Influence of scanning parameters on image quality, and repeatability of renal blood oxygenation level-dependent imaging: A preliminary study on 5 T MRI

Objective

To investigate the influence of scanning parameters on image quality and the repeatability of renal Blood Oxygenation Level-Dependent (BOLD) imaging at 5 T.

Methods

20 healthy subjects and 25 patients with chronic kidney disease (CKD) were prospectively recruited for BOLD-MRI scans at 5 T using multiple parameter combinations. The Fisher’s exact test, ANOVA, the Friedman test, and paired t-tests were used to compare the qualitative and quantitative indices across groups. The generalized linear models (GLM) analysis was further used to evaluate the effect of acquisition parameters on the measured R2* values. Subsequently, Pearson correlation and the intraclass correlation coefficient (ICC) were applied to assess the repeatability of R2* values in the high-resolution parameters in patients.

Results

Renal cortical and medullary R2* values demonstrated excellent agreement (all ICCs > 0.75) across varied in-plane resolution, slice thickness, echo number, and maximum TE. GLM revealed a significant positive effect of slice thickness on R2* in both cortex and medulla, a region-specific positive effect of maximum TE in the cortex only, and no significant effect of in-plane resolution or echo number. High resolution (1.25 mm × 1.25 mm × 3 mm) provided superior corticomedullary demarcation and clinical image quality, and renal cortical and medullary R2* values exhibited high inter-observer agreement (ICC: 0.992 and 0.971) and test–retest repeatability (all r > 0.90, P < 0.05). Compared with healthy subjects, the renal cortical and medullary R2* values in patients with CKD were significantly higher (cortical R2*: 21.13 Hz vs. 22.88 Hz, P < 0.001; medullary R2*: 40.69 Hz vs. 49.14 Hz, P < 0.001).

Conclusion

This study showed that image resolution may slightly affect the quantification of the R2* values on 5 T renal BOLD-MRI. High-resolution BOLD imaging (1.25 mm × 1.25 mm × 3 mm, 10 echoes, maximum TE 40 ms) can be achieved at 5 T MRI with excellent inter-observer agreement and test–retest repeatability, validating its clinical applicability.