What is the clinical evidence from this study?

Study design: Observational. Population: Healthy volunteers and myocardial disease (n=14). Intervention: Motion corrected, parametric T1ρ mapping sequence vs. Uncorrected T1ρ images. Primary outcome: Dice Score Coefficient (DSC) for image alignment (p=<< 0.01).

March 22, 2016Open Access

Measurement of Myocardial T1ρ with a Motion Corrected, Parametric Mapping Sequence in Humans

Q: What are the key findings of this study?

Motion correction using optical flow significantly improved the alignment of myocardial T1ρ images, increasing the Dice Score Coefficient from 0.76 to 0.88.

Key Result

Motion correction using optical flow significantly improved the alignment of myocardial T1ρ images, increasing the Dice Score Coefficient from 0.76 to 0.88.

Study Design

Type

Observational (n=14)

Multicenter

Structured PICO

Does a single-shot, motion-corrected T1ρ MRI sequence improve the accuracy and reproducibility of myocardial T1ρ mapping in humans?

Population

10 healthy subjects (mean age 29±7 years, 7 men, 3 women) without previous history of cardiovascular events, and 4 patients (1 with PVCs, 1 with chronic MI, 2 with HCM), plus phantoms.

Intervention

Breath-held T1ρ mapping method using a single-shot, T1ρ-prepared balanced steady-state free-precession (bSSFP) sequence with optical flow-based image registration for motion correction.

Comparator

Uncorrected T1ρ images and late-gadolinium enhanced (LGE) MRI.

Outcome

Accuracy (mean bias), reproducibility (coefficient of variation, intra-class correlation coefficient), and alignment improvement (Dice Score Coefficient) of T1ρ mapping.surrogate

A novel single-shot, motion-corrected T1ρ MRI sequence provides accurate and reproducible myocardial tissue characterization in a single breath-hold, correlating well with LGE MRI.

Main Result

Absolute Event Rate: 0.88% vs 0.76%

p-value: p=<< 0.01

Limitations

Low number of subjects
Absence of causal data linking fibrosis to relaxation time changes
Moving images were not well corrected if they were significantly different from the chosen reference image
Did not account for potential effects of age or gender in the populations

Abstract

PURPOSE: To develop a robust T1ρ magnetic resonance imaging (MRI) sequence for assessment of myocardial disease in humans. MATERIALS AND METHODS: We developed a breath-held T1ρ mapping method using a single-shot, T1ρ-prepared balanced steady-state free-precession (bSSFP) sequence. The magnetization trajectory was simulated to identify sources of T1ρ error. To limit motion artifacts, an optical flow-based image registration method was used to align T1ρ images. The reproducibility and accuracy of these methods was assessed in phantoms and 10 healthy subjects. Results are shown in 1 patient with pre-ventricular contractions (PVCs), 1 patient with chronic myocardial infarction (MI) and 2 patients with hypertrophic cardiomyopathy (HCM). RESULTS: In phantoms, the mean bias was 1.0 ± 2.7 msec (100 msec phantom) and 0.9 ± 0.9 msec (60 msec phantom) at 60 bpm and 2.2 ± 3.2 msec (100 msec) and 1.4 ± 0.9 msec (60 msec) at 80 bpm. The coefficient of variation (COV) was 2.2 (100 msec) and 1.3 (60 msec) at 60 bpm and 2.6 (100 msec) and 1.4 (60 msec) at 80 bpm. Motion correction improved the alignment of T1ρ images in subjects, as determined by the increase in Dice Score Coefficient (DSC) from 0.76 to 0.88. T1ρ reproducibility was high (COV < 0.05, intra-class correlation coefficient (ICC) = 0.85-0.97). Mean myocardial T1ρ value in healthy subjects was 63.5 ± 4.6 msec. There was good correspondence between late-gadolinium enhanced (LGE) MRI and increased T1ρ relaxation times in patients. CONCLUSION: Single-shot, motion corrected, spin echo, spin lock MRI permits 2D T1ρ mapping in a breath-hold with good accuracy and precision.

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