WO2015092872A1 - 生体光計測装置およびそれを用いた生体光計測方法 - Google Patents
生体光計測装置およびそれを用いた生体光計測方法 Download PDFInfo
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- 238000005259 measurement Methods 0.000 title claims abstract description 108
- 238000000691 measurement method Methods 0.000 title claims 3
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Classifications
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- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/02—Detecting, measuring or recording pulse, heart rate, blood pressure or blood flow; Combined pulse/heart-rate/blood pressure determination; Evaluating a cardiovascular condition not otherwise provided for, e.g. using combinations of techniques provided for in this group with electrocardiography or electroauscultation; Heart catheters for measuring blood pressure
- A61B5/026—Measuring blood flow
- A61B5/0261—Measuring blood flow using optical means, e.g. infrared light
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- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
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- A61B5/0059—Measuring for diagnostic purposes; Identification of persons using light, e.g. diagnosis by transillumination, diascopy, fluorescence
- A61B5/0075—Measuring for diagnostic purposes; Identification of persons using light, e.g. diagnosis by transillumination, diascopy, fluorescence by spectroscopy, i.e. measuring spectra, e.g. Raman spectroscopy, infrared absorption spectroscopy
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- A61B5/145—Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue
- A61B5/1455—Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue using optical sensors, e.g. spectral photometrical oximeters
- A61B5/14551—Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue using optical sensors, e.g. spectral photometrical oximeters for measuring blood gases
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- A61B5/7207—Signal processing specially adapted for physiological signals or for diagnostic purposes for noise prevention, reduction or removal of noise induced by motion artifacts
- A61B5/7214—Signal processing specially adapted for physiological signals or for diagnostic purposes for noise prevention, reduction or removal of noise induced by motion artifacts using signal cancellation, e.g. based on input of two identical physiological sensors spaced apart, or based on two signals derived from the same sensor, for different optical wavelengths
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- A61B2562/0233—Special features of optical sensors or probes classified in A61B5/00
- A61B2562/0238—Optical sensor arrangements for performing transmission measurements on body tissue
Definitions
- the present invention relates to a technique for separating and removing the influence of surface layer components such as a skin blood flow component mixed with a signal component in a biological light measurement device using visible light or near infrared light.
- NIRS signal light detection signal and biological signal obtained by non-invasive optical brain functional imaging using NIRS, including optical topography
- the head structure is assumed to be a two-layer model, and it is necessary to further assume the partial average optical path length of each layer, but it is difficult to estimate the optical path length of the subject.
- a subtraction method using an adaptive filter has been proposed.
- the skin blood flow-derived signal is removed (for example, see Non-Patent Document 3).
- a subtraction method using linear regression a method of obtaining a brain activity signal by subtracting a fitting signal obtained by linear regression of a short SD signal to a long SD signal from the long SD signal has been proposed (for example, non-patent literature). 4).
- Patent Document 2 aims to provide an optical measurement device capable of removing unnecessary information due to skin blood flow or the like using a light transmitting / receiving unit having a plurality of light transmitting probes and a plurality of light receiving probes. There is a method in which a plurality of irradiation-detector pairs are arranged so that the midpoints are equal, measurement is performed, and unnecessary information is removed by arithmetic processing.
- Patent Document 3 describes an apparatus configuration that uses two detectors for one light source, and appropriately distinguishes information obtained from the two detectors, thereby causing overlap with adjacent tissues. There are ways to obtain results that mainly characterize the state in the brain tissue itself without the effect of doing so.
- Patent Documents 4, 5, and 6 have a method of calculating a change in absorbance and performing an operation such as subtraction between a long SD signal and a short SD signal.
- these methods have the following problems.
- short SD signal acquisition the SD distance is often 10 mm or less, and signal components that are influenced by changes in absorption only in the skin are acquired without being influenced by cerebral blood flow. Since the amplitude ratio is unknown, it is difficult to determine an appropriate coefficient in the calculation.
- Patent Document 7 discloses that each independent component calculated using independent component analysis from signals measured using a plurality of SD distances is derived from cerebral blood flow using SD distance dependency. A method is disclosed in which a signal component and a signal component derived from skin blood flow are separated and a brain blood flow derived signal and a skin blood flow derived signal at each SD distance are reconstructed.
