Breast cancer is one of the most common cancers in women. In the United States alone, it accounts for 31% of new cancer cases, and is second only to lung cancer as the leading cause of deaths in American women. More than 184,000 new cases of breast cancer are diagnosed each year resulting in approximately 41,000 deaths. Early detection and intervention is one of the most significant factors in improving the survival rates and quality of life experienced by breast cancer sufferers, since this is the time when treatment is most effective. One of the most promising breast imaging modalities is microwave imaging. The physical basis of active microwave imaging is the dielectric contrast between normal and malignant breast tissue that exists at microwave frequencies. The dielectric contrast is mainly due to the increased water content present in the cancerous tissue. Microwave imaging is non-ionizing, does not require breast compression, is less invasive than X-ray mammography, and is potentially low cost. While several prototype microwave breast imaging systems are currently in various stages of development, the design and fabrication of anatomically and dielectrically representative breast phantoms to evaluate these systems is often problematic. While some existing phantoms are composed of dielectrically representative materials, they rarely accurately represent the shape and size of a typical breast. Conversely, several phantoms have been developed to accurately model the shape of the human breast, but have inappropriate dielectric properties. This study will brie y review existing phantoms before describing the development of a more accurate and practical breast phantom for the evaluation of microwave breast imaging systems.
Ultra Wide Band (UWB) radar is a promising emerging technology for breast cancer detection that makes use of the
dielectric contrast between normal and tumour tissues at microwave frequencies.
An important consideration in UWB imaging system design is the configuration of the antenna array. Two antenna
configurations have been previously proposed to image the breast: the planar and the circular distributions. The planar
configuration involves a 2D array of antennas placed on the naturally flattened breast with the patient lying in the supine
position. Conversely, the circular configuration involves the patient lying in the prone position, with the breast
surrounded by a circular array of antennas. In this paper, the two different configurations are compared using various
metrics, including the minimum number of antennas needed to successfully detect the presence and location of tumours
of different sizes in the breast.
In order to effectively test both supine and prone imaging approaches, two 2D Finite-Difference Time-Domain (FDTD)
models of the breast are created. The backscattered signals recorded from each antenna configuration are passed through
a simple delay and sum beamformer and images of the backscattered energy are created. The images obtained using both
antenna configurations are compared and the performance of each imaging approach is evaluated by quantitative
methods and visual inspection, for a number of test conditions.
Motility assays are the tools of choice for the studies regarding the motility of protein molecular motors in vitro. Despite
their wide usage, some simple, but fundamental issues still need to be specifically addressed in order to achieve the best
and the most meaningful motility analyses. Several tracking methods used for the study of motility have been compared.
By running different statistical analyses, the impact of space versus time resolution was also studied. It has been found
that for a space resolution of 80 nm and 145 nm per pixel for kinesin-microtubule and actomyosin assays, respectively,
the best time resolution was ~0.9 and ~10 frame per second, respectively. A rough relationship - Ratio<sub>A</sub> and Ratio<sub>M</sub> - between space and time resolutions and velocity for actin filaments and microtubules, respectively, was found. The
motility parameters such as velocity, acceleration and deflection angle were statistically analysed in frequency
distribution and time domain graphs for both motors assays. One of the aims of these analyses was to study if one or two
populations were present in either assay. Particularly for actomyosin assays, electric fields varying from 0 to ~10000
Vm<sup>-1</sup> were applied and the previous parameters and the angle between filaments motion and the electric field vector were
also statistically analysed. It was observed that this angle was reduced by ~55º with ~5900 Vm<sup>-1</sup>. The overall behaviour
of the motors was discussed bearing in mind both present and previous results and some physio-biological
characteristics. Kinesin-microtubule and actomyosin (simple and electric fields) assays were compared. Some new
experiments are suggested in order to accomplish a better understanding of these motors and optimise their role in the
applications that depend on them.