Laser Breast Scanner (LBS) instruments in use during clinical studies in breast (left) and muscle (right) tissues.
Diffuse Optical Spectroscopy and Imaging (DOS/I) is a non-invasive optical technique that quantifies thick tissues (up to several cm) absorption (μa) and reduced scattering (μs) coefficients. Near-infared (NIR) absorption spectra measurements provide the concentrations of functional tissue components:tissue hemoglobin (total, oxy- & deoxy- forms), water, and bulk lipid. Tissue scattering properties are related to important morphological data, such as collagen density and orientation. Measured tissue absorption spectra also provide detailed information on subtle biochemical shifts in water, (such as temperature, bound water state) hemoglobin (variant forms such as met-hemoglobin), and cytochrome (oxidation state). The combination of high-spectral and temporal resolution data from DOS/I provides a detailed measure of the hemodynamic, energetic, and morphological states of a tissue. Quantification of tissue biochemical state is possible because of a model-based approach that separates absorption from scattering across the entire measured spectrum.
The Laser Breast Scanner (LBS) instrument (left) can be used with different handheld probes to non-invasively interrogate deep (few cm) or superficial (~1mm) tissues.
DOS/I is currently featured in the Laser Breast Scanner (LBS), which was designed, built, and tested as part of LAMMP core research. The LBS represents the very essence of the NIH technology center program: after starting in the laboratory, subsequent refinement has transformed LBS technology into a useful translational clinical research device. Current collaborative projects are driving the need to improve the LBS instrument for specific applications in breast as well as other tissues. A number of applications is tissues such as muscle involve probing layered and heterogeneous structures.
Examples of LBS clinical data. Left: 2D map of an optical contrast function (TOI) in a young breast cancer patient. Right: Pathology-specific NIR absorption signatures from a population of breast cancer patients.
The high spectral information content of the LBS allows for quantitative deep tissue spectral imaging. The left figure above provides an in vivo functional map using the LBS of a 1.3x0.9x1.0 cm infiltrating ducal carcinoma tumor in a 37 year-old subject. Three specific regions are identified within the map: a normal region far from the lesion site (C), a region directly over the lesion site (B), and a second suspicious near the primary lesion site (A). Broadband absorption and scattering spectra are shown from each region to the right, and reveal important functional differences between the regions. The figure on the right further demonstrates the power of quantitative model-based spectroscopic imaging. Recent evidence using the LBS suggests that there are pathology-specific NIR absorption signatures that are unique to malignant lesions and are not found in normal tissues. These specific biomarkers were discovered using novel spectroscopy analysis tools developed through LAMMP.