardiac function, cardiac anatomy, viability and perfusion which magnetic resonance imaging reliably allows. However, cardiac and respiratory motion and the small size of the coronary vessels present a challenge and require several technical solutions for image optimization. Furthermore, the acquisition protocols need to be adapted to the specific clinical question. This review provides an update on the current clinical applications of cardiovascular magnetic resonance coronary angiography, recent technical advances and describes the acquisition protocols in use.

Coronary imaging with cardiovascular magnetic resonance: current state of the art

Cardiovascular magnetic resonance allows noninvasive and radiation-free visualization of both the coronary arteries and veins, with the advantage of an integrated assessment of cardiac function, viability, perfusion, and anatomy. This combined approach provides valuable integrated information for patients with coronary artery disease and patients undergoing cardiac resynchronization therapy. Moreover, magnetic resonance offers the possibility of coronary vessel wall imaging, therefore assessing the anatomy and pathology of the normal and diseased coronary vessels noninvasively. Coronary magnetic resonance angiography is challenging because of cardiac and respiratory motion and the small size and tortuous path of the coronary vessels. Several technical solutions have been developed to optimize the acquisition protocol to the specific clinical question. The aims of this review are to provide an update on current technical improvements in coronary magnetic resonance angiography, including how to optimize the acquisition protocols, and to give an overview of its current clinical application.

Coronary MR imaging: effect of timing and dose of isosorbide dinitrate administration

PURPOSE

To quantify the effect of sublingual isosorbide dinitrate (ISDN) administration on coronary magnetic resonance (MR) imaging.

MATERIALS AND METHODS

Written informed consent was obtained from all participants, and the HIPAA-compliant protocol was approved by the Institutional Review Board. Coronary MR imaging was performed at 1.5 T before and after administration of ISDN (2.5 or 5 mg) in 25 healthy adult volunteers (mean age, 23 years +/- 4; nine men, 16 women) with three-dimensional targeted (n = 20, randomized into four groups) or whole-heart (n = 5) acquisitions with gradient-recalled echo (GRE) or balanced steady-state free precession (SSFP) sequences. Image quality was assessed by two cardiologists on a four-point scale. Signal-to-noise ratio (SNR), vessel diameter, and vessel sharpness were characterized. A linear mixed-effects model was used for data analysis. A P value of less than .05 was considered to indicate a significant difference.

RESULTS

The maximum SNR enhancement with 5 mg of ISDN (GRE: 22.0% +/- 10.7%; SSFP: 20.1% +/- 6.0%) was similar (P > .05) to that with 2.5 mg (GRE: 21.9% +/- 5.4%; SSFP: 19.1% +/- 3.0%). However, the time to maximum SNR enhancement for the 5-mg dose (15.5 minutes +/- 6.0) was earlier (P < .01) than that for 2.5 mg (23.5 minutes +/- 6.7). The increase in vessel diameter with 5 mg of ISDN was greater than that with 2.5 mg (P < .05 for both GRE and SSFP sequences). The coronary images were sharper after ISDN administration (P < .03). Subjective image quality score significantly improved after ISDN administration for GRE images (P < .05 for both doses) but was similar for SSFP images (P = .24 for 2.5 mg; P = .27 for 5 mg). Whole-heart coronary SNR was improved about 10% after ISDN administration (P < .05).

CONCLUSION

Sublingual ISDN improves coronary MR imaging SNR. Practitioners need to consider the dose and temporal effects of ISDN when performing coronary MR imaging.

A qualitative and quantitative study of coronary artery MRA

In this paper, we propose an analysis of the coronary arterial tree obtained through magnetic resonance angiography (MRA). Ten datasets of the state-of-the-art SSFP MRI sequence are first qualitatively evaluated and labelled. Second, a quantitative analysis of anatomical and image features is performed. Finally, a comparison with an existing semi-automatic centreline extraction method is reported. The discussion deals with the clinical usage of such an imaging modality for both global anatomy visualisation and quantification purpose.

Inflow quantification in three-dimensional cardiovascular MR imaging

PURPOSE

To investigate blood inflow enhancement (or lack thereof) in three-dimensional (3D) cardiovascular MR for both single phase whole-heart and cine biventricular functions.

MATERIALS AND METHODS

A 3D imaging sequence is proposed in which radiofrequency excitation gradient is changed without modifying image acquisition or phase/slice encoding. This imaging sequence enables direct inflow measurement while retaining static voxel signal-to-noise ratio. Inflow measurements were performed for both spoiled gradient-echo (GRE) imaging and balanced steady-state free precession (SSFP) in 18 healthy subjects.

RESULTS

For single phase imaging, increasing slab thickness from 3 to 10 cm lead to 73% and 59% reductions in contrast-to-noise ratio (CNR) with GRE and SSFP, respectively. For cine acquisitions, systolic CNR was reduced by 85% and 50% for the GRE and SSFP acquisitions, respectively, while diastolic CNR was reduced by 64% and 42%.

CONCLUSION

There is significant loss of CNR between blood and myocardium when using larger 3D slabs due to saturation of inflowing spins. The loss of contrast is less pronounced for SSFP than for GRE, though both acquisition techniques suffer.

