Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
Comparative Study
. 2012 Jul 16;61(4):1120-8.
doi: 10.1016/j.neuroimage.2012.01.124. Epub 2012 Feb 10.

A quantitative spatial comparison of high-density diffuse optical tomography and fMRI cortical mapping

Adam T Eggebrecht  1 , Brian R White, Silvina L Ferradal, Chunxiao Chen, Yuxuan Zhan, Abraham Z Snyder, Hamid Dehghani, Joseph P Culver
Affiliations
Comparative Study

A quantitative spatial comparison of high-density diffuse optical tomography and fMRI cortical mapping

Adam T Eggebrecht et al. Neuroimage. .

Abstract

Functional neuroimaging commands a dominant role in current neuroscience research. However its use in bedside clinical and certain neuro-scientific studies has been limited because the current tools lack the combination of being non-invasive, non-ionizing and portable while maintaining moderate resolution and localization accuracy. Optical neuroimaging satisfies many of these requirements, but, until recent advances in high-density diffuse optical tomography (HD-DOT), has been hampered by limited resolution. While early results of HD-DOT have been promising, a quantitative voxel-wise comparison and validation of HD-DOT against the gold standard of functional magnetic resonance imaging (fMRI) has been lacking. Herein, we provide such an analysis within the visual cortex using matched visual stimulation protocols in a single group of subjects (n=5) during separate HD-DOT and fMRI scanning sessions. To attain the needed voxel-to-voxel co-registration between HD-DOT and fMRI image spaces, we implemented subject-specific head modeling that incorporated MRI anatomy, detailed segmentation, and alignment of source and detector positions. Comparisons of the visual responses found an average localization error between HD-DOT and fMRI of 4.4+/-1mm, significantly less than the average distance between cortical gyri. This specificity demonstrates that HD-DOT has sufficient image quality to be useful as a surrogate for fMRI.

PubMed Disclaimer

Figures

Figure 1
Figure 1
Subject-specific head modeling. (A) T1-weighted MRI volume. (B) Segmented head volume displaying scalp, skull, CSF, gray matter and white matter. (C) High-density tetrahedral mesh for finite element forward light model. (D) Optode positions localized on mesh. The high-density optode grid is composed of 24 sources (red) and 28 detectors (blue). (E) Surface rendering of cortex. Yellow coloring denotes FOV of HD-DOT imaging pad derived from top 50% of the summed sensitivity matrix (see Methods) on the cortical ribbon of Subject 2.
Figure 2
Figure 2
Experimental design. Subject head model fixating on a stimulus screen placed 90 cm away. The visual stimulus is an angularly sweeping black and white reversing radial grid (10 Hz reversal) on a 50% gray background. The wedge extends over a polar angle of 60° and a radial angle of 2.5° – 10.5° and was rotated in steps of 10° each second.
Figure 3
Figure 3
Quadrant activations of BOLD and each hemoglobin concentration species. (A) Parasagittal slice through the T1-weighted MRI of Subject 1. Activations are shown in response to a wedge within the opposite visual quadrant (see visual stimulus key in (C)). Activations for each contrast are thresholded at 50% maximum for that specific activation. (B) Axial slice with activations. Slices are shown in Neurological space (left is left). (C) Visual stimulus key and surface rendering of cortex with activations overlaid for each quadrant. Note there is qualitative agreement between the measured BOLD activation and each of the HD-DOT reconstructed hemoglobin concentrations both in activation location and spatial extent. All activations are the block-averaged responses (10 repetitions) from Subject 1.
Figure 4
Figure 4
Time course of activations in a single voxel in Subject 1. (A) Time trace of hemoglobin concentrations (measured with HD-DOT) in response to eight repetitions of the wedge stimulus. (ΔHbO2, red; ΔHbR, blue; ΔHbT, green). The time trace of BOLD signal is shown in black. (B) Fourier transforms of the time traces in (A). Note the strong peak at the rotation frequency of the stimulus wedge, with little background noise in the signal.
Figure 5
Figure 5
Quadrant activations for all five subjects. All HD-DOT quadrants are ΔHbR contrast. Note that for all subjects, there is qualitative agreement between HD-DOT and fMRI activations both in location as well as extent. The blue quadrant is nearly absent in Subject 4’s BOLD response because the actual recorded activation is deeper in the cortical folds than can be seen within this view. Note that the activation to that quadrant is detected with HD-DOT, but part of the activation is localized on the gyri superficial to the BOLD-measured location.
Figure 6
Figure 6
Overlay of HD-DOT (ΔHbO2) and fMRI activation in Subject 1. Visual stimulus in the lower right visual field gives rise to a strong response in the upper left visual cortex. Red: Overlap of HD-DOT and fMRI measured response. Yellow: HD-DOT but not fMRI. Green: fMRI but not HD-DOT. Note that the majority of the HD-DOT signal is co-localized with the fMRI response along the top 10 mm of the gyral ridges of the cortical surface. Activations are thresholded at 50% maximum for each modality. D: dorsal. A: anterior. L: left.
Figure 7
Figure 7
Phase map error analysis in Subject 2. (A) A map of phase is defined throughout the visual cortex for the BOLD response, shown here for Subject 2. (B) Visual stimulus key for the phase maps. (C) Phase map for HD-DOT (ΔHbO2 contrast). Note spatial correspondence with (A). (D) Scatter plot of circular correlation coefficient of BOLD and ΔHbO2 phases in each voxel within the field of view. Black line is the zero-error line. (E) A phase error plot is created by subtracting the HD-DOT phase in each voxel from the fMRI phase. All phase errors greater than +/− π are corrected via phase wrapping. (F) An estimate of the localization error between fMRI and DOT derived from the phase maps.
See this image and copyright information in PMC

References

    1. Belliveau JW, Kennedy DN, Jr, McKinstry RC, Buchbinder BR, Weisskoff RM, Cohen MS, Vevea JM, Brady TJ, Rosen BR. Functional mapping of the human visual cortex by magnetic resonance imaging. Science. 1991;254:716–719. - PubMed
    1. Benaron DA, Hintz SR, Villringer A, Boas D, Kleinschmidt A, Frahm J, Hirth C, Obrig H, van Houten JC, Kermit EL, Cheong WF, Stevenson DK. Noninvasive functional imaging of human brain using light. Journal of cerebral blood flow and metabolism : official journal of the International Society of Cerebral Blood Flow and Metabolism. 2000;20:469–477. - PubMed
    1. Bevilacqua F, Piguet D, Marquet P, Gross JD, Tromberg BJ, Depeursinge C. In vivo local determination of tissue optical properties: applications to human brain. Appl Opt. 1999;38:4939–4950. - PubMed
    1. Blasi A, Fox S, Everdell N, Volein A, Tucker L, Csibra G, Gibson AP, Hebden JC, Johnson MH, Elwell CE. Investigation of depth dependent changes in cerebral haemodynamics during face perception in infants. Physics in medicine and biology. 2007;52:6849–6864. - PubMed
    1. Bluestone A, Abdoulaev G, Schmitz C, Barbour R, Hielscher A. Three-dimensional optical tomography of hemodynamics in the human head. Optics express. 2001;9:272–286. - PubMed

Publication types