Free‐breathing delayed hyperenhanced imaging of the myocardium: A clinical application of real‐time navigator echo imaging

Abstract

Purpose:To compare a free-breathing (FB) acquisition with the current standard of breath-holding (BH) in a clinical setting using identical two-dimensional MR pulse sequences for imaging of myocardial delayed hyperenhancement. Materials and Methods:Two-dimensional gadolinium-enhanced images were acquired using FB and BH techniques in 18 subjects to evaluate delayed enhancement of myocardial infarction. The FB acquisition used a navigator echo to monitor the position of the right hemidiaphragm for respiratory gating and correction. Visual analysis using a 16-segment model, quantitative signal difference to noise ratios, and percent left ventricle (LV) viability measurements for the two acquisition types were statistically compared.Results: An excellent agreement between two-dimensional BH and two-dimensional FB acquisitions was found. In one patient, a nontransmural infarct was seen only in the FB images. There were no statistically significant differences in the number of infarcted segments or the measured signal difference to noise ratios (SDNR) between the two methods. Linear regression and Bland Altman analysis of the percentage LV viable myocardium yielded a good fit and narrow limits of agreement. Conclusion:An FB navigator echo acquisition can be effectively used in the setting of myocardial delay hyperenhanced imaging. Image quality is similar or superior to that of BH imaging. RECENT STUDIES have shown that reversible myocardial dysfunction can be identified using gadoliniumenhanced MRI (1-5). Images of the myocardium are made after a delay of several minutes following T1 shortening contrast agent administration; this technique is often called "delayed hyperenhanced (DHE) imaging." Nonviable tissue is identified as having a slightly higher concentration than viable tissue of an intravenously injected gadolinium contrast agent. An inversion recovery (IR) T1 weighted sequence (6) is used to minimize the signal intensity from viable myocardium. The inversion time (TI) parameter of the pulse sequence, which is the time between the inversion pulse and the acquired data, is adjusted to minimize the image intensity of healthy myocardium. In these images, nonviable myocardium is identified as hyperenhancing regions.To reduce or eliminate artifacts from motion of the heart during the normal respiratory cycle, image data are most commonly acquired over several heartbeats using pulse sequences synchronized with the cardiac cycle and during suspended respiration. Two-dimensional breath-hold (BH) IR spoiled gradient-echo imaging has been validated in animal models and human studies (7-10) and is currently the standard of reference for MR DHE imaging. Since one slice is acquired each BH, this technique requires many breath-holds for the evaluation of the entire left ventricle. Single-slice BH MRI techniques (11,12) have been proposed and adopted to reduce acquisition time, increase image contrast, resolution, or spatial coverage, but BH-DHE techniques remain limited by BH time and patient cooperation.Free-breathing (F...

Recent Myocardial Infarction: Assessment with Unenhanced T1-weighted MR Imaging

“…T1-weighted MR imaging has many variants. We used an IR cine true fast imaging with steady-state precession technique, but T1-weighted MR imaging can also be performed in a single heartbeat (23,27), in a three-dimensional acquisition (30), or during free breathing (31).…”

Free‐breathing high‐spatial‐resolution delayed contrast‐enhanced three‐dimensional viability MR imaging of the myocardium at 3.0T: A feasibility study

“…A constant correction of 0.6 was used (17). These parameters of navigator gating were determined based on previous reports on free-breathing 2D or 3D viability imaging techniques (11,12,18). The phase-encoding (y) direction was an anteroposterior direction, and the linear k-space data sampling was employed at diastole for both 2D and 3D viability MRI sequences.…”

Left ventricular infarct size, peri‐infarct zone, and papillary scar measurements: A comparison of high‐resolution 3D and conventional 2D late gadolinium enhancement cardiac MR

“…While 2D breath-hold LGE is most commonly used for clinical imaging, several studies have presented good quality results using 2D free-breathing (11), 3D breath-hold (12-14) or 3D free-breathing (15, 16) techniques. However, those efforts focused on alternative methods for those patients who cannot perform repeated breath-holding.…”