- the measurement signal needs to be a time-series signal for a certain period. Therefore, after the measurement, a process for separating the signal derived from the skin blood flow and the signal derived from the cerebral blood flow was performed, and the result could not be obtained during the measurement.
- An object of the present invention is to separate and extract a cerebral blood flow-derived signal and a skin blood flow-derived signal contained in an NIRS signal during measurement.
- the measured value of the hemoglobin concentration length change at a plurality of SD distances measured at the timing that can be considered at the same time is converted into the skin blood flow-derived signal and the cerebral blood flow-derived signal component in real time using the SD distance dependency. It is characterized by separating.
- a cerebral blood flow-derived signal and a skin blood flow-derived signal can be separated and extracted in real time during measurement.
- the measurement can be interrupted and started again, and efficient and reliable data acquisition can be performed.
- the figure which shows the apparatus structure of this invention The figure which shows the example of the measurement sectional drawing of a multi SD system. The figure which shows the relationship between SD distance and the partial average optical path length of a scalp and gray matter. The figure which shows the SD dependence model of the hemoglobin concentration length change of a scalp and gray matter.
- positioning with respect to a human head The figure which shows the example of the grid
- FIG. 1 shows an example of a device configuration in the present invention.
- a biological light measurement device capable of detecting light incident on a living body and detecting light that has been scattered and absorbed in the living body and propagated
- the light 30 emitted from one or a plurality of light sources 101 included in the apparatus main body 20
- the light is incident on the subject 10 through the waveguide 40.
- the light 30 enters the subject 10 from the irradiation point 12, passes through and propagates through the subject 10, and then passes through the waveguide 40 from the detection point 13 at a position away from the irradiation point 12. It is detected by one or more photodetectors 102.
- the SD distance is defined by the distance between the irradiation point 12 and the detection point 13 as described above.
- the one or more light sources 101 are a semiconductor laser (LD), a light emitting diode (LED) or the like, and the one or more photodetectors are an avalanche photodiode (APD), a photodiode (PD), a photoelectron amplifier, or the like.
- a double tube (PMT) or the like may be used.
- the waveguide 40 may be an optical fiber, glass, light guide, or the like.
- the light source 101 is driven by a light source driving device 103, and the gain of one or more photodetectors 102 is controlled by a control / analysis unit 106.
- the control / analysis unit 106 also controls the light source driving device 103 and receives an input of conditions and the like from the input unit 107.
- the electrical signal photoelectrically converted by the photodetector 102 is amplified by the amplifier 104, converted from analog to digital by the analog-digital converter 105, sent to the control / analysis unit 106, and processed.
- the control / analysis unit 106 includes a control unit that controls the light source driving device and / or the photodetector, and an analysis unit that analyzes a signal obtained by the photodetector, and is based on the signal detected by the photodetector 102. Run the analysis. Specifically, based on the method described in Non-Patent Document 1, for example, based on the received digital signal obtained by conversion by the analog-digital converter 105, the detected light amount change or absorbance From the change, oxygen concentration and deoxygenated hemoglobin concentration length change (oxy-Hb, deoxy-Hb) is calculated.
- the density length change is a change amount of the product of the density and the optical path length.
- control / analysis unit 106 has been described on the assumption that the driving of the light source 101, the gain control of the photodetector 102, and the signal processing from the analog-digital converter 105 are all performed. And having the means for integrating them can also realize the same function.
- the received light amount detection signal and the oxygenated or deoxygenated hemoglobin concentration length change signal calculated using these signals are stored in the storage unit 108, and the measurement result is displayed on the display unit 109 based on the analysis result and / or the stored data. Can be displayed.
- the light transmitter 50 and the light receiver 60 are not shown in FIG. 1, the light transmitter 50 includes, for example, a waveguide 40 on the light source 101 side, and is installed in contact with or close to contact with the subject 10.
