Quantitative evaluation of renal injury in the early diabetic nephropathy with quantitative susceptibility mapping / 中华放射学杂志

Objective:To explore the value of quantitative susceptibility mapping (QSM) in evaluating renal injury in patients with early diabetic nephropathy (DN).Methods:From October 2019 to December 2020, 32 patients with early DN were prospectively enrolled in the Third Affiliated Hospital of Soochow University. According to the estimated glomerular filtration rate (eGFR), they were divided into three groups: DN1 (eGFR≥90 ml·min -1·1.73 m -2, 11 cases), DN2 (60-<90 ml·min -1·1.73 m -2, 11 cases) and DN3 (30-<60 ml·min -1·1.73 m -2, 10 cases). At the same time, 32 normal volunteers were recruited as the control group. Both kidneys were scanned by QSM to measure the susceptibility of renal cortex and medulla. Paired samples t-test was used to compare the differences of the susceptibility between left and right kidneys and between cortex and medulla. One-way analysis of variance was performed to compare the differences of corresponding susceptibility values among different groups, and LSD- t was used for the pairwise comparison. Pearson correlation test was performed between the susceptibility value of the medulla and eGFR. The ROC curve was used to analyze the diagnostic efficacy of QSM parameters in the diagnosis of DN and different degrees of severity of DN. Results:The susceptibility values of bilateral renal medulla in normal volunteers and patients with DN were lower than those of renal cortex (all P<0.001). There was no significant difference in the susceptibility value between left and right renal cortex (all P>0.05). There was significant difference in the susceptibility value between left and right medulla (all P<0.05). There was no significant difference in the susceptibility value of bilateral renal cortex among the control group and the DN1－DN3 groups (both P>0.05). The susceptibility values of left renal medulla in control group, DN1, DN2 and DN3 groups were (-4.46±1.16)×10 -2, (-5.96±0.97)×10 -2, (-7.97±1.25)×10 -2, (-9.58±1.45)×10 -2 ppm, of right renal medulla were (-3.70±0.65)×10 -2, (-5.06±1.28)×10 -2, (-7.33±1.46)×10 -2, (-9.09±2.22)×10 -2 ppm, respectively. The overall difference of the susceptibility value of bilateral renal medulla was statistically significant (both P<0.05), and there were significant differences between each two groups (all P<0.05). The linear positive correlation were found between the susceptibility values of renal medulla and the corresponding eGFR (left kidney r=0.732, P<0.001; right kidney r=0.684, P<0.001). The areas under the ROC curve (AUC) of left and right renal medulla susceptibility value in diagnosis of normal and DN were 0.931 and 0.943, of DN1 and DN (2 and 3) were 0.952 and 0.883, of DN (1 and 2) and DN3 were 0.888 and 0.831, respectively. Conclusion:The susceptibility value of QSM quantitative parameter has a certain value in the staging and differential diagnosis of early DN, among which the susceptibility value of renal medulla has higher diagnostic efficiency.

Initial study on quantitative evaluation of iron load in diabetic kidneys using susceptibility-weighted imaging / 中华放射学杂志

