Free‐breathing, nongated real‐time delayed enhancement MRI of myocardial infarcts: A comparison with conventional delayed enhancement

Abstract

Purpose:To compare a free-breathing, nongated, and black-blood real-time delayed enhancement (RT-DE) sequence to the conventional inversion recovery gradient echo (IR-GRE) sequence for delayed enhancement MRI. Materials and Methods:Twenty-three patients with suspected myocardial infarct (MI) were examined using both the IR-GRE and RT-DE imaging sequences. The sensitivity and specificity of RT-DE for detecting MI, using IR-GRE as the gold standard, was determined. The contrast-to-noise ratios (CNR) between the two techniques were also compared.Results: RT-DE had a high sensitivity and specificity (94% and 98%, respectively) for identifying MI. The total acquisition time to image the entire left ventricle was significantly shorter using RT-DE than IR-GRE (5.6 Ϯ 0.9 versus 11.5 Ϯ 1.9 min). RT-DE had a slightly lower infarct-myocardium CNR but a higher infarct-blood CNR than IR-GRE imaging. Compared with IR-GRE, RT-DE accurately measured total infarct sizes. Conclusion:RT-DE can be used for delayed enhancement imaging during free-breathing and without cardiac gating. DELAYED ENHANCEMENT MRI (DE-MRI) is the method of choice for detecting and measuring myocardial infarct (MI) (1). DE-MRI is conventionally acquired with a segmented inversion-recovery gradient echo (IR-GRE) sequence. IR-GRE imaging requires repeated breath-holds which can be difficult to achieve in a patient population with cardiac disease. Breath-holds can be reduced or eliminated by using a single-shot readout (2,3) or navigators (4). These methods, however, still require cardiac gating, which can be problematic in patients with arrhythmias. In addition, these methods yield images where small subendocardial infarcts can be masked by the bright blood pool (5).A method for real-time delayed enhancement (RT-DE) imaging has been previously developed (6) to alleviate the limitations of the IR-GRE sequence. RT-DE is a free-breathing, nongated approach that consists of a continuous, real-time stream of images acquired using a steady-state free precession (SSFP) sequence (7) with intermittent inversion pulses (8) to create infarct-enhanced images. RT-DE is a black-blood DE-MRI technique that allows for improved visualization of the infarct-blood border. RT-DE would be useful for rapidly assessing the presence or absence of infarcted tissue, or to allow for infarct assessment (including size and transmurality) in patients where cardiac gating or breath-holds are not possible. The goals of this study are to compare RT-DE to IR-GRE in terms of sensitivity and specificity for detecting MI, and for measuring infarct size in a patient population with cardiac disease. MATERIALS AND METHODS Pulse SequenceThe RT-DE sequence (Fig. 1) continually uses an inversion pulse and variable delay time (TD) followed by single-shot SSFP readouts. The first image acquired after the inversion pulse is the infarct-enhanced image, and four subsequent anatomical images are acquired while the magnetization recovers toward its steady state. Immediately after the acquisition of the fifth...

Multicontrast late gadolinium enhancement imaging enables viability and wall motion assessment in a single acquisition with reduced scan times

“…Single‐shot sequences also do not provide any functional information. A real‐time delayed enhancement sequence (20) has been recently shown to provide viability and anatomical images (during free‐breathing and without cardiac gating) with improved contrast between infarct and blood (21); however, the temporal resolution of this method does not allow for the visualization of cardiac wall motion. MCLE imaging can be acquired at the same (or higher) resolution as IR‐GRE imaging with the same temporal resolution as cine SSFP acquisitions.…”

Cardiac Imaging: Part 1, MR Pulse Sequences, Imaging Planes, and Basic Anatomy

“…Similarly, the presence of gadolin-ium can interfere with nulling of blood signal and should be administered after dark blood imaging. However, real-time nongated black blood sequences with gadolinium contrast administration have proven to be effective for evaluating myocardial ischemia [9].…”

“…However, the saturation-recover pulse consists of applying a 90° flip angle and is less subject to signal intensity variations than IR techniques. Smaller flip angles can be used to maintain spatial resolution [9]. The saturation-recover pulse is often used in combination with GRE and hybrid GRE-EPI pulse sequences for perfusion-weighted imaging and myocardial tagging.…”

“…This enables quantification of myocardial strain and assessment of pericardial constriction. Tagging is also a more accurate method of assessing infarct-related dysfunction than wall thickness analysis [9]. Unfortunately, the grid tends to fade by early diastole.…”

Accelerated multicontrast volumetric imaging with isotropic resolution for improved peri‐infarct characterization using parallel imaging, low‐rank and spatially varying edge‐preserving sparse modeling

“…Another retrospective clinical study on 25 patients referred for implantable cardioverter defibrillator (ICD) therapy has revealed that peri‐infarct border zone measurement along with papillary muscle infarct assessment using 2D MCLE prior to ICD implantation might be more sensitive, compared to using 2D LGE, in predicting proper ICD therapy in patient with prior MI . To date, MCLE has demonstrated clear clinical benefits in a range of clinical studies to advance myocardial viability assessment , particularly delineation of the peri‐infarct border zone.…”