Patients suffering with Head and Neck Cancer often must wait 3 months or more to know if their treatment has been effective, which can be very stressful. The investigators are developing an imaging tool that may be useful to help clinicians understand if patients need secondary treatment, surgery to remove lymph nodes in the neck, sooner. Evidence suggests that lymph nodes containing cancer are stiffer than normal lymph nodes.

The investigator's tool, vibrational shear wave elastography, measures the stiffness of tissue using shear waves. Gentle vibrations, like those of a mobile phone, applied to the skin surface can create shear waves in the body. The investigators use ultrasound imaging and an algorithm the investigators have developed to measure shear wave speed which is related to tissue stiffness. The algorithm is applied to ultrasound images using software we have written.

To help develop the software the investigators wish to explore different ways of creating shear waves in the neck and see how well the investigators can detect shear waves as they pass through tissues such as muscle, the thyroid and other glands in the neck. The investigators will recruit healthy volunteers to participate in this study. The investigators will use external vibrational sources gently placed against the neck in different positions to understand what the best approach to achieve the best measurement of tissue stiffness is. The investigators will also ask healthy volunteers to generate vibrations themselves using their vocal cords, a process called vocal fremitus. Participants will be asked utter 'aaa' sounds at different pitches, and the investigators will image the shear wave generated by the vibrating vocal cords. The investigators will also ask volunteers how comfortable they found the external vibrations and how easy or difficult they found it to utter and hold the sounds. This study is an exploratory benchmarking study of the software that will help the investigators develop our technique further, and design and build optimal equipment before testing it in patients.

Inclusion Criteria:

• Healthy adult volunteers

Exclusion Criteria:

• Healthy volunteers who do not consider themselves to currently have normal neck mobility and feel able to lie supine with their neck supported for up to 90 minutes.
• Volunteers who are receiving treatment for diseases of the thyroid, glands, or lymph nodes.

Healthy adult volunteers