Detailing magnetic field strength dependence and segmental artifact distribution of myocardial effective transverse relaxation rate at 1.5, 3.0, and 7.0 T

Abstract

Purpose: Realizing the challenges and opportunities of effective transverse relaxation rate (R2*) mapping at high and ultrahigh fields, this work examines magnetic field strength (B0) dependence and segmental artifact distribution of myocardial R2* at 1.5, 3.0, and 7.0 T. Methods: Healthy subjects were considered. Three short-axis views of the left ventricle were examined. R2* was calculated for 16 standard myocardial segments. Global and mid-septum R2* were determined. For each segment, an artifactual factor was estimated as the deviation of segmental from global R2* value. Results: The global artifactual factor was significantly enlarged at 7.0 T versus 1.5 T (P=0.010) but not versus 3.0 T. At 7.0 T, the most severe susceptibility artifacts were detected in the inferior lateral wall. The mid-septum showed minor artifactual factors at 7.0 T, similar to those at 1.5 and 3.0 T. Mean R2* increased linearly with the field strength, with larger changes for global heart R2* values. Conclusion: At 7.0 T, segmental heart R2* analysis is challenging due to macroscopic susceptibility artifacts induced by the heart-lung interface and the posterior vein. Myocardial R2* depends linearly on the magnetic field strength. The increased R2* sensitivity at 7.0 T might offer means for susceptibility-weighted and oxygenation level-dependent MR imaging of the myocardium. © 2013 Wiley Periodicals, Inc.