Quantification of Myocardial Creatine and Triglyceride Content in the Human Heart: Precision and Accuracy of in vivo Proton Magnetic Resonance Spectroscopy.

BACKGROUND

Proton magnetic resonance spectroscopy ( H-MRS) of the human heart is deemed to be a quantitative method to investigate myocardial metabolite content, but thorough validations of in vivo measurements against invasive techniques are lacking.

PURPOSE

To determine measurement precision and accuracy for quantifications of myocardial total creatine and triglyceride content with localized H-MRS.

STUDY TYPE

Test-retest repeatability and measurement validation study.

SUBJECTS

Sixteen volunteers and 22 patients scheduled for open-heart aortic valve replacement or septal myectomy.

FIELD STRENGTH/SEQUENCE: Prospectively ECG-triggered respiratory-gated free-breathing single-voxel point-resolved spectroscopy (PRESS) sequence at 3 T.

ASSESSMENT

Myocardial total creatine and triglyceride content were quantified relative to the total water content by fitting the H-MR spectra. Precision was assessed with measurement repeatability. Accuracy was assessed by validating in vivo H-MRS measurements against biochemical assays in myocardial tissue from the same subjects.

STATISTICAL TESTS

Intrasession and intersession repeatability was assessed using Bland-Altman analyses. Agreement between H-MRS measurements and biochemical assay was tested with regression analyses.

RESULTS

The intersession repeatability coefficient for myocardial total creatine content was 41.8% with a mean value of 0.083% ± 0.020% of the total water signal, and 36.7% for myocardial triglyceride content with a mean value of 0.35% ± 0.13% of the total water signal. Ex vivo myocardial total creatine concentrations in tissue samples correlated with the in vivo myocardial total creatine content measured with H-MRS: n = 22, r = 0.44; P < 0.05. Likewise, ex vivo myocardial triglyceride concentrations correlated with the in vivo myocardial triglyceride content: n = 20, r = 0.50; P < 0.05.

DATA CONCLUSION

We validated the use of localized H-MRS of the human heart at 3 T for quantitative assessments of in vivo myocardial tissue metabolite content by estimating the measurement precision and accuracy.

LEVEL OF EVIDENCE

2 TECHNICAL EFFICACY STAGE: 2.