High density functional diffuse optical tomography based on frequency domain measurements improves image quality and spatial resolution

TY - JOUR

T1 - High density functional diffuse optical tomography based on frequency domain measurements improves image quality and spatial resolution

AU - Doulgerakis, Matthaios

AU - Eggebrecht, Adam T

AU - Dehghani, Hamid

PY - 2019/8/21

Y1 - 2019/8/21

N2 - Measurements of dynamic Near Infrared (NIR) light attenuation across the human head together with model-based image reconstruction algorithms allow the recovery of three-dimensional spatial brain activation maps. Previous studies using high-density diffuse optical tomography (HD-DOT) systems have reported improved image quality over sparse arrays. These HD-DOT systems incorporated multi-distance overlapping continuous wave measurements that only recover differential intensity attenuation. In this study, we investigate the potential improvement in reconstructed image quality due to the additional incorporation of phase shift measurements, which reflect the time-of-flight of the measured NIR light, within the tomographic reconstruction from high-density measurements. To evaluate image reconstruction with and without the additional phase information we simulated point spread functions across a whole-scalp field of view in 24 subject specific anatomical models using an experimentally derived noise model. The addition of phase information improves the image quality by reducing localization error by up to 59% and effective resolution by up to 21% as compared to using the intensity attenuation measurements alone. Furthermore, we demonstrate that the phase data enable images to be resolved at deeper brain regions where intensity data fails, which is further supported by utilizing experimental data from a single subject measurement during a retinotopic experiment.

AB - Measurements of dynamic Near Infrared (NIR) light attenuation across the human head together with model-based image reconstruction algorithms allow the recovery of three-dimensional spatial brain activation maps. Previous studies using high-density diffuse optical tomography (HD-DOT) systems have reported improved image quality over sparse arrays. These HD-DOT systems incorporated multi-distance overlapping continuous wave measurements that only recover differential intensity attenuation. In this study, we investigate the potential improvement in reconstructed image quality due to the additional incorporation of phase shift measurements, which reflect the time-of-flight of the measured NIR light, within the tomographic reconstruction from high-density measurements. To evaluate image reconstruction with and without the additional phase information we simulated point spread functions across a whole-scalp field of view in 24 subject specific anatomical models using an experimentally derived noise model. The addition of phase information improves the image quality by reducing localization error by up to 59% and effective resolution by up to 21% as compared to using the intensity attenuation measurements alone. Furthermore, we demonstrate that the phase data enable images to be resolved at deeper brain regions where intensity data fails, which is further supported by utilizing experimental data from a single subject measurement during a retinotopic experiment.

KW - Frequency Domain

KW - High Density Diffuse Optical Tomography

KW - Functional Near Infrared Imaging

U2 - https://doi.org/10.1117/1.NPh.6.3.035007

DO - https://doi.org/10.1117/1.NPh.6.3.035007

M3 - Article

VL - 6

JO - Neurophotonics

JF - Neurophotonics

SN - 2329-423X

IS - 3

M1 - 035007

ER -