Self-Calibration Phenomenon for Near-Infrared Clinical Measurements: Theory, Simulation, and Experiments

Feder, Idit; Duadi, Hamootal; Chakraborty, Ruchira; Fixler, Dror

doi:10.1021/acsomega.8b00018

Cited by 19 publications

(14 citation statements)

References 29 publications

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“…2). This finding was expected, since we have projected in the past that the IPL point phenomena in different geometries can be predicted by the distance between the light source and the detector [20]. The simulation results will encourage further experimental studies of IPL behaviors in such a convex geometry, both in MC simulation and using phantom materials, for gauging the solution of steady steady-state photon diffusion.…”

Section: Discussionmentioning

confidence: 63%

Self calibration iso-pathlength point in cylindrical tissue geometry: solution of steady-state photon diffusion based on the extrapolated zero-boundary

2018

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Near-infrared optical techniques permit tissue diagnosis by surface measurement. However, the geometrical shape of this interface profiles the intensity of the surface measurement, which is found to have an iso-pathlength (IPL) point allowing for absorption identification independent of tissue scattering. The IPL point was projected in Monte Carlo (MC) simulation, validated experimentally in cylindrical tissues, but remains underappreciated through analytical approaches. In this work, we present an analytical solution of an IPL point for steady-state diffusion based on the extrapolated zero-boundary condition. The same IPL points were found when comparing this solution to 3-D MC simulations for a tissue radius range of 5-8mm.

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Section: Discussionmentioning

confidence: 63%

Self calibration iso-pathlength point in cylindrical tissue geometry: solution of steady-state photon diffusion based on the extrapolated zero-boundary

2018

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“…Furthermore, fNIRS suffered from an inherent error due to spectral-dependent scattering which was not been considered in simulations. Some recent study presented an iso-pathlength (IPL) point, at which the intensity of re-emitted light remains constant [34], [35]. This result may provide a useful idea and method for our further research to improve fNIRS performance.…”

Section: Discussionmentioning

confidence: 91%

Systematic Analysis for fNIRS Measurement Combining Sensitivity and SNR Based on the Colin27 Brain Template

Wang

Chen

2020

IEEE Photonics J.

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Functional near-infrared spectroscopy (fNIRS) is widely used in brain science. The sensitivity and signal-to-noise ratio (SNR) are core parameters during the measurement. However, previous studies have not systematically analyzed the parameters in wholebrain measurements which limits its further improvement. In this paper, a noise model was established, including electronic noise, shot noise and speckle noise. Considering different brain regions and different source-detector(S-D) separation, a Monte Carlo simulation tool was utilized to simulate the photons migration inside a realistic human-brain template (Colin27). Based on the simulation, we analyzed the light fluence-rate distribution, detection-sensitivity, noise composition and SNR. The results show that sensitivity is positively correlated with S-D separations and the parietal region has the lowest sensitivity. In terms of noise, the equivalent noise power in different brain regions were consistent, and the noise proportions varied greatly under different S-D conditions and the SNR decreased by about 45 dB in the S-D range 10 mm∼45 mm. Based on the results, a fNIRS system optimization strategy is proposed and in our simulation conditions, we suggest an optimal S-D in frontal, temporal, parietal and occipital lobes are 30 mm, 25 mm, 30 mm, 30 mm respectively. The systematical analysis method will contribute to guiding the optimal design of the fNIRS system.

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“…It also exists in semi-infinite geometry, more relevant in clinical applications of NIR spectroscopy on the head, arm, leg, etc. [23]. This phenomenon was demonstrated in a range of scatterings that fulfills the multiple scattering condition [24].…”

Section: Introductionmentioning

confidence: 80%

Influence of Detector Size and Positioning on Near-Infrared Measurements and Iso-pathlength Point of Turbid Materials

2021

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Measuring physical phenomena in an experimental system is commonly limited by the detector. When dealing with spatially defined behaviors, the critical parameter is the detector size. In this work, we examine near-infrared (NIR) measurements of turbid media using different size detectors at different positions. We examine cylindrical and semi-infinite scattering samples and measure their intensity distribution. An apparent crossing point between samples with different scatterings was previously discovered and named the iso-pathlength point (IPL). Monte Carlo simulations show the expected changes due to an increase in detector size or similarly as the detector’s location is distanced from the turbid element. First, the simulations show that the intensity profile changes, as well as the apparent IPL. Next, we show the average optical pathlength, and as a result, the differential pathlength factor, are mostly influenced by the detector size in the range close to the source. Experimental measurements using different size detectors at different locations validate the influence of these parameters on the intensity profiles and apparent IPL point. These findings must be considered when assessing optical parameters based on multiple scattering models. In cases such as NIR assessment of tissue oxygenation, size and location may cause false results for absorption or optical path.

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Self-Calibration Phenomenon for Near-Infrared Clinical Measurements: Theory, Simulation, and Experiments

Cited by 19 publications

References 29 publications

Self calibration iso-pathlength point in cylindrical tissue geometry: solution of steady-state photon diffusion based on the extrapolated zero-boundary

Self calibration iso-pathlength point in cylindrical tissue geometry: solution of steady-state photon diffusion based on the extrapolated zero-boundary

Systematic Analysis for fNIRS Measurement Combining Sensitivity and SNR Based on the Colin27 Brain Template

Influence of Detector Size and Positioning on Near-Infrared Measurements and Iso-pathlength Point of Turbid Materials

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