Magnetic Resonance Imaging Study Of The Damaging Role Of Different Injection Routes Of Iodixanol On Rabbit Kidney

Preface:With the rapid development of medical imaging equipment and technology,iodine contrast media are increasingly used in percutaneous cardiac intervention,arterial intervention,and computed tomography(CT)contrast-enhanced scanning and vascular imaging.However,iodine contrast media can cause contrast-induced acute kidney injury(CI-AKI),especially in patients with pre-existing renal insufficiency,endothelial dysfunction and/or diabetes and inadequate pre-hydration.Contrast-induced acute kidney injury occurs in up to 30%of patients receiving iodine contrast media,leading to CI-AKI becoming a common iatrogenic event.It is generally considered to be the third most common cause of hospital-acquired acute kidney injury,second only to renal hypoperfusion and nephrotoxic drugs.Clinically defined CI-AKI is an increase in serum creatinine levels(>25%or absolute increase>0.5 mg/mL)within 24 h to 5 days after contrast injection.Fortunately,most CI-AKI patients have transient dysfunction,but CI-AKI also has serious consequences,such as increased rates of hospitalization complications,increased mortality,and long-term renal function loss into chronic kidney disease or renal function.Both the intraarterial(IA)DSA and the intravenous(IV)CT angiography procedures require the administration of an iodine contrast media.However,after the IA or IV injection,the blood circulation of the contrast media in the body,buffering of the capillary bed,dilution with the venous volume vasculature,the proportion of contrast media reaching the kidney,the drug concentration in the renal artery is not the same.This raises some questions about whether CI-AKI has IA and IV injection path dependence.Which injection path has a higher CI-AKI?How many doses can cause long-term renal dysfunction?Because it directly affects the doctor to develop a reasonable diagnosis plan and CI-AKI preventive measures,it is of great clinical significance to solve the above problems.It is worth noting that most of the previous clinical studies directly evaluated the risk of IA and IV injection routes using serum creatinine(SCr)levels after digital subtraction angiography(DSA)and CT examinations.This study has certain defects,because the injected dose can not be kept constant,the contrast media with different kinds or molecular structure,the normal fluctuation of SCr value,these are confounding factors,leading to bias and controversy in the results of the experiment.And SCr does not provide separate functional information for each side of the kidney.In this study,the non-ionic dimer isotonic contrast media iodixanol was injected through three different routes of renal artery,ear vein and femoral artery to investigate the effects of different injection routes on the kidney.In order to study the course of CI-AKI,blood oxygen level-dependent-magnetic resonance imaging(BOLD-MRI)and irrelevance within voxels were performed within 72 hours after the injection of the isotonic contrast media iodixanol.Intravoxel incoherent motion(IVIM)longitudinally monitors bilateral renal function images of rabbits after injection of the same contrast media in different injection routes.BOLD-MRI obtained the relative spin-spin relaxation rate(R2*)map,IVIM obtained the apparent diffusion coefficient(ADC),the pure molecular diffusion(D),and the perfusion-related diffusion coefficient(D*)and volume fraction(f).The dynamic changes were compared with the histological changes of the kidney and the expression of hypoxia-inducible factor-1α(HIF-1α)immunohistochemistry to determine the observations of BOLD-MRI and IVIM parameters.In the future,it will provide a non-invasive,convenient,fast and accurate examination method for clinical use as well as a reasonable and safe use of iodine contrast media.Materials and Methods:contrast mediaIodixanol(GE Healthcare,Shanghai,China);English name:Iodixanol;molecular formula:C35H44I6N6O15;molecular weight:1550.1819;concentration320mg iodine/mL;iso-osmolal pressure 290mOsm/kg H2O;viscosity 25.4mPa·s at 20°C,11.4 mPa·s at 37°C;pH 6.8-7.6.The effects of different injection routes of iodixanol on rabbit kidney injury and functional magnetic resonance imaging evaluationExperimental group:Compare the effects of three different injection routes on the kidney.Sixty-three male New Zealand rabbits were randomly divided into A:left renal artery injection group,B:ear vein injection group,C:femoral artery injection group,21 rabbits in each group.The high-pressure syringe was used,and iodixanol was injected at a dose of 1.0 g iodine/kg and 1 ml/s.BOLD-MRI and IVIM scans were performed on the bilateral kidneys of each group of rabbits 24 hours before the contrast injection,1 hour,24 hours,48 hours,and 72 hours after the injection to observe the renal cortex(CO)and the outer pulp(outer).The changes of R2*value,ADC value,D value,D*value and f value of renal cortex(CO),outer medulla(OM)and inner medulla(IM)were observed.Control group:63 male rabbits were divided into three groups according to the above injection route,AS:left renal artery injection group,BS:ear vein injection group,CS:femoral artery injection group,21 rabbits in each group.The same volume of saline was injected.BOLD-MRI and IVIM scans were performed on bilateral kidneys of each group of rabbits 24 hours before saline injection,1 hour,24hours,48 hours,and 72 hours after injection.Observe the changes in R2*value,ADC value,D value,D*value,and f value of CO,OM,and IM.The effects of routes and doses of iodixanol on renal injury in rabbits and functional magnetic resonance imaging evaluationExperimental group:63 rabbits were injected into the femoral artery.According