| According to Canadian Cancer Statistics, breast cancer continues to be the most frequent type of cancer diagnosed among Canadian women. An estimated 18,700 new cases of breast cancer will be diagnosed in 1999. During their lifetime, 1 woman in 9 is expected to develop breast cancer and 1 woman in 25 is expected to die from it. Early detection is a woman's hope for effective treatment and better survival rates. Unfortunately, present imaging modalities are either ineffective or financially unjustifiable for mass screening. A new non-invasive screening and diagnostic technique (viz., Electrical Impedance Tomography, EIT) with high potential has recently been given much attention. However, the transition of EIT from the laboratory to the clinic is yet to occur. The main problem appears to be one of spatial resolution, usually attributed to the lack of a robust and fast algorithm capable of producing 3-D clinically useful images.; An existing EIT image reconstruction algorithm, the Wexler 3-D EIT algorithm, is further refined to address the problem. A new and efficient scheme, the Modeller-Predictor-Corrector (MPC) method, is devised and implemented on the original Wexler 3-D EIT algorithm to improve its convergence rate. Images are recovered within a time period comparable to that of existing clinical imaging modalities. The spatial resolution of the MPC-recovered image, though recovered in a reasonable time period, is far from what is desired. To this end, a novel approach, the Locator-Compensator (LC) algorithm is developed and implemented to improve EIT's resolution limit, in particular at normal-to-diseased tissue interfaces. Both schemes (viz. LC and MPC) were implemented on 3-D computer simulations of small breast tumour (i.e., benign and malignant) imaging. Using the improved Wexler 3-D EIT algorithm, breast tumours of size 2.35 mm in diameter were detected and diagnosed. Implementation of this improved imaging algorithm in conjunction with the appropriate EIT hardware system is anticipated to provide a safe, cost-effective, and easily accessible screening and diagnostic tool for the detection of small breast tumours. EIT could serve as a complementary tool to conventional X-ray mammography, considering its advantages. |
