Magnetic resonance diffusion tensor imaging is superior to arterial spin labeling in detecting renal allograft fibrosis

Abstract

Background: Although both magnetic resonance (MR) diffusion tensor imaging (DTI) and arterial spin labeling (ASL) have been demonstrated to be useful for the assessment of renal allograft fibrosis, their diagnostic value for renal allograft fibrosis is rarely compared. In this study, we collected a relatively large sample size to compare the value of DTI and ASL in the assessment of renal transplantation (RT) fibrosis.

Methods: This study included 141 kidney transplant recipients who underwent DTI, ASL, and biopsy. The renal allograft fibrosis was divided into ci0, ci1, ci2, and ci3 fibrosis groups according to the biopsy results. The apparent diffusion coefficient (ADC), fractional anisotropy (FA), and renal blood flow (RBF) were calculated. One-way analysis of variance (ANOVA) was used to compare the differences of functional magnetic resonance imaging (MRI) parameters between different fibrosis subgroups. The area under the receiver operating characteristic curve (AUC) was calculated to evaluate diagnostic performance.

Results: The medullary FA values in ci2 (0.27±0.04, P<0.001) and ci3 (0.21±0.03, P<0.001) groups were significantly lower than those in ci0 group (0.31±0.05). The medullary FA value in ci3 group (0.21±0.03) was significantly lower than that in ci1 group (0.30±0.07, P<0.001) and ci2 group (0.27±0.04, P<0.01). The AUC of DTI was found to be higher than that of ASL in accurately identifying renal allograft fibrosis, and the result was statistically significant in differentiating ci0-2 group and ci3 group (ci0 vs. ci1-3, 0.725 vs. 0.712, P>0.05; ci0-1 vs. ci2-3, 0.787 vs. 0.735, P>0.05; ci0-2 vs. ci3, 0.945 vs. 0.802, P<0.05).

Conclusions: DTI has a higher diagnostic value than ASL in noninvasive identification of the degree of renal allograft fibrosis.

Keywords: Renal transplantation (RT); diffusion; fibrosis; perfusion.

Figure 1

Relations between functional MRI parameters and the Banff fibrosis score. Scatterplots show negative relations between (A) cortical FA and Banff fibrosis score, (B) medullary FA and Banff fibrosis score, (C) cortical ADC and Banff fibrosis score, (D) medullary ADC and Banff fibrosis score, (E) RBF and Banff fibrosis score. MRI, magnetic resonance imaging; FA, fractional anisotropy; ADC, apparent diffusion coefficient; RBF, renal blood flow.

Figure 2

Comparison of functional MRI parameters among fibrosis score groups. *, **, and *** indicate P<0.05, P<0.01, and P<0.001, respectively. ci0, no fibrosis (<5% of cortex occupied by fibrosis); ci1, mild fibrosis (5–25% of cortex occupied by fibrosis); ci2, moderate fibrosis (26–50% of cortex occupied by fibrosis); ci3, severe fibrosis (>50% of cortex occupied by fibrosis). MRI, magnetic resonance imaging; ADC, apparent diffusion coefficient; FA, fractional anisotropy; RBF, renal blood flow.

Figure 3

Comparison of DTI and pathological findings. (A-F) A 17-year-old woman with no fibrosis (ci0), while panels (G-L) are from a 42-year-old man with moderate fibrosis (ci2). (A,G) T2-weighted images; (B,H) b0 images; (C,I) ADC maps; (D,J) FA maps; (E,K) hematoxylin-eosin; (F,L) periodic acid-silver methenamine. ci0, no fibrosis (<5% of cortex occupied by fibrosis); ci2, moderate fibrosis (26–50% of cortex occupied by fibrosis). ADC, apparent diffusion coefficient; DTI, diffusion tensor imaging; FA, fractional anisotropy; HE, hematoxylin-eosin; PASM, periodic acid-silver methenamine.

Figure 4

Comparison of RBF derived from ASL and pathological findings. (A-C) A 56-year-old woman with mild fibrosis (ci1); (D-F) a 43-year-old woman with severe fibrosis (ci3). (A,D) RBF maps; (B,E) periodic acid-Schiff; (C,F) periodic acid-silver methenamine. ci1, mild fibrosis (5–25% of cortex occupied by fibrosis); ci3, severe fibrosis (>50% of cortex occupied by fibrosis). RBF, renal blood flow; ASL, arterial spin labeling; PAS, periodic acid-Schiff; PASM, periodic acid-silver methenamine.