Improved dark blood late gadolinium enhancement (DB‐LGE) imaging using an optimized joint inversion preparation and T2 magnetization preparation
Late gadolinium enhancement imaging uses an inversion recovery (IR) preparation pulse 9 and a Look‐Locker sequence to identify the ideal inversion time 10. Using this approach, the normal myocardium is nulled, whereas areas of scar and blood remain bright 9. The past decades have yielded numerous advances in LGE imaging: higher spatial resolution with 3D imaging 12, improved detection of scar with phase‐sensitive inversion recovery (PSIR) 14, free‐breathing LGE 15, and faster/more efficient data acquisition 13. Despite these advances, low scar–blood contrast remains a major technical challenge, often making it challenging to accurately define scar–blood border 8. The LGE sequences also have difficulty detecting scar in thin‐walled chambers, particularly the right ventricular (RV) free wall and left atrium (LA) 15.
There are several approaches to suppress the blood pool signal and improve scar–blood contrast 21. Multiple inversion pulse strategies decouple the blood and infarct relaxation curves 21. These include quadruple IR 23, double IR with slice‐selective and nonselective inversions 21, and nonselective double IR with two time delays 22. However, these sequences are usually sensitive to blood flow, require precise inversion pulse timing, and penalize overall signal‐to‐noise ratio (SNR) and scar–myocardium contrast. The use of magnetization transfer preparation before inversion circumvents this flow dependence 24. Other methods have used motion‐sensitizing gradients to create a dark blood image 25, but minimal improvement was reported in contrast studies 28. Additional images with different weighting can be acquired to improve the scar–blood contrast 29. The large T2 difference between blood and myocardial tissue has also been exploited to improve scar–blood contrast by adding a T2 magnetization preparation (T2 Prep) directly before the inversion pulse (T2 Prep IR) 32. However, in this sequence, the selection of timing parameters is challenging. Therefore, there is still an unmet clinical need to develop an LGE sequence with improved scar–blood contrast.
In this work, we propose a dark‐blood LGE (DB‐LGE) sequence that uses an optimized combination of IR and T2 Prep to simultaneously null both the normal myocardium and blood pool signals by leveraging their T2 disparity. We hypothesized that DB‐LGE would increase the scar–blood contrast and improve delineation of scar region without adversely influencing the overall image quality.