Is diffusion-weighted MRI useful for differentiation of small non-necrotic cervical lymph nodes in patients with head and neck malignancies?

Objective: To evaluate the usefulness of measuring the apparent diffusion coefficient (ADC) in diffusion-weighted magnetic resonance imaging to distinguish benign from small, non-necrotic metastatic cervical lymph nodes in patients with head and neck cancers.

Materials and methods: Twenty-six consecutive patients with head and neck cancer underwent diffusion-weighted imaging (b value, 0 and 800 s/mm(2)) preoperatively between January 2009 and December 2010. Two readers independently measured the ADC values of each cervical lymph node with a minimum-axial diameter of ≥ 5 mm but < 11 mm using manually drawn regions of interest. Necrotic lymph nodes were excluded. Mean ADC values were compared between benign and metastatic lymph nodes after correlating the pathology.

Results: A total of 116 lymph nodes (91 benign and 25 metastatic) from 25 patients were included. Metastatic lymph nodes (mean ± standard deviation [SD], 7.4 ± 1.6 mm) were larger than benign lymph nodes (mean ± SD, 6.6 ± 1.4 mm) (p = 0.018). Mean ADC values for reader 1 were 1.17 ± 0.31 × 10(-3) mm(2)/s for benign and 1.25 ± 0.76 × 10(-3) mm(2)/s for metastatic lymph nodes. Mean ADC values for reader 2 were 1.21 ± 0.46 × 10(-3) mm(2)/s for benign and 1.14 ± 0.34 × 10(-3) mm(2)/s for metastatic lymph nodes. Mean ADC values between benign and metastatic lymph nodes were not significantly different (p = 0.594 for reader 1, 0.463 for reader 2).

Conclusion: Measuring mean ADC does not allow differentiating benign from metastatic cervical lymph nodes in patients with head and neck cancer and non-necrotic, small lymph nodes.