To evaluate the damage of renal function in CIAKI rats at 3T: Using ASL and BOLD MRI
Yuhao Dong1, Wenbo Chen1, Long Liang1, Bin Zhang1, and Shuixing Zhang1

1Radiology, Department of Radiology, Guangdong Academy of Medical Sciences/Guangdong General Hospital, Guangzhou, Guangzhou, China, People's Republic of

Synopsis

Contrast induced acute kidney injury (CIAKI) is a common complication after the administration of contrast media. The universally acknowledged mechanisms of CIAKI are the ischemia-mediated oxidative stress as well as the arteriolar vasoconstriction resulted from sustained contrast-induced, hypoxia in cortex and medulla. Our study aims to investigate noninvasive arterial spin-labeling (ASL) and blood oxygen level-dependent imaging (BOLD) sequences for measuring renal hemodynamics and oxygenation in different time points and different sites of kidney after contrast media administration. The results showed that ASL combining BOLD can further identify the primary cause of the decrease of renal oxygenation in CIAKI, which provides means for noninvasive monitoring renal function during the first 4 days of CIAKI in clinical routine work.

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Abstract: Contrast induced acute kidney injury (CIAKI) is a common complication after the administration of contrast media. The universally acknowledged mechanisms of CIAKI are the ischemia-mediated oxidative stress as well as the arteriolar vasoconstriction resulted from sustained contrast-induced, hypoxia in cortex and medulla.(1,2,3) Our study aims to investigate noninvasive arterial spin-labeling (ASL) and blood oxygen level-dependent imaging (BOLD) sequences for measuring renal hemodynamics and oxygenation in different time points and different sites of kidney after contrast media administration. The results showed that ASL combining BOLD can further identify the primary cause of the decrease of renal oxygenation in CIAKI, which provides means for noninvasive monitoring renal function during the first 4 days of CIAKI in clinical routine work.

Target audience: Physicians interested in accurately assessing kidney diseases using noninvasive MRI techniques.

Purpose: To investigate noninvasive arterial spin-labeling (ASL) and blood oxygen level-dependent imaging (BOLD) sequences for measuring renal hemodynamics and oxygenation in contrast induced acute kidney injury (CIAKI) rat model after the administration of iodinated contrast media (CM).

Materials and Methods: Animals. All procedures were approved by the local Research Ethics Committee. Rats were injected to receive ionic iodinated contrast agent (Meglumine Diatrizoate, 370mg/ml, 6 ml/kg) to induce CIAKI. MRI. Both BOLD MRI and ASL MRI were performed on CIN rats (n=6) before and after (0.5, 12, 24, 48, 72 and 96h time point) the onset using a GE 3T MRI scanner to detect the dynamic change.(4,5) The BOLD MRI was performed using BOLD-MFGRE sequence. ASL MRI was performed using an ASL-FAIR-SSFSE sequence. Renal blood flow (RBF) and Parametric images of T2* and R2* for cortex (CO), outer medulla (OM) and inner medulla (IM) were calculated using Functool-fair software provided by GE (Advantage Workstation 4.3 GE Medical System). Statistics. All results are reported as mean ± SD. Data were analyzed using SPSS 13.0 for Windows or GraphPad Prism V6.0. K independent and Mann–Whitney U test for further comparisons between specific group pairs were used. P<0.05 was used as the criteria for the statistical difference among groups. Biochemistry. Venous blood was obtained to measure the serum creatinine concentration.

Results: All the data of each rats were successfully recorded and both the RBF values and R2* values could be calculated from each time point (0.5, 12, 24, 48, 72 and 96h) (Figure 1), except for 3 rats sacrificed at 96h for narcotized. As shown in figure 2 and 3, the value of RBF in the cortex (CO) and outer medulla (OM) of the kidney were significantly decreased (P<0.05 vs. baseline, n=6) at 12 to 48 h, respectively, whereas those values at 72 to 96 h gradually regressed to approximately baseline level (P=NS vs baseline). As was shown in figure 4, the value of R2* in the OM of kidney were markedly increased at 0.5 to 48 h (P<0.05 vs. baseline, n=6), respectively; whereas the difference between those value at 72 and 96 h were not statistically significant (P=NS vs. baseline). There was no statistical significance in the mean RBF and R2* during the time course of our study, indicating that the changes were directly resulted from kidney injury. Serum creatinine was obtained to verify the renal injury, which changed relatively later than both the changes in R2* value and RBF value as was shown in Figure 5.

Discussion: Our study successfully employed noninvasive ASL and BOLD MRI to acquire high-quality images using 3.0T MRI clinical scanner, allowing the measurement of renal hemodynamics and oxygenation. Our results revealed a significant and prolonged decrease of RBF in OM and CO and also a decreased oxygen level in OM after CM injection, indicating that ASL and BOLD MRI are potentially useful in the clinic for noninvasive assessing of renal function in the case of CIAKI.

Conclusions: A decrease of RBF in OM and CO and oxygen level in OM were found post-injection of iodinated CM. ASL and BOLD sequence could obtain high-quality imaging, which allowed to measure renal hemodynamics and oxygenation in different structure of damaged kidney. ASL combining BOLD can further identify the primary cause of the decrease of renal oxygenation in CIAKI. This approach provides means for noninvasive monitoring renal function during the first 4 days of CIAKI in clinical routine work.

Acknowledgements

This study was funded by the National Scientific Foundation of China (81171329, 81571664) and the Science and Technology Planning Project of Guangdong Province, China (2014A020212244).

References

1. McCullough PA. Contrast-induced acute kidney injury. Journal of the American College of Cardiology 2008; 51: 1419-28.

2. Reed M, Meier P, Tamhane UU et al. The relative renal safety of iodixanol compared with low-osmolar contrast media: a meta-analysis of randomized controlled trials. JACC Cardiovascular interventions 2009; 2: 645-54.

3. McCullough PA, Brown JR. Effects of Intra-Arterial and Intravenous Iso-Osmolar Contrast Medium (Iodixanol) on the Risk of Contrast-Induced Acute Kidney Injury: A Meta-Analysis. Cardiorenal medicine 2011; 1: 220-34.

4. Neugarten J. Renal BOLD-MRI and assessment for renal hypoxia. Kidney international 2012; 81: 613-4. 5. Karger N, Biederer J, Lusse S et al. Quantitation of renal perfusion using arterial spin labeling with FAIR-UFLARE. Magnetic resonance imaging 2000; 18: 641-7.

Figures

Figure 1. Representative coronal MR image (A) and the R2* map (B) acquired using a BOLD sequence. Representative coronal MR image (C) the RBF map (D) acquired using an ASL sequence. The ROI putting on each kidney structure assembles the CO (1), OM (2), and IM (3).

Figure 2. Box plots of RBF values in CO showing that 50% of the values at 12h, 24h, 48h were lower than baseline.

Figure 3. Box plots of RBF values in OM implying that 50% of the values at 12 h, 24 h, 48 h were lower than baseline.

Figure 4. Box plots of R2* values in OM. The asterisk mean the extremum. This box plot demonstrate the 50% of the values at 0.5, 24 and 48 h were larger than baseline, while at 72 h and 96 h time point the overlap was present with baseline.

Figure 5. The R2* value, RBF value of OM and the concentration of serum creatinine. The changes of serum creatinine values were relatively later than both the changes of R2* value and RBF value.



Proc. Intl. Soc. Mag. Reson. Med. 24 (2016)
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