Endogenous assessment of myocardial injury with single-shot model-based non-rigid motion-corrected T1 rho mapping

Abstract

Background Cardiovascular magnetic resonance T1ρ mapping may detect myocardial injuries without exogenous contrast agent. However, multiple co-registered acquisitions are required, and the lack of robust motion correction limits its clinical translation. We introduce a single breath-hold myocardial T1ρ mapping method that includes model-based non-rigid motion correction. Methods A single-shot electrocardiogram (ECG)-triggered balanced steady state free precession (bSSFP) 2D adiabatic T1ρ mapping sequence that collects five T1ρ-weighted (T1ρw) images with different spin lock times within a single breath-hold is proposed. To address the problem of residual respiratory motion, a unified optimization framework consisting of a joint T1ρ fitting and model-based non-rigid motion correction algorithm, insensitive to contrast change, was implemented inline for fast (~ 30 s) and direct visualization of T1ρ maps. The proposed reconstruction was optimized on an ex vivo human heart placed on a motion-controlled platform. The technique was then tested in 8 healthy subjects and validated in 30 patients with suspected myocardial injury on a 1.5T CMR scanner. The Dice similarity coefficient (DSC) and maximum perpendicular distance (MPD) were used to quantify motion and evaluate motion correction. The quality of T1ρ maps was scored. In patients, T1ρ mapping was compared to cine imaging, T2 mapping and conventional post-contrast 2D late gadolinium enhancement (LGE). T1ρ values were assessed in remote and injured areas, using LGE as reference. Results Despite breath holds, respiratory motion throughout T1ρw images was much larger in patients than in healthy subjects (5.1 ± 2.7 mm vs. 0.5 ± 0.4 mm, P < 0.01). In patients, the model-based non-rigid motion correction improved the alignment of T1ρw images, with higher DSC (87.7 ± 5.3% vs. 82.2 ± 7.5%, P < 0.01), and lower MPD (3.5 ± 1.9 mm vs. 5.1 ± 2.7 mm, P < 0.01). This resulted in significantly improved quality of the T1ρ maps (3.6 ± 0.6 vs. 2.1 ± 0.9, P < 0.01). Using this approach, T1ρ mapping could be used to identify LGE in patients with 93% sensitivity and 89% specificity. T1ρ values in injured (LGE positive) areas were significantly higher than in the remote myocardium (68.4 ± 7.9 ms vs. 48.8 ± 6.5 ms, P < 0.01). Conclusions The proposed motion-corrected T1ρ mapping framework enables a quantitative characterization of myocardial injuries with relatively low sensitivity to respiratory motion. This technique may be a robust and contrast-free adjunct to LGE for gaining new insight into myocardial structural disorders.

Robust cardiac T1ρ$$ {\mathrm{T}}_{1_{\boldsymbol{\rho}}} $$ mapping at 3T using adiabatic spin‐lock preparations

“…27 Furthermore, Bustin et al have found a +40% elevation in infarcted myocardium of LGE-positive patients. 29 These trends are in agreement with the T 1ρ,adiab enhancement measured in patient 1. On the other hand, T 1ρ,adiab in the scar area of patient 2 was decreased.…”

“…28,64,65 Furthermore, several motion correction approaches have been proposed to improve the quality of reconstructed T 1ρ maps and mitigate the contribution of motion. 26,29 These efforts are key to enabling the widespread use of quantitative parametric mapping sequences in clinical practice. Our aSL preparations are fully compatible with these sequence designs and reconstruction approaches and could, in the future, be integrated into accelerated and motion-corrected T 1ρ mapping sequences.…”

“…24 In vivo T 1ρ mapping has been successfully applied in patients with ischemic and nonischemic cardiomyopathies at 1.5T. [25][26][27][28][29][30] Implementing T 1ρ mapping at 3T could further improve the diagnostic value of this approach, due to an increase in signal-to-noise ratio and CNR, and the applicability in a growing number of 3T cardiac examinations. However, at 3T, only a few studies have been reported, [31][32][33] highlighting limitations related to system imperfections and the specific absorption rate (SAR) at high field strengths.…”

Quantitative MRI in cardiometabolic disease: From conventional cardiac and liver tissue mapping techniques to multi-parametric approaches

“…Application of non-contrast T1 ρ -mapping in CMR has been reported to discriminate between infarcted and healthy myocardium in animal models (97). Oedema also induces enhancement in T1 ρ values, as demonstrated in the area-at-risk in acutely ischemic myocardium, in acute myocarditis and Takotsubo cardiomyopathy (98,99). This mapping technique sequence is yet to be routinely used in clinical practice.…”

Smart cardiac magnetic resonance delivering one-click and comprehensive assessment of cardiovascular disease

“…In the first work package, novel CMR sequences will enable 3D imaging of cardiac anatomy and function (cine), cardiac tissue mapping (T1/T2/T1-rho/extracellular volume fraction), and myocardial scars (with joint bright- and black-blood imaging) with minimal scan planning and patient cooperation. 9 , 10 The uninterrupted fashion of the sequences will eliminate the need for multiple highly specialized scans, whereas the black-blood technology will provide unprecedented contrast for automated analysis of myocardial injuries. In work package 2, the consortium will exploit the co-registered contrasts to automatically extract healthy and injured cardiac tissue parameters.…”