Rotating frame spin lattice relaxation in a swine model of chronic, left ventricular myocardial infarction

Witschey, Walter R.; Pilla, James J.; Ferrari, Giovanni; Koomalsingh, Kevin J.; Haris, Mohammad; Hinmon, Robin; Zsido, Gerald A; Gorman, Joseph H.; Gorman, Robert C.; Reddy, Ravinder

doi:10.1002/mrm.22543

Cited by 47 publications

(71 citation statements)

References 33 publications

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“…T2-weighted CMR is ambiguously sensitive to chronic MI, with no observed increase in signal intensity or T2 relaxation at the site of infarct [6] or changes in T2 that were dependent on the location of infarction [26]. These mixed results would reinforce the hypothesis that there are low frequency relaxation mechanisms unrelated to disease that obscure contrast [7]. T2-weighted CMR has been observed to overestimate the size of MI compared to LGE in acute MI [22].…”

Section: Discussionmentioning

confidence: 99%

In vivo chronic myocardial infarction characterization by spin locked cardiovascular magnetic resonance

Witschey

Zsido

Koomalsingh

et al. 2012

Journal of Cardiovascular Magnetic Resonance

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BackgroundLate gadolinium enhanced (LGE) cardiovascular magnetic resonance (CMR) is frequently used to evaluate myocardial viability, estimate total infarct size and transmurality, but is not always straightforward is and contraindicated in patients with renal failure because of the risk of nephrogenic systemic fibrosis. T2- and T1-weighted CMR alone is however relatively insensitive to chronic myocardial infarction (MI) in the absence of a contrast agent. The objective of this manuscript is to explore T1ρ-weighted rotating frame CMR techniques for infarct characterization without contrast agents. We hypothesize that T1ρ CMR accurately measures infarct size in chronic MI on account of a large change in T1ρ relaxation time between scar and myocardium.Methods7Yorkshire swine underwent CMR at 8 weeks post-surgical induction of apical or posterolateral myocardial infarction. Late gadolinium enhanced and T1ρ CMR were performed at high resolution to visualize MI. T1ρ-weighted imaging was performed with a B1 = 500 Hz spin lock pulse on a 3 T clinical MR scanner. Following sacrifice, the heart was excised and infarct size was calculated by optical planimetry. Infarct size was calculated for all three methods (LGE, T1ρ and planimetry) and statistical analysis was performed. T1ρ relaxation time maps were computed from multiple T1ρ-weighted images at varying spin lock duration.ResultsMean infarct contrast-to-noise ratio (CNR) in LGE and T1ρ CMR was 2.8 ± 0.1 and 2.7 ± 0.1. The variation in signal intensity of tissues was found to be, in order of decreasing signal intensity, LV blood, fat and edema, infarct and healthy myocardium. Infarct size measured by T1ρ CMR (21.1% ± 1.4%) was not significantly different from LGE CMR (22.2% ± 1.5%) or planimetry (21.1% ± 2.7%; p < 0.05).T1ρ relaxation times were T1ρinfarct = 91.7 ms in the infarct and T1ρremote = 47.2 ms in the remote myocardium.ConclusionsT1ρ-weighted imaging using long spin locking pulses enables high discrimination between infarct and myocardium. T1ρ CMR may be useful to visualizing MI without the need for exogenous contrast agents for a wide range of clinical cardiac applications such as to distinguish edema and scar tissue and tissue characterization of myocarditis and ventricular fibrosis.

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Section: Discussionmentioning

confidence: 99%

In vivo chronic myocardial infarction characterization by spin locked cardiovascular magnetic resonance

Witschey

Zsido

Koomalsingh

et al. 2012

Journal of Cardiovascular Magnetic Resonance

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“…A posterolateral infarction was induced by ligation of the left circumflex artery (LCX) and select obtuse marginal (OM) branches. In all cases, this pattern of coronary ligations produced an infarct comprising 20–25% of the left ventricle [29]. Akinesis of the infarcted myocardium was confirmed using intraoperative echocardiography.…”

Section: Methodsmentioning

confidence: 99%

MRI evaluation of injectable hyaluronic acid-based hydrogel therapy to limit ventricular remodeling after myocardial infarction

et al. 2015

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Injectable biomaterials are an attractive therapy to attenuate left ventricular (LV) remodeling after myocardial infarction (MI). Although studies have shown that injectable hydrogels improve cardiac structure and function in vivo, temporal changes in infarct material properties after treatment have not been assessed. Emerging imaging and modeling techniques now allow for serial, non-invasive estimation of infarct material properties. Specifically, cine MRI assesses global LV structure and function, late-gadolinium enhancement (LGE) MRI enables visualization of infarcted tissue to quantify infarct expansion, and spatial modulation of magnetization (SPAMM) tagging provides passive wall motion assessment as a measure of tissue strain, which can all be used to evaluate infarct properties when combined with finite element (FE) models. In this work, we investigated the temporal effects of degradable hyaluronic acid (HA) hydrogels on global LV remodeling, infarct thinning and expansion, and infarct stiffness in a porcine infarct model for 12 weeks post-MI using MRI and FE modeling. Hydrogel treatment led to decreased LV volumes, improved ejection fraction, and increased wall thickness when compared to controls. FE model simulations demonstrated that hydrogel therapy increased infarct stiffness for 12 weeks post-MI. Thus, evaluation of myocardial tissue properties through MRI and FE modeling provides insight into the influence of injectable hydrogel therapies on myocardial structure and function post-MI.

