Keywords: breast blood-oxygen; three operators; breast disease; diagnosis One, technical background

At present, the main methods to diagnose breast disease include several morphological examinations such as near infrared spectroscopy, diagnostic ultrasound, molybdenum target radiography, cytolgical examination and so on. Although functional examination has not been used widely in the clinical diagnosis, but it is the development trend of diagnostic equipment. Breast blood-oxygen function imaging system made by Wuhan Yihai Digital Engineering Co., Ltd., can show oxygen content, abnormal blood vessel, the expression of same gray-scale curve and the edge characteristic of breast lesion area by means of its breast blood-oxygen function imaging and three-operator imaging. Based on the pathological features of breast cancer, the whole system is designed and it includes two functions as follows:

1.Breast Blood-oxygen Function Imaging (Functional Imaging)
When cancerous lesion occurs in the breast tissue, the proliferation of cancer cells will lead to a lot of new blood vessels. It has been made certain that cancer is an angiogenesis-dependent disease and tumor angiogenesis is the process within which new blood vessels form in the cancer on the base of existing vessels; in addition, angiogenesis can promote the growth of tumor and be relevant with prognosis. After neoplasia, its external drainage blood vessels change gradually too (Thickening, distortion, interruption, abnormal course). A large number of blood vessels in the Lesion area will lead to the increase of blood content in the local tissues (accordingly, hemoglobin increase too); however, the proliferation and the activity of cancer cells will consume a large amount of oxygen and lead to the deoxygenization of hemoglobin which show high blood content but hypoxia (Figure 1).

a. Blood content:-0.81812

b. Oxygen content: 0.365318

Figure 1 oxygen functional imaging (Breast cancer case: high blood oxygen capacity but low oxygen content)

How to realize a non-invasive detection of blood oxygen content? Hemoglobin (Hb) and oxygenated haemoglobin (HbO₂) show the characteristics of opposite absorption spectra when wavelength is at 760nm and 850nm or at similar light intensity (Figure 2 denotes the Hb and HbO₂ absorption characteristics curves). When breast is transilluminated by broad-spectrum light, blood-oxygen system just receives two specific wavelengths of light (wavelength: 760nm and 850nm); then by means of comparative analysis between incident and excident intensities of light, the oxygen content in the tissues can be calculated finally. Owing to the oxygen contents in the two sides of the breast are basically symmetrical; therefore, comparing the changes in the oxygen contents of normal and abnormal breast can determine the relative value of oxygen content of abnormal breast (See figure 1), which can reflect physiological-pathological state-related physiological functions and functional changes of tissues and organs.

Figure 2 Hb and HbO₂ absorption characteristic curves

2. Three-operator Imaging (Morphological Imaging)
Infrared light is an electromagnetic wave and it has a relatively long wavelength. When it penetrates through breast tissues, the route of it is not linear but scattered, so it carries a large number of information about tissues. However, owing to there is a small difference between the optical absorption information of various breast tissues which is beyond the scope human vision can distinguish, therefore, many information can not be distinguished by naked eyes (Implied information). By means of digital image processing technology and medical image analysis technique, the information in the breast transillumination image can be excavated by three-operator system, and thus more relevant information about lesions can be obtained finally.

a. one-operator imaging: structural analysis
The structure of breast tissue can be reflected by same gray-scale curve. In accordance with the laws of light transmission, normal tissues show regularly same gray-scale curve, but lesions (especially cancerous tissues such as hemorrhage, necrosis, calcification, hemosiderosis, reaction cell incursion and canal expansion) present irregularly same gray-scale curve [see figure 3; a: normal breast structural map (Uniform structure); b: breast cancer structural map (pane area denotes cancerous tissue: disorganized structure)].

a

b

Figure 3 structural analysis

b. two-operator imaging: vascular display
It can display the information of blood vessels more clearly and reveal effectively small vessels in the lesions [see figure 4, a: original transillumination image; b: vascular display image (pane area denotes cancerous tissue: increased number and bended shapes)].

a

b

Figure 4 vascular display

c. three-operator imaging: edge detection
the gray shadow corresponded to the lump in the optical image has unclear edges which can be intensified by edge detection operator and malignant tumor has irregular edges such as burr-like shape (see figure 5, shadow denotes cancerous tissue, it has crab-like edges)

Figure 5 edge detection

3. Discussion
As early as in 1945, animal experiment has put forward the concept that tumor angiogenesis, it is suggested that neovascularization is the reaction between the tumor and its adjacent normal tissues. The blood volume will increase in that increased blood vessels in the tumor tissues; high metabolism of cancer cells will lead to increased consumption of oxygen, which will finally result in the deoxygenization of hemoglobin (high blood oxygen capacity but low oxygen content).

Study has showed that hemoglobin (Hb) and oxygenated haemoglobin (HbO₂) show the characteristics of opposite absorption spectra when wavelength is at 760nm and 850nm or at similar light intensity; by means of dual-wavelength light transillumination image of breast tissues, the difference between the blood oxygen capacity and oxygen content of test breast and control breast can be calculated by formula, and thus it can be used in the examination of breast tissues. Clinical experiments showed that malignant tumors generally show high blood oxygen capacity and low oxygen content but benign diseases often show low blood oxygen capacity and high oxygen content or other characteristics. At the same time, cancer cells with high metabolism have a variety of structural changes such as hemorrhage, necrosis, calcification etc; moreover, increased, expanded and distorted blood vessels can be found in the lesion area and the edges of them are irregular.

Infrared light is an electromagnetic wave and it has a relatively long wavelength. When it penetrates through breast tissues, the route of it is not linear but scattered and it is specifically sensitive to Hb, so it carries a large number of information about tissues. By means of digital image processing technology and medical image analysis technique, information in the breast transillumination image can be excavated by three-operator system, and thus more relevant information about lesions, changes in blood vessels and edge characteristics can be obtained finally.

This examination method has many advantages such as non-invasive, non-potential injury and convenient use etc; it is characterized in that it can display the functional images of cells or tissues and realize the qualitative (imaging) and quantitative (oxygen content) determination of local breast tissues. This new diagnostic system adopted breast tissue functional imaging technology, breast oxygen non-invasive detection technology and three-operator technology, therefore, it integrated anatomical (structural) information and functional information of breast and put forward a novel, simple and convenient principle and method of functional imaging, and thus provided effective basis for the early diagnosis, the lesion-positioning and the treatment of breast. Moreover, its diagnostic accuracy for breast disease has been improved greatly.