Dark-blood late gadolinium enhancement without additional magnetization preparation

Robert J Holtackers,David M Higgins,René M Botnar,Torben Schneider,Amedeo Chiribiri

doi:10.1186/s12968-017-0372-4

Abstract

BackgroundThis study evaluates a novel dark-blood late gadolinium enhancement (LGE) cardiovascular magnetic resonance imaging (CMR) method, without using additional magnetization preparation, and compares it to conventional bright-blood LGE, for the detection of ischaemic myocardial scar. LGE is able to clearly depict myocardial infarction and macroscopic scarring from viable myocardium. However, due to the bright signal of adjacent left ventricular blood, the apparent volume of scar tissue can be significantly reduced, or even completely obscured. In addition, blood pool signal can mimic scar tissue and lead to false positive observations. Simply nulling the blood magnetization by choosing shorter inversion times, leads to a negative viable myocardium signal that appears equally as bright as scar due to the magnitude image reconstruction. However, by combining blood magnetization nulling with the extended grayscale range of phase-sensitive inversion-recovery (PSIR), a darker blood signal can be achieved whilst a dark myocardium and bright scar signal is preserved.MethodsLGE was performed in nine male patients (63 ± 11y) using a PSIR pulse sequence, with both conventional viable myocardium nulling and left ventricular blood nulling, in a randomized order. Regions of interest were drawn in the left ventricular blood, viable myocardium, and scar tissue, to assess contrast-to-noise ratios. Maximum scar transmurality, scar size, circumferential scar angle, and a confidence score for scar detection and maximum transmurality were also assessed. Bloch simulations were performed to simulate the magnetization levels of the left ventricular blood, viable myocardium, and scar tissue.ResultsAverage scar-to-blood contrast was significantly (p < 0.001) increased by 99% when nulling left ventricular blood instead of viable myocardium, while scar-to-myocardium contrast was maintained. Nulling left ventricular blood also led to significantly (p = 0.038) higher expert confidence in scar detection and maximum transmurality. No significant changes were found in scar transmurality (p = 0.317), normalized scar size (p = 0.054), and circumferential scar angle (p = 0.117).ConclusionsNulling left ventricular blood magnetization for PSIR LGE leads to improved scar-to-blood contrast and increased expert confidence in scar detection and scar transmurality. As no additional magnetization preparation is used, clinical application on current MR systems is readily available without the need for extensive optimizations, software modifications, and/or additional training.

Highlights

This study evaluates a novel dark-blood late gadolinium enhancement (LGE) cardiovascular magnetic resonance imaging (CMR) method, without using additional magnetization preparation, and compares it to conventional bright-blood LGE, for the detection of ischaemic myocardial scar
The inversion times used for left ventricular (LV) blood nulling and viable myocardium nulling were 168 ± 28 ms and 259 ± 25 ms, respectively
signal-to-noise ratio (SNR) and Contrast-to-noise ratio (CNR) measurements The average scar-to-blood CNR in the phase-sensitive inversion-recovery (PSIR) images was significantly increased (p < 0.001) by 99% to 8.78 when nulling LV blood magnetization instead of viable myocardium (Fig. 3)

Summary

Introduction

This study evaluates a novel dark-blood late gadolinium enhancement (LGE) cardiovascular magnetic resonance imaging (CMR) method, without using additional magnetization preparation, and compares it to conventional bright-blood LGE, for the detection of ischaemic myocardial scar. Nulling the blood magnetization by choosing shorter inversion times, leads to a negative viable myocardium signal that appears as bright as scar due to the magnitude image reconstruction. As survivors of myocardial infarction face a substantially higher risk of new cardiovascular events due to heart failure, accurate diagnosis and guidance of treatment are crucial in these patients. An accurate assessment of the extent and transmurality of the irreversibly injured cardiac tissue (scar tissue) is essential information in the identification of patients at increased risk of future events and in the selection of the best therapeutic approach. Even tiny regions of scar tissue of only 2% of the mean left ventricular (LV) mass are linked with a sevenfold increase in major cardiac events [2]. Transmurality of the affected area is of great importance, as it plays a major role in the prediction of the likelihood of regional functional recovery after revascularization [3,4,5,6]

Methods

Results

Conclusion