Dark-blood late gadolinium enhancement without additional magnetization preparation

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.

Clinical evaluation of two dark blood methods of late gadolinium quantification of ischemic scar

“…Quantitatively derived scar size was not significantly different between the three LGE methods despite the two dark blood methods objectively identifying a greater transmural extent of scar to the two readers. Other LGE studies have demonstrated an increase in scar size using dark blood sequences; however, these have been by visual assessment only or using less conventional methods of LGE quantitation . There is no histological correlation for these findings; this corroborates those seen previously where histological correlation was performed …”

“…Most of these sequences currently remain research investigations and are vendor/platform‐specific and are yet to see mainstream clinical adoption. The recent study by Holtackers et al demonstrated an increased scar to blood contrast when nulling blood in a standard PSIR pulse sequence, without the need for additional preparation pulses …”

“…The selected short axis slice was then reacquired using the PSIR LGE sequence with the inversion time set to null myocardium (MN), the inversion time set to null the blood pool (BN), and a T 1 ρ FIDDLE sequence. A dedicated noise scan (identical pulse sequence without excitation pulses) was performed after each slice acquisition, in order to enable accurate measurement of the signal/noise level . The T 1 ρ‐prepared and the two standard PSIR sequences were all performed in random order to avoid systematic bias caused by differences in contrast washout.…”

“…A PSIR reconstruction reduces sensitivity to inversion time precision and removes the risk of tissues with different T 1 relaxation times appearing isointense. Recently, a method using a standard PSIR sequence with the inversion time set to null the blood pool rather than the myocardium was described in a group of nine patients . This method, albeit in a small number of patients, led to improved scar to blood contrast‐to‐noise ratio (CNR) and improved reader confidence …”

Feasibility study of a single breath‐hold, 3D mDIXON pulse sequence for late gadolinium enhancement imaging of ischemic scar

“…In 25 consecutive patients CNR measurement was performed, a single slice containing both hyperenhanced and healthy myocardium was selected and for this corresponding slice a dedicated noise scan (identical pulse sequence without excitation pulses) was performed immediately afterwards in order to assess the noise levels. 26 ROIs were drawn on the normal 3D and 2D LGE images in areas of hyperenhancement, a remote area of normal-appearing myocardium, and in blood pool. ROIs contained at least 30 pixels, aside from the areas of hyperenhancement, where size of the ROI was governed by the size of the scar.…”