ABSTRACT
Objective To explore the repeatability and consistency of MR intravoxel incoherent motion (IVIM) parameters of rectal cancers.Methods Routine high resolution rectal MR and IVIM sequence were performed on 128 patients with pathologically proved rectal cancers before treatment.IVIM maps were generated from two sets of b-values (group A:0,5,10,20,30,40,60,80,100,150,200,400,600 and 1000 s/mm2;group B:0,5,10,20,30,40,60,80,100,150,200,400,600,1000,1500 and 2000 s/mm2),and IVIM parameters (D,D* and f) were measured.Then IVIM parameters were measured again by the same observer three months later.The intra-class correlation coefficient (ICC) and Bland-Altman graph analysis were performed to explore the repeatability and consistency of IVIM parameters.Results The differences of IVIM parameters (D,D* and f) derived from the two sets of b-values were statistically different (all P＜0.001).ICC and 95％ confidence interval (CI) of D,D* and f was 0.968 (0.955,0.977),0.780 (0.688,0.845) and 0.957 (0.934,0.970),respectively.Bland-Altman analysis showed that the 95 ％ limits of agreement of D,D* and f was (10.8％,22.4％),(14.8％,61.9％) and (-45.3％,-10.2％),respectively.There was significant difference of D* between twice measurement by the same observer (P=0.001);ICC and 95％CI of D,D* and f was 0.826(0.670,0.908),0.678 (0.392,0.830) and 0.910 (0.830,0.952),respectively.Furthermore,Bland-Altman analysis showed that the 95％ limits of agreement of D,D* and f were (-15.3％,12.4％),(-39.6％,61.2％) and (-22.6％,22.9％),respectively.Conclusion Under the two different sets of b-values,all IVIM parameters of rectal cancers demonstrate good consistency.In addition,D and f value show good repeatability.