Breast cancer is one of the most common forms of cancer and the most prevalent type among women. To monitor how tumors and suspicious areas respond to chemotherapy and other treatments, physicians will often implant a biopsy marker (also known as a clip) into the tissue to mark the area during imaging. These markers are usually made of metal materials such as titanium, steel, and nickel alloys due to their robust mechanical properties and radiopacity (ability to be seen in imaging modalities such as X-ray). However, some patients have metal allergies and hypersensitivities to the materials above, particularly nickel with an allergy rate of 18% in North America. To allow patients with metal sensitivities to have access to the same quality of care as patients without these sensitivities, our Bioengineering Capstone team worked for one full semester and one summer term to develop a competitive non-metal biopsy marker design. 

The team generated an extensive list of design inputs to capture the goals of the project and qualify the design solution. Notably, these design inputs included biocompatibility with patients that have metal allergies and sensitivities, visibility under multiple imaging modalities including mammograms, ultrasound, and MRI, and various mechanical and structural properties important to deployment and visualization of the markers. 

Based on these design inputs, as well as an extensive understanding of the existing products and background science, the team worked together to develop various ideas for marker shapes and materials to use in manufacturing the markers. Trade studies were conducted to identify which design solutions met the most amount of our design goals while being realistic for the scope of capstone. These designs ended up being the Flower shape, T shape, and Lucky Charm shape made from polyetheretherketone (PEEK) material. Drawings of the shapes are shown in the above image carousel, as well as images of our prototypes. Materials were ordered by the team and the markers were manufactured in the Bioengineering Capstone Collaborative (BCC) on campus using CNC routing. 

The testing efforts of the marker aimed to generate data on two performance attributes: migration and visibility. Migration is the distance the marker moves from the original position of deployment after the procedure concludes. Visibility is how well the marker can be seen in imaging. To test these attributes, a fixture (see image carousel) was developed that simulated the mammogram paddles and pressure expected during a stereotactic breast biopsy procedure. The markers were deployed into breast tissue models using a modified pipette tip and a stylet, representing the mechanisms of industry standard deployment devices. In this way the testing of the marker was representative of expected use. Additionally, images of the tissue model were taken using an animal ultrasound machine. The fixture was equipped with markings to represent looking at the breast model from various angles. A select few samples were also imaged via MRI. 

The selection of material for the silicon breast tissue models was difficult, and the team quickly found that the initially proposed material was not representative of breast tissue. After much troubleshooting and trial-and-error, the team made a decision to use agarose instead. Due to the material properties of agarose, the team was not able to recreate conditions to study the migration of the markers within the tissue, however data on visualization of the marker shapes was generated for ultrasound and MRI as shown at the top of this page. 

If this project were to continue beyond capstone, one of the first major tasks would be to further develop the tissue model. Creating a representative model to study the migration of the markers would be key to comparing its performance to control groups and similar products. Additionally, upgrading the imaging modality from animal ultrasound to the more commonly used mammogram (X-ray) technique would allow the team to generate more accurate and representative data. 

Throughout my time working on this project I learned a great deal about working together on a cross-functional team of engineers. Dividing labor while understanding the entireity of the project was very important for our success, and this mostly came through a deep understanding of how the team worked together. Gaining this experience during undergraduate capstone was very enlightening and important. 

Additionally, I learned to trust my own talents and knowledge while working on this project, advocating for myself and for my ideas in a professional and effective way.