ADC measurements of lymph nodes: Inter- and intra-observer reproducibility study and an overview of the literature

PurposeApparent diffusion coefficient (ADC) measurements in diffusion-weighted magnetic resonance imaging (DWI) may be of value in discriminating malignant from non-malignant lymph nodes, provided that they are reproducible. The aim of this study was to determine the inter- and intra-observer reproducibilities of ADC measurements of lymph nodes and to provide an overview of the current literature on ADC measurements in the characterization of lymph nodes.Materials and methodsTwenty healthy volunteers underwent DWI of the head and neck region and the pelvic region, at b-values of 0 and 1000 s/mm2. Two observers independently and blindly measured ADCs of lymph nodes. Inter- and intra-observer reproducibilities were assessed using the Bland–Altman method.ResultsMean ADCs of normal lymph nodes (in 10−3 mm2/s) varied between 1.15 and 1.18. Ranges of mean ADC difference ± limits of agreement (in 10−3 mm2/s) for inter-observer agreement were −0.03 to 0.02 ± 0.15 to 0.31. Ranges of mean ADC difference ± limits of agreement (in 10−3 mm2/s) for intra-observer agreement were 0.00 to 0.04 ± 0.13 to 0.32.ConclusionIn conclusion, in light of previously reported data, the results of the present study suggest that ADC measurements may not always be sufficiently reproducible to discriminate malignant from non-malignant lymph nodes. Future studies which directly compare the ADCs of different nodal pathologies/conditions are required to further investigate the inter- and intra-observer reproducibilities of ADC measurements of lymph nodes.