Objective:To explore the value of susceptibility-weighted imaging (SWI) in quantitative evaluation of iron load in diabetic kidneys.Methods:Thirty two healthy New Zealand white rabbits were randomly divided into diabetic group (DM, n = 20) and control group (NC, n = 12). DM model was established by injecting 5% alloxan solution (100 ml/kg) through ear vein. 12 rats were finally enrolled into the group. NC group was injected with the same dose of normal saline. DM group and NC group were intramuscularly injected with 60 mg/kg iron dextran. The left kidney was scanned by MRI immediately after iron injection (0 weeks) and 12 weeks after feeding. The left kidney was killed after 12 weeks of scanning. The left kidney was examined by Prussian blue staining and atomic absorption spectrophotometer. The value of SWI in quantitative evaluation of renal iron content was evaluated by using the iron content measured by atomic absorption spectrophotometer as the gold standard. On SWI phase diagram, the region of interest (ROI) was manually drawn along the renal cortical vagal area, and the measured phase values were converted into angular radians. Mann Whitney U test was used to compare the blood glucose value and the angle radian value at 0 week and 12 week between the two groups; independent sample t test was used to compare the difference of iron content between the two groups; nonparametric Wilcoxon signed rank test was used to compare the difference of angle radian between DM group and NC group at 0 and 12 weeks; Spearman correlation analysis was used to study the correlation between angle radian value and atomic absorption spectrophotometer results. Results:The blood glucose level in DM group [28.0 (10.6) mmol/L] was significantly higher than that in NC Group [6.5 (1.9) mmol/L], and the difference was statistically significant (U = 0, P<0.001). At week 0, there was no significant difference between DM group [-0.04 (-0.02)] and NC Group [-0.02 (0.06)] in angle radian value (U=105.50, P>0.05); at 12 weeks, the angle radian value of DM group [0.22 (0.17)] was higher than that of NC Group [0.17 (0.05)], the difference was statistically significant (U=35.50, P<0.05). The angle radian of DM group and NC group at 12 weeks were higher than that of 0 weeks, and the differences were statistically significant ( P<0.05). Prussian blue staining showed that iron was mainly deposited in renal cortex, and the blue staining in DM group was more obvious than that in NC group. The signal intensity of renal cortex on SWI images in DM group was significantly lower than that in 0 week group at 12 weeks, and slightly decreased in NC group. The iron content of DM group and NC group were (171.39±20.13) mg/kg and (116.21±28.90) mg/kg, respectively, and the difference was statistically significant ( t=5.428, P<0.001). Spearman correlation analysis showed that the angle radian was positively correlated with iron content ( r=0.67, P<0.001). Conclusions:Diabetic kidneys have more iron deposits than normal kidneys. As a non-invasive, simple and convenient examination technique, SWI has the potential to quantitatively evaluate the iron load of diabetic kidneys.

Feasibility of using T2*mapping to quantitatively evaluate ischemia-reperfusion injury / 中华放射学杂志

Objective@#To explore the feasibility of evaluating renal ischemia-reperfusion injury (IRI) at different time by using T2*mapping.@*Methods@#Eighteen New Zealand white rabbits were used to build therenal IRI injury model by blocked the left renal arteries and veins by using noninvasive arterial clip, left renal ischemia-reperfusion was performed by clamping of the left renal pedicle for 60 minutes, followed by reperfusion. All the rabbits underwent MRI examination including axial T2WI and T2*mapping before scanning and 1 h, 12 h, 24 h and 48 h after reperfusion. Every two rabbits were randomly sacrificed at 1 h, 12 h, and 24 h after reperfusion. The rest of the rabbits were sacrificed for pathological examination at 48 h after reperfusion. All specimens were cut into slices and stained with hematoxylin-eosin (HE). The values of T2*, R2* and the pathological scores of cell edema, cell necrosis, interstitial inflammation and tubular castin renal tissues at different time points were measured. Repetitive measurement deviation analysis was performed to compare difference of T2* and R2* at 5 time-points. The relationship between the value of T2* and R2* in renal tissues and the scores of cell edema, cell necrosis, interstitial inflammation and tubular castin renal tissues was analyzed by Spearman correlation analysis.@*Results@#T2* value and R2* value in both inner medulla and outer medulla were statistically significant (P<0.05), while there was no statistically significant in the cortex (P>0.05).Pairwise comparison of T2* and R2* at different time points in the cortex showed statistically significant difference between before and 24 h,before and 48 h, 12 h and 48 h were statistically significant (P<0.05), while the remaining were no statistically significant difference (P>0.05).T2* value of the outer medullar after IRI positively correlated with the scores of cell edema, interstitial inflammation and tubular castin renal tissues (r values were 0.57, 0.38, 0.33; P<0.05). R2* value of the outer medullar after IRI negatively correlated with the scores of cell edema (r value was -0.52, P<0.05).@*Conclusion@#T2* mapping could reflect the dynamic changes in different zones and different time points after renal IRI, especially in the outer medullary band which has good consistency with pathological score.

Value of histogram analysis of susceptible signal intensity in differentiating papillary from chromophobe renal cell carcinoma / 中华放射学杂志

Objective To evaluate the feasibility of histogram analysis of susceptible signal intensity in differentiating papillary (pRCC) from chromophobe renal cell carcinoma(ChRCC). Methods Thirteen cases with pRCC and 9 cases with ChRCC, who underwent susceptible-weighted imaging(SWI), MR common scanning and enhancement, were assessed retrospectively. The histogram parameters of susceptible signal intensity were measured, including maximum, minimum, mean, median, skewness and kurtosis. The independent samples t test(normal distribution) and Mann-Whitney rank sum test(skewed distribution) were used to compare the differences in SWI parameters between pRCCs and ChRCCs. Receiver operating characteristic curve was used to evaluate the efficiency of the whole-tumor SWI parameters in differentiating pRCCs from ChRCCs. Results The significant differences of the minimum, mean, median and skewness between pRCCs and ChRCCs were present(P0.05). In all the histogram parameters, the area of ROC curve of mean value was largest(0.80). The sensitivity of minimum value (84.62％) was the highest and and the specificity of skewness(100.00％) was the highest. Conclusion Histogram analysis of susceptible signal intensity can help differentiate pRCCs from ChRCCs.

