| Objective To investigate the diagnostic value of blood oxygen level-dependent(BOLD) MR imaging in renal ischemiareperfusion injury(IRI) of rabbit.Methods Forty-two New Zealand rabbits were randomly divided into three groups(IR1~3 group) and set up the model of IRI in the left kidney. The time of left renal artery occlusion in IR 1~3 group was respective40, 60 and80 minutes. Coronal T2 WI and blood oxygenation sensitive sequence were performed in Siemens verio 3.0 T MR scanner, using a 6-channel abdominal coil. Respectively, each rabbit was studied before IRI and at the time of 0.5, 12, 24 and 48 hours after reperfusion. At the same time, each rabbit was drawn one milliliter blood through saphenous vein. The R2* values of the renal outer stripe of outer medulla(outer stripe of outer medulla, OSOM) layer and left psoas muscle were measured, then calculated the R2* value ratio(rR2*=R2*OSOM/R2*muscle) and compared the difference of rR2* between before and after IRI(△ rR2*=pre IRI rR2*-post IRI rR2*). The serum creatinine concentration was tested by Sarcosine oxidase. The differences of each group about △ rR2* values and serum creatinine concentrations were compared with Single factor analysis of variance(one-way ANOVA) test. LSD test was used to compare the differences of △ rR2* values and serum creatinine concentrations between IR 1~3 groups at each scanning time. P<0.05 was considered statistically significant in all tests.Results 1. The rR2* values of IR1~3 after IRI were overall higher than before IRI. The highest value of △ rR2* of left renal OSOM in IR1 was at the time of reperfusion 0.5 hour, and then decreasedgradually. The △ rR2* value of 0.5 hour after reperfusionwas higher than that of 24 and 48 hours, the difference was significant(P<0.05). The △ rR2* values of IR2 and IR3 at every scanning time were substantially the same. The highest value of △ rR2* in IR2 and 3 were at the time of reperfusion 0.5 hour, and then declined gradually, but increased againat the time of reperfusion 48 hours. There was statistically significant difference only between reperfusion 0.5 and 24 hours, whilethe values of △ rR2* at reperfusion0.5, 12 and 48 hours showed no significant difference. At the time of reperfusion 0.5 hour, the values of △ rR2* were increased in all groups, and IR1 were significantly higher than IR2 and IR3(P<0.05), but the difference between IR2 and IR3 was not statistically significant(P>0.05). At the time of reperfusion 48 hours, the value of △ rR2* of IR1 was lower than IR2 and IR3(P<0.05), while IR2 and IR3 showed no significant difference(P>0.05). At the time of reperfusion 12 and 24 hours, the values of △ rR2* of IR1~3 showed no significant difference(P>0.05).2. The trend of Scr increased first and then declined in IR 1~3 after IRI. At the time of reperfusion 0.5 hour, Scr increased most significantly. After a gradual decline, atthe time of reperfusion 48 hoursScr returned to baseline in all groups. There was no significant difference of Scr between before and after IRI(P>0.05), for all Scrs of IR 1~3 were less than the upper limit in normalrabbit.Conclusions 1. The longer renal ischemic time, the heavier renal IRI. 2. When renal ischemic time is over 60 minutes, the degree of renal IRI has reached to maximum level. 3. MR BOLD imaging can noninvasively reflect the degree of blood oxygen level of renal outer stripe of outer medullary and indirectly reflect the trend between renal ischemic time and the degree of IRI, that will help the detection of renal IRI. |
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