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Detection of Recent Myocardial Infarction Using Native T1 Mapping in a Swine Model: A Validation Study.

ABSTRACT: Late gadolinium enhancement (LGE) imaging is the currently the gold standard for in-vivo detection of myocardial infarction. However, gadolinium contrast administration is contraindicated in patients with renal insufficiency. We aim to evaluate the diagnostic sensitivity and specificity of this contrast-free MRI technique, native T1 mapping, in detecting recent myocardial infarction versus a reference histological gold standard. Ten pigs underwent CMR at 2 weeks after induced MI. The infarct size and transmural extent of MI was calculated using native T1 maps and LGE images. Histological validation was performed using triphenyl tetrazolium chloride (TTC) staining in the corresponding ex-vivo slices. The infarct size and transmural extent of myocardial infarction assessed by T1 mapping correlated well with that assessed by LGE and TTC images. Using TTC staining as the reference, T1 mapping demonstrated underestimation of infarct size and transmural extent of infarction. Additionally, there was a slight but not significant difference found in the diagnostic performance between the native T1 maps and LGE images for the location of MI. Our study shows that native T1 mapping is feasible alternative method to the LGE technique for the assessment of the size, transmural extent, and location of MI in patients who cannot receive gadolinium contrast.

SUBMITTER: Cui C

PROVIDER: S-EPMC5943450 | biostudies-literature | 2018 May

REPOSITORIES: biostudies-literature

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Detection of Recent Myocardial Infarction Using Native T1 Mapping in a Swine Model: A Validation Study.

Cui Chen C Wang Shuli S Lu Minjie M Duan Xuejing X Wang Hongyue H Jia Liujun L Tang Yue Y Sirajuddin Arlene A Prasad Sanjay K SK Kellman Peter P Arai Andrew E AE Zhao Shihua S

Scientific reports 20180509 1

Late gadolinium enhancement (LGE) imaging is the currently the gold standard for in-vivo detection of myocardial infarction. However, gadolinium contrast administration is contraindicated in patients with renal insufficiency. We aim to evaluate the diagnostic sensitivity and specificity of this contrast-free MRI technique, native T1 mapping, in detecting recent myocardial infarction versus a reference histological gold standard. Ten pigs underwent CMR at 2 weeks after induced MI. The infarct siz ...[more]

PMID: 29743511

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Project description:BackgroundQuantitative relaxation time measurements by cardiovascular magnetic resonance (CMR) are of paramount importance in contrast-enhanced studies of experimental myocardial infarction. First, compared to qualitative measurements based on signal intensity changes, they are less sensitive to specific parameter choices, thereby allowing for better comparison between different studies or during longitudinal studies. Secondly, T1 measurements may allow for quantification of local contrast agent concentrations. In this study, a recently developed 3D T1 mapping technique was applied in a mouse model of myocardial infarction to measure differences in myocardial T1 before and after injection of a liposomal contrast agent. This was then used to assess the concentration of accumulated contrast agent.Materials and methodsMyocardial ischemia/reperfusion injury was induced in 8 mice by transient ligation of the LAD coronary artery. Baseline quantitative T1 maps were made at day 1 after surgery, followed by injection of a Gd-based liposomal contrast agent. Five mice served as control group, which followed the same protocol without initial surgery. Twenty-four hours post-injection, a second T1 measurement was performed. Local ΔR1 values were compared with regional wall thickening determined by functional cine CMR and correlated to ex vivo Gd concentrations determined by ICP-MS.ResultsCompared to control values, pre-contrast T1 of infarcted myocardium was slightly elevated, whereas T1 of remote myocardium did not significantly differ. Twenty-four hours post-contrast injection, high ΔR1 values were found in regions with low wall thickening values. However, compared to remote tissue (wall thickening > 45%), ΔR1 was only significantly higher in severe infarcted tissue (wall thickening < 15%). A substantial correlation (r = 0.81) was found between CMR-based ΔR1 values and Gd concentrations from ex vivo ICP-MS measurements. Furthermore, regression analysis revealed that the effective relaxivity of the liposomal contrast agent was only about half the value determined in vitro.Conclusions3D cardiac T1 mapping by CMR can be used to monitor the accumulation of contrast agents in contrast-enhanced studies of murine myocardial infarction. The contrast agent relaxivity was decreased under in vivo conditions compared to in vitro measurements, which needs consideration when quantifying local contrast agent concentrations.

Project description:BackgroundMyocardial mapping techniques can be used to quantitatively assess alterations in myocardial tissue properties. This study aims to evaluate the influence of spatial resolution on quantitative results and reproducibility of native myocardial T1 mapping in cardiac magnetic resonance imaging (MRI).MethodsIn this cross-sectional study with prospective data collection between October 2019 and February 2020, 50 healthy adults underwent two identical cardiac MRI examinations in the radiology department on the same day. T1 mapping was performed using a MOLLI 5(3)3 sequence with higher (1.4 mm × 1.4 mm) and lower (1.9 mm × 1.9 mm) in-plane spatial resolution. Global quantitative results of T1 mapping were compared between high-resolution and low-resolution acquisitions using paired t-test. Intra-class correlation coefficient (ICC) and Bland-Altman statistics (absolute and percentage differences as means ± SD) were used for assessing test-retest reproducibility.ResultsThere was no significant difference between global quantitative results acquired with high vs. low-resolution T1 mapping. The reproducibility of global T1 values was good for high-resolution (ICC: 0.88) and excellent for low-resolution T1 mapping (ICC: 0.95, P=0.003). In subgroup analyses, inferior test-retest reproducibility was observed for high spatial resolution in women compared to low spatial resolution (ICC: 0.71 vs. 0.91, P=0.001) and heart rates >77 bpm (ICC: 0.53 vs. 0.88, P=0.004). Apical segments had higher T1 values and variability compared to other segments. Regional T1 values for basal (ICC: 0.81 vs. 0.89, P=0.023) and apical slices (ICC: 0.86 vs. 0.92, P=0.024) showed significantly higher reproducibility in low-resolution compared to high-resolution acquisitions but without differences for midventricular slice (ICC: 0.91 vs. 0.92, P=0.402).ConclusionsBased on our data, we recommend a spatial resolution on the order of 1.9 mm × 1.9 mm for native myocardial T1 mapping using a MOLLI 5(3)3 sequence at 1.5 T particularly in individuals with higher heart rates and women.