The value of susceptibility weighted imaging in evaluating ischemia-reperfusion injury of the rabbit kidney / 中华放射学杂志

Objective To explore the value of susceptibility weighted imaging (SWI) in the quantitative analysis of ischemia-reperfusion injury (IRI) of the rabbit kidneys . Methods Thirty New Zealand white rabbits were randomly assigned to IRI group (n=24, operation with clamping) and Sham group (n=6, operation without clamping). Left renal ischemia-reperfusion was performed by occlusion (calmping) of the left renal arterial for 60 minutes, followed by reperfusion. All the rabbits underwent MRI including T2WI and SWI before and 0.5 h, 12 h, 24 h and 48 h after the establishments of models . Three rabbits in IRI group were randomly sacrificed 0.5 h, 12 h, and 24 h after the establishment of model. The rest of the rabbits in IRI group and 6 rabbits in sham group were sacrificed for pathological examination 48 h after the establishment of model All specimen were cut into slices and stained with hematoxylin-eosin (HE). Region of interest ( ROI) was manually created by outlining the inner medulla, inner stripe of outer medulla, outer stripe of outer medulla, and cortex, then relative signal-to-noise ratio of the kidney (rSNR) to muscle in SWI sequence was recorded. and compared with histopathologic features. One-way ANOVA was performed to compare difference of rSNR to muscle in respective location at 5 time-points between Sham group and IRI group, and the differences between groups were tested using repetitive measure analysis of variance, repetitive measure analysis of variance was performed to compare difference of rSNR to muscle in respective location at respective time-points between Sham group and IRI group. Results rSNR value in the inner medulla 0.5 h, 12 h, 24 h and 48 h after the establishments of models were 0.28 ± 0.04, 0.98 ± 0.14, 0.69 ± 0.07, 0.57±0.06, 0.43±0.03, respectively (F=69.82,P<0.01), the inner stripe of outer medulla at the five time-points 0.08 ± 0.03, 0.57 ± 0.05, 0.32 ± 0.07, 0.16 ± 0.02, 0.04 ± 0.01, respectively(F=16.59,P<0.01), the outer stripe of outer medulla were 0.31 ± 0.04, 0.86 ± 0.09, 0.65 ± 0.07, 0.55 ± 0.06 0.43 ± 0.04(F=67.52,P<0.01), respectively,the cortex 0.05±0.01, 0.80±0.04, 0.68±0.07, 0.47±0.07, 0.36±0.08, respectively(F=118.96,P<0.01). The difference of the rSNR was statistically significant in the inner medulla, inner stripe of outer medulla, outer stripe of outer medulla, and cortex at the five different time-points. The differences between two groups were significant (F=206.29, 14.25, 42.8, 39.12, P all<0.05). The pathological findings in Sham group included normalglomerular structure l, clear cavity of tubular, no interstitial hyperemia and edema. The pathological findings in IRI group demonstated, at 0.5 h after IRI, Bowman's capsule cavity expansion, glomerular shrinkage, swelling of renal tubular epithelial cells, vacuoles degeneration, the tube cavity expansion, interstitial edema and congestion ecta became slender, andat 12 h after IR, Bowman's capsule expansion became more obvious, foam degeneration of renal tubular epithelial cells, apoptosis, partial loss of the brush border of the proximal convoluted tubule, formation of protein cast, and a small amount of inflammatory cells appeared in the renal interstitium, swelling of endothelial cells of the vasa recta, congestion of small vessels, and at 24 and 48 h after IRI, more serious injury of renal tubular in the outer stripe of outer medulla , massive necrosis of renal tubular epithelial cells, apoptosis, parts of the renal tubular had the contour lines, and renal tubular outline, increment in inflammatory cells, red cell and protein cast. Conclusion rSNR of SWI in the inner medulla, inner stripe of outer medulla, outer stripe of outer medulla, and cortex of the kidney varies with the degree of IRI over time, and is consistent with corresponding pathological feature, suggesting SWI is useful imaging tool to detect early damage of renal IRI quantitatively.