- the light receiver 60 includes, for example, the waveguide 40 on the light detector 102 side, and is placed in contact with or close to contact with the subject 10. At this time, the light transmitter 50 and the light receiver 60 are arranged on the subject 10 so that the light received by each light receiver propagates through both the gray matter and the scalp.
- FIG. 2 shows an example of a measurement sectional view of the multi-SD method.
- Light 30 emitted from the light transmitter 50 is incident on the scalp and propagates in all directions in the tissue.
- the light receiver 60 is arranged at an SD distance of 15 mm and 30 mm as shown in FIG. 2, the light 30 received by the light receiver 60 having an SD distance of 15 mm is received by the light receiver 60 having an SD distance of 30 mm.
- the SD distance is set to be larger than about 10 mm.
- FIG. 3 is a diagram showing the relationship between the SD distance and the partial average optical path lengths of the scalp and gray matter determined by Monte Carlo simulation, where (a) shows the relationship between the scalp and (b) shows the relationship between the gray matter.
- the horizontal axis is the SD distance [mm]
- the vertical axis is the partial average optical path length [mm] of the scalp and gray matter.
- the partial average optical path length of the scalp varies because the number of calculated photons in the simulation is small and the results do not converge.
- Non-Patent Document 1 Since the NIRS signal intensity is proportional to the partial optical path length of the site where the blood flow change occurs (see Non-Patent Document 1) (assuming uniform blood flow change in the partial optical path), as shown in FIG. It can be seen that the component derived from cerebral blood flow in the oxygenated hemoglobin concentration length change signal increases, but the component derived from skin blood flow does not change. In the present invention, attention is paid to the change amount of the signal amplitude with respect to the SD distance, that is, the gradient (gradient).
- FIG. 4 shows a signal derived from the skin blood flow and a signal derived from the cerebral blood flow modeling the simulation result shown in FIG.
- the horizontal axis represents the SD distance [mm]
- the vertical axis represents the change in hemoglobin concentration length.
- the measurement signal of hemoglobin concentration length change is expressed as Equation 3 as the sum of these.
- y is a hemoglobin concentration length change
- x is an SD distance
- xs0 is an x intercept
- a and c are inclinations
- a time-series signal of a skin blood flow-derived signal and a time series signal of a cerebral blood flow-derived signal are obtained.
- xs0 corresponds to the shortest SD distance at which light can reach the brain, and can be considered constant regardless of the time.
- a plurality of measurement signals that are measured in association with signals at a certain measurement time, using the SD distance dependency of the measurement signal, a signal derived from the skin blood flow corresponding to the measurement time or / and A cerebral blood flow-derived signal is calculated.
- the value of Xs0 may be obtained by Monte Carlo simulation using the subject's own head structure.
- a value obtained by Monte Carlo simulation using a standard head structure or a value obtained empirically may be set in advance.
- An arbitrary value may be set by external input.
- xs0 may be measured and set by measuring skin activity at a plurality of SD distances by stopping skin blood flow by pressing the skin.
- the cerebral blood flow-derived signal amplitude value at time (t) of the oxygenated hemoglobin concentration length change measured at an SD distance of 30 mm is a (t) * (30-xs0), and the skin blood flow-derived signal amplitude value is c (t).
- the brain contribution rate and skin contribution rate at time t can be obtained.
- the cerebral blood flow-derived signal amplitude value, the skin blood flow-derived signal amplitude value, the brain contribution rate, and the skin contribution rate at time t can be obtained.
- Fig. 5 shows the measurement flowchart.
- subject information and various measurement conditions are set (S301).
- the various measurement conditions include, for example, a measurement time, the number of times of measurement, a threshold value of a skin contribution rate at which an alert should be issued, and the like.
- measurement preparations such as probe mounting and gain adjustment (S302) are performed. Note that the order of S301 and S302 may be reversed.
- measurement signal acquisition is started (S303), and hemoglobin concentration length change signals at the measurement time t are measured at all measurement points (S304).
- FIG. 6 shows an example of probe arrangement with respect to the human head.
- This probe can be installed on the entire head including the forehead, the temporal region, the parietal region, and the occipital region.