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“…The mFI imaging is based on T 1 ρ dispersion contrast, rather than the absolute T 1 ρ contrast. The latter has been reported by several groups to show up to a 1-fold higher T 1 ρ value for myocardial scar tissue induced by MI [12,13,20]. For other regions with less collagen content, such as the border zone of the infarct, the amount of increase in T 1 ρ is much less, making the distinction and quantification of differences in fibrosis more problematic.…”

Section: Discussionmentioning

confidence: 80%

“…For other regions with less collagen content, such as the border zone of the infarct, the amount of increase in T 1 ρ is much less, making the distinction and quantification of differences in fibrosis more problematic. On the other hand, the T 1 ρ dispersion contrast produced a much greater difference in T 1 ρ between two SLFs, resulting in detection of more subtle differences in the extent of fibrosis, even within the border zone region [20]. For this reason, mFI is defined as the difference between T 1 ρ (0) and T 1 ρ (ω 1 ), rather than a composite metric R 2 − R 1 ρ (R 1 ρ = 1/T 1 ρ) [16] or the ratio of T 1 ρ (ω 1 ) and T 1 ρ (0) [34].…”

Section: Discussionmentioning

confidence: 99%

“…Several studies have adopted a T 1 ρ dispersion contrast, rather than a T 1 ρ contrast, to improve the sensitivity for assessing early cartilage degeneration [16], to investigate aging difference in skeletal muscle [17], and to explore metabolite with chemical exchange sensitive MRI [18]The fundamental mechanism is likely to be the chemical exchange contribution, between free water protons and protons bound with macromolecules, on a time scale of the spin-locking field [19]. In this study, we hypothesized that a T 1 ρ dispersion contrast would provide another imaging approach with improved sensitivity for the assessment of diffuse myocardial fibrosis [20]. Based on a cardiac T 1 ρ technique reported previously [21], we report initial evaluation for detection of myocardial fibrosis in a canine model of MI after coronary reperfusion.…”

Section: Introductionmentioning

confidence: 99%

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A non-contrast CMR index for assessing myocardial fibrosis

Yin

Abendschein

Muccigrosso

et al. 2017

Magnetic Resonance Imaging

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Purpose: Safe, sensitive, and non-invasive imaging methods to assess the presence, extent, and turnover of myocardial fibrosis are needed for early stratification of risk in patients who might develop heart failure after myocardial infarction. We describe a non-contrast cardiac magnetic resonance (CMR) approach for sensitive detection of myocardial fibrosis using a canine model of myocardial infarction and reperfusion. Methods: Seven dogs had coronary thrombotic occlusion of the left anterior descending coronary arteries followed by fibrinolytic reperfusion. CMR studies were performed at 7 days after reperfusion. A CMR spin-locking T1ρ mapping sequence was used to acquire T1ρ dispersion data with spin-lock frequencies of 0 and 511 Hz. A fibrosis index map was derived on a pixel-by-pixel basis. CMR native T1 mapping, first-pass myocardial perfusion imaging, and post-contrast late gadolinium enhancement imaging were also performed for assessing myocardial ischemia and fibrosis. Hearts were dissected after CMR for histopathological staining and two myocardial tissue segments from the septal regions of adjacent left ventricular slices were qualitatively assessed to grade the extent of myocardial fibrosis. Results: Histopathology of 14 myocardial tissue segments from septal regions was graded as grade 1 (fibrosis area, <20% of a low power field, n = 9), grade 2 (fibrosis area, 20–50% of field, n = 4), or grade 3 (fibrosis area, >50% of field, n = 1). A dramatic difference in fibrosis index (183%, P < 0.001) was observed by CMR from grade 1 to 2, whereas differences were much smaller for T1ρ (9%, P = 0.14), native T1 (5.5%, P = 0.12), and perfusion (−21%, P = 0.05). Conclusion: A non-contrast CMR index based on T1ρ dispersion contrast was shown in preliminary studies to detect and correlate with the extent of myocardial fibrosis identified histopathologically. A non-contrast approach may have important implications for managing cardiac patients with heart failure, particularly in the presence of impaired renal function.

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Rotating frame spin lattice relaxation in a swine model of chronic, left ventricular myocardial infarction

Cited by 47 publications

References 33 publications

In vivo chronic myocardial infarction characterization by spin locked cardiovascular magnetic resonance

In vivo chronic myocardial infarction characterization by spin locked cardiovascular magnetic resonance

MRI evaluation of injectable hyaluronic acid-based hydrogel therapy to limit ventricular remodeling after myocardial infarction

A non-contrast CMR index for assessing myocardial fibrosis

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