Carotid Ultrasound to Identify Head and Neck Cancer Survivors With High Cardiovascular Risk After Radiation Therapy

Primary Objective: To determine the proportion of patients with clinically significant carotid artery stenosis (≥50% stenosis) in head and neck cancer survivors treated with head and neck radiotherapy. Secondary Objectives: * To measure the intima-media thickness (IMT) of the carotid arteries in head and neck cancer survivors treated with head and neck radiotherapy. * To determine the proportion of patients with carotid intima-media thickness of at least 0.9 mm in head and neck cancer survivors treated with head and neck radiotherapy. * To determine the proportion of patients with carotid plaque of maximum thickness 2 mm or greater in head and neck cancer survivors treated with head and neck radiotherapy. * To determine the proportion of patients identified as having a high risk of cardiovascular events (relative risk 1.50 or greater) based on intima-media thickness measurements in head and neck cancer survivors treated with head and neck radiotherapy. * To describe the risk of significant carotid artery stenosis based on various clinical factors in head and neck cancer survivors treated with head and neck radiotherapy. * To determine the feasibility of carotid ultrasound in head and neck cancer survivors treated with head and neck radiotherapy. * To obtain preliminary data on the acceptability of carotid ultrasound among head and neck cancer survivors treated with head and neck radiotherapy. * To obtain preliminary data on barriers to potential carotid ultrasound screening in head and neck cancer survivors treated with head and neck radiotherapy. * To obtain preliminary data on stroke risk perception among head and neck cancer survivors treated with radiotherapy in head and neck cancer survivors treated with head and neck radiotherapy.