Estimation of optical pathlength through tissue from direct time of flight measurement

Delpy, David T.; Cope, M; Zee, Pieter van der; Arridge, Simon; Wray, Susan; Wyatt, John

doi:10.1088/0031-9155/33/12/008

Cited by 1,928 publications

(1,243 citation statements)

References 17 publications

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“…Most devices measure relative changes in [O 2 Hb] and [HHb] using the MBLL (Delpy et al, 1988). No information was obtained about the algorithms used in proprietary software of instruments D3, D4 and D13.…”

Section: Overview Of Commercially Available Imaging Instrumentationmentioning

confidence: 99%

“…Typically, two or a few more discrete wavelengths are used in NIRI, and the MBLL equations are evaluated at these selected wavelengths (Delpy et al, 1988;Kocsis et al, 2006). In broadband NIRI, however, light from a continuous portion of the spectrum is required in order to obtain the continuous absorption spectrum of the diffuse reflectance (Diop et al, 2009;Kashyap et al, 2007;Tisdall et al, 2007).…”

Section: Light Sources For Fniri Instrumentsmentioning

confidence: 99%

“…From the instrumentation point of view this means that an extremely high dynamic range is required to implement these simulation results in a real system. (Delpy et al, 1988) and multi-distance (MD) approaches, making use of several source-detector distances.…”

Section: Probe Designmentioning

confidence: 99%

“…The MBLL (Delpy et al, 1988) extends the Beer-Lambert law by introducing a scattering dependent light intensity loss parameter, here denoted by G. The law describes the loss of light intensity (I) in tissue (optical density OD, also sometimes attenuation A, unitless) as a function of the chromophore concentrations (c, units [M]), molar extinction coefficients (ε, [M −1 cm −1 ], not to be mistaken with the molar absorption coefficient α = ln(10)ε or the absorption coefficient μ a = αc), differential path length factor (DPF, unitless; accounts for the increased distance the light travels due to μ s ′), source-detector separation (d, [cm]) and G (unitless):…”

Section: Modified Beer-lambert Law (Mbll)mentioning

confidence: 99%

“…Since the Beer-Lambert law is only valid in non-scattering media, it cannot be applied to biological tissue. Relatively recently therefore the modified Beer-Lambert law (MBLL) was developed by the British Delpy (Delpy et al, 1988), to take into account the light scattering. The MBLL is often used by many instruments described in this review.…”

Section: Introductionmentioning

confidence: 99%

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A review on continuous wave functional near-infrared spectroscopy and imaging instrumentation and methodology

Scholkmann¹,

Kleiser²,

Metz³

et al. 2014

NeuroImage

1,471

1,394

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This year marks the 20th anniversary of functional near-infrared spectroscopy and imaging (fNIRS/fNIRI). As the vast majority of commercial instruments developed until now are based on continuous wave technology, the aim of this publication is to review the current state of instrumentation and methodology of continuous wave fNIRI. For this purpose we provide an overview of the commercially available instruments and address instrumental aspects such as light sources, detectors and sensor arrangements. Methodological aspects, algorithms to calculate the concentrations of oxy-and deoxyhemoglobin and approaches for data analysis are also reviewed. From the single-location measurements of the early years, instrumentation has progressed to imaging initially in two dimensions (topography) and then three (tomography). The methods of analysis have also changed tremendously, from the simple modified Beer-Lambert law to sophisticated image reconstruction and data analysis methods used today. Due to these advances, fNIRI has become a modality that is widely used in neuroscience research and several manufacturers provide commercial instrumentation. It seems likely that fNIRI will become a clinical tool in the foreseeable future, which will enable diagnosis in single subjects. This year marks the 20th anniversary of functional near-infrared spectroscopy and imaging (fNIRS/fNIRI). As the vast majority of commercial instruments developed until now are based on continuous wave technology, the aim of this publication is to review the current state of instrumentation and methodology of continuous wave fNIRI. For this purpose we provide an overview of the commercially available instruments and address instrumental aspects such as light sources, detectors and sensor arrangements. Methodological aspects, algorithms to calculate the concentrations of oxy-and deoxyhemoglobin and approaches for data analysis are also reviewed. From the single-location measurements of the early years, instrumentation has progressed to imaging initially in two dimensions (topography) and then three (tomography). The methods of analysis have also changed tremendously, from the simple modified Beer-Lambert law to sophisticated image reconstruction and data analysis methods used today. Due to these advances, fNIRI has become a modality that is widely used in neuroscience research and several manufacturers provide commercial instrumentation. It seems likely that fNIRI will become a clinical tool in the foreseeable future, which will enable diagnosis in single subjects. Contents