- FIG. 7 shows a lattice-like probe arrangement (a) and measurement point arrangement (b) in the prior art (for example, see Non-Patent Document 1).
- the distance between the normal light transmitter 50 and the light receiver 60 is about 30 mm, and the approximate middle point is taken as the measurement point 11a.
- “ ⁇ ”, “ ⁇ ”, and “ ⁇ ” represent a light transmitter, a light receiver, and a measurement point, respectively.
- the SD distance is 30 mm at all measurement points 11a. Measurement with a SD distance of 60 mm is possible, but the signal-to-noise ratio (SNR) is small, which is not practical.
- SNR signal-to-noise ratio
- FIG. 8 shows the double density probe arrangement (a) and the measurement point arrangement (b).
- the probe arrangement is disclosed in Patent Document 8.
- This arrangement is an arrangement in which the lattice-like probe arrangement of FIG. 7 is overlapped by shifting 15 mm on the x-axis.
- “ ⁇ ”, “ ⁇ ”, “ ⁇ ”, and “ ⁇ ” represent the light transmitter 50, the light receiver 60, the measurement point 11a at the SD distance of 30 mm, and the measurement point 11 at the SD distance of 15 mm, respectively.
- measurement signals at a plurality of SD distance measurement points are used.
- mapping is performed by interpolation using only measurement signals having the same SD distance, for example, if the SD distance is about 15-20 mm, a map having a large contribution of the signal derived from the shallow part including the skin can be obtained.
- the resolution may be low due to the small number of measurement points.
- the measurement points with an SD distance of 15 mm have a smaller number of measurement points than the measurement points with an SD distance of 30 mm, and therefore the distribution density is small.
- FIG. 9 shows a configuration diagram of an experiment using the whole brain measurement type optical brain function measuring device 90.
- the local cerebral blood volume oxygenated hemoglobin / deoxygenated hemoglobin / total hemoglobin concentration length change
- the optical brain function measuring device 90 by irradiating the subject's head with light having a wavelength belonging to the visible to infrared region. It is obtained by detecting and measuring light of a plurality of wavelengths of signals that have passed through the inside of the specimen with the same photodetector.
- an appropriate stimulus / command can be given to the subject 10 by the stimulus / command presenting device 415.
- the stimulus / command presentation device 415 is controlled by the computer 412 by a control signal 414.
- a plurality of light sources 402a to 402d having different wavelengths (for example, 695 nm for the light sources 402a and 402c and 830 nm for the light sources 402b and 402d), and light from the plurality of light sources 402a and 402b (402c and 402d)
- modulators or oscillators 401a and 401b (401c and 401d) for intensity-modulating at different frequencies, respectively, and the intensity-modulated light are optical fibers 403a and 403b, respectively.
- a plurality of light receiving means including light receivers 408a and 408b provided in the light receiving optical fibers 407a and 407b so that the tips are located at predetermined distances (for example, 15 mm and 30 mm), respectively. It has been.
- the light passing through the living body is collected on the optical fiber by the optical fibers 407a and 407b for receiving light, and the light passing through the living body is photoelectrically converted and amplified by the light receivers 408a and 408b, respectively.
- light transmitting probes 501a and 501b for receiving and transmitting optical fibers 405a and 405b and light receiving optical fibers 407a and 407b, respectively, for holding the optical fibers appropriately and being placed on the subject 10 are received.
- the probe holder 503 is fixed to the subject 10 to hold a plurality of probes.
- the light receiving means detects light reflected and transmitted inside the subject 10 and converts it into an electric signal.
- a photoelectric conversion element represented by a photomultiplier tube or a photodiode is used.
- FIG. 9 illustrates the case where two types of wavelengths are used, it is possible to use three or more types of wavelengths.
- FIG. 8 shows two light irradiating means and two light receiving means, but in this embodiment, it is necessary to have a multi-SD arrangement, so there are a plurality of light receiving means not shown. .
- the electrical signals representing the in-vivo light intensity photoelectrically converted by the light receivers 408a and 408b are input to the lock-in amplifiers 409a to 409d, respectively.
