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: ~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. Evidence Level Level 2. Technical Efficacy Stage 1.