ABSTRACT
Objective:To explore the relationship between MRI texture features with the histopathology in early renal ischemia-reperfusion injury (IRI).Methods:Forty-eight healthy New Zealand rabbits were randomly divided into the IRI group ( n=40) and the sham group ( n=8). As for the IRI group, rabbits underwent the left kidney surgery by clamping the left renal artery for 60 mins and then releasing the clamp to establish renal IRI model. The rabbits in the sham group underwent the same operation, but without clamping the left renal artery. MR examination were performed before and at 1 h, 12 h, 24 h, and 48 h after the operations. As for the IR group, eight rabbits were randomly sacrificed at each time point immediately after MR exam. The eight rabbits in the sham group were sacrificed after MR exam at 48 h after the operation. The left kidney was harvested for histopathological examination. The single item score of the histopathological features, the microvessel density (MVD), and the pathological total score were calculated. Differences in the single item score of the histopathological features, MVD, and the pathological total score among IRI group with different time points and sham group were determined using the Kruskal-Wallis test. MRI texture features of the left kidney were extracted. Multiple dimensionality reduction for MRI texture features were performed, and the features associated with the pathological total score were selected. The relationship between MRI texture features with the single item score of the histopathological features and MVD was assessed by Pearson correlation coefficients. Results:There were significant differences in renal tubular brush border destruction, renal tubular epithelial edema, necrosis, cast, interstitial inflammatory cell infiltration, MVD, and the pathological total score in IRI group among the different time points (all P<0.05). T 2WI_S (3, -3) InvDfMom had the highest correlation with renal tubular brush border destruction, renal tubular epithelial edema, necrosis, and cast ( r=0.56, -0.58, 0.62, 0.69, all P<0.01). BOLD_S (4, -4) Correlat had the highest correlation with interstitial inflammatory cell infiltration ( r=0.63, P<0.01). SWI_S (4, 4) DifEntrp had the highest correlation with MVD ( r=0.61, P<0.01). Conclusion:MRI texture analysis can provide valuable information for evaluating early renal IRI.
ABSTRACT
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.
ABSTRACT
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.
ABSTRACT
Objective To explore the value of abnormal imaging findings on susceptibility weighted imaging (SWI) in delayed graft function (DGF). Methods The conventional MRI and SWI images of 26 cases with DGF and 20 cases with normal renal function of transplanted kidneys were retrospectively analyzed. Patients with cysts and angiomyolipomas were excluded. Normal structures of transplanted kidney were identified. If lesions of abnormal signal intensity were found in the transplanted kidney, the location, border and signal intensity compared to renal cortex would be analyzed. The differences in signal intensity between the abnormal signal lesions and normal renal cortex in the same SWI layer of DGF were compared by using independent-sample t test. The differences in positive detection rate of discovering the abnormal signal lesions in DGF between conventional MRI and SWI were compared by using McNemar test. Results Of the 26 cases with DGF, one case was found to exhibit abnormally low signal lesions with fuzzy boundary located at junctional zone between cortex and medulla on both conventional MRI and SWI images. Ten cases were found to exhibit abnormally low signal lesions with fuzzy boundary located at junctional zone between cortex and medulla on SWI images only. Fifteen cases exhibited no abnormal signal lesions on both conventional MRI and SWI images. Twenty cases with normal renal function of transplanted kidney, no abnormal signal lesions were found on both conventional MRI and SWI images. The differences in signal intensity between the abnormally low signal lesions (130±20) and normal renal cortex (177±25) in the same SWI layer of 11 cases with DGF were statistically significant (t=-4.582,P<0.01). The differences in positive detection rate of discovering the abnormally low signal lesions in DGF between conventional MRI [3.8%(1/26)] and SWI [42.3% (11/26)] were statistically significant (χ2=8.100,P=0.002). Conclusions Abnormally low signal lesions with fuzzy boundary located at junctional zone between cortex and medulla on SWI images suggest the presence of DGF. Compared with conventional MRI, SWI appears to be superior in detecting the abnormally low signal lesions.