Development Of A System For The Early Diagnosis Of Breast Cancer

By Masami Ando

This article is on the current status of our attempt to develop a new X-ray imaging system for application to the clinical diagnosis of breast cancer, which utilizes the refraction principle. Due to the increase of morbidity of female breast cancer, it has become a serious social issue, and there has been growing awareness of the importance of early diagnosis. Corresponding to this trend, active efforts have been made, primarily by medical professionals and medical device manufacturers, to develop sophisticated technology for the early diagnosis of breast cancer. Mammography, which uses X-rays, was developed as an example of such technology. What can be visualized by mammography are primarily calcified tissue and the structure of mammary glands. Mammography creates images through detection of the difference in t ransmit tance of X-ray bet ween nor mal tissue and calcified areas or affected tissue. Technically, differences in X-ray absor ption are detected by mammography. Because of these features, the X-ray energy needs to be as low as possible for mammography, resulting in the clinical practice whereby the accelerating voltage of the X-ray device used for mammography is at 30 kV or less and the effective X-ray energy is 20 keV or less.

We are now developing a system which allows the visualization of the structure and tissue associated with breast cancer, which is difficult to achieve with conventional mammography, by utilizing X-ray refraction. This system is expected to achieve an approximately 1000-fold higher contrast and high spatial resolution at low dose; compared to techniques by use of X-ray absorption. Monochromatic and plane wave X-rays, produced by the diffraction of asymmetric reflection, are applied to the sample, and, corresponding to calcification and tissue structure, X-rays, which is going through slight refraction, are isolated from straight X-rays with an angle analysis plate. With a method called the "X-ray dark field method" which uses a transmission type angle analysis plate, transfer imaging created by refractive X-rays alone can be obtained, making use of the feature that straight X-rays do not go through the angle analysis plate of a certain thickness. Furthermore, a mathematical algorithm concerning refraction contrast was developed to get CT images, and we obtained world's first 3D images of noninvasive ductal carcinoma, etc., based on the refraction principle.