- Reference signals 417a to 417d from oscillators [modulators] 401a and 401b (401c and 401d) are also input to the lock-in amplifiers 409a to 409d.
- 409a and 409b 695 nm light from the light sources 402a and 402c is separated and output, and is extracted by lock-in processing.
- 409c and 409d 830 nm light from the light sources 402b and 402d is separated and output. At this time, in FIG.
- two measurement points are assumed between the light transmission probe 501a and the light reception probe 502a and between the light transmission probe 501b and the light reception probe 502b.
- two points between the light transmission probe 501a and the light reception probe 502b and between the light transmission probe 501b and the light reception probe 502a can be used as measurement points.
- the separated transmitted light intensity signals of the respective wavelengths which are the outputs of the lock-in amplifiers 409a to 409d, are analog-to-digital converted by the analog-to-digital converter 410 and then sent to the measurement control computer 411.
- the measurement control computer 411 uses the passing light intensity signal to change the oxygenated hemoglobin concentration and deoxygenated hemoglobin concentration length from the detection signal at each detection point by a well-known procedure described in Non-Patent Document 1 and the like.
- the total hemoglobin concentration length change is calculated and stored in the storage device as time-lapse information at a plurality of measurement points.
- lock-in processing can also be performed digitally after amplifying and analog-to-digital conversion of the signal from the light receiver. is there.
- determines several light by shifting the timing which irradiates several light temporally is used. It is also possible. In this case, the timing shift time can be treated as a measured value at the same time if it is set sufficiently short so that it can be approximated if the hemoglobin concentration length value does not change. In order to avoid saturation of the learning device, it is possible to measure a hemoglobin concentration length change value that can be regarded as the same time even when the irradiation and detection timings are shifted.
- the computer 412 includes an input unit, an analysis unit, a storage unit, and an extraction unit, and the analysis unit analyzes the result calculated by the measurement control computer 411.
- the input unit inputs settings such as analysis conditions from the outside. Note that when the computer 412 has a display function, the display unit 413 may be omitted.
- the analysis result of the analysis unit is stored in the storage unit.
- the extraction unit extracts information related to the local cerebral hemodynamics of the subject 10 from the signal analyzed by the analysis unit. Information regarding the local cerebral hemodynamics of the subject 10 extracted by the extraction unit is displayed on the display unit 413.
- the measurement control computer 411 and the computer 412 are drawn separately, but may be a single computer.
- FIG. 10 shows a display example when the method of the present invention is applied and the hemoglobin concentration length change signal is measured while being separated and extracted into a cerebral blood flow-derived signal and a skin-derived component.
- the measurement signal 171 is arranged and displayed at the corresponding measurement position and the hemoglobin concentration length change signal value is acquired, the separation and extraction into a brain blood flow-derived signal and a skin-derived component are performed in real time.
- the waveform display is updated.
- An alert 172 is issued for a measurement signal whose skin contribution rate exceeds a preset threshold value.
- a measurement signal to be displayed can be selected and a display method suited to the purpose can be realized.
- a change in oxygenated hemoglobin concentration length, a change in deoxygenated hemoglobin concentration length, and a change in total hemoglobin concentration length may be selectable.
- an alert is issued in real time, so that measures such as re-measurement can be quickly performed.
- an example of an alert displayed on the screen is shown, but an alert by voice, text, or the like may be used.
- a brain contribution rate may be used.
- FIG. 11 shows a display example in the case where a plurality of light transmitters 50 and light receivers 60 are two-dimensionally arranged to image and measure cerebral blood flow-derived signals and skin blood flow-derived signals.
- This is a display example during measurement by the whole brain measurement type optical brain function measuring device.
- An oxygenated hemoglobin concentration length change (oxy-Hb) map 301 is displayed for each of the frontal region, the parietal region, the left and right temporal regions, and the occipital region.
- the amplitude value is represented by shading shown in the gray scale bar 302.
- the radio button 304 can be used to select whether or not to display a brain-derived signal, a skin-derived signal, and an SD distance of 30 mm.
- FIG. 1 shows a display example in the case where a plurality of light transmitters 50 and light receivers 60 are two-dimensionally arranged to image and measure cerebral blood flow-derived signals and skin blood flow-derived signals.
