Inclusion Criteria:  Patients ≥ 18 years old Histologically confirmed head and neck cancer. Patients treated with radiotherapy (RT) as primary treatment. An Eastern Cooperative Oncology Group (ECOG) Performance Status grade of 0-1 as defined in Appendix 3. Each subject must sign an informed consent form (ICF) indicating that he understands the purpose of and procedures required for the study and is willing to participate in the study. Patients must be willing to comply with treatment plan and other study procedures  Exclusion Criteria:  Patients with significantly altered mental status or with psychological, familial, sociological or geographical condition potentially hampering compliance with the study. Patients who cannot stay still during fraction because of a disorder (e.g. Parkinson's disease)