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Section: Overview Of Commercially Available Imaging Instrumentationmentioning

confidence: 99%

Section: Light Sources For Fniri Instrumentsmentioning

confidence: 99%

Section: Probe Designmentioning

confidence: 99%

Section: Modified Beer-lambert Law (Mbll)mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

A review on continuous wave functional near-infrared spectroscopy and imaging instrumentation and methodology

Scholkmann¹,

Kleiser²,

Metz³

et al. 2014

NeuroImage

1,471

1,394

View full text Add to dashboard Cite

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Fetal cerebral oxygenation and hemodynamics during labour measured by near-infrared spectroscopy

Peebles¹,

O’Brien²

1997

Ment. Retard. Dev. Disabil. Res. Rev.

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The failure of modern fetal monitoring techniques to measure either oxygenation or perfusion within the fetal brain may underlie their poor specificity in the detection of intrapartum hypoxia‐ischaemia. We have adapted the technique of near‐infrared spectroscopy (NIRS) to obtain continuous, quantified measurements of changes in human fetal cerebral oxygenation and blood volume during labour. More than 140 fetuses have been studied at University College London for periods ranging from 10 to 765 minutes. Reciprocal changes in the cerebral concentrations of oxyhemoglobin and deoxyhemoglobin, indicating changing cerebral haemoglobin saturation, have been observed during uterine hyperstimulation with oxytocin, administration of maternal oxygen, changing maternal posture, and late fetal heart rate decelerations. Uterine contraction frequency greater than 1 every 2 minutes was associated with a fall in fetal cerebral oxygenation. A method for quantifying the oxygen saturation of hemoglobin derived from all vascular compartments (SmcO2) is described. There was a significant positive correlation between SmcO2 and umbilical artery pH. Conversely, the base deficit of blood from the umbilical artery showed a negative correlation with SmcO2. Changes in optical pathlength due to probe movement during uterine contractions are a potential source of error in the measurements. Preliminary data obtained using intensity modulated optical spectrometry, a technique that continuously measures optical pathlength, suggest that the maximum contribution of movement artifact to observed changes in chromophore concentration is 12%. These preliminary data demonstrate that NIRS is capable of measuring fetal cerebral oxygenation and blood volume during labour. However, because none of the fetuses in this study was born with evidence of intrapartum hypoxia‐ischaemia, we cannot comment on the value of NIRS as a means of intrapartum surveillance. Further developments, including the routine use of IMOS and rigorous testing by randomized trials, will be required before this question is answered. MRDD Research Reviews 3:59–68, 1997. © 1997 Wiley‐Liss, Inc.

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Effects of endotracheal suctioning in high-frequency oscillatory and conventionally ventilated low birth weight neonates on cerebral hemodynamics observed by near infrared spectroscopy (NIRS)

et al. 2000

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Estimation of optical pathlength through tissue from direct time of flight measurement

Cited by 1,928 publications

References 17 publications

A review on continuous wave functional near-infrared spectroscopy and imaging instrumentation and methodology

A review on continuous wave functional near-infrared spectroscopy and imaging instrumentation and methodology

Fetal cerebral oxygenation and hemodynamics during labour measured by near-infrared spectroscopy

Effects of endotracheal suctioning in high-frequency oscillatory and conventionally ventilated low birth weight neonates on cerebral hemodynamics observed by near infrared spectroscopy (NIRS)

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