Improvements to ergonomics and reliability of the digital image elasto-tomography breast cancer screening device.
Thesis DisciplineMechanical Engineering
Degree GrantorUniversity of Canterbury
Degree NameMaster of Engineering
Breast cancer is a major health problem. It has been recognised as the most common cancer among women in both developed, and developing nations. Early detection of breast cancer can significantly reduce mortality, as well as the cost of treatment. Numerous screening systems are used today, but these have limitations including pain or discomfort, high costs and radiation exposure. Digital image elasto-tomography (DIET) is a novel breast screening technique that is non-invasive, low cost and painless. The technology uses tissue stiffness to identify tumours, which are 4-10 times stiffer than healthy breast tissue. Early results from a large clinical trial on a prototype DIET system highlighted two important areas requiring development: ergonomics and the system’s breast opening. These two aspects form the focus of this thesis.
During a DIET screening process, a woman must lie prone for up to five minutes for each breast. Any patient motion may lead to reduced quality imaging data. Therefore, the top surface of the DIET system must be ergonomically designed. As part of this research, ergonomic trials were performed on three unique prototype surfaces. Participants were found to prefer a flat surface that gave them an option of where to rest their arms. This surface was developed further with a mechanical loading analysis performed to guide material selection. A design specification has been included for manufacture of the ergonomic surface.
Currently, breast rings isolate the cup of the breast from the chest, and block external light from entering the DIET system. However, breast rings have caused issues during clinical trials, resulting in the need for a new breast opening. A unique shape was chosen for the top surface opening, which allows for imaging all parts of the breast tissue. This shape exposes the patient’s chest. Thus, segmentation methods are investigated to isolate the breast cup during imaging. Three phantom breasts with properties that mimic human breasts were created and tested with the new breast opening. When a combination of region and edge detection methods were used, the breast cup was successfully isolated. Additional changes to the DIET system hardware, such as changing the colour of internal components, would reduce the computation required for this process.
This thesis results in a design specification for an improved top surface of the DIET breast screening system. The specification allows manufacture of the ergonomically designed surface, with a unique breast opening shape, for further clinical trials. The improved surface is enabled by improved imaging processes, and is necessary to ameliorate the existing machine’s current limitations.