- This is a display example during measurement by the whole brain measurement
- the upper figure is a signal derived from cerebral blood flow
- the lower figure is a signal derived from skin blood flow.
- the SD distance can be switched with the radio button 314. It becomes possible to confirm at a glance the distribution state of the cerebral blood flow-derived signal and the skin blood flow-derived signal. The skin contribution rate and brain contribution rate will be described.
- the separation signal is displayed, but the brain contribution rate or the skin contribution rate may be displayed in the same manner.
- the brain contribution rate or the skin contribution rate may be displayed in the same manner.
- components derived from cerebral blood flow and skin blood flow can be separated and extracted in real time from measurement signals according to the purpose. Measurement accuracy and reproducibility can be improved.
- Detection point 20 Device main body 30: Light 50: Light transmitter 60: Light receiver 90: Optical brain function measuring device 101: Light source 102: Light detector 103: Light source driving device 104: Amplifier 105: Analog Digital converter 106: Control / analysis unit 107: Input unit 108: Storage unit 109: Display unit 171: Measurement signal 172: Alert 173: Original signal, cerebral blood flow origin, skin blood flow origin signal display method selection check box 301: oxygenated hemoglobin concentration length change (oxy-Hb) map 302: gray scale bar 304: radio button 314: radio button 401: oscillator (modulator) 402: Light source 403: Optical fiber 404: Coupler 405: Light transmitting optical fiber 407: Light receiving optical fiber 408: Light receiver (including amplifier) 409: Lock-in amplifier 410: Analog
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Abstract
Description
特許文献2には、複数の送光プローブと、複数の受光プローブとを有する送受光部を用いて、皮膚血流等による不要な情報を除去することができる光計測装置を提供することを目的とし、複数照射-検出器ペアを、中点が等しくなるように配置し、計測を実施し、演算処理により不要な情報を除去する方法がある。また、特許文献3には、1つの光源に対して2つの検出器を用いる装置構成で、2つの検出器から得られた情報を適切に区別することによって、隣接する組織との重なり等に起因する影響なしに、脳組織自体内の状態を主に特徴づける結果を得る方法がある。さらに、特許文献4、5、6には、吸光度変化を算出し、長SD信号と短SD信号とで引き算等の演算を行う方法がある。ただし、これらの手法には、以下に述べる課題があった。
