Information rich phase content of frequency domain functional Near Infrared Spectroscopy

Doulgerakis, Matthaios; Eggebrecht, Adam T.; Dehghani, Hamid

doi:10.1117/12.2505874

Cited by 9 publications

(10 citation statements)

References 10 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Furthermore, in functional studies, the mean time‐of‐flight has been shown to have better correlation with functional magnetic resonance imaging (fMRI) activation signals . In FD NIRS, ϕ has been used to measure functional brain activation at shorter source‐detector distance and to show less sensitivity to superficial hemodynamics . We observe that at the frequencies typically used in FD NIRS (100‐150 MHz) ϕ is proportional to the first moment of the photon time‐of‐flight distribution (ϕ ≅ ω 〈 t 〉).…”

Section: Discussionsupporting

confidence: 92%

“…Time‐resolved methods have shown a higher sensitivity to deeper changes in tissues compared to CW methods, either in TD through mean time‐of‐flight, higher moments (like the variance), or late time gates of the photon time‐of‐flight distribution , or in FD through phase (ϕ) measurement . Moreover, slope methods based on multidistance measurements of the first and second moments in TD or ϕ in FD have shown to feature a reduced sensitivity to superficial changes in the tissue than single‐distance (SD) methods.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Phase dual‐slopes in frequency‐domain near‐infrared spectroscopy for enhanced sensitivity to brain tissue: First applications to human subjects

Blaney

Sassaroli

Pham

et al. 2019

Journal of Biophotonics

View full text Add to dashboard Cite

We present a first in vivo application of phase dual‐slopes (DSϕ), measured with frequency‐domain near‐infrared spectroscopy on four healthy human subjects, to demonstrate their enhanced sensitivity to cerebral hemodynamics. During arterial blood pressure oscillations elicited at a frequency of 0.1 Hz, we compare three different ways to analyze either intensity (I) or phase (ϕ) data collected on the subject's forehead at multiple source‐detector distances: Single‐distance, single‐slope and DS. Theoretical calculations based on diffusion theory show that the method with the deepest maximal sensitivity (at about 11 mm) is DSϕ. The in vivo results indicate a qualitative difference of phase data (especially DSϕ) and intensity data (especially single‐distance intensity [SDI]), which we assign to stronger contributions from scalp hemodynamics to SDI and from cortical hemodynamics to DSϕ. Our findings suggest that scalp hemodynamic oscillations may be dominated by blood volume dynamics, whereas cortical hemodynamics may be dominated by blood flow velocity dynamics.

show abstract

Section: Discussionsupporting

confidence: 92%

Section: Introductionmentioning

confidence: 99%

Phase dual‐slopes in frequency‐domain near‐infrared spectroscopy for enhanced sensitivity to brain tissue: First applications to human subjects

Blaney

Sassaroli

Pham

et al. 2019

Journal of Biophotonics

View full text Add to dashboard Cite

show abstract

“…We have recently demonstrated the information content of phase data from a retinotopic experiment showing that the phase data do contain rich information, potentially arriving from deeper regions within the brain and therefore minimizing the superficial tissue contamination. 44 In this work, we have undertaken a detailed study of the potential improvements to image quality gained through incorporating measurements of the phase along with intensity in the reconstruction process. Utilizing a simple layered slab model, the Jacobean (i.e., the sensitivity of both log amplitude and absolute phase to absorption changes) has been calculated and shown in Fig.…”

Section: Discussionmentioning

confidence: 99%

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

2019

Self Cite

View full text Add to dashboard Cite

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 multidistance overlapping continuous wave measurements that only recover differential intensity attenuation. 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 fail, which is further supported by utilizing experimental data from a single subject measurement during a retinotopic experiment.

show abstract

“…Alternatively, the differential approach of slopes, i.e., gradients of optical signals versus source-detector separation, was found to be weakly sensitive to a uniform superficial layer that is a few millimeters thick [10]. It is also relevant to observe that quantities measured in frequency-domain (FD) and time-domain (TD) spectroscopy, namely the phase of photon-density waves and late-time-gate photons, carry a stronger sensitivity to deep tissue than continuous-wave (CW) measurements [11,12]. Furthermore, measurements performed at larger source-detector separations generally sense broader and deeper tissue volumes.…”

Section: Introductionmentioning

confidence: 99%

Multi-Distance Frequency-Domain Optical Measurements of Coherent Cerebral Hemodynamics

et al. 2019

View full text Add to dashboard Cite

We report non-invasive, bilateral optical measurements on the forehead of five healthy human subjects, of 0.1 Hz oscillatory hemodynamics elicited either by cyclic inflation of pneumatic thigh cuffs, or by paced breathing. Optical intensity and the phase of photon-density waves were collected with frequency-domain near-infrared spectroscopy at seven source-detector distances (1140 mm). Coherent hemodynamic oscillations are represented by phasors of oxyhemoglobin (O) and deoxyhemoglobin (D) concentrations, and by the vector D/O that represents the amplitude ratio and phase difference of D and O. We found that, on an average, the amplitude ratio (|D/O|) and the phase difference (∠(D/O)) obtained with single-distance intensity at 11–40 mm increase from 0.1° and −330° to 0.2° and −200°, respectively. Single-distance phase and the intensity slope featured a weaker dependence on source-detector separation, and yielded |D/O| and ∠(D/O) values of about 0.5 and −200°, respectively, at distances greater than 20 mm. The key findings are: (1) Single-distance phase and intensity slope are sensitive to deeper tissue compared to single-distance intensity; (2) deeper tissue hemodynamic oscillations, which more closely represent the brain, feature D and O phasors that are consistent with a greater relative flow-to-volume contributions in brain tissue compared to extracerebral, superficial tissue.

show abstract

Information rich phase content of frequency domain functional Near Infrared Spectroscopy

Cited by 9 publications

References 10 publications

Phase dual‐slopes in frequency‐domain near‐infrared spectroscopy for enhanced sensitivity to brain tissue: First applications to human subjects

Phase dual‐slopes in frequency‐domain near‐infrared spectroscopy for enhanced sensitivity to brain tissue: First applications to human subjects

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

Multi-Distance Frequency-Domain Optical Measurements of Coherent Cerebral Hemodynamics

Contact Info

Product

Resources

About