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目的 探讨体素内不相干运动DWI(IVIM-DWI)在慢性肾脏病(CKD)分期诊断中的价值.方法 前瞻性收集2016年5月至2017年4月复旦大学附属中山医院符合临床CKD诊断标准的72例患者作为CKD组,同期20名健康志愿者作为对照组.CKD组患者根据MRI检查当日的血清肌酐值计算估算的肾小球滤过率(eGFR),并根据eGFR将患者分为2个亚组,轻度CKD组(45例, eGFR≥60 ml·min-1·1.73 m-2)和中重度CKD组(27例,eGFR<60 ml·min-1·1.73 m-2).所有受试者均行双肾MRI常规扫描和IVIM-DWI检查,获得肾皮质和髓质IVIM-DWI参数,包括单纯扩散系数(D)、微循环灌注系数(D*)、灌注分数(f)和ADC值.采用配对样本t检验比较各组肾脏皮、髓质间各参数值的差异,3组受试者间肾皮质及髓质各参数值的比较采用单因素方差分析,采用Pearson相关性分析评价肾脏皮、髓质各参数值与eGFR的相关性,采用ROC评价IVIM-DWI参数诊断慢性肾损害和评价CKD分期的效能.结果 对照组皮质ADC、D、D*及f值均高于髓质,差异有统计学意义(P均<0.05);轻度CKD组皮质ADC、D*及f值明显高于髓质,差异有统计学意义(P均<0.05),皮质和髓质间的D值差异无统计学意义(P>0.05);中重度CKD组皮质ADC、D及f值均明显高于髓质,差异有统计学意义(P均<0.05),而皮、髓质间D*值差异无统计学意义(P>0.05).对照组、轻度CKD组、中重度CKD组间皮质和髓质ADC、D、D*及f值差异均有统计学意义(P均<0.05).CKD患者髓质D*值、f值与eGFR不具有相关性(r值分别为0.229、0.130,P值分别为0.053、0.275).CKD患者的皮质ADC、D、D*、f值和髓质ADC、D值与eGFR呈弱或中度正相关(r值分别为0.475、0.362、0.625、0.276、0.427、0.615,P均<0.05).鉴别轻度和中重度CKD,皮质D*值的ROC下面积最大(0.965),以皮质f值=32.99%为截断值鉴别CKD分期的敏感度为92.6%,以皮质D*值=17.07×10-3mm2/s为截断值鉴别CKD分期的特异度为97.8%;鉴别轻度CKD与对照组,皮质D*值的ROC下面积最大(0.885),以髓质ADC值=1.83×10-3mm2/s为截断值诊断的敏感度为82.2%,以髓质f值=21.70%或髓质D值=1.75×10-3mm2/s为截断值诊断的特异度为100.0%.结论 IVIM-DWI可以为CKD的分期诊断提供有价值的信息.

Objective To investigate the value of intravoxel incoherent motion diffusion-weighted imaging (IVIM-DWI) in the staging of chronic kidney disease(CKD).Methods From May 2016 to April 2017,seventy-two patients diagnosed as CKD according to the criteria of clinical diagnostic and 20 healthy volunteers (control group) underwent routine MRI and IVIM-DWI ( 8 b values, 0 to 800 s/mm2).CKD patients were divided into two groups based on their estimated glomerular filtration rate (eGFR): mild CKD group(45 cases,eGFR≥60 ml·min-1·1.73m-2)and moderate to severe CKD group(27 cases,eGFR<60 ml·min-1·1.73 m-2).The ADC,true diffusion coefficient(D),pseudo-diffusion coefficient(D*),perfusion fraction (f) were measured on both cortex and medulla. The paired-samples t test was used to compare the cortico-medullary difference of the ADC,D,D*and f values in three groups.Differences of the ADC,D, D*and f values among three groups were compared using the one-way analysis of variance (ANOVA). Correlations between eGFR and the IVIM-DWI parameters in CKD were evaluated by using Pearson correlation analysis. ROC was performed to evaluate the diagnostic efficiency of using IVIM-DWI parameters to distinguish CKD with moderate to severe renal impairment from mild renal impairment, as well as distinguish CKD with mild renal impairment from healthy volunteers.Results The cortical ADC,D, D*and f values were significantly higher than that in the medulla in healthy volunteers(all P<0.05). The cortical ADC,D*and f values were significantly higher than that in the medulla in mild CKD group(all P<0.05). The cortical ADC,D and f values were significantly higher than that in the medulla in moderate to severe CKD group (all P<0.05). The ADC,D,D*and f values of cortex and medulla showed significantly differences among three groups(all P<0.05).In CKD patients,no significant correlation was found between medullary D*,f values and eGFR, there was a significant positive correlation between eGFR and cortical ADC,D,D*and f values(r=0.475,0.362,0.625,0.276;all P<0.05),as well as between eGFR and medullary ADC,D values(r=0.427,0.615;P<0.05). The results of the ROC analysis for distinguishing the mild CKD group from the moderate to severe CKD group revealed that the cortical D*value had the highest area under the ROC curve (AUC=0.965), cortical f value showed high sensitivity(92.6%) to distinguish CKD with different degree of renal impairment, with the threshold of 32.99%, and cortical D*value showed high specificity(97.8%)with the threshold of 17.07×10-3mm2/s;the results of the ROC analysis for distinguishing the mild CKD group from healthy volunteers revealed that the cortical D*value had the highest AUC(0.885), medullary ADC value showed high sensitivity (82.2%) to distinguish mild CKD group from healthy volunteers,with the threshold of 1.83×10-3mm2/s,and medullary f value showed high specificity(100.0%)with the threshold of 21.70%,as well as medullary D value showed high specificity(100.0%)with the threshold of 1.75× 10-3mm2/s.Conclusion IVIM-DWI may be useful for CKD early diagnosis and assessing renal function.