Diffusion-weighted magnetic resonance imaging in neck lymph adenopathy

In patients with head and neck squamous cell carcinoma (SCC), nodal metastases are an adverse prognostic factor compromising long term patient survival. Therefore, accurate detection of regional nodal metastases is required for optimization of treatment. Computed tomography (CT) and magnetic resonance imaging (MRI) remain the primary imaging modalities for locoregional staging of head and neck SCC. Next to evaluation of the primary tumour, both modalities facilitate detection of non-palpable lymph nodes (LN). However, both modalities rely on size-related and morphological criteria to differentiate between benign and malignant lymph nodes, decreasing the sensitivity for detection of small metastases. Diffusion-weighted MRI (DW-MRI) measures differences in tissue microstructure, based on the random displacement of water molecules. The differences in water mobility are quantified using the apparent diffusion coefficient (ADC), which has an inverse relationship with tissue cellularity. As such the technique is able to differentiate between tumoral tissue and normal or necrotic tissue. The added value of DW-MRI to conventional imaging for staging of lymph nodes in head and neck cancer is discussed, before and after treatment. The possible consequences regarding therapeutic management are outlined.