Head and neck squamous cell carcinoma are frequent. The chemoradiotherapy protocols are part of the reference treatment of locally advanced stage tumors. Diffusion-weighted MRI (DW-MRI) is a non radiating imaging, not requiring injection of gadolinium, giving informations on tumor activity, based on the brownian motion of water molecules. The differences in motion are expressed by the apparent diffusion coefficient (ADC). The ADC variations reflect changes in water molecules motion and redistribution between the intra- and extracellular compartments. Several studies have shown that malignant lesions have an ADC coefficient lowered as compared to benign lesions.

study the diagnostic performance of diffusion MRI performed in early post treatment, notably changes in the ADC factor, in the onset of tumor recurrence or progression in patients showing no residual tumor at the end a treatment by chemoradiotherapy for squamous cell carcinoma of head and neck seat.

compare the characteristics of diffusion MRI, such as ADC coefficient, between patients with residual tumor and patients with no residual tumor after chemoradiotherapy for squamous cell carcinoma of head and neck location.

Inclusion Criteria:

• patients with head and neck squamous cell carcinoma
• patients with indication of a treatment by chemoradiotherapy (without surgical indication)
• patient consenting to participate to the study
• patient enrolled in the national healthcare insurance program
• patient older than 18 years

Exclusion Criteria:

• patients with contraindications for MRI