Dual-slope imaging of cerebral hemodynamics with frequency-domain near-infrared spectroscopy

Blaney, Giles; Fernandez, Cristianne; Sassaroli, Angelo; Fantini, Sergio

doi:10.1117/1.nph.10.1.013508

Cited by 11 publications

(21 citation statements)

References 83 publications

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“…2 Previous work has also found a transition between measuring hemodynamics that are mostly driven by BV oscillations when probing superficial tissue and by BF when probing deeper cerebral tissue with point measurements and imaging. 8,13 Figure 2: Amplitude ratio (a and b) and phase difference (c and d) for the phasor ratio for Total hemoglobin versus Arterial Blood Pressure (𝑇 ̃/𝐴 ̃) for single-distance intensity (a and c) and dual-slope phase (b and d).…”

Section: Resultsmentioning

confidence: 99%

“…Channels with a noise level higher than 1 µM or an amplitude ratio for either O ̃/A ̃ or D ̃/A ̃smaller than 0.001 µM/mmHg was disregarded in further analysis. 8 Image reconstruction for each data type was done by converting the averaged O ̃/A ̃ and D ̃/A ̃ values into phasor ratios of the absorption coefficient (𝜇 ̃𝑎) versus A ̃ (𝜇 ̃𝑎/A ̃) for each wavelength using Beer's law, multiplying the vector of these measurements by the Moore-Penrose inverse of the matrix of sensitivity to absorption changes (S). This S was generated using a semi-infinite homogenous medium using optical properties measured during baseline and consisted of 2-layers of voxels size 1 mm x 1 mm x 5 mm for the top layer and 1 mm x 1 mm x 25 mm for the bottom layer, where z is depth.…”

Section: Discussionmentioning

confidence: 99%

“…This S was generated using a semi-infinite homogenous medium using optical properties measured during baseline and consisted of 2-layers of voxels size 1 mm x 1 mm x 5 mm for the top layer and 1 mm x 1 mm x 25 mm for the bottom layer, where z is depth. 8 Images shown are of the bottom layer voxels. Reconstructed images of 𝜇 ̃𝑎/A ̃ were translated back to O ̃/A ̃ and D ̃/A ̃ using Beer's Law.…”

Section: Discussionmentioning

confidence: 99%

“…The combination of DOI and CHS applied to the human brain has the potential to provide spatial information relating cerebral autoregulation over a brain region, and when applied with DS preferentially reconstruct deeper cerebral hemodynamics. 8 Here, we will use DS DOI with NIRS during a CHS protocol and demonstrate the ability of this method to achieve a preferential sensitivity to the brain in comparison to the dominant sensitivity to extracerebral, superficial tissue featured by traditional SDI measurements.…”

Section: Introductionmentioning

confidence: 99%

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Mapping of coherent cerebral hemodynamics with dual-slope imaging

Fernandez

Blaney²,

Sassaroli

et al. 2023

Optical Tomography and Spectroscopy of Tissue XV

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Cerebral hemodynamics, measured with near-infrared spectroscopy, that are coherent with changes in blood pressure can be analyzed with Coherent Hemodynamics Spectroscopy (CHS). Performing diffuse optical imaging during a CHS protocol provides the ability to spatially map cerebral hemodynamics and elucidate their relation to blood flow and blood volume dynamics. Here, we apply frequency-domain dual-slope optical imaging during a CHS protocol to demonstrate the preferential sensitivity to cerebral hemodynamics of dual-slope frequency-domain measurements as compared to traditional single-distance intensity measurements. Specifically, the results show that dual-slope phase measurements recorded hemodynamics that are mostly associated with blood-flow oscillations (as expected in the brain), while singledistance intensity measurements recorded hemodynamics that are mostly associated with blood-volume oscillations (as expected in the scalp). Reconstructed dual-slope phase images showed the effect of a spatially variable skull thickness, which can cause heterogeneity within the reconstructed images. Future work will include measurements on multiple subjects and across multiple oscillation frequencies to further investigate the spatial distribution and frequency dependence of cerebral hemodynamic oscillations.