第一に、各SD距離での計測信号間における引き算等の演算における、各種係数の決め方が難しいという課題がある。このような演算において、各種係数は結果に影響するため、適切な値を設定する必要がある。また、短SD信号取得において、SD距離をしばしば10 mm 以下とし、脳血流に左右されず皮膚のみの吸収変化に左右される信号成分を取得しているため、脳・皮膚血流由来成分の振幅比が未知であり、演算における適切な係数を決めることが困難になる。皮膚の寄与と脳の寄与を含む長SD計測信号を適切に補正するためには、皮膚・脳の各寄与率および光路長比を知る必要がある。
さらに、短SD信号を長SD信号にフィッティングさせることは、皮膚血流由来信号と脳血流由来信号が独立ではない場合、つまり、皮膚血流由来信号と脳血流由来信号に相関がある場合、長SD信号から、脳血流由来信号を除去してしまう可能性を排除できない。
これらを解決する手段として、特許文献7には、複数のSD距離を用いて計測した信号から、独立成分解析を用いて算出した独立成分ごとに、SD距離依存性を用いて脳血流由来の信号成分と皮膚血流由来の信号成分に分離し、各々のSD距離における脳血流由来信号と皮膚血流由来信号を再構成する方法が開示されている。
ここで、1つまたは複数の光源101は半導体レーザ(LD)や発光ダイオード(LED)等であり、1つまたは複数の光検出器はアバランシェフォトダイオード(APD)やフォトダイオード(PD)、光電子増倍管(PMT)等であれば良い。また、導波路40は光ファイバ、ガラス、ライトガイド等であれば良い。
光源101は、光源駆動装置103により駆動され、1つまたは複数の光検出器102のゲインは制御・解析部106により制御される。制御・解析部106は、光源駆動装置103の制御も行い、入力部107からの条件等の入力を受ける。
光検出器102で光電変換した電気信号は、増幅器104で増幅され、アナログ-デジタル変換器105でアナログ-デジタル変換され、制御・解析部106へ送られ、処理される。
ここでは、制御・解析部106は光源101の駆動、光検出器102のゲイン制御、アナログ-デジタル変換器105からの信号処理を全て行うことを想定して記述したが、それぞれ別個の制御部を有し、さらにそれらを統合する手段を有することでも同機能を実現できる。
また、受光量検出信号およびこれらを用いて算出された酸素化または脱酸素化ヘモグロビン濃度長変化信号は、記憶部108に保存され、解析結果および/または保存データに基づいて表示部109で計測結果を表示することが可能である。
送光器50、受光器60は、図1に記載していないが、送光器50は、例えば光源101側の導波路40を含み、被検者10に接触あるいは接触に近い状態で設置され、受光器60は、例えば光検出器102側の導波路40を含み、被検者10に接触あるいは接触に近い状態で設置される。このとき、被検者10上においては、各受光器が受光する光が、灰白質、頭皮をともに伝播するよう、各々の送光器50、受光器60が配置される。
図3は、モンテカルロシミュレーションにより求めた、SD距離と、頭皮および灰白質の部分平均光路長との関係を示す図で、(a)は頭皮の、(b)は灰白質の関係を示す。横軸はSD距離[mm]、縦軸は頭皮および灰白質の部分平均光路長[mm]である。頭皮の部分光路長にはSD距離依存性は見られないが、灰白質には線形的なSD距離依存性が見られる。頭皮の部分平均光路長がばらついているのは、シミュレーションの計算光子数が少なく、結果が収束していないためである。NIRS信号強度は血流変化が生じる部位の部分光路長に比例する(非特許文献1参照)ので(当該部分光路において一様な血流変化を仮定)、図3より、SD距離が大きくなると、酸素化ヘモグロビン濃度長変化信号における脳血流由来成分は大きくなるが、皮膚血流由来成分は変化しないことがわかる。本発明では、このSD距離に対する信号振幅の変化量、すなわち、勾配(傾き)に着目する。
a(t)=(y30(t)-y15(t))/(30-15)
SD距離30 mmで計測された酸素化ヘモグロビン濃度長変化の時刻(t)における脳血流由来信号振幅値は、a(t)*(30-xs0)であり,皮膚血流由来信号振幅値はc(t)である。これらの値を数5,数6に代入すれば,時刻tにおける脳寄与率と皮膚寄与率を求めることができる。脱酸素化ヘモグロビン濃度長変化についても同様に、時刻tにおける脳血流由来信号振幅値、皮膚血流由来信号振幅値、脳寄与率、および皮膚寄与率を求めることができる。
ここで、皮膚血流由来信号の抽出のために、複数のSD距離の計測点における計測信号を使用する。同じSD距離の計測信号のみを用いて補間によりマッピングした場合、例えばSD距離が15-20 mm程度であれば、皮膚を含む浅い部分由来信号の寄与の大きいマップが得られる。
