Application Of Diffusion-weighted And Blood Oxygen Level-dependent MR Imaging In The Evaluation Of Renal Function Of Chronic Kidney Disease

Objective：To investigate the values of diffusion-weighted and blood oxygen level-dependent MR imaging in diagnosis and stage of chronic kidney disease(CKD)，andthe values in evaluation the kidney function and the degree of pathological injury.There were two parts included，the first part of diffusion-weighted imaging(DWI)，the second part of blood oxygen levd dependent(BOLD).Materials and Methods：sixty-five patients with chronic kidney disease were enrolled in this study fromFebruary2012to December2012. The patients were all diagnosis of diffuse renallesions，kidney stones，kidney seeper，multiple renal cyst were eliminated.Accordingto K/DOQI guidelines，the glomerular filtration rate were calculated with99Tcm-DTPA scintigraphy，the stage of CKD were determined.Among the CKD patients，eighteen received kidney tissue puncturation biopsy examination，and the score ofpathological injury degree were decided. The control group was composed of20healthy volunteers matched for sex and age.All of the subjects underwent studies on3.0T MR scanner(GE Singa HDxt GE3.0T) as follows：1. The first part were DWI，EPI sequence with use of the surface phase control loop and respiratory gating.Thecortical and medullary ADC values were got through DWI in b(gradient factor)=800s/mm2。2. The second part were conventional T1WI(T1-weight image)，T2WI(T2-weight image) and BOLD MRI examinations，mGRE sequence with12echoes were used for BOLD scan with use of the surface phase control loop andrespiratory gating. Parameters evaluated and calculated consisted of:1.two parameterswere evaluated in the fisrt part，include cortical and medullary ADC values of allsubjects in b=800s/mm2；2. cortical and medullary R2*(apparent spin-spin relaxation)values were evaluated in the second part.The following data were analyzed:1.Paired TTest was used to compare ADC values between cortex and medulla in control groupand CKD group.One-Way ANOVA(analysis of variance) were used to compare meancortical ADC values，medullary mean ADC values between control group and different stage of CKD group.2.the correlation of the cortical and medullary ADCvalues with single kidney GFR were compared. Correlation between cortical andmedullary ADC values with pathological lesion were analyzed in18patients whoreceived renal biopsy.3. Paired T Test was used to compare mean R2*valuesbetween cortex and medulla in control group and CKD group.One-Way ANOVA(analysis of variance) were used to compare mean cortical R2*values，medullary R2*values between control group and different stage of CKD group.2.T-he correlation ofthe cortical and medullary R2*values with single kidney GFR were compared.Correlation between cortical and medullary R2*values with pathological lesion wereanalyzed in18patients who received renal biopsy.Results:The images of27healthy volunteers，16cases of CKD1stage，13cases ofCKD2stage，21cases of CKD3stage were finally analyzed．1. The cortical mean ADC value was higher than medullary among control groupand different stage of CKD group（P<0.05）. The mean renal cortex and medullarADCs of control group，CKD1group，CKD2group，CKD3group were2.32±0.07vs2.18±0.07；2.06±0.17vs1.89±0.17；1.81±0.09vs1.68±0.09；1.70±0.05vs1.56±0.04，respectively.There was a statistically significant difference in renal cortex ADCsamong the four groups（P<0.05）. Similarly，there wasa statistically significantdifference in renal medullar ADCs among the four groups（P<0.05）.2. There was a positive correlation between the split ADC value(both cortex andmedullar)and single kidney GFR(rcortical=0.697，rmedullar=0.800，P<0.05). Negativecorrelations were found between ADC value (both cortex and medullar) of the rightkidney with score of pathological lesion (rcortical=-0.800，rmedullar=-0.814，P<0.05).3. The medullary mean R2*value was higher than cortical among control groupand different stage of CKD group（P<0.05）. The mean renal cortex and medullar R2*values of control group，CKD1group，CKD2group，CKD3group were31.22±1.24vs15.58±0.46；30.13±2.95vs16.05±0.61；25.46±1.44vs18.38±1.89；21.88±2.85vs20.63±0.53，respectively.There was a statistically significant difference in renal meancortex and medullar R2*values between CKD2-3stage group and control group、CKD1stage group（P<0.05）.But there was no significant difference in renal mean cortex and medullar R2*values between CKD1stage group and control group（P>0.05）.4. There was a correlation between the split R2*value(both cortex andmedullar)and single kidney GFR(rcortical=-0.850，rmedullar=0.874，P<0.05).Negativecorrelations were found between R2*value of the right kidney with score ofpathological lesion (rmedullar=-0.659，P<0.05).There was no linear relationshipbetween the split medullar R2*value and pathological degree(P>0.05).Conclusions:Functional magnetic resonance imaging of kidney could reveal thepathophysiological changes and the physiological status reflect of kidney fromdifferent aspects，such as kidney oxygen bioavailability and pathologic state.1. The first part1.1Renal3.0T MR diffusion imaging can display the cortimedullarydifferntiation clearly，which can reflect the physiological functions of the kidney.1.2DWI may find the renal micropathology change earlier to GFR，can be usedin the early diagnosis and the assessment of clinical stage.1.3DWI can be used in the evaluation of glomerular filtration function andassessment of renal pathological，which is expected to become a non-invasiveimagine technique in the assessment of renal function and renal patholigical damage.2. The second part2.1The normal renal cortex and medulla oxygenation is nonuniform，With thedevelopment of renal injury aggravated，medullary oxygen metabolism decreased，oxgenation level difference between the cortex and medulla reduced.2.2Renal3.0T BOLD MRI is not sensitive to early lesion in CKD，but as forassessment of clinical stage,BOLD MRI has its certain clinical value.2.3BOLD MRI can be used in the evaluation of glomerular filtration function；medullary R2*value is significant for judging the degree of pathological damage ofCKD.In a word，combination of DWI and BOLD MRI can reflect the functional stateof glomerulus and renal tubule，and can find renal injury earlier to GFR，which hascertain diagnostic value in early renal injury of CKD.