Repeatability and reproducibility of variable flip angle T 1 quantification in the prostate at 3 T

BACKGROUND: Variable flip angle (VFA) imaging is widely used for the estimation of T1 relaxation in the prostate, but may have limited repeatability and reproducibility due to its sensitivity to B1+ inhomogeneity. PURPOSE: To assess the repeatability and reproducibility of prostate T1 estimation with and without compensating for B1+ variation. STUDY TYPE: Prospective. POPULATION: Twenty-one volunteers were prospectively recruited and scanned twice on two 3 T MRI scanners, resulting in 84 VFA T1 exams. FIELD STRENGTH/SEQUENCE: 3 T/2D saturated turbo fast low angle shot (FLASH) and 3D dual-echo FLASH. ASSESSMENT: Two B1+ mapping techniques, including reference region VFA (RR-VFA) and saturated turbo FLASH (satTFL), were used for B1+ correction, and T1 maps with and without B1+ correction were tested for intrascanner repeatability and interscanner reproducibility. Volumetric regions of interest (ROIs) were drawn on the transition zone, peripheral zone of the prostate, and the obturator internus left and right muscles in the corresponding slices. STATISTICAL TESTS: The average T1 within each ROI for each scan was compared for both intra- and interscanner variability using concordance correlation coefficient and a Bland-Altman plot. RESULTS: Both RR-VFA-corrected T1 and satTFL-corrected T1 showed higher intra- and interscanner correlation (0.89/0.87 and 0.87/0.84, respectively) than VFA T1 (0.84 and 0.74). Bland-Altman plots showed that VFA T1 had wider 95% limits of agreement and a larger range of T1 for each tissue compared with T1 with B1+ correction. DATA CONCLUSION: The application of B1+ correction (both RR-VFA and satTFL) to VFA T1 results in more repeatable and reproducible T1 estimation than VFA T1 . This can potentially provide improved quantification of the prostate dynamic contrast-enhanced MRI parameters. Level of Evidence 1. Technical Efficacy Stage 1. J. Magn. Reson. Imaging 2018.