Time-efficient myocardial contrast partition coefficient measurement from early enhancement with magnetic resonance imaging

Abstract

Objective: Our purpose was to validate an early enhancement time point for accurately measuring the myocardial contrast partition coefficient (lambda) using dynamic-equilibrium magnetic resonance imaging. Materials and Methods: The pre- and post-contrast longitudinal relaxation rates (reciprocal of T1) of the interventricular septum (R1 m ) and blood pool (R1 b ) were obtained from fifteen healthy volunteers and three diabetic patients with hypertension using two optimized T1 mapping sequences (modified Look-Locker inversion recovery) on a 3-Tesla magnetic resonance scanner. Reference lambda values were calculated as the slope of the regression line of R1 m versus R1 b at dynamic equilibrium (multi-point regression method). The simplified pre-/post-enhancement two-acquisition method (twopoint method) was used to calculate lambda by relating the change in R1 m and R1 b using different protocols according to the acquisition stage of the post-enhancement data point. The agreement with the referential method was tested by calculating Pearson's correlation coefficient and the intra-class correlation coefficient. Results: The lambda values measured by the two-point method increased (from 0.479±0.041 to 0.534±0.043) over time from 6 to 45 minutes after contrast and exhibited good correlation with the reference at each time point (r≥0.875, p<0.05). The intra-class correlation coefficient on absolute agreement with the reference lambda was 0.946, 0.929 and 0.922 at the 6 th , 7 th and 8 th minutes and dropped from 0.878 to 0.403 from the 9 th minute on. Conclusions: The time-efficient two-point method at 6-8 minutes after the Gd-DTPA bolus injection exhibited good agreement with the multi-point regression method and can be applied for accurate lambda measurement in normal myocardium. © 2014 Zhang et al.