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

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.

To assess the effects of field strength, age, and sex on renal perfusion and T ₁ values and measure reproducibility.

Prospective.

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.

1.5 T/3 T multi-delay PCASL with spin-echo EPI readout, inversion-recovery T ₁ mapping, B ₀ and B ₁ mapping.

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.

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.

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%).

Cortical perfusion parameters and T ₁ were reproducible. However, age, sex, and field strength affect the values, requiring consideration in renal imaging.

Level 2.

Stage 1.