Diffuse optical imaging of brain activation: approaches to optimizing image sensitivity, resolution, and accuracy

Abstract

Near-infrared spectroscopy (NIRS) and diffuse optical imaging (DOI) are finding widespread application in the study of human brain activation, motivating further application-specific development of the technology. NIRS and DOI offer the potential to quantify changes in deoxyhemoglobin (HbR) and total hemoglobin (HbT) concentration, thus enabling distinction of oxygen consumption and blood flow changes during brain activation. While the techniques implemented presently provide important results for cognition and the neurosciences through their relative measures of HbR and HbT concentrations, there is much to be done to improve sensitivity, accuracy, and resolution. In this paper, we review the advances currently being made and issues to consider for improving optical image quality. These include the optimal selection of wavelengths to minimize random and systematic error propagation in the calculation of the hemoglobin concentrations, the filtering of systemic physiological signal clutter to improve sensitivity to the hemodynamic response to brain activation, the implementation of overlapping measurements to improve image spatial resolution and uniformity, and the utilization of spatial prior information from structural and functional MRI to reduce DOI partial volume error and improve image quantitative accuracy. D 2004 Elsevier Inc. All rights reserved.

Coupling between somatosensory evoked potentials and hemodynamic response in the rat

“…During forepaw stimulation the electrodes near the primary somatosensory cortex (SI) resolve the characteristic SEP components, which correspond to SI activation. DOI has been used to measure hemodynamic evoked responses in several cortical areas in both humans and animals (Boas et al, 2004;Durduran et al, 2004;Gibson et al, 2005;Hillman et al, 2007;Hoshi, 2003;Obrig and Villringer, 1997;Villringer and Chance, 1997). Previously, we have shown that in rats we are able to detect evoked hemodynamic responses both spatially and temporally equivalent to fMRI (Culver et al, 2005;Culver et al, 2003;Siegel et al, 2003).…”

Task complexity relates to activation of cortical motor areas during uni- and bimanual performance: A functional NIRS study

“…We benefited both advantages in the development of our fNIRS system. For review and discussion over existing methods and systems, see (Strangman et al, 2002a, Hoshi, 2003, Obrig and Villringer, 2003, Boas et al, 2004, Wolf et al, 2007.…”

A near infrared instrument to monitor relative hemoglobin concentrations of human bone tissue in vitro and in vivo

“…It is well known that the wavelength pairs 830 and 750 nm, or 830 and 690 nm are best suited because the wavelengths in these pairs lie above and below the isobestic point of 805 nm, where oxyhemoglobin and deoxy-hemoglobin have the same intrinsic absorption coefficient. 20 The above wavelength pairs minimize random wavelength dependent measurement errors as well as systematic errors arising from inaccuracies in model parameters. 20 With this in mind, laser diodes of wavelengths 685 ͑close to 690 nm͒ and 830 nm are used as diodes of these wavelengths are readily available.…”

“…20 The above wavelength pairs minimize random wavelength dependent measurement errors as well as systematic errors arising from inaccuracies in model parameters. 20 With this in mind, laser diodes of wavelengths 685 ͑close to 690 nm͒ and 830 nm are used as diodes of these wavelengths are readily available. As detailed in Sec.…”