Diffuse optical tomography using phased-array structured interrogation frequency domain near-infrared spectroscopy

We demonstrate improvements in diffuse optical tomography image quality by using phased sources in frequency domain near-infrared spectroscopy. We developed a framework for modeling interfering photon density waves with varying phase and amplitude.</p

Comparison of multi-distance and multi-frequency methods in frequency-domain near-infrared spectroscopy

Functional Near-Infrared Spectroscopy (fNIRS) is a non-invasive, non-ionizing imaging tool that can map brain hemodynamics. While not the most common fNIRS approach, frequency-domain NIRS (FD-NIRS) has shown an ability to estimate the absolute optical properties of tissues and, consequently, accurately estimate tissue chromophores concentrations. FD-NIRS can probe different depths in the tissue using multiple source-detector separations (multi-distance) or multiple modulation frequencies (multi-frequency). In this work, through experimental and simulation results, we demonstrate that using multi-distance and multi-frequency FD-NIRS yields similar results when estimating the optical properties of homogeneous and multi-layered tissues with less than ±10% error in estimations. We also examined some parameters that can affect the accuracy of the estimated optical properties, such as using different modulation frequencies in a multi-distance configuration and different source-detector separations for multi-frequency configuration.</p

Diffuse optical spectroscopic imaging for the investigation of human lactation physiology: a case study on mammary involution

Relatively few imaging and sensing technologies are employed to study human lactation physiology. In particular, human mammary development during pregnancy as well as mammary involution after lactation have been poorly described, despite their importance for breast cancer diagnosis and treatment during these phases. Our case study shows the potential of diffuse optical spectroscopic imaging (DOSI) to uniquely study the spatiotemporal changes in mammary tissue composition during the involution of the lactating breast toward its pre-pregnant state. At nine time intervals over a period of eight months after the cessation of breastfeeding, we reconstructed 2-D maps of mammary water content, lipid content, total hemoglobin (THb) concentration, oxygen saturation (StO2), and tissue optical scattering. Mammary lipid content in the nonareolar region showed a significant relative increase of 59%, whereas water content and THb concentration showed a significant relative decrease of 50% and 48%, respectively. Significant changes were also found in StO2 and tissue optical scattering. Our findings are consistent with the gradual replacement of fibroglandular tissue by adipose tissue and vascular regression during mammary involution. Moreover, our data provide unique insight into the dynamics of breast tissue composition and demonstrate the effectiveness of DOSI as a technique to study human lactation physiology