Image Quality Analysis of High-Density Diffuse Optical Tomography Incorporating a Subject-Specific Head Model

School of Computer Science, University of Birmingham Birmingham, UK.
Frontiers in Neuroenergetics 05/2012; 4:6. DOI: 10.3389/fnene.2012.00006
Source: PubMed


High-density diffuse optical tomography (HD-DOT) methods have shown significant improvement in localization accuracy and image resolution compared to traditional topographic near infrared spectroscopy of the human brain. In this work we provide a comprehensive evaluation of image quality in visual cortex mapping via a simulation study with the use of an anatomical head model derived from MRI data of a human subject. A model of individual head anatomy provides the surface shape and internal structure that allow for the construction of a more realistic physical model for the forward problem, as well as the use of a structural constraint in the inverse problem. The HD-DOT model utilized here incorporates multiple source-detector separations with continuous-wave data with added noise based on experimental results. To evaluate image quality we quantify the localization error and localized volume at half maximum (LVHM) throughout a region of interest within the visual cortex and systematically analyze the use of whole-brain tissue spatial constraint within image reconstruction. Our results demonstrate that an image quality with less than 10 mm in localization error and 1000 m(3) in LVHM can be obtained up to 13 mm below the scalp surface with a typical unconstrained reconstruction and up to 18 mm deep when a whole-brain spatial constraint based on the brain tissue is utilized.

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Available from: Joseph P Culver
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    • "This is why GLM-based analysis has been developed and popularly used for topographic image analysis [Cui et al., 2011; Tak et al., 2010, 2011; Ye et al., 2009]. To address the second limitation in DOT, several studies have reconstructed DOT images using MRI-based 3D human head structure templates [Boas and Dale, 2005; Cooper et al., 2012; Custo et al., 2010; Zhan et al., 2012] to greatly improve 3D visualization and spatial localization/identification of activated cortical regions under respective stimulations [Eggebrecht et al., 2012; White and Culver, 2010a]. Regarding the third limitation, several DOT reconstruction algorithms including hard-prior usage [Boas and Dale, 2005], spatial variant regularization (SVR) [Culver et al., 2003; Pogue et al., 1999], and depth-compensation algorithm (DCA) [Niu et al., 2010a, b] have been developed to compensate or counter-balance the sensitivity of DOT that exponentially attenuates with the increase of penetration depth to reduce the localization error of brain activation with respect to the depth. "
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    ABSTRACT: Diffuse optical tomography (DOT) is a variant of functional near infrared spectroscopy and has the capability of mapping or reconstructing three dimensional (3D) hemodynamic changes due to brain activity. Common methods used in DOT image analysis to define brain activation have limitations because the selection of activation period is relatively subjective. General linear model (GLM)-based analysis can overcome this limitation. In this study, we combine the atlas-guided 3D DOT image reconstruction with GLM-based analysis (i.e., voxel-wise GLM analysis) to investigate the brain activity that is associated with risk decision-making processes. Risk decision-making is an important cognitive process and thus is an essential topic in the field of neuroscience. The Balloon Analog Risk Task (BART) is a valid experimental model and has been commonly used to assess human risk-taking actions and tendencies while facing risks. We have used the BART paradigm with a blocked design to investigate brain activations in the prefrontal and frontal cortical areas during decision-making from 37 human participants (22 males and 15 females). Voxel-wise GLM analysis was performed after a human brain atlas template and a depth compensation algorithm were combined to form atlas-guided DOT images. In this work, we wish to demonstrate the excellence of using voxel-wise GLM analysis with DOT to image and study cognitive functions in response to risk decision-making. Results have shown significant hemodynamic changes in the dorsal lateral prefrontal cortex (DLPFC) during the active-choice mode and a different activation pattern between genders; these findings correlate well with published literature in functional magnetic resonance imaging (fMRI) and fNIRS studies. Hum Brain Mapp, 2014. © 2014 Wiley Periodicals, Inc.
    Full-text · Article · Aug 2014 · Human Brain Mapping
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    • "In recent years DOT has been developing quickly, with the aim of improving the accuracy, the resolution and the sensitivity of the reconstructed images (Abdelnour et al., 2010; Boas et al., 2004; Gregg et al., 2010; Heiskala et al., 2012). Eggebrecht et al. (2012) and Zhan et al. (2012) have recently shown that, thanks to the recent advances in array design, signal analysis and head modeling , high-density DOT can achieve a spatial resolution comparable to that of functional magnetic resonance imaging (fMRI). Diffuse optical techniques provide no information about the anatomical structure of the brain. "
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    ABSTRACT: Diffuse optical tomography is most accurate when an individual's MRI data can be used as a spatial prior for image reconstruction and for visualization of the resulting images of changes in oxy- and deoxy-hemoglobin concentration. As this necessitates an MRI scan to be performed for each study, which undermines many of the advantages of diffuse optical methods, the use of registered atlases to model the individual's anatomy is becoming commonplace. Infant studies require carefully age-matched atlases because of the rapid growth and maturation of the infant brain. In this paper, we present a 4D neonatal head model which, for each week from 29 to 44 weeks post-menstrual age, includes: 1) A multi-layered tissue mask which identifies extra-cerebral layers, cerebrospinal fluid, grey matter, white matter, cerebellum and brainstem, 2) A high-density tetrahedral head mesh, 3) Surface meshes for the scalp, grey-matter and white matter layers and 4) Cranial landmarks and 10-5 locations on the scalp surface. This package, freely available online at can be applied by users of near-infrared spectroscopy and diffuse optical tomography to optimize probe locations, optimize image reconstruction, register data to cortical locations and ultimately improve the accuracy and interpretation of diffuse optical techniques in newborn populations.
    Full-text · Article · Jun 2014 · NeuroImage
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    • "It is well known that reconstruction performances and spatial resolutions of DOT can be enhanced by using a priori structural information (Brooksby et al., 2006; Pogue and Paulsen, 1998), where imaging volumes can be divided into anatomical regions or contours , as ROIs, identified from prior images by MRI or CT. Accordingly , the identified ROIs can be assigned with heterogeneous optical properties so as to reduce the number of unknown optical properties in image reconstructions or in spatial constraint methods (Zhan et al., 2012). However, the key issue of these methods is that accurate subject-specific prior information needs to be acquired. "
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    ABSTRACT: Diffuse optical tomography (DOT) has been used by several groups to assess cerebral hemodynamics of cerebral ischemia in humans and animals. In this study, we combined DOT with an indocyanine green (ICG)-tracking method to achieve interleaved images of cerebral hemodynamics and blood flow index (BFI) using two middle cerebral artery occlusion (MCAO) rat models. To achieve volumetric images with high-spatial resolution, we first integrated a depth compensation algorithm (DCA) with a volumetric mesh-based rat head model to generate three-dimensional (3D) DOT on a rat brain atlas. Then, the experimental DOT data from two rat models were collected using interleaved strategy for cerebral hemodynamics and BFI during and after ischemic stroke, with and without a thrombolytic therapy for the embolic MCAO model. The acquired animal data were further analyzed using the integrated rat-atlas-guided DOT method to form time-evolving 3D images of both cerebral hemodynamics and BFI. In particular, we were able to show and identify therapeutic outcomes of a thrombolytic treatment applied to the embolism-induced ischemic model. This paper demonstrates that volumetric DOT is capable of providing high-quality, interleaved images of cerebral hemodynamics and blood perfusion in small animals during and after ischemic stroke, with excellent 3D visualization and quantifications.
    Full-text · Article · Jul 2013 · NeuroImage
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