Diffuse optical imaging (DOI) is becoming increasingly a very important neuroimaging

Diffuse optical imaging (DOI) is becoming increasingly a very important neuroimaging device when fMRI is precluded. In the lack of subject-specific anatomical pictures atlas-based mind models signed up towards the subject’s mind using cranial fiducials offer an substitute solution. Furthermore a typical atlas is of interest since it defines a common organize space where to compare outcomes across topics. The question therefore arises as to whether atlas-based forward light modeling ensures adequate HD-DOT image quality at the individual and group level. Herein we demonstrate Geniposide the feasibility of using atlas-based forward light modeling and spatial normalization methods. Both techniques are validated using subject-matched HD-DOT and fMRI data sets for visual evoked responses measured in Rabbit Polyclonal to mGluR7. five healthy adult subjects. HD-DOT reconstructions obtained with the registered atlas anatomy (atlas DOT) were compared to reconstructions obtained with the subject-specific anatomical images (subject-MRI DOT) and to subject-matched BOLD fMRI data at the single subject level. Additionally group level comparisons were performed in atlas space. All comparisons were evaluated in terms of localization error and three-dimensional overlaps. Overall the atlas DOT reconstructions showed a good agreement with results obtained with both subject-MRI DOT reconstructions and fMRI data thereby providing support for the use of atlas HD-DOT as surrogate for fMRI when anatomical imaging is not available. 2 Methods The different processing steps involved in the atlas head modeling and spatial normalization methods are outlined in Figure 1. Figure 1 Flowchart of atlas-based head modeling in subject space and spatial normalization in atlas space. DOTsubject-MRI denotes subject-MRI DOT reconstruction; DOTatlas denotes atlas DOT reconstruction. Solid boxes denote measurements/data: MRI (cyan); DOT (orange); … 2.1 Subjects and protocol Five healthy adult participants (aged 21-30 years) were recruited for this study. The research was approved by the Human Research Protection Office at Washington University School of Medicine and informed consent was obtained from each participant before scanning. The visual stimuli consisted of angularly sweeping reversing checkerboard wedges (10 Hz reversal) rotating around a white cross located at the center of the screen on a 50% background. The grid rotated 10 times at 10°/sec to complete a sweep of the entire visual field every 36 seconds. Gray screens were also presented for 30 seconds before and after the complete sweep sequence (Engel et al. Geniposide 1994 Warnking et al. 2002 2.2 High-density DOT system and Geniposide acquisition Subjects were seated in an adjustable chair in a low ambient light room facing a 19-inch LCD screen at a viewing distance of 90 cm. All measurements were performed with a continuous wave high-density DOT imaging system (Zeff et al. 2007 The instrument consists of 24 source positions and 28 Geniposide detector positions interleaved in a high-density array. Each source position has LEDs emitting at two near-infrared wavelengths (750 and 850 nm). Optical fibers are coupled to a flexible plastic cap that is attached to the head by means of Velcro straps. Source-detector (SD) pair measurements at multiple distances (namely first- through fourth-nearest neighbors at 13 30 39 and 47 mm respectively) were sampled simultaneously at a frame rate of 10 Hz. A set of fiducial points were also measured during the HD-DOT scan in order to determine the location of the optode array relative to the head. Specifically fiducial points were measured on the subject’s head surface (including nasion inion and pre-auricular points) as well as the outer four corners of the optode array using an RF pen based 3D digitizer (FastTrack Polhemus USA). 2.3 fMRI acquisition All Geniposide MRI scans were collected on a Siemens Trio (Erlagen Germany) 3T scanner. Anatomical T1-weighted (T1) MPRAGE (echo time (TE) = 3.13 ms repetition time (TR) = 2400 ms flip angle = 8° 1 × 1 × 1 mm isotropic voxels) and T2-weighted (T2) scans (TE = 84 ms flip angle = 120° 1 × 1 × 4 mm voxels) were taken at each session. Functional images were collected using a series of asymmetric gradient spin-echo echo-planar (EPI) sequences (each brain volume had a TE = 27 ms TR = 2000 ms flip angle = 90° 4 × 4 × 4 mm voxels) to measure the blood-oxygenation-level-dependent (BOLD) contrast. In keeping with standard methods for performing BOLD analysis.