[Comparison of 3 Tesla whole heart coronary MRA (WHCA) with 1.5 Tesla]

Whole heart coronary MRA (WHCA) is a noninvasive method used to image all coronary arteries with cardiac and real-time respiratory gating. We compared the coronary depiction ability of 3T WHCA with that of 1.5T using healthy volunteers. In addition, we compared the study performance rate, which might differ at 3T and 1.5T due to the difference in specific absorption rate (SAR) limits. The coronary artery was classified into nine segments, based on the classification of the American Heart Association (AHA). Each observer was asked to evaluate WHCA with the three-point scale rating for each segment, and to measure the visible length of each coronary artery utilizing reconstructed CPR and VR images. Depiction at 3T was superior to that at 1.5T. The completion rate of study was 100% at 1.5T, but just 63% at 3T owing to SAR limits. Thus it was suggested that 3T WHCA might be feasible with the advantage of high depiction ability, if adequate SAR reduction techniques were developed.

Combined magnetic resonance coronary artery imaging, myocardial perfusion and late gadolinium enhancement in patients with suspected coronary artery disease

BACKGROUND

Cardiovascular magnetic resonance (CMR) imaging offers methods for the detection of ischemia and myocardial infarction as well as visualization of the coronary arteries (MRCA). However, a direct comparison of adenosine perfusion (PERF), late gadolinium enhancement (LGE) and MRCA or the results of their combination has not been performed. Aim of the study was to evaluate the feasibility/diagnostic performance of rest/stress perfusion, late gadolinium enhancement and MRCA and their combination in patients with suspected coronary artery disease (CAD) in comparison to invasive angiography.

METHODS

Fifty-four patients (60 +/- 10 years, 35 men, CAD 48%) underwent CMR including MRCA (steady state free precession, navigator whole heart approach, spatial resolution 0.7 x 0.7 x .0.9 mm, trigger delay and temporal resolution adjusted individually), stress PERF (adenosine 140 mug/min/kg), rest PERF (SSFP, 3 short axis, 1 saturation prepulse per slice) and LGE (3D inversion recovery technique) using Gd-BOPTA. Images were analyzed visually. Stenosis >50% in invasive angiography was considered significant.

RESULTS

Mean study time was 68 +/- 11 minutes. Sensitivity for PERF, LGE, MRCA and the combination of PERF/LGE and PERF/LGE/MRCA was 87%, 50%, 91%, 88% and 92%, respectively and specificity 88%, 96%, 46%, 88% and 56%, respectively. If image quality of MRCA was excellent (n = 18) the combination of MRCA/PERF/LGE yield a sensitivity of 86% and specificity of 91%. However, no test or combination improved diagnostic performance significantly compared to PERF alone.

CONCLUSION

In patients with CAD, the combination of stress PERF, LGE and MRCA is feasible. When compared to invasive angiography, adenosine stress perfusion outperforms CMR coronary angiography in direct comparison and yields the best results with non-significant improvement in combination with LGE and significant deterioration in combination with MRCA. MRCA may be of additional value only in a minority of patients with excellent image quality.

Intraindividual comparison of 3D coronary MR angiography and coronary CT angiography

RATIONALE AND OBJECTIVES

To compare the diagnostic value of magnetic resonance (MR) and computed tomography (CT) for the detection of coronary artery disease (CAD) with special regard to calcifications.

MATERIALS AND METHODS

Twenty-seven patients with known CAD were examined with a targeted, navigator-gated, free-breathing, steady-state free precession MR angiography sequence (repetition time = 5.6 milliseconds, echo time = 2.8 milliseconds, flip angle 110 degrees ) and 16-slice coronary CT angiography. Segment-based sensitivity, specificity, and accuracy for the detection of stenoses larger than 50% were determined as defined by the gold standard catheter coronary angiography along with the subjective image quality (Grade 1-4). The degree of calcifications in each segment was quantified using a standard calcium scoring tool.

RESULTS

Of 115 possible segments, 7% had to be excluded in MR imaging because of poor image quality. In CT, 3% were nondiagnostic because of image quality and 15% were not evaluable because of calcifications. Values for the detection of relevant coronary artery stenoses in the evaluated segments were: sensitivity: MR imaging 85% versus CT 96%; specificity: 88% versus 96%; accuracy: 87% versus. 96%. Average subjective image quality was 1.8 for MR imaging and 1.6 for CT. Of the 15% of segments that had to be excluded from CT evaluation because of calcifications, MR imaging provided the correct diagnosis segments in 67%.

CONCLUSIONS

CT provided a better image quality with superior accuracy for the detection of CAD. Despite its overall inferiority, MR imaging proved to be helpful method in interpreting coronary stenosis in severely calcified segments.

Coronary Magnetic Resonance Imaging

This article highlights the technical challenges and general imaging strategies for coronary MRI. This is followed by a review of the clinical results for the assessment of anomalous CAD, coronary artery aneurysms, native vessel integrity, and coronary artery bypass graft disease using the more commonly applied MRI methods. It concludes with a brief discussion of the advantages/disadvantages and clinical results comparing coronary MRI with multidetector CT (MDCT) coronary angiography.

Coronary magnetic resonance imaging: current state-of-the-art

Over the past decade, coronary magnetic resonance imaging has been transformed from a scientific curiosity to a clinically useful imaging tool for patients with known or suspected anomalous coronary arteries or coronary artery aneurysms and for assessment of coronary artery bypass graft patency. Coronary magnetic resonance imaging also appears to be of clinical value for assessment of native vessel integrity in selected patients, especially those patients with suspected left main/multivessel disease. Among patients referred for X-ray angiography, a normal coronary magnetic resonance imaging strongly suggests the absence of severe multivessel disease. Technical and methodological advances in motion suppression, along with increasing clinical experience will no doubt facilitate improved visualization of the distal and branch vessel.