Diffusion tensor imaging of metastatic axillary lymph nodes

Objective: It was aimed to investigate whether the fractional anisotropy (FA) differs for the benign and metastatic axillary lymph nodes (LNs).Material and Methods: 58 women with benign (n=33) and metastatic (n=25) axillary LNs who underwent diffusion weighted and tensor imaging with a 3T scanner were enrolled. Apparent diffusion coefficient (ADC) and FA, cortex thickness, long and short axes were measured retrospectively and compared statistically. Observer reliabilities were also assessed in terms of intra and inter-reviewer variability.Results: Metastatic LNs showed significantly lower ADC and FA values and greater cortex thickness, long and short axes. ROC test showed the area under the curve values of 0.876 for ADC, 0.661 for FA and 0.960 for cortex thickness. Cortex thickness had excellent sensitivity, specificity, and accuracy. A cutoff value of 3.5 mm for cortex thickness had 92% sensitivity, 94% specificity, 92% positive predictive value (PV), 93% negative PV, and 93% accuracy. A cutoff value of 0.774x10-3 mm2/s for ADC had 84% sensitivity, 82% specificity, 79% positive PV, 90% negative PV, and 84% accuracy. A cutoff value of 0.423 x10-3 mm2/s for FA had 64% sensitivity, 76% specificity, 67% positive PV, 71% negative PV, and 71% accuracy. High intra- and inter-observer reliabilities were seen.Conclusion: Among the parameters assessed by our study, cortex thickness had superior accuracy. ADC and FA showed a respectable diagnostic performance, especially the first one having a high negative PV and the second one relatively high specificity.