Abstract
BACKGROUND: Proton magnetic resonance spectroscopy ((1) 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 (1) 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 (1) H-MR spectra. Precision was assessed with measurement repeatability. Accuracy was assessed by validating in vivo (1) 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 (1) 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 (1) 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 (1) 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.