Project description:BACKGROUND:T1 mapping based on cardiovascular magnetic resonance (CMR) is a novel approach using the magnetic relaxation T1 time as a quantitative marker for myocardial tissue composition. Various T1 mapping sequences are being used, with different strengths and weaknesses. Data comparing different sequences head to head however are sparse. METHODS:We compared three T1 mapping sequences, ShMOLLI, MOLLI and SASHA in phantoms and in a mid-ventricular slice of 40 healthy individuals (mean age 59?±?7 years, 45 % male) with low (68 %) or moderate cardiovascular risk. We calculated global and segmental T1 in vivo through exponential curve fitting and subsequent parametric mapping. We also analyzed image quality and inter-observer reproducibility. RESULTS:There was no association of T1 with cardiovascular risk groups. T1 however differed significantly depending on the sequence, with SASHA providing consistently higher mean values than ShMOLLI and MOLLI (1487?±?36 ms vs. 1174?±?37 ms and 1199?±?28 ms, respectively; p?<?0.001). This difference between sequences was much smaller in phantom measurements. In patients, segmental values were lower in the anterior wall for all sequences. Image quality, in general good for the steady-state-free-precession readouts in all sequences, was lower for SASHA parametric maps. On multivariate regression analysis, a longer T1 measured by MOLLI was correlated with lower ejection fraction and female gender. Inter-observer variability as assessed by intra-class correlation coefficients was excellent for all sequences (ShMOLLI: 0.995; MOLLI: 0.991; SASHA: 0.961; all p?<?0.001). CONCLUSION:In a cross-sectional population with low to moderate cardiovascular risk, we observed a variation in T1 mapping results between inversion-recovery vs. saturation-recovery sequences in vivo, which were less evident in phantom images, despite a small interobserver variability. Thus, physiological factors, most likely related to B1 inhomogeneities, and tissue-specific properties, like magnetization transfer, that impact T1 values in vivo, render phantom validation insufficient, and have to be further investigated for a better understanding of the clinical utility of different T1 mapping approaches. TRIAL REGISTRATION:"Canadian Alliance For Healthy Hearts and Minds" - ClinicalTrials.gov NCT02220582 ; registered August 18, 2014.

Project description:BackgroundNative T1 may be a sensitive, contrast-free, non-invasive cardiovascular magnetic resonance (CMR) marker of myocardial tissue changes in patients with pulmonary artery hypertension. However, the diagnostic and prognostic value of native T1 mapping in this patient group has not been fully explored. The aim of this work was to determine whether elevation of native T1 in myocardial tissue in pulmonary hypertension: (a) varies according to pulmonary hypertension subtype; (b) has prognostic value and (c) is associated with ventricular function and interaction.MethodsData were retrospectively collected from a total of 490 consecutive patients during their clinical 1.5 T CMR assessment at a pulmonary hypertension referral centre in 2015. Three hundred sixty-nine patients had pulmonary hypertension [58 ± 15 years; 66% female], an additional 39 had pulmonary hypertension due to left heart disease [68 ± 13 years; 60% female], 82 patients did not have pulmonary hypertension [55 ± 18; 68% female]. Twenty five healthy subjects were also recruited [58 ±4 years); 51% female]. T1 mapping was performed with a MOdified Look-Locker Inversion Recovery (MOLLI) sequence. T1 prognostic value in patients with pulmonary arterial hypertension was assessed using multivariate Cox proportional hazards regression analysis.ResultsPatients with pulmonary artery hypertension had elevated T1 in the right ventricular (RV) insertion point (pulmonary hypertension patients: T1 = 1060 ± 90 ms; No pulmonary hypertension patients: T1 = 1020 ± 80 ms p < 0.001; healthy subjects T1 = 940 ± 50 ms p < 0.001) with no significant difference between the major pulmonary hypertension subtypes. The RV insertion point was the most successful T1 region for discriminating patients with pulmonary hypertension from healthy subjects (area under the curve = 0.863) however it could not accurately discriminate between patients with and without pulmonary hypertension (area under the curve = 0.654). T1 metrics did not contribute to prediction of overall mortality (septal: p = 0.552; RV insertion point: p = 0.688; left ventricular free wall: p = 0.258). Systolic interventricular septal angle was a significant predictor of T1 in patients with pulmonary hypertension (p < 0.001).ConclusionsElevated myocardial native T1 was found to a similar extent in pulmonary hypertension patient subgroups and is independently associated with increased interventricular septal angle. Native T1 mapping may not be of additive value in the diagnostic or prognostic evaluation of patients with pulmonary artery hypertension.

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Detection of Recent Myocardial Infarction Using Native T1 Mapping in a Swine Model: A Validation Study.

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Detection of Recent Myocardial Infarction Using Native T1 Mapping in a Swine Model: A Validation Study.

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