Influence of Field Strength, Sex, and Age on Pseudo-Continuous Arterial Spin Labeling and T1 Mapping in the Kidney

Background: Pseudo-continuous arterial spin labeling (PCASL) and T-1 mapping have been used for renal imaging at 1.5 T and 3 T. However, direct comparisons between field strengths, age, and sex are lacking. Purpose: To assess the effects of field strength, age, and sex on renal perfusion and T-1 values and measure reproducibility. Study Type: Prospective. Population: Sixteen healthy volunteers (eight females, age 41.8 +/- 13.3 years) underwent same-day scans at 1.5 T and 3 T, repeated 1 week later. Field Strength/Sequence: 1.5 T/3 T multi-delay PCASL with spin-echo EPI readout, inversion-recovery T-1 mapping, B-0 and B-1 mapping. Assessment: Multi-delay PCASL was employed to calculate renal blood flow (RBF) and arterial transit time (ATT) maps; single-delay PCASL (PLD = 1.3 s) assessed RBF and technical parameters. Cortical and medullary RBF, ATT, and T-1 were compared between field strengths, age, and sex groups. Reproducibility and inter-observer agreement were evaluated. Statistical Tests: Shapiro-Wilk test, analysis of variance, Levene test, Box M-test, Pearson's correlation, within-subject coefficient of variation (wsCV), and intraclass correlation coefficient (ICC). P-value < 0.05 was significant. Results: 3 T yielded significantly higher cortical T-1 (1356.02 +/- 3.72 vs. 1023.29 +/- 39.30 ms), and lower RBF (310.63 +/- 52.72 vs. 347.65 +/- 54.08 [mL/min/100 g]) than 1.5 T. Eight older (>= 40 years) participants had significantly lower cortical RBF (1.5 T: 312.23 +/- 37.59 vs. 383.06 +/- 43.91 [mL/min/100 g]). Females showed significantly shorter ATT (1.5 T: 0.75 +/- 0.11 s vs. 0.96 +/- 0.22 s) and longer medullary T-1 (1.5 T: 1388.12 +/- 33.68 ms vs. 1308.97 +/- 28.52 ms). T-1 showed excellent reproducibility and inter-observer agreement (wsCV: < 2%, ICC: > 0.8). Cortical RBF was reproducible (wsCV: similar to 10%, ICC: > 0.7) with strong inter-observer agreement (wsCV: < 2.5%, ICC > 0.95). Medullary RBF had good inter-observer agreement (wsCV: < 4.7%, ICC: > 0.75) but poor reproducibility (wsCV: 15.78%-19.38%). Data Conclusion: Cortical perfusion parameters and T-1 were reproducible. However, age, sex, and field strength affect the values, requiring consideration in renal imaging.