Value Of Intravoxel Incoherent Motion MRI For Differentiating Metastatic From Non-metastatic Mesorectal Lymph Nodes With Different Short-axis Diameters In Rectal Cancer

Objective:To evaluate the diagnostic value of intravoxel incoherent motion(IVIM)in differentiating metastatic and non-metastatic mesorectal lymph nodes with different short-axis diameters in patients with rectal cancer.Materials and Methods:A total of 60 patients(149 lymph nodes)with rectal cancer underwent preoperative IVIM examination.The lymph nodes were divided into 3 subgroups based on short-axis diameter:3mm≤x≤4mm,4mm<x≤8mm,and x>8mm.Short-axis diameters and IVIM parameters were compared between metastatic and non-metastatic lymph nodes,the diagnostic power of parameters was analyzed in each subgroup.Results:In the subgroup 3mm≤x≤4mm,the mean D values of metastatic lymph nodes were significantly lower than those of non-metastatic lymph nodes(P<0.05).In the subgroup 4mm<x≤8mm,the mean f values of metastatic lymph nodes were significantly lower than those of non-metastatic lymph nodes(P<0.05).For the subgroup x>8mm,the short-axis diameters of metastatic lymph nodes were significantly greater than those of non-metastatic lymph nodes(P<0.05).The area under the curve(AUC),sensitivity,specificity,and cutoff values for differentiating metastatic from non-metastatic lymph nodes in each subgroup were as follows:3mm≤x≤4mm,D,0.779,83.7%,66.7%,and0.001035 mm~2/s;4 mm<x≤8mm,f,0.707,72.7%,71.1%,and 0.308;x>8mm,short-axis diameter,0.905,94.7%,75.0%,and 8.835mm(P<0.05).Conclusions:IVIM is useful for differentiating metastatic from non-metastatic lymph nodes in rectal cancer but affected by lymph node size.