[Value of magnetic resonance imaging texture analysis in evaluating renal allograft injury].

Objective: To explore the value of magnetic resonance imaging (MRI) texture analysis in evaluating renal allograft injury. Methods: A retrospective review was performed on sixty-six patients who underwent allograft renal transplantation (42 males, 24 females; age range, 22-63 years; mean age, (40±10) years) between November 2013 and December 2016. All the patients were divided into three groups according to their eGFR on the day of MRI examination: normal renal allograft function (nRAF) group (n=15), mild to moderate renal allograft injury (mRAI) group (n=18), and severe renal allograft injury (sRAI) group (n=33). All the patients underwent conventional T(2) weighted image (T(2)WI), susceptibility weighted imaging (SWI), and blood-oxygen level dependent (BOLD) MRI examination. MRI texture features of renal allograft were extracted. The texture features based on T(2)WI, SWI, and BOLD with absolute correlation coefficient of eGFR greater than or equal to 0.3 (P<0.05)and also with the highest Z value for Boruta algorithmwere selected. The diagnostic performance of the selected texture features in differentiating the three groups was assessed by receiver operating characteristic (ROC) curve analysis. Results: T(2)WI_Perc.50%, SWI_Perc.01%, BOLD_S(4,4)Contrast, and BOLD_S(5,5)Correlat with absolute correlation coefficient of eGFR greater than or equal to 0.3 (P<0.05) and also with the highest Z value for Boruta algorithm were selected. The AUC for T(2)WI_Perc.50%, SWI_Perc.01%, and BOLD_S(5,5)Correlat in differentiating the nRAF group with the mRAI group was 0.785, 0.720, and 0.700. The AUC for T(2)WI_Perc.50%, SWI_Perc.01%, BOLD_S(4,4)Contrast, and BOLD_S(5,5)Correlat in differentiating the nRAF group with the sRAI group was 0.687, 0.733, 0.784, and 0.737.The AUC for BOLD_S(4,4) Contrast in differentiating the mRAI group with the sRAI group was 0.667. Conclusion: MRI texture analysis can provide valuable information for evaluating renal allograft injury.

[Feasibility of susceptibility weighted imaging in the evaluation of renal fibrosis induced by unilateral ureteral obstruction in white rabbits].

Objective: To evaluate the feasibility of susceptibility weighted imaging (SWI) to reflect the progression of renal fibrosis (RF) induced by unilateral ureteral obstruction (UUO) in rabbits. Methods: Total of 32 New Zealand white rabbits (aged 4-5 months) were used to establish the UUO model (RF group) and were divided into 4 subgroups (including RF-2W group, RF-4W group , RF-6W group and RF-8W group) according to the duration of obstruction(2, 4, 6 and 8 weeks). Another 8 rabbits, underwent sham operation, were used as the control group (Sham group). T2 weighted imaging (T(2)WI) and SWI sequences were performed on the rabbits at 2, 4, 6 and 8 weeks after UUO, respectively. Rabbits were sacrificed and specimens were obtained after MR examination, then hematoxylin&eosin staining and Masson staining were performed to explore the renal tubular injury and interstitial fibrosis. The relationship between the relative signal-to-noise ratio(rSNR)measured on the SWI fusion maps and the degree of renal fibrosis was analyzed. Analysis of variance was used to compare the difference of rSNRs among 5 groups. Results: The rSNRs of the inner medulla gradually decreased over time, the rSNRs of Sham group, RF-2W group, RF-4W group, RF-6W group and RF-8W group was 2.29±0.18, 1.73±0.30, 1.67±0.08, 1.42±0.28, 1.12±0.15, respectively (F=25.876, P<0.01). In RF-2W group, the rSNRs of the outer medulla and cortex increased when compared with those in the Sham group, then they decreased gradually over time in the other groups (F=5.230, 7.621, both P<0.05). The pathological results demonstrated that the morphology of renal tubules in Sham group was normal and no apoptosis or necrosis was seen in the tubular epithelial cells. In the RF-2W group, the main pathological manifestations included renal tubules dilatation, tubular epithelial cell degeneration or necrosis and the infiltration of inflammatory cell. In Masson staining, lots of blue areas were present in the interstitial. As the obstruction time prolonged, the renal tubular collapse, inflammatory cells and fibroblasts increased significantly. Meanwhile blue area also increased significantly in Masson staining. Conclusion: SWI can be used as a noninvasive method to evaluate the pathological progression of fibrosis in the rabbit UUO model.

[Feasibility of using blood oxygen level-dependent magnetic resonance imaging to evaluate renal fibrosis of ureteral obstruction of rabbits].