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Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Mapping of coherent cerebral hemodynamics with dual-slope imaging

Fernandez

Blaney²,

Sassaroli

et al. 2023

Optical Tomography and Spectroscopy of Tissue XV

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show abstract

“…3,4 We have also introduced the Dual-Slope (DS) technique which localizes the S region deeper within the medium compared to traditional Single-Distance (SD) measurements. 4 Herein we expand on previous work involving DS FD fNIRS DOI 5 to achieve functional brain activation measurements on a large population of subjects. This is achieved in two steps.…”

Section: Introductionmentioning

confidence: 99%

Dual-slope diffuse optical imaging with a modular source-detector array

Blaney¹,

Fernandez

Sassaroli

et al. 2023

Neural Imaging and Sensing 2023

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Functional Near-InfraRed Spectroscopy (NIRS) (fNIRS) is a powerful method for non-invasively measuring cerebral hemodynamics on human subjects. Measurement contamination from superficial tissue which do not represent the brain continues to be an issue. We have proposed the Dual-Slope (DS) approach which is less sensitive to superficial tissue compared to typical Single-Distance (SD) methods. This DS method has been applied to Diffuse Optical Imaging (DOI), designing and constructing a large source-detector array. Previous results suggested that DS phase (φ) has intrinsically higher sensitivity to the brain compared to SD Intensity (I). To further investigate this finding, on a large population of subjects, a modular DS array is designed. Allowing for collection from different cortical locations during various protocols. These source-detector modules are hexagonal and contain 4 intra-module DS sets. Tessellation greatly expands the number of measurement sets through the creation of inter-module DS sets. In one example, we found a tessellation of 7 modules which generated 94 DS sets. The modules will be used to enable large population DS DOI studies. Here we present one example trace during a 3-back protocol. Examination of the DS traces suggest the expected higher DS φ sensitivity to cerebral hemodynamics. Further, close observation of the results demonstrate the importance of considering both the Oxy-hemoglobin concentration change (∆O) and Deoxy-hemoglobin concentration change (∆D) during such protocols. The results indicated that if one observed only ∆O they would have mis-identified brain activation in the short SD I measurement. Other data-types and ∆D dynamics suggested that the short SD I was dominated by superficial blood-volume instead of the blood-flow dynamics associated with brain activation.

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Spectroscopic assessment of flavor-related chemical compounds in fresh tea shoots using deep learning

Denaro,

Lin,

Huang

2024

Preprint

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This study employs a deep-learning method, Y-Net, to estimate 10 tea flavor-related chemical compounds (TFCC), including gallic acid, caffeine and eight catechin isomers, using fresh tea shoot reflectance and transmittance. The unique aspect of Y-Net lies in its utilization of dual inputs, reflectance and transmittance, which are seamlessly integrated within the Y-Net architecture. This architecture harnesses the power of a convolutional neural network-based residual network to fuse tea shoot spectra effectively. This strategic combination enhances the capacity of the model to discern intricate patterns in the optical characteristics of fresh tea shoots, providing a comprehensive framework for TFCC estimation. In this study, we destructively sampled tea shoots from tea farms in Alishan (Ali-Mountain) in Central Taiwan within the elevation range of 879-1552 m a.s.l. Tea shoot reflectance and transmittance data (n = 2032) within the optical region (400-2500 nm) were measured using a portable spectroradiometer and pre-processed using an algorithm; corresponding TFCC were qualified using the high-performance liquid chromatography analysis. To enhance the robustness and performance of Y-Net, we employed data augmentation techniques for model training. We compared the performances of Y-Net and seven other commonly utilized statistical, machine-/deep-learning models (partial least squared regression, Gaussian process, cubist, random forests and three feedforward neural networks) using root-mean-square error (RMSE). Furthermore, we assessed the prediction accuracies of Y-Net and Y-Net using spectra within the visible and near-infrared (VNIR) regions (for higher energy throughput and low-cost instruments) and reflectance only (for airborne and spaceborne remote sensing applications). The results showed that overall Y-Net (mean RMSE +/- standard deviation [SD] = 2.51 +/- 2.20 mg g-1) outperformed the other statistical, machine- and deep-learning models (>= 2.59 +/- 2.64 mg g-1), demonstrating its superiority in predicting TFCC. In addition, this original Y-Net also yielded slightly lower mean RMSE (+/- SD) compared with VNIR (2.76 +/- 2.41 mg g-1) and reflectance-only (2.68 +/- 2.74 mg g-1) Y-Nets using validation data. This study highlights the feasibility of using spectroscopy and Y-Net to assess minor biochemical components in fresh tea shoots and sheds light on the potential of the proposed approach for effective regional monitoring of tea shoot quality.

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Dual-slope imaging of cerebral hemodynamics with frequency-domain near-infrared spectroscopy

Cited by 11 publications

References 83 publications

Mapping of coherent cerebral hemodynamics with dual-slope imaging

Mapping of coherent cerebral hemodynamics with dual-slope imaging

Dual-slope diffuse optical imaging with a modular source-detector array

Spectroscopic assessment of flavor-related chemical compounds in fresh tea shoots using deep learning

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