CN1223842C - Method and system in diffused light for scatheless monitoring blood-oxygen metabolizability of biologic tissue - Google Patents

Abstract

The present invention relates to a non-destructive monitoring method and a system thereof for blood-oxygen metabolism of biologic tissues based on diffused light, which belongs to the technical field of biomedical engineering. The present invention is characterized in that three light emitting diodes which can respectively emit light with two wavelength in different positions sequentially emit light within time intervals less than 0.5 ms in turn, and then a photoelectric detector positioned on one side of the three light emitting diodes is used for sequentially detecting the light intensity of the light diffused from the three light emitting diodes by passing through deep-layer tissues; in this way, optical density OD and the blood-oxygen saturation of tissues to be measured are worked out in sequence. The present invention can accurately work out the blood-oxygen saturation of tissues and is more suitable for practical requirements because of a simple system structure.

Description

The non-destructive monitoring method and the system thereof of biological tissue's blood oxygen metabolism of diffused light

Technical field

Belonging to spectral technique based on the non-destructive monitoring method of biological tissue's blood oxygen metabolism of diffused light uses and biomedical engineering field.

Background technology

The blood fortune situation of monitoring local organization (comprising brain and muscle) is observed its time dependent rule, for the patient in the surgical procedure, urgent patient and suffer from the baby of Hypoxia and ischemia encephalopathic and significant to the monitoring of survival rate after the tissue transplantation.

Determine local organization oxygen metabolism situation, mainly contain based on the direct measuring method that wound PtO2 is arranged of electrochemical principle with based on the lossless detection method of optical measurement.And optical means can realize noninvasive monitoring, and safety easy to use is reliable and stable.The invention belongs to a kind of in the optical means.The method of describing in the file of publication number CN1365649A is based on the Lambert-Beer law of classics, this classical law is the situation at no scattering, for human body with strong scattering optical characteristics and other biological tissue, this law could use after must revising in such cases.On principle, directly under strong scattering, use classical Lambert-Beer law and can't obtain any correct result.The method that publication number US005632273A uses is based on the big uniform dielectric of semiinfinite, the blood oxygen saturation of the deep tissues that its steady-state spatially resolved computational algorithm that adopts is detected when having outer tissue is influential, the method of using in the patent of publication number CN1333011A and CN1331953A is not for having deterministic algorithm steps and detected value, can not accurately detect and organize blood oxygen saturation, and the weak accuracy of detection, system architecture complexity of influencing of signal.Compare with CN1331953A with publication number US005632273A, CN1333011A, the present invention and its difference are: (1) this patent clearly is to detect " the blood oxygen parameter " of organizing blood oxygen saturation rather than general reference.(2) this patent utilizes the method for multiple light courcess and single detecting device to be different from the method for single light source and multi-detector, the signal to noise ratio (S/N ratio) height, and the accuracy of detection height, system architecture is simple.(3) the present invention provided available, exist and accurately detect the experimental formula of organizing oximetry value under the outer tissue condition.Fig. 1 gives the detection synoptic diagram that has patent, and wherein a is a light source, and b is a detecting device, and c is probe, and d is a detecting device, and e is a deep layer tissue to be measured, and f is an outer tissue.

Summary of the invention

The present patent application and in the past method and at present domestic disclosed patented technology compare its characteristics and superior be first it clearly to provide measured be the absolute value of blood oxygen saturation but not " blood oxygen parameter " ambiguous like this notion.Known the absolute value of tissue oxygenation saturation degree can judge definitely whether patient's blood fortune state is normal, thereby this parameter has more clinical meaning.The second, the thickness of outer tissue causes the key factor of blood oxygen parameter error often, but the method for this patent can be eliminated this influence.From implementation method, although utilize the something in common of many measuring technologies in this field of absorption spectrum of oxyhemoglobin and reduced hemoglobin, but the characteristics of this patent are: first, adopted a plurality of light sources arranged point-blank and the method for single detector, it can improve accuracy of detection and be convenient to and adjusts; The second, considered the height scattering of biological tissue, semiempirical formula has been proposed, these all are different from the scheme that is proposed in the patent that has now both at home and abroad.

