Native T Mapping for Non-invasive Quantitative Evaluation of Renal Function and Renal Fibrosis in Patients with Chronic Kidney Disease

Background: To investigate the role of native T mapping in the non-invasive quantitative assessment of renal function and renal fibrosis (RF) in chronic kidney disease (CKD) patients.

Methods: A prospective analysis of 71 consecutive patients [no RF (0%): 9 cases; mild RF (<25%): 36 cases; moderate RF (25-50%): 17 cases; severe RF (>50%): 9 cases] who were clinically diagnosed with CKD that was pathologically confirmed and who underwent magnetic resonance imaging (MRI) examination between October 2021 and September 2022 was performed. T-C (mean cortical T value), T-M (mean medullary T value), ΔT (mean corticomedullary difference) and T% (mean corticomedullary ratio) values were compared. Correlations between T parameters and clinical and histopathological values were analyzed. Regression analysis was performed to determine independent predictors of RF. The areas under the receiver operating characteristic curve (AUC) were calculated to assess the diagnostic value of RF.

Results: The T-C, ΔT and T% values (P<0.05) were significantly different in the CKD group, but T-M was not (P>0.05). The ΔT and T% values showed significant differences in pairwise comparisons among CKD subgroups (P<0.05) except for CKD 2 and 3. ΔT and T% were moderately correlated with the estimated glomerular filtration rate (ΔT: r=-0.561; T%: r=-0.602), serum creatinine (ΔT: r=0.591; T%: r=0.563), blood urea nitrogen (ΔT: r=0.433; T%: r=0.435) and histopathological score (ΔT: r=0.630; T%: r=0.658). ΔT and T%, but not T-C, were independent predictors of RF (P<0.05). ΔT and T% were set as -410.07 ms and 0.8222 with great specificity [ΔT: 91.7% (77.5-98.2%); T%: 97.2% (85.5-99.9%)] to identify mild RF and moderate-severe RF. The optimal cutoff values for differentiating severe RF from mild-moderate RF were -343.81 ms (ΔT) and 0.8359 (T%) with high sensitivity [both 100% (66.4-100%)] and specificity [ΔT: 90.6% (79.3-96.9%); T%: 94.3% (84.3-98.8%)].

Conclusions: ΔT and T% overwhelm T-C for assessment of renal function and RF in CKD patients. ΔT and T% identify patients with <25% and >50% fibrosis, which can guide clinical decision-making and help to avoid biopsy-related bleeding.