Transillumination breast spectroscopy (TiBS) uses nonionizing optical radiation to gain information about breast tissue morphological and structural properties. TiBS spectra are obtained from 232 women and compared to mammographic density (MD) quantified using Cumulus. The ability of TiBS to estimate MD is assessed using partial least-squares (PLS) regression methods, which requires TiBS spectra as input (X) and Cumulus MD as target (Y) data. Multiple PLS models are considered to determine the optimal processing technique(s) for the input (X) and target (Y) data. For each model, the association between TiBS estimated MD () and Cumulus MD (Y) is established using Spearman's rank correlation and linear regression analysis. The model that best estimates MD has the fewest assumptions regarding target (Y) and spectral (X) processing. The Spearman's correlation coefficient between predicted MD and Cumulus MD for this model is 0.88, with a regression slope () of 0.93 (95% CI 0.83–1.02) and an R2 of 0.78. The approximation of individual MD was within 10% of Cumulus MD for the majority of women (80%), without stratification on age, body mass index (BMI), and menopausal status. TiBS provides an alternative to mammography assessed MD enabling frequent and earlier use of MD as a risk marker in preventive oncology.
Medical diagnostics and screening are becoming increasingly demanding applications for spectroscopy. Although for many years the demand was satisfied with traditional spectrometers, analysis of complex biological samples has created a need for instruments capable of detecting small differences between samples. One such application is the measurement of absorbance of broad spectrum illumination by breast tissue, in order to quantify the breast tissue density. Studies have shown that breast cancer risk is closely associated with the measurement of radiographic breast density measurement. Using signal attenuation in transillumination spectroscopy in the 550-1100nm spectral range to measure breast density, has the potential to reduce the frequency of ionizing radiation, or making the test accessible to younger women; lower the cost and make the procedure more comfortable for the patient. In order to determine breast density, small spectral variances over a total attenuation of up to 8 OD have to be detected with the spectrophotometer. For this, a high performance system has been developed. The system uses Volume Phase Holographic (VPH) transmission grating, a 2D detector array for simultaneous registration of the whole spectrum with high signal to noise ratio, dedicated optical system specifically optimized for spectroscopic applications and many other improvements. The signal to noise ratio exceeding 50,000 for a single data acquisition eliminates the need for nitrogen cooled detectors and provides sufficient information to predict breast tissue density. Current studies employing transillumination breast spectroscopy (TIBS) relating to breast cancer risk assessment and monitoring are described.
Optical technology holds considerable promise to improve early detection, diagnosis and risk assessment of breast cancer. Unlike current clinical risk assessment tools such as the Gail model, the most widely accepted risk assessment tool, optical risk assessment technology can be applied to the entire female population of all ages. This study is investigating the use of optical reflectance spectroscopy (ORS) as a possible breast tissue development monitoring tool for adolescent girls. Changes in breast development due to proliferation of mammary gland and the surrounding stroma are reflected in changes in breast tissue density and composition which can be interrogated optically. Modifications of development influenced by micronutrients and hormonal status from exposures (e.g. toxins), lifestyle and diet effects, may ultimately be tracked. Preliminary data suggests that ORS has the ability to detect differences in bulk tissue properties in the developing breast of adolescent girls when compared to developmental stages assessed by Tanner, regional variation within breast tissue structure and asymmetries between left and right breast size and shape. Spectral comparison of unilateral breast development permits adjusting the optode separation as function of developmental breast size to minimize optical sampling of pectoral muscle.