Objective: To investigate the feasibility of blood oxygen level-dependent MR (MR-BOLD) in assessing renal fibrosis of ureteral obstruction of rabbits. Methods: Forty healthy New Zealand rabbits were randomly divided into control group (n=8) and unilateral ureteral obstruction (UUO) group (n=32). The rabbits in the UUO group were subjected to unilateral ureteral obstruction of the left kidney.Coronal T(2) weighted imaging (T(2)WI) and axial BOLD examinations were performed before operation, 2, 4, 6 and 8 W after operation (each subgroup n=8). After the examinations, nephrectomy was performed for histologic evaluation.The T(2)(*) relaxation rate of the renal cortex (CR(2)(*)) , medulla (MR(2)(*)) and the same level of muscle(R(2)(*)(muscle)) were measured separately.The normalization of the cortex and medulla (sR(2)(*)), and the difference of sR(2)(*) between renal cortex and medulla before and post UUO (ΔsR(2)(*)) were calculated.The differences of sR(2)(*) (sCR(2)(*), sMR(2)(*), sCR(2)(*)(control), sMR(2)(*)(control)) at each time point between control and UUO group were compared by using independent sample t test.The LSD test was used to compare the sR(2)(*) in the control with that in the UUO group.The ΔsCR(2)(*) and ΔsMR(2)(*) values of the subgroups at UUO 2, 4, 6 and 8 W were compared by independent sample t test. Results: The sR(2)(*) values of UUO group were all lower than those of control group (all P<0.05), while sR(2)(*)(control) and sR(2)(*) in UUO group before operation were not significant different (P>0.05). The sCR(2)(*) values of UUO 2, 4, 6 and 8 W were 0.32±0.01, 0.37±0.01, 0.47±0.02 and 0.50±0.03.The sMR(2)(*) values were 0.39±0.02, 0.48±0.02, 0.58±0.04 and 0.65±0.05.There were significant differences of sCR(2)(*)(between) UUO 2 W and 6 W, UUO 2 W and 8 W, UUO 4 W and 6 W, UUO 4 W and 8 W (all P<0.01). There were significant differences of sMR(2)(*)(between) UUO 2 W and 6 W, UUO 2 W and 8 W, UUO 4 W and 8 W (all P<0.01). No significant difference was founded between sCR(2)(*) and sMR(2)(*) at each time point in control group (P>0.05). The ΔsCR(2)(*) values of UUO 2, 4, 6 and 8 W were 0.31±0.02, 0.20±0.02, 0.14±0.20, 0.09±0.04; the ΔsMR(2)(*) values were 0.51±0.05, 0.36±0.04, 0.28±0.05, 0.19±0.05. The ΔsCR(2)(*) values of UUO 2, 4 and 6 W were less than ΔsMR(2)(*) (P<0.05). There was no significant difference between ΔsCR(2)(*) and ΔsMR(2)(*) in UUO 8 W (P>0.05). Conclusions: The R(2)(*) change in medulla resulted from renal fibrosis is more significant than cortex.MR-BOLD can reflect the process of renal fibrosis.It's feasible and of great value to use renal MR-BOLD for the assessment of renal fibrosis induced by unilateral ureteral obstruction.

[Correlation between susceptibility weighted imaging manifestation and serum cystatin C for delayed graft function].

OBJECTIVE: To explore the correlation between susceptibility weighted imaging (SWI) manifestation and serum cystatin C level for delayed graft function (DGF). METHODS: The conventional MRI, SWI and serum cystatin C of 27 cases with DGF in nephrotransplantation center in Third Affiliated Hospital of Suzhou University from September 2014 and August 2015 were retrospectively analyzed.By contrasting conventional MRI images of transplanted kidney in DGF, the imaging manifestations of benign tumors such as cysts and angiomyolipomas were excluded on SWI images, and then making the renal cortex as the reference, if the abnormal signal lesions were found in the transplanted kidney, the location and signal intensity would be analyzed. The differences in serum cystatin C level between DGF groups without and with abnormal signal lesions were compared by using independent-sample t-test.The correlation between SWI manifestation and serum cystatin C level for DGF was assessed with Spearman rank correlation analysis. RESULTS: A total of 15 cases were found without abnormal signal lesions and the average value of their serum cystatin C level was (2.92±0.44) mg/L.A total of 12 cases were found with abnormal low signal lesions located at junctional zone between cortex and medulla, and the average value of their serum cystatin C level was (6.91±0.96) mg/L. The differences in serum cystatin C level between the two DGF groups were statistically significant (t=-4.040, P=0.000). There was a positive correlation between the abnormal low signal lesions on SWI and serum cystatin C level (r=0.660, P=0.000). CONCLUSION: The status of renal function impairment could be reflected by being with or without abnormal signal lesions on SWI. A relatively big renal function impairment may be predicted by the appearance of abnormal low signal lesions at junctional zone between cortex and medulla on SWI.