ここで、SD距離によっては、同じSD距離における信号のみでイメージングしようとすると、計測点数が少ないために分解能が低くなる場合がある。図8の例ではSD距離15 mmの計測点はSD距離30 mmの計測点に比べて計測点数が少なく、従って分布密度が小さい。このように分布密度の小さいSD距離の計測信号でも、SD距離30 mmの計測点の信号から分離しようとする信号(脳血流由来信号、皮膚血流由来信号)を抽出するためには効果がある。よって計測点数が少なくても有効な計測データになり得る。
受講器の飽和を避けるために、照射や検出のタイミングをずらす場合でも同様にして同時刻とみなせるヘモグロビン濃度長変化値を計測できる。
皮膚寄与率と脳寄与率について説明する。
11:計測点
11a:計測点(SD = 30 mm)
11c:計測点(SD = 15 mm)
12:照射点
13:検出点
20:装置本体
30:光
50:送光器
60:受光器
90:光脳機能計測装置
101:光源
102:光検出器
103:光源駆動装置
104:増幅器
105:アナログ-デジタル変換器
106:制御・解析部
107:入力部
108:記憶部
109:表示部
171:計測信号
172:アラート
173:元信号、脳血流由来、皮膚血流由来信号表示方法選択のチェックボックス
301:酸素化ヘモグロビン濃度長変化(oxy-Hb)マップ
302:グレースケールバー
304:ラジオボタン
314:ラジオボタン
401:発振器(変調器)
402:光源
403:光ファイバ
404:結合器
405:送光用光ファイバ
407:受光用光ファイバ
408:受光器(増幅器含む)
409:ロックインアンプ
410:アナログ-デジタル(A/D)変換器
411:計測制御用計算機
412:計算機
413:表示部
414:制御信号
415:刺激・命令呈示装置
416:光源駆動信号
417:発振器(変調器)からの参照信号
501:送光用プローブ
502:受光用プローブ
503:プローブホルダ。
Claims (6)
- 被検体に光を照射するための1つまたは複数の光照射手段と、
前記1つまたは複数の光照射手段から前記被検体上の照射点に照射され、被検体内を伝播してきた光を前記被検体上の検出点において検出するための1つまたは複数の光検出手段と、
前記1つまたは複数の光照射手段および前記1つまたは複数の光検出手段を制御する制御部と、
前記1つまたは複数の光検出手段で得られる信号を解析する解析部と、
前記解析部での解析結果を表示するための表示部とを有し、
前記光照射手段と前記光検出手段の各々は、前記被検体上における、前記照射点と前記検出点間の距離として定義されるSD距離が少なくとも2種以上であって、かつ、前記SD距離が10 mm程度よりも大きくなるように前記被検体上に配置され、
前記解析部は、前記光照射手段と前記光検出手段との組み合わせにより、ある計測時刻の信号として対応付けられて計測された複数の計測信号を、前記計測信号のSD距離依存性を用いて前記計測時刻に対応した皮膚血流由来信号および脳血流由来信号の少なくとも一方を算出することを特徴とする生体光計測装置。 - 請求項1に記載の生体光計測装置において、特に、皮膚血流由来信号と脳血流由来信号の少なくとも一方の、時間波形または強度分布図またはその両方を計測中に表示すことを特徴とする生体光計測装置。
- 請求項1に記載の生体光計測装置において、特に、皮膚寄与率か脳寄与率の少なくとも一方の、時間波形または強度分布図またはその両方を計測中に表示すことを特徴とする生体光計測装置
- 請求項1から3に記載の生体光計測装置において、特に、皮膚寄与率があらかじめ設定した閾値を超えた場合、あるいは脳寄与率があらかじめ設定した閾値を下回った場合に警告を出力することを特徴とする生体光計測装置。
- 前記1つまたは複数の光検出手段は、少なくとも2種の前記複数の光照射手段からの信号を、異なるタイミングで検出することを特徴とする請求項1記載の生体光計測装置。
- 被検体に光を照射するための1つまたは複数の光照射手段と、前記1つまたは複数の光照射手段から前記被検体上の照射点に照射され、被検体内を伝播してきた光を前記被検体上の検出点において検出するための1つまたは複数の光検出手段と、前記1つまたは複数の光照射手段および前記1つまたは複数の光検出手段を制御するための制御部と、前記1つまたは複数の光検出手段で得られる信号を解析するための解析部とを有する生体光計測装置を用いた生体光計測方法であって、
前記光照射手段と前記光検出手段の各々を、前記被検体上における、前記照射点と前記検出点間の距離として定義されるSD距離が少なくとも2種以上あって、かつ、前記SD距離が10 mm程度よりも大きくなるように前記被検体上に配置するステップと、
前記光照射手段と前記光検出手段との組み合わせにより、ある計測時刻の信号として対応付けられて計測された複数の計測信号を、前記計測信号のSD距離依存性を用いて前記計測時刻に対応した皮膚血流由来信号および脳血流由来信号を算出するステップと
を備えたことを特徴とする生体光計測方法。
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