to the injection dose,they were divided into group D:1.5g iodine/kg,group E:2.0g iodine/kg,group F:2.5g iodine/kg,21 per group,high pressure syringe 1ml/s rate injection of iodixanol.According to the results of Experiment 1,the femoral artery injection was the same as the kidney injury,and only the left kidney was measured in this group.BOLD-MRI and IVIM scans were performed 24 hours prior to the injection of the contrast media,1 hour,24 hours,48 hours,and 72 hours after the injection.Observe the changes of R2*value,ADC value,D value,D*value and f value of CO,OM and IM and compare with the A group.Compare the extent of the same kidney injury,the relationship between the different injection paths of the renal artery and the femoral artery and the dose of iodine contrast media.Control group:63 male rabbits were divided into three groups according to the dose of appeal,DS,ES and FS,with 21 rabbits in each group.Different volumes of saline were injected.BOLD-MRI and IVIM scans were performed on left kidney of each group of rabbits 24 hours before saline injection,1 hour,24 hours,48 hours,and72 hours after injection.Observe the changes in R2*value,ADC value,D value,D*value,and f value of CO,OM,and IM.BOLD-MRI and IVIM image post processingThe ADVANCE 4.4 Post-Processing Workstation(General Electric Medical Systems)analyzes and processes BOLD-MRI and IVIM images.The half-moon region of interest(ROI)selects a wide range of kidneys for CO,OM,and IM,avoiding the renal sinus,vascular and adipose tissue,each ROI is not less than10mm~2.Histological analysisAfter each magnetic resonance scan,3 rabbits were sacrificed by excessive pentobarbital(100 mg/kg)in the ear vein.The kidneys were removed,the capsule was removed,and the incision was performed in the longitudinal axis.4%paraformaldehyde fixed,conventional dehydration,paraffin embedded.The sections were serially sectioned at a thickness of 5μm and made into a conventional optical microscope section,and stained with haematoxylin and eosin(HE).Immunochemistry of HIF-1αImmunostaining of HIF-1αwas performed on 5μm paraffin-embedded tissue sections using streptavidin-peroxidase technology.Briefly,paraffin sections were dewaxed,hydrated,antigen-repaired,and blocked by endogenous peroxidase activity,and sections were sectioned with a 1:500 dilution of the first antibody murine polyclonal anti-HIF-1α(Novus,Littleton,USA)overnight at 4°C,followed by incubation with non-biotinylated(EliVisionTM super,China)reagents A,B for 15minutes to allow horseradish peroxidase polymer to bind to primary antibody,diaminobenzidine color,hematoxylin counterstained.Statistical analysisComparison between groups was performed using one-way analysis of variance and Tukey’s post hoc test.Intra-group comparisons were performed using repeated measures of variance analysis and Bonferroni post hoc tests.Histological scores and HIF-1αexpression scores were compared using the Kruskal–Wallis test and pairwise comparison.Spearman correlation analysis was used to assess the relationship between renal tissue damage,HIF-1αexpression scores,and MRI parameters.Statistical analysis was performed with SPSS v.24.0(Chicago,IL)software.p<0.05 was statistically different.Result:Results of different injection routes of iodixanol on rabbit kidney injury:R2*value,ADC value,D value,D*value and f value of CO,OM and IM in bilateral kidney before and after injection of saline were no statistical difference.After injection of three different path contrast media,the R2*values of CO,OM and IM in the bilateral kidneys increased significantly,and gradually decreased to baseline after24 hours;ADC values,D values and f values decreased significantly,and gradually increased after 24 hours;D*value decreased significantly,gradually increased to baseline after 1 hour,and all parameters returned to baseline levels within 72 hours.R2*value was positively correlated with HIF-1αexpression;ADC value,D value and f value were negatively correlated with renal tissue damage score.The left kidney of group A was the most obvious change at 24 hours,the most serious kidney injury,pathological glomerular atrophy,tubular epithelial cell swelling,vacuolization,tubular dilatation,debris accumulation in the lumen,and obvious expression of HIF-1αin the nucleus.Results of different doses of iodixanol on rabbit kidney injury:R2*,ADC,D,D*,and f values of CO,OM,and IM in left kidney before and after injection of different volume of saline in femoral artery were no statistical difference.After different doses of contrast media femoral artery injection,the changes of CO,OM and IM parameters in the left kidney of group D and group E were no statistical difference from those of left kidney of group A.The parameters of left kidney in group F did not return to baseline level at 72 hours.Conclusion:At the same dose and injection rate,iodixanol contrast media renal artery injection caused heavier ipsilateral renal injury,while injection of the ear vein and femoral artery caused relatively mild bilateral kidney injury.As the dose of the femoral artery increases,the degree of kidney damage increases significantly.1.5-2.0 g iodine/kg femoral artery injection was the same as renal injury caused by 1.0 g iodine/kg renal artery injection,and renal function was restored in 72 hours.After 2.5 g iodine/kg high-dose contrast media femoral artery injection,renal function continued to decrease and could not be recovered in 72 hours.The R2*value was linearly positively correlated with HIF-1αexpression.ADC values,D values,and f values were linearly negatively correlated with renal tissue damage.It is indicated that BOLD-MRI and IVIM have important value in judging the oxygen content and histological changes of bilateral renal tissues.