Abstract
BACKGROUND: T(2)-mapping has promise to evaluate kidney pathophysiology. Prior studies show a large variance in kidney T(2), likely due to the differing acquisition sequences. PURPOSE: To compare four T(2)-mapping sequences to investigate kidney T(2). STUDY TYPE: Phantom and prospective in vivo assessments. PARTICIPANTS: ISMRM/NIST and QASPER phantoms; 8 healthy volunteers (4 female, 30 ± 8 years). FIELD STRENGTH/SEQUENCE: 3 T, spin echo-echo planar imaging (SE-EPI), multi-echo-spin echo (ME-SE), Gradient and Spin Echo (GraSE) vendor-provided sequences, and custom T(2)-prepared EPI, Dual-echo B(0)-mapping and DREAM B(1)-mapping. ASSESSMENT: T(2)-mapping accuracy in the ISMRM/NIST phantom in the presence of B(0) frequency offset and B(1) (+) by scaling of flip angles, and in the QASPER phantom in the presence of diffusion by altering pump rate compared to being turned off. Participants underwent a single 45-min exam to collect four T(2)-mapping sequences, B(0) and B(1) maps. In vivo T(2) values compared across sequences and the influence of B(0) and B(1) (+) was evaluated. STATISTICAL TESTS: Shapiro-Wilk, Wilcoxon signed-rank, Student's t-test, Coefficient of Variation, Pearson's correlation coefficient, linear mixed effect model. p < 0.05 considered statistically significant. RESULTS: SE-EPI, ME-SE, GraSE, and T(2)-prepared EPI had a mean absolute scaled error of 0.52, 0.52, 0.36, and 0.27 over the kidney T(2) range of the ISMRM/NIST phantom. GraSE was most robust to perturbations in B(0)/B(1) (+). In the QASPER phantom, SE-EPI was highly sensitive to diffusion leading to T(2) shortening (66%), while multi-echo sequences had lower diffusion sensitivity ordered by shortest echo spacing (ME-SE 81%, T(2)-prepared EPI 90%, GraSE 95% reduction in T(2)). In vivo, SE-EPI measured T(2) was significantly lower than multi-echo sequences, and SE-EPI and T(2)-preparation had a -0.52 ± 0.08 and -0.57 ± 0.06 ms/% dependence on B(1) (+). DATA CONCLUSION: To reduce B(0), B(1) (+), and diffusion sensitivity for kidney T(2)-mapping, a multi-echo sequence spanning echo times up to the kidney T(2) (~140 ms at 3 T) is recommended. Collecting data with different echo spacings can isolate the diffusion-related T(2) component. EVIDENCE LEVEL: 2. TECHNICAL EFFICACY: Stage 1.