Three-Dimensional Self-Navigated T2 Mapping for the Detection of Acute Cellular Rejection After Orthotopic Heart Transplantation

BACKGROUND: T(2) mapping is a magnetic resonance imaging technique measuring T(2) relaxation time, which increases with the myocardial tissue water content. Myocardial edema is a component of acute cellular rejection (ACR) after heart transplantation. This pilot study compares in heart transplantation recipients a novel high resolution 3-dimensional (3D) T(2)-mapping technique with standard 2-dimensional (2D) T(2)-mapping for ACR detection. METHODS: Consecutive asymptomatic patients (n = 26) underwent both 3D T(2) mapping and reference 2D T(2) mapping magnetic resonance imaging on the day of endomyocardial biopsy (EMB). 3D T(2) maps were obtained at an isotropic spatial resolution of 1.72 mm (voxel volume 5.1 mm(3)). 2D and 3D maps were matched anatomically, and maximum segmental T(2) values were compared blinded to EMB results. In addition, all 3D T(2) maps were rendered as 3D images and inspected for foci of T(2) elevation. RESULTS: T(2) values of segments from 2D and reformatted 3D T(2) maps agreed (p > 0.5). The highest 2D segmental T(2) values were 49.9 ± 4.0 ms (no ACR = 0R, n = 18), 48.9 ± 0.8 ms (mild ACR = 1R, n = 3), and 65.0 ms (moderate ACR = 2R). Rendered 3D T(2) maps of cases with 1R showed foci with significantly elevated T(2) signal (T(2) = 58.2 ± 3.6 ms); 5 cases (28%) in the 0R group showed foci with increased T(2) values (>2 SD above adjacent tissue) that were not visible on the 2D T(2) maps. CONCLUSIONS: This pilot study in a small cohort suggests equivalency of standard segmental analysis between 3D and 2D T(2)-mapping. 3D T(2) mapping provides a spatial resolution that permits detection of foci with elevated T(2) in patients with mild ACR.