Near-infrared optical mammography: Imaging methods and human pilot studies

Optical breast imaging uses near-infrared light, utilizes intrinsic optical absorption signatures of tissue chromophores such as hemoglobin, and localizes optical inhomogeneities including subsurface blood vessel structures and breast lesions that have increased vascular density. The different optical absorption signatures of oxy- and deoxy-hemoglobin can be exploited to yield some physiological information of the optical inhomogeneities such as tissue oxygenation.;The advantages of optical mammography include the lack of ionizing radiation, its non-invasiveness, the relatively compact instrumentation, and its cost-effectiveness. More importantly, it has the potential to distinguish malignant tumors from benign lesions or normal tissue non-invasively. The primary limitation of optical breast imaging is the relatively poor spatial resolution compared with conventional techniques such as x-ray mammography. Another challenge is how to exploit its potential for quantitative and absolute measurements of oxygenation.;In this work we show some strategies to improve the spatial resolution and to estimate the absolute oxygen saturation of breast tumors from a collinear tandem scan of source and detector in a planar geometry optical mammography. In particular we designed and constructed a hybrid continuous-wave/frequency-domain optical breast imaging system capable of taking one full breast image in 5 minutes or less. We developed a three-element phased-array approach to enhance spatial resolution and achieve depth discrimination, and a paired-wavelength spectral approach for quantitative and absolute oxygenation measurement. The theoretical analysis and experimental results have demonstrated the efficiency of the methods. The initial results in health breasts demonstrate the practical feasibility of our imaging method and its implementation into a clinical instrumentation. A whole-breast oxygenation map has been obtained, which, to the best of our knowledge, is so far the first non-invasive optical mammogram with quantitative and absolute oxygenation values associated to the fine structure inside breast.