Hyperthermia (HT) is a cancer treatment that is generally used in combination with chemotherapy or radiotherapy. During this therapy, electromagnetic energy is used to elevate the temperature of a tumour to 40–44 °C for 60–90 minutes. This process makes the tumourous cells more sensitive to radiation and chemotherapy.

Deep hyperthermia treatment of head and neck cancers is usually administered for recurring tumours in this area that are positioned more than 4 cm under the skin. Patients with recurrent head and neck cancer have a 2-year survival rate of only 10-20 % when retreated with chemotherapy and radiotherapy. Furthermore, toxic side-effects of these therapies are even more severe after re-treatment. Hyperthermia treatment can be a good solution for these problems, but currently, there is a lack of deep heating equipment for neck and head. That is why Erasmus MC is developing applicators for deep, targeted heating of these areas.

After two iterations, Erasmus MC has recently developed a novel MR compatible head and neck hyperthermia applicator (MRcollar). A water bolus needs to be placed between the applicator and the patient’s skin to act as a cooling agent to prevent skin burns and as a transferring agent to conduct the electromagnetic energy to the internal tumour tissue. However, there is no water bolus developed yet to be used in this applicator. Therefore, this thesis focused on developing a bolus for the MRcollar.

By analysing the treatment context, the previous applicators and boli and talking to stakeholders, the main challenges for this project could be defined. The bolus should be comfortable for the patients: the pressure on the skin should be minimized and enough space for breathing and seeing should be provided to reduce claustrophobic feelings. The cooling must be effective and uniform throughout the bolus volume. Furthermore, the shape of the bolus should be stable, predictable and reproducible to efficiently simulate the treatment. The bolus should function in the MRcollar, not disrupting electromagnetic waves or MR imaging and being watertight. Lastly, the bolus should be easy to install by the clinicians.

Different ideas and concepts were generated based on these challenges, after which it was decided to make the bolus out of a flexible 3D printed inner structure, surrounded by a plastic film. This concept was further detailed, tested and improved during the embodiment phase with a main focus on creating an anthropometric fit, good water flow, flexibility and stability and creating a watertight enclosure.

The final design is a flexible, 3D printed structure with an implemented water guidance system. The shape is designed to ergonomically follow the shape of the head. The bolus is made watertight by gluing and sealing a plastic film around the structure. This design was validated and found to be successful on all earlier defined challenges.