| Objective:This study was to investigate the value of 3.0T blood oxygen level-dependent magnetic resonance imaging?BOLD MRI?and diffusion kurtosis imaging?DKI?in the assessment of contrast-induced acute kidney injury?CIAKI?oxygenation status and microstructure changes in pig kidney.Methods:Seven Bama suckling pigs weighing 80-90 Kg were fasted and watered for 12hours before the start of the experiment.After successful anesthesia,the first MR routine and BOLD MRI and DKI examinations were performed on a 3.0T magnetic resonance scanner?Achieva TX,Philips Healthcare,Best,the Netherlands?.At the end of the first examination,the CIAKI was induced by injecting an iodine contrast agent?ioversol,320 mgI/mL?into the ear vein of the pig.And the injection rate was 3mL/s with a dose of 6mL/kg.After infusion of iodine contrast agent,MR routine sequence and BOLD MRI and DKI examinations were performed again.The BOLD MR images were sent to the post-processing workstation EWS,and the renal cortical R2*values and medulla R2*values were measured and calculated.The IVIM v3.2software was used to post-process DKI images and measure cortical MK and MD values and medulla MK and MD values.Paired sample t-test was used to compare the differences in parameters of renal cortex and medulla before and after injection of iodine contrast agent within groups and between groups.P<0.05 was considered statistically significant.At the end of the second MRI examination,the Bama pigs were sacrificed and their kidneys were prepared for sectioning and HE staining,and histopathological changes were observed under a 400-fold light microscope.Results:1?There was no significant difference in R2*value,MK value and MD value between the left and right renal cortex before and after the injection of iodine contrast agent?all P>0.05?.There was no significant difference in R2*value,MK value and MD value between the left and right renal medulla before and after the injection of iodine contrast agent?all P>0.05?.2?Before and after the injection of iodine contrast agent,the R2*value and MK value of medulla in pig kidney were higher than those in the same side cortex,and the differences were statistically significant?all P<0.05?.Before and after the injection of iodine contrast agent,the MD value of porcine kidney cortex was higher than that of medulla,and the difference was statistically significant?both P<0.05?.3?The R2*value of medulla after injection of iodine contrast agent was higher than that before injection,which were?45.74±2.86?1/s and?41.00±2.97?1/s respectively,and the difference was statistically significant?P<0.05?.The cortical R2*value after injection of iodine contrast agent was lower than that before injection,which were?17.83±2.60?1/s and?19.80±2.39?1/s,respectively,and the difference was statistically significant?P<0.05?.4?The MK value of medulla after iodine contrast agent injection were lower than those before injection,which were?0.72±0.02?and?0.86±0.03?respectively,and the difference was statistically significant?P<0.05?.The cortical MK values after iodine contrast agent injection were lower than those before injection,which were?0.62±0.03?and?0.69±0.02?respectively,and the difference was statistically significant?P<0.05?.The MD value of medulla after injection of iodine contrast agent was higher than that before injection,which were?2.93±0.29?×10-3mm2/s and?2.75±0.33?×10-3mm2/s respectively,and the difference was statistically significant?P<0.05?.The cortical R2*value after injection of iodine contrast agent was lower than that before injection,which were?3.04±0.30?×10-3mm2/s and?3.18±0.37?×10-3mm2/s respectively,and the difference was statistically significant?P<0.05?.5?After injection of ioversol,we can see the renal tubular cells turbid swelling,vacuole formation,brush edge disintegrating off,and in renal tubular cavity we can find shedding cell debris,renal interstitial edema.No obvious abnormalities were observed in the glomerular.Conclusion:1?BOLD MRI and DKI were viable in normal and CIAKI pig kidneys.2?There was no significant difference in measured values between the left and right kidneys,suggesting that oxygen partial pressure and the microstructure of the kidneys on both sides were similar.The R2*value and MK value of normal porcine kidney medulla were higher than that of the cortex,and MD value of cortex was higher than that of the medulla.It is suggested that under normal physiological conditions,the medulla of the kidney has a lower oxygen partial pressure and more complex microstructure than the cortex.3?After iodine contrast agent injection,the R2*value of the medulla was significantly higher and the cortical R2*value was significantly lower than that of the normal pig kidney before injection.This indicated that the content of deoxyhemoglobin in the medulla was increased?the oxygen content was decreased?and the content of cortical deoxyhemoglobin was decreased?the oxygen content was increased?after iodine contrast agent injection;MK values of the cortex and medulla were significantly decreased and MD values of the medulla were significantly increased,suggesting that kidney especially the medullar microstructures were damaged after iodine contrast agent injection.4?3.0T BOLD MRI and DKI combined imaging can detect and evaluate the changes of cortical and medulla oxygenation levels and microstructural changes in kidneys of CIAKI pigs at an early stage.To some extent,changes in R2*value,MK value and MD value can reflect renal pathological lesions. |
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