Background and Problem Definition
In stereotactic radiation therapy (SRT), a linear accelerator is used to deliver a dose of radiation to a tumor at several beam angles, targeting primarily the tumor and reducing the amount of radiation to surrounding areas. SRT is commonly used to treat cancers including brain tumors, oral tumors, and nasal tumors in animals.
One major challenge in veterinary oncology is accurately administering radiation therapy to the head and neck areas of patients. There currently does not exist an economical, reusable head-holding device that accurately positions patients to receive therapy.
Our team visited the veterinary clinic and extensively interviewed our clinical mentor, Dr. Eric Green, and his team to develop objectives for the device. Early objectives were summarized as the following:
Capable of comfortably securing the animal's head so that it does not change position while undergoing treatment
Have multiple settings to fit small, medium and large patients
Attach to both the linear accelerator and CT machine tables
Idea Generation and Refinement
Once our team had an idea of the problems we wanted to address with our device, we began the brainstorming and idea generation phase. As part of the capstone class assignment, each team member contributed at least 20 unique sketched ideas for the device or its components. A selection of my sketches are shown here.
After further discussion among the team, including construction of a cardboard mockup of multiple designs, we decided that our best direction involved using a dental mold to secure the animal's head. This was in combination with a height-adjustable table to accommodate different sizes of canine heads.
Building and Testing the Prototype
The prototype was built using a variety of materials and methods, including milling, laser cutting, and CNC. Because metal components can cause artifacts in CT scans, all materials in the plane of the CT image needed to be free of metals. Acrylic was used for the base and bite plate, while metal parts and fasteners were purchased when needed. We 3D printed a model of a canine skull to use in our bite trays and easily simulate the effect of placing the animal's teeth in the tray.
Various tests were conducted on the prototype, including force deflection of the bite plate and CT imaging of the device to check for potential image artifacts. A two-axis position repeatability test was performed with an edge finder and a mill.
Results and Feedback
The final result of the capstone project was a prototype canine radiation therapy device that interfaced successfully with CT and linear accelerator tables. The device had three different sized bite trays to use in canine patients of different sizes. To better bring the design to life, I also created a name and logo for the device (see "Headloc" image below).
The device had satisfactory performance in all of the tests that our team developed. Our team successfully presented our poster to the faculty judges and also received positive feedback from the veterinary team when we presented them with our prototype. Overall, this project gave me invaluable experience with all phases of the design process from observation and idea generation through prototyping and testing. My experience working on this project affirmed my passion for medical device design.