Evaluating the Potential of Quantitative Susceptibility Mapping for Detecting Iron Deposition of Renal Fibrosis in a Rabbit Model.

Background: As ferroptosis is a key factor in renal fibrosis (RF), iron deposition monitoring may help evaluating RF. The capability of quantitative susceptibility mapping (QSM) for detecting iron deposition in RF remains uncertain.

Purpose: To investigate the potential of QSM to detect iron deposition in RF.

Study Type: Animal model.

Animal Model: Eighty New Zealand rabbits were randomly divided into control (N = 10) and RF (N = 70) groups, consisting of baseline, 7, 14, 21, and 28 days (N = 12 in each), and longitudinal (N = 10) subgroups. RF was induced via unilateral renal arteria stenosis.

Field Strength/sequence: 3 T, QSM with gradient echo, arterial spin labeling with gradient spin echo.

Assessment: Bilateral kidney QSM values (χ) in the cortex (χ) and outer medulla (χ) were evaluated with histopathology.

Statistical Tests: Analysis of variance, Kruskal-Wallis, Spearman's correlation, and the area under the receiver operating characteristic curve (AUC). P < 0.05 was significant.

Results: In fibrotic kidneys, χ decreased at 7 days ([-6.69 ± 0.98] × 10 ppm) and increased during 14-28 days ([-1.85 ± 2.11], [0.14 ± 0.58], and [1.99 ± 0.60] × 10 ppm, respectively), while the χ had the opposite trend. Both significantly correlated with histopathology (|r| = 0.674-0.849). AUC of QSM for distinguishing RF degrees was 0.692-0.993. In contralateral kidneys, the χ initially decreased ([-6.67 ± 0.84] × 10 ppm) then recovered to baseline ([-4.81 ± 0.89] × 10 ppm), while the χ at 7-28 days ([2.58 ± 1.40], [2.25 ± 1.83], [2.49 ± 2.11], [2.43 ± 1.32] × 10 ppm, respectively) were significantly higher than baseline ([0.54 ± 0.18] × 10 ppm).

Data Conclusion: Different iron deposition patterns were observed in RF with QSM values, suggesting the potential of QSM for iron deposition monitoring in RF.

Plain Language Summary: Renal fibrosis (RF) is a common outcome in most kidney diseases, leading to scarring and loss of kidney function. Increasing evidence suggests that abnormal iron metabolism plays an important role in RF. This study used a technique called quantitative susceptibility mapping (QSM) to measure kidney iron levels in rabbits with RF. Specifically, rabbits with advanced RF exhibited higher kidney iron concentrations, and moderate to strong correlations between QSM values and histopathology demonstrated that QSM could accurately detect changes in iron levels and assess RF severity. Overall, QSM shows promise as a tool for monitoring iron deposition in RF progression.

Evidence Level: 2 TECHNICAL EFFICACY: Stage 3.