<title>Breast tumor characterization using near-infrared spectroscopy</title>

Abstract

INTRODUCFIONNIR time resolved spectroscopy (TRS) is one of the most feasible methods which can be used for the characterization of biological systems, due to its non-invasive nature and safety features in measurement. Breast cancer is the leading cause of death in women ages 40-44 and accounts for 32 % of all cancer diagnosis in women. The occurrence rate is as high as one out of nine women in the USA. Breast cancer is the most common form of cancer and the second leading cause of cancer death in North America4. Therefore, it is natural for researchers in the field of NIR spectroscopy to have strong interest in optical properties of normal and abnormal breast tissue. One of the main interest of NIR spectroscopy in breast cancer is the localization of the tumor. Another important feature is to characterize an anomaly non-invasively since more than 75 % ofmammographycal anomalies are found to be benign. This could reduce the anxiety that the patients would have, as well as lower the clinical expense for the biopsy and operation (approximately $4,000 per a case).Compared to other types of tissue, breast tissue has a lower absorption coefficient due to high fatty tissue content and a low number of blood vessels (Chance, unpublished data). During the tumor's growth vasculature development occurs at a denser level than the surrounding tissue7. Therefore, it was expected that tumors with a dense vasculature in breasts would be more easily detected than in other tissue with high absorption. (HUP) have a joint research program on the characterization of optical properties of normal breasts and breasts with anomalies, by using TRS. Appropriate protocols for the measurements of the observable absorption and the scattering coefficients were designed for normal subjects and patients. Measurements for normal subjects were performed to see the optical properties of breast (4 African-Americans and 6 Caucasians) from different locations. Breast anomalies from 51 patients were characterized by measuring the observable absorption and the scattering coefficients. Non-parametric and parametric analyses were performed with the collected data.It should be noted that the absorption coefficient in the text is presented in log10 scale (not in loge). THEORYThe photon transport in a highly scattering medium can be analogous to the dye molecule transport in a liquid containing bleach. Photons are diffused in a scattering medium at a certain diffusion rate, at the same time consumed by the media. Therefore, the governing equation for the photon energy density, P (x, y, z, t), in an isotropic scattering medium can be expressed as a simple diffusion equation with a constant consumption rate, Ja6.-DV2P + j.iP = S(x,y, z,t)(1) where x, y, z is the spatial location in x, y, z direction (cm), respectively, t is the time (ps), and S (x, y, z, t) is a source term. C is the speed of the light in the media. D is the diffusion coefficient, which is 0-8194-11 15-91931$6.O() SPIE Vol. 1888 /487 Downloaded From: http://proceedings.spiedigitallibrary.org/ o...

Characterization of female breasts in vivo by time-resolved and spectroscopic measurements in the near infrared spectroscopy

“…Similar results have also been found by Kang et al from measurements of the time-resolved reflectance of breast tissue in vivo. 14 The advantage of time-resolved measurements is that they allow direct detection of the extremely weak absorption of highly scattering media. The procedure is sensitive enough to detect variations in tissue composition, as demonstrated by measurements on different positions of the breast.…”

“…34 Thus the absorption coefficients in particular provide only a global reference point for the total absorption of the heterogeneous tissue body and are therefore not useful for the model described above. The reduced scattering coefficients used are based on our in vivo and in vitro measurements, 1,3 and on in vivo data published by other authors, 14,15 Figure 8. However, these data do not allow us to distinguish meaningfully between different types of tissue (water-or fat-containing tissues).…”

“…Very few in vivo data on the female breast 14,15 have hitherto been available. We therefore performed time-resolved in vivo experiments on volunteers using a Ti:sapphire laser at a wavelength of 800 nm.…”

Frequency-domain techniques enhance optical mammography: Initial clinical results

“…The ultimate goal of optical mammography is in diagnostic rather than in radiological capabilities. In addition to contrast enhancement, time-resolved methods (either in the frequency domain or the time domain) have the potential to provide an in situ optical biopsy by measuring localized optical properties (20)(21)(22). The information necessary to determine the local absorption and scattering values is contained in the timeresolved signal, and it may provide an additional avenue to discriminate healthy from diseased tissue.…”

Endoscopic subsurface imaging in tissues

“…These optical "signatures" may arise from differences in the cellular level (size of the cells and nucleus, density and cell makeup). The differences between cancer tissue when compared to normal tissue offers the promise for the development of optical imaging technology particularly suitable for cancer detection [3][4]. Except for skin cancer, all the other types of cancer occur inside the body and are very difficult to be detected at early stages.…”