SUMMARY Diffuse optical tomography, also known as near infrared tomography, has been under investigation, for non-invasive functional imaging of tissue, specifically for the detection and characterization of breast cancer or other soft tissue lesions. Much work has been carried out for accurate modeling and image reconstruction from clinical data. NIRFAST, a modeling and image reconstruction package has been developed, which is capable of single wavelength and multi-wavelength optical or functional imaging from measured data. The theory behind the modeling techniques as well as the image reconstruction algorithms is presented here, and 2D and 3D examples are presented to demonstrate its capabilities. The results show that 3D modeling can be combined with measured data from multiple wavelengths to reconstruct chromophore concentrations within the tissue. Additionally it is possible to recover scattering spectra, resulting from the dominant Mie-type scatter present in tissue. Overall, this paper gives a comprehensive over view of the modeling techniques used in diffuse optical tomographic imaging, in the context of NIRFAST software package.

Mapping of human brain function has revolutionized systems neuroscience. However, traditional functional neuroimaging by positron emission tomography or functional magnetic resonance imaging cannot be used when applications require portability, or are contraindicated because of ionizing radiation (positron emission tomography) or implanted metal (functional magnetic resonance imaging). Optical neuroimaging offers a non-invasive alternative that is radiation free and compatible with implanted metal and electronic devices (for example, pacemakers). However, optical imaging technology has heretofore lacked the combination of spatial resolution and wide field of view sufficient to map distributed brain functions. Here, we present a high-density diffuse optical tomography imaging array that can map higher-order, distributed brain function. The system was tested by imaging four hierarchical language tasks and multiple resting-state networks including the dorsal attention and default mode networks. Finally, we imaged brain function in patients with Parkinson’s disease and implanted deep brain stimulators that preclude functional magnetic resonance imaging.

Functional neuroimaging is a vital element of neuroscience and cognitive research and, increasingly, is an important clinical tool. Diffuse optical imaging is an emerging, noninvasive technique with unique portability and hemodynamic contrast capabilities for mapping brain function in young subjects and subjects in enriched or clinical environments. We have developed a high-performance, high-density diffuse optical tomography (DOT) system that overcomes previous limitations and enables superior image quality. We show herein the utility of the DOT system by presenting functional hemodynamic maps of the adult human visual cortex. The functional brain images have a high contrast-to-noise ratio, allowing visualization of individual activations and highly repeatable mapping within and across subjects. With the improved spatial resolution and localization, we were able to image functional responses of 1.7 cm in extent and shifts of <1 cm. Cortical maps of angle and eccentricity in the visual field are consistent with retinotopic studies using functional MRI and positron-emission tomography. These results demonstrate that high-density DOT is a practical and powerful tool for mapping function in the human cortex. functional brain mapping ͉ near-infrared spectroscopy ͉ neuroimaging ͉ retinotopy F unctional mapping of the human brain is an important aspect of cognitive neuroscience that is used to study brain organization and development. Increasingly, functional neuroimaging is being used as a diagnostic and prognostic tool in the clinical setting. Its expanding application in the study of disease and development necessitates new, flexible functional neuroimaging tools. Many situations are not amenable to scanner logistics, such as subjects who are in the intensive care unit, who are performing complex tasks, or who might otherwise require sedation for imaging, such as infants and young children. Additionally, there are imaging situations in which the neurovascular coupling either is not mature, such as in neonates and very young infants (1-3), or is altered due to injury or illness (4, 5). Diffuse optical imaging (DOI) is a methodology uniquely suited to such tasks, because it is a mobile system that uses a small, flexible imaging cap (6, 7). DOI images hemodynamic contrasts similar to functional MRI (fMRI) with blood oxygen-level dependent (BOLD) signals (fMRI-BOLD); however, DOI can measure changes in oxygenated hemoglobin (⌬HbO 2 ), deoxygenated hemoglobin (⌬Hb R ), and total hemoglobin (⌬Hb T ), whereas the BOLD signal is mainly dependent on ⌬Hb R (8). The ability to simultaneously image these contrasts allows DOI to distinguish differences in their magnitude (3, 4, 9), timing (3, 10-12), and localization (13-15), forming a more complete picture of neurovascular function. In contrast to positron emission tomography (PET), which uses ionizing radiation, DOI uses safe, infrared light for imaging. Despite unique strengths, however, DOI as a standard tool for functional mapping has been limited by low spatial resolution...

Near-infrared spectroscopic tomography was used to measure the properties of 24 mammographically normal breasts to quantify whole-breast absorption and scattering spectra and to evaluate which tissue composition characteristics can be determined from these spectra. The absorption spectrum of breast tissue allows quantification of (i) total hemoglobin concentration, (ii) hemoglobin oxygen saturation, and (iii) water concentration, whereas the scattering spectrum provides information about the size and number density of cellular components and structural matrix elements. These property data were tested for correlation to demographic information, including subject age, body mass index, breast size, and radiographic density. Total hemoglobin concentration correlated inversely to body mass index, likely because lower body mass indicates proportionately less fat and more glandular tissue, and glandular tissue contains greater vascularity, hence, more total hemoglobin. Optical scattering was correlated to breast diameter, subject age, and radiographic density. In the radiographic density, fatty breasts had low scattering power and extremely dense breasts had higher values. This observation is consistent with low attenuation of conventional x-rays with fat and higher attenuation in glandular tissues. Optically, fatty tissues have large scatterers leading to a low scattering power, whereas glandular or fibrous tissues have more cellular and collagen-based structures that lead to high scattering power. The study presents correlative data supporting the hypothesis that optical measurements of absorption and scattering can provide physiologically relevant information about breast tissue composition. These breast constituents vary significantly between individuals and can be altered because of changes in breast physiology or pathological state.T he breast is a highly heterogeneous and dynamically complex organ whose characteristics depend on factors such as age, hormonal status, habitus, family and medical history, and genetics (1-3). Normal breast tissue changes considerably during development, pregnancy, and menopause, and throughout the menstrual cycle. It has been documented that blood flow can increase up to 50% at the time of ovulation; and by the end of the monthly cycle, some women may undergo breast enlargement of up to 20% because of increased vascularity and water content (1). Total blood content can vary up to a factor of 5 or more between women based on their body-fat content, making the breast one of the most physiologically variable tissues in the human body. With nearinfrared (NIR) spectral imaging, hemoglobin concentration, oxygen saturation, and water content can yield information about the current physiological state of the normal breast.The relatively good transparency of tissue in the red and NIR spectrum (i.e., 600-1,000 nm) permits sufficient light penetration to detect signals through as much as a dozen centimeters of the breast. In the NIR spectrum, the primary absorbers of light are hemoglobin, oxyh...