1 is to be the light source LS1 of r1 with optical sensor OPSU distance in Fig. 2, the 2nd, with optical sensor OPUS distance be the light source LS2 of r2, the 3rd, with optical sensor OPUS distance be the light source LS3 of r3, the 4th, optical sensor OPSU, 5 are the 1st layer tissue and represent with T1,6 are the 2nd layer tissue and represent that with T2 7 are the 3rd layer tissue and represent with T3, in the organize models that human muscular tissue's blood oxygen is measured, T1 is a skin, and T2 muscle hypodermis, T3 are musculature; In the organize models that human body brain blood oxygen is measured, T1 is a skin, and T2 is a skull, and T3 is brain tissue (grey matter and a white matter).B1, b2, b3 are the track of photon transport.Detect the tissue of different depth, LS is placed on the different distance with optical sensor OPUS, LS3 is luminous, and what detected by OPUS mainly is the information of T1 layer, and LS2 is luminous, and what detected by OPUS is the information of T1 and T2 layer, and LS1 is luminous, and what detected by OPUS mainly is the information of T1, T2 layer and T3 layer.Light source LS1, LS2, LS3 are r to the distance of OPUS ₁, r ₂, r ₃

The near infrared multiple light courcess biological tissue method for detecting blood oxygen saturation that the present invention proposes is characterized in that: it make on three diverse locations and each all can send respectively two wavelength light LED successively in less than the time interval of 0.5ms order luminous, detect successively by a photoelectric detector that is positioned at above-mentioned three light emitting diode one sides again and pass through the deep structure tissue and the light intensity of diffusion bright dipping from above-mentioned three light emitting diodes, and thus by calculating the blood oxygen saturation that optical density value OD calculates the local tissue to be measured of deep layer, this non-destructive monitoring method contains following steps successively:

(1) utilize the formula of optical density to detect the different optical density OD that detect under the distance of photoelectric detector by computing machine _k, and preserve.

(1.1) three light sources are fixed on three diverse locations.

(1.2) it is luminous to drive each light source order under microprocessor controls, and according to the value of time-ordered measurement scattered light intensity correspondence.

(1.3) utilize following optical density formula to calculate from the different optical density OD that detect under the distance of photoelectric detector _k:

${\mathrm{OD}}_k=\log \frac{I_k}{I_{\mathrm{kr}}},$

Wherein, k=1,2,3, the footnote of three Different Light of expression;

I _KrThe light that sends for the light source of diverse location is through detecting reflective light intensity by photoelectric detector after the organization internal scattering,

I _kIt is the light intensity of three light source outgoing;

(2), calculate the oxygen saturation rSO of the local tissue to be measured of deep layer according to above-mentioned test result ₂, show and preservation;

(2.1) in the same sense cycle but different detect distance down detected optical density subtract each other and ask poor:

$\mathrm{\Δ}{\mathrm{OD}}_2^{{\mathrm{\λ}}_j}={\mathrm{OD}}_2^{{\mathrm{\λ}}_j}-{\mathrm{OD}}_{{\mathrm{\λ}}_j}^{{\mathrm{\λ}}_j},$

$\mathrm{\&Delta;}{\mathrm{OD}}_1^{{\mathrm{\&lambda;}}_j}={\mathrm{<figure-callout\; id="3"\; label="OD"\; filenames="C20031010305300113.png"\; state="\{\{state\}\}">OD</figure-callout>}}_3^{{\mathrm{\&lambda;}}_j}-O{D}_2,$

Wherein, j=1,2, represent different wavelength respectively, i.e. λ ₁, λ ₂Represent the optical wavelength under the different wave length respectively:

Δ OD ₂ ^{λ j}Represent that its wavelength that the 2nd light source sends is λ _jThe optical density of light and its wavelength that the 1st light source sends be λ _jOptical density poor of light;

