Spectral dependence of temporal point spread functions in human tissues

Essenpreis, Matthias; Elwell, Clare E.; Cope, M; Zee, Pieter van der; Arridge, Simon; Delpy, David T.

doi:10.1364/ao.32.000418

Cited by 188 publications

(120 citation statements)

References 18 publications

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“…Duncan et al, 1995;Matcher et al, 1995a). The DPF was found to be age, gender and wavelength dependent and varies between subjects (Duncan et al, 1996;Essenpreis et al, 1993) and different tissues (Duncan et al, 1995). For example the average DPF for the adult head for 100 subjects given by Duncan et al is 6.53 ± 0.99, i.e.…”

Section: Modified Beer-lambert Law (Mbll)mentioning

confidence: 97%

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: Modified Beer-lambert Law (Mbll)mentioning

confidence: 97%

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

show abstract

“…Essenpreis et al have published a DPF value of 4.48 ± 0.41 at 800 nm measured in the adult forearm assessing a gender mixed group [5], while Duncan et al found a significant gender dependence of the DPF (4.57 ± 0.74 for females and 3.75 ± 0.57 for males at 807 nm) [6]. For the arterial occlusion experiment described hereafter, the DPF values published in [6] were interpolated according to the DPF as a function of wavelength published in [5]: we used 4.48 for 760 nm and 3.81 for 870 nm. For the reconstruction of the cortical hemodynamic signals a DPF of 7.75 for 760 nm and 7.25 for 870 nm was chosen [7].…”

Section: Theorymentioning

confidence: 99%

Wireless miniaturized in-vivo near infrared imaging

Muehlemann¹,

Haensse²,

Wolf³

2008

Opt. Express

145

108

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Our group measures tissue oxygenation and the cortical hemodynamic response to sensory stimuli applying continuous wave near-infrared imaging (NIRI). To improve the method's quality and applicability and to explore new fields in clinical practice and research, we developed a miniaturized wireless NIRI system. It was validated by measuring muscle oxygenation in a blood-flow occlusion experiment and brain activity in adults. Abstract: Our group measures tissue oxygenation and the cortical hemodynamic response to sensory stimuli applying continuous wave nearinfrared imaging (NIRI). To improve the method's quality and applicability and to explore new fields in clinical practice and research, we developed a miniaturized wireless NIRI system. It was validated by measuring muscle oxygenation in a blood-flow occlusion experiment and brain activity in adults. Wireless miniaturized in-vivo near infrared imaging

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“…Algorithms for measuring Cu A redox state changes in i o rely on converting optical density changes into the three chromophore concentration changes-deoxyhaemoglobin (Hb), oxyhaemoglobin (HbO # ) and Cu A (the other major tissue chromophore in this region, water, is presumed to maintain a constant concentration). Although the purified spectra of these compounds are well characterized, problems arise in allowing for tissue-specific effects, such as the wavelength dependence of the tochrome oxidase IRS optical path length (Essenpreis et al 1993) and possible changes in light scattering. Three algorithms, those developed at University College London (UCL) (Wray et al 1988), Keele University (Wickramasinghe et al 1990) and that used in the commercial Critikon NIRS 2000 are based on similar assumptions and would be expected to yield similar results (Matcher et al 1995).…”

Section: Algorithms For Cytochrome Oxidase Determination and Their Vamentioning

confidence: 99%

Measurement of cytochrome oxidase and mitochondrial energetics by near–infrared spectroscopy

Cooper

Springett

1997

Phil. Trans. R. Soc. Lond. B

139

111

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SUMMARYCytochrome oxidase is the terminal electron acceptor of the mitochondrial respiratory chain. It is responsible for the vast majority of oxygen consumption in the body and essential for the efficient generation of cellular ATP. The enzyme contains four redox active metal centres ; one of these, the binuclear Cu A centre, has a strong absorbance in the near-infrared that enables it to be detectable in i o by near-infrared spectroscopy. However, the fact that the concentration of this centre is less than 10 % of that of haemoglobin means that its detection is not a trivial matter.Unlike the case with deoxyhaemoglobin and oxyhaemoglobin, concentration changes of the total cytochrome oxidase protein occur very slowly (over days) and are therefore not easily detectable by nearinfrared spectroscopy. However, the copper centre rapidly accepts and donates an electron, and can thus change its redox state quickly ; this redox change is detectable by near-infrared spectroscopy. Many factors can affect the Cu A redox state in i o , but the most significant is likely to be the molecular oxygen concentration (at low oxygen tensions, electrons build up on Cu A as reduction of oxygen by the enzyme starts to limit the steady-state rate of electron transfer).The factors underlying haemoglobin oxygenation, deoxygenation and blood volume changes are, in general, well understood by the clinicians and physiologists who perform near-infrared spectroscopy measurements. In contrast, the factors that control the steady-state redox level of Cu A in cytochrome oxidase are still a matter of active debate, even amongst biochemists studying the isolated enzyme and mitochondria. Coupled with the difficulties of accurate in i o measurements it is perhaps not surprising that the field of cytochrome oxidase near-infrared spectroscopy has a somewhat chequered past. Too often papers have been written with insufficient information to enable the measurements to be repeated and few attempts have been made to test the algorithms in i o.In recent years a number of research groups and commercial spectrometer manufacturers have made a concerted attempt to not only say how they are attempting to measure cytochrome oxidase by nearinfrared spectroscopy but also to demonstrate that they are really doing so. We applaud these attempts, which in general fall into three areas : first, modelling of data can be performed to determine what problems are likely to derail cytochrome oxidase detection algorithms (Matcher et al. 1995) ; secondly haemoglobin concentration changes can be made by haemodilution (using saline or artificial blood substitutes) in animals (Tamura 1993) or patients (Skov & Greisen 1994) ; and thirdly, the cytochrome oxidase redox state can be fixed by the use of mitochondrial inhibitors and then attempts made to cause spurious cytochrome changes by dramatically varying haemoglobin oxygenation, haemoglobin concentration and light scattering (Cooper et al. 1997).We have previously written reviews covering the difficulties of measuring the cyt...

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Spectral dependence of temporal point spread functions in human tissues

Cited by 188 publications

References 18 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

Wireless miniaturized in-vivo near infrared imaging

Measurement of cytochrome oxidase and mitochondrial energetics by near–infrared spectroscopy

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