Intravoxel incoherent motion diffusion weighted imaging in the assessment of the renal functional alternation in contrast-induced acute kidney injury models

Objective: To demonstrate that intravoxel incoherent motion (IVIM) imaging can assess temporal renal functional changes in contrast-induced acute kidney injury (CI-AKI). Methods: Twenty-seven male Sprague-Dawley (SD) rats with weight of 200 to 250 g were injected with meglumine diatrizoate (370 mg/ml, 6 ml/kg body weight) to induced CI-AKI. Six rats were randomly selected and imaged at 24 h prior to and at 30 min, 12 h, 24 h, 48 h, 72 h and 96 h after injection, and three rats were sacrificed for histological analysis at each time point. The coronal MR imaging of right kidney was analyzed. The IVIM parameters (D^* and f) from regions of cortex (CO), outer medulla (OM), and inner medulla (IM) were obtained and compared with the pathologic findings. We used Two way repeated measures ANOVA for statistical analysis. Results: At 24 h prior to the injection, the ADC value for CO was (1.74±0.06)×10^-3 mm²/s, and then decreased to (1.59±0.06)×10^-3 mm²/s at 30 min after the injection (P=0.014). The D value for CO was (1.63±0.05)×10^-3 mm²/s, and then decreased to (1.58±0.06)×10^-3 mm²/s at 30 min after the injection (P<0.05). In the CO, a progressive reduction was observed in D and ADC from 24 h to 48 h, and a progressive increase starting from 72 h, while a later changed pattern was found in OM and IM, where D and ADC values decreased until 72 h, followed by a progressive increase starting from 96 h. D^* decreased in CO, OM and IM early at 30 min and to the bottom at 24 h. The recovery for D^* was found at 48 h. A significant decrease was shown for f in both the cortex and medullar in an early stage of CI-AKI (12 to 48 h) and then ascend in the later stage (72 to 96 h), which was later than D^* in CO and OM. The HE staining were obtained fully and serial pathological change in different degree could be seen including tubule epithelial cells and glomerulus cells cloudy swelling, atrophy, even necrosis and interstitial vasodilator. Conclusion: IVIM DWI techniques is useful to demonstrate temporal renal functional alteration of CI-AKI.