Inclusion Criteria:

• Patients admitted to Hôpital Forcilles for head and neck cancer radiotherapy;
• Ultrasound operator available ;
• Patient at least 18 years old at the time of inclusion;
• Membership of a social security scheme or beneficiary of such a scheme ;
• Oral, free, informed and express patient consent.

Exclusion Criteria:

• Patients with neurological disorders;
• Patients with DR before the start of radiotherapy;
• Patient's refusal to participate in the study ;
• Person subject to a safeguard of justice measure ;
• Patient under guardianship;
• Patient with limited care.