Study details:

Radiation therapy (RT) is a central treatment modality for 74% of head and neck cancer (HNC) patients where preservation of the form and function of localised organs and tissue is of prime importance. Radiation therapy offers the possibility of organ preservation by providing a non-surgical approach to curative treatment, while helping to limit the extent of surgery in cases where definitive surgery is unavoidable. Radiation therapy also has an important role in maintaining quality of life in the palliative management of incurable HNC, where it can prevent and alleviate pain, bleeding, tumour fungation and difficulty with swallowing, breathing and speech.

State-of-the-art RT for HNC delivers lethal radiation doses to the cancer while sparing vital organs situated just a few millimetres away. To achieve this level of accuracy, tight-fitting thermoplastic head and neck masks are used to immobilise the patient in the desired treatment position for the duration of each of their RT treatments. These thermoplastic immobilisation devices are accepted internationally as the necessary standard and included in published guidelines.

Open masks are an emerging immobilisation measure and a first step to reduce patient discomfort and anxiety. An open mask has a smaller visual restriction and fewer restraint points. Although, thermoplastic immobilisation masks are the accepted clinical standard for HNC RT, it is widely recognised and acknowledged that there are several limitations with their use.

Changes to the mask's fit may be needed due to patient weight loss, tumour shrinkage, or treatment related oedema. Thus, radiation therapists are required to monitor the mask for fit throughout the treatment course, undertake imaging at regular intervals and make corrections as per published guidelines and local protocols. There is also risk of movement of the patient within the mask, which may lead to under dosing of the target and overdosing of organs at risk.

Court et al. reported that patients in their study needed to be repositioned in the immobilisation mask before treatment for 14% of fractions; 30% of the repositioning was for shoulder shifts of 1 cm or greater. Neubauer et al.

observed shoulder motion of 2-5 mm in each direction on average (20 mm max). These shifts resulted in coverage loss (dose to 99% of the clinical target volume decreased by up to 1Gy) or increased dose to organs at risk (e. g.

, dose to brachial plexus increased by 0. 7Gy). The ACRF Image X Institute at the University of Sydney has developed a novel surface guidance system that can be mounted to any RT imaging and treatment couch.

This system is currently being used in a clinical trial (NCT02881203) to guide breast cancer patients into a reproducible breath hold: the patient's chest position is measured via surface imaging and the system delivers visual feedback to the patient via a screen for the patient to correct their breath hold level if necessary (i. e. , surface guidance).

This system uses off-the-shelf electronics, most importantly a sensor which includes an optical and a depth camera, delivering frames at a rate of 30Hz and allowing the patient and operator to see an augmented reality video feed, including the surface depth information. Similar to this, we will apply optical and depth cameras for head and neck surface monitoring by integrating a second sensor and adapting it to the different location of treatment. Pilot-stage, single-arm study investigating the technical feasibility and patient acceptance of a non-interventional, non-invasive, mask-free surface detection system.

Towards the end of their scheduled radiation therapy treatments, people being treated for HNC with RT using a thermoplastic immobilisation mask will be asked to lie in a treatment position on a treatment couch using a standard radiation therapy headrest without the mask, for the normal amount of time taken for individual radiation therapy treatments (20 minutes). During this time, the mask-free surface detection system will detect and record their location and movement. Data collected by the surface detection system during this couch session will be analysed to determine the feasibility of using the equipment to detect location and movement over this period.

Data collected directly from the participants immediately before, during and following the couch session will be used to determine their acceptance of the system in terms of comfort and anxiety when compared with wearing the mask, and any suggestions for improvement of the system. Data collected directly from the radiation therapists following the couch session will be used to investigate their thoughts on the abilities of the system, ease of use and suggestions they may have. To investigate the effect of changes in appearance due to weight loss over the course of HNC radiation therapy treatment, a 5-minute surface monitoring couch session conducted before the start of radiation therapy will record baseline surface-monitoring information only.

Data analysis will occur at the University of Sydney outside of participant sessions.

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