Optical tomography of breast cancer-monitoring response to primary medical therapy.

Diffuse optical imaging and spectroscopy use near-infrared light to derive physiological parameters such as total hemoglobin concentration and tissue oxygen saturation. Numerous clinical studies have been carried out, either using stand-alone optical methods or in combination with alternative imaging techniques. Studies have demonstrated that diffuse optical imaging and spectroscopy are able to distinguish malignant lesions from benign tissues. Breast cancer is characterized by an increase in total hemoglobin and a decrease in tissue oxygen saturation. Benign lesions such as cysts and fibroadenomas have also been studied, with less conclusive results. As diffuse optical imaging and spectroscopy do not use ionizing radiation, they are a suitable technique for performing repeated scans, such as for monitoring treatment response. This provides a unique functional and dynamic imaging method that reflects changes in tumor angiogenesis and hypoxia. When breast cancers are treated with primary medical therapy, this can result in a selective antiangiogenic effect that could help predict response to treatment earlier than by assessment of tumor size. Diffuse optical imaging and spectroscopy have been used to scan women at several points prior to and during their neoadjuvant chemotherapy treatment, with images and data showing physiological changes in the tumor in response to treatment. In the women who respond to therapy, the total hemoglobin concentration decreases and the level of oxygenation increases in the tumor over the course of the treatment. It is possible to predict a response to treatment as little as 4 days after the start of treatment. These findings demonstrate that optical techniques could play a role in the monitoring of changes in angiogenesis, apoptosis and hypoxia due to neoadjuvant chemotherapy.

Diffuse optical imaging of the healthy and diseased breast: a systematic review.

Screening X-ray mammography is limited by false positives and negatives leading to unnecessary physical and psychological morbidity. Diffuse Optical Imaging using harmless near infra red light, provides lesion detection based on functional abnormalities and represents a novel diagnostic arm that could complement traditional mammography. Reviews of optical breast imaging have not been systematic, are focused mainly on technological developments, and have become superseded by rapid technological advancement. The aim of this study is to review clinically orientated studies involving approximately 2,000 women in whom optical mammography has been used to evaluate the healthy or diseased breast. The results suggest that approximately 85% of breast lesions are detectable on optical mammography. Spectroscopic resolution of tissue haemoglobin composition and oxygen saturation may improve the detectability of breast diseases. Results suggest that breast lesions contain approximately twice the haemoglobin concentration of background tissue. Current evidence suggests that it is not possible to distinguish benign from malignant disease using optical imaging techniques in isolation. Methods to improve the performance of Diffuse Optical Imaging, such as better spectral coverage with additional wavelengths, improved modelling of light transport in tissues and the use of extrinsic dyes may augment lesion detection and characterisation. Future research should involve large clinical trials to determine the overall sensitivity and specificity of optical imaging techniques as well as to establish patient satisfaction and economic viability.

Three-dimensional time-resolved optical mammography of the uncompressed breast.

Optical tomography is being developed as a means of detecting and specifying disease in the adult female breast. We present a series of clinical three-dimensional optical images obtained with a 32-channel time-resolved system and a liquid-coupled interface. Patients place their breasts in a hemispherical cup to which sources and detectors are coupled, and the remaining space is filled with a highly scattering fluid. A cohort of 38 patients has been scanned, with a variety of benign and malignant lesions. Images show that hypervascularization associated with tumors provides very high contrast due to increased absorption by hemoglobin. Only half of the fibroadenomas scanned could be observed, but of those that could be detected, all but one revealed an apparent increase in blood volume and a decrease in scatter and oxygen saturation.