Δ OD ₁ ^{λ j}Represent that its wavelength that the 3rd light source sends is λ _jThe optical density of light and its wavelength that the 2nd light source sends be λ _jOptical density poor of light:

(2.2) calculate the oxygen saturation rSO of the local tissue to be measured of deep layer with computing machine with following experimental formula ₂:

$\mathrm{rS}{O}_2=C{\left(\frac{\mathrm{\&Delta;}{\mathrm{OD}}_1^{{\mathrm{\&lambda;}}_1}}{\mathrm{\&Delta;}{\mathrm{OD}}_1^{{\mathrm{\&lambda;}}_2}}\right)}^2+B_1\left(\frac{{\mathrm{\&Delta;OD}}_1^{{\mathrm{\&lambda;}}_1}}{\mathrm{\&Delta;}{\mathrm{OD}}_1^{{\mathrm{\&lambda;}}_2}}\right)+B_2\left(\frac{\mathrm{\&Delta;}{\mathrm{OD}}_2^{{\mathrm{\&lambda;}}_1}}{\mathrm{\&Delta;}{\mathrm{OD}}_2^{{\mathrm{\&lambda;}}_2}}\right)+A$

Wherein: C:0.16～0.25; B ₁:-1.66～-2.5

B ₂：-0.13～-0.25；A：1.8～2.7。

2. described three light sources and photoelectric detector are on the same straight line.

3. the centre distance of two adjacent light sources is between 5mm～10mm, and the centre distance of photoelectric detector and all light sources is between 30mm～50mm.

4. described all light sources are to send ruddiness and near infrared light respectively.

The synoptic diagram of the general monitoring method of description of drawings Fig. 1.

Fig. 2 monitoring method schematic diagram of the present invention.

Fig. 3 haemoglobin absorption spectrum.

The program flow diagram of the detection of biological tissue oxygenation metabolism that Fig. 4 the present invention proposes.

Fig. 5 hardware unit structural drawing.

Fig. 6 sensor outside drawing.

Fig. 7 hardware unit outside drawing of the present invention.

Fig. 8 experimental result.

Embodiment:

It contains and is distributed in 3 last infrared light supply LS of the distance different with photoelectric detector, 1 photoelectric detector OPUS, and their linear arrangements constitute probe 8, as shown in Figure 6.The present invention is according to a plurality of optical density value that measure on diverse location, and process is carried out the tissue oxygenation saturation that algebraic operation obtains regional area to its experimental formula that provides.System is by sensor, pre-amplification circuit, A/D converter, embedded microcontroller, and external SRAM, LCD and touch-screen are formed system, as shown in Figure 5.Described microcontroller adopts AT89C52, and the OPUS that is adopted is a silicon photocell, and LCD resolution is the touch-screen of a 320*240 and a 1024*1024.Outward appearance as shown in Figure 7, probe 8 is connected to plug 9 on the instrument 10,11 is liquid crystal and touch-screen, 12 is reset button.

The typical hardware unit that goes out according to the diffused light principle design, as shown in Figure 5.Light source LS is with 3 LED and 1 OPUS on different distances (become a line, LED respectively), and 3 LED difference photoelectric detector OPUS detect light intensity by photoelectric detector OPUS and change at a distance of 30mm, 35mm, 40mm.Silicon photocell OPUS is connected to prime amplifier TLC27L4, and the LF398 work of microcontroller AT89C52 control sampling holder also starts A/D TLC2543 conversion, and transformation result is read and write down sampled value.LS is luminous for the microcontroller driving light source, and will be saved in storage chip 6264 by the A/D conversion value of OPUS detected value, and above-mentioned advantage: the consistance of passage is fine, makes data that comparability be arranged.

3 LED are arranged, r in the probe among the present invention in the device ₂, r ₃2 influences that LED is used to proofread and correct outer tissue at place.In whole tissue, owing to certain feature that is absorbed with of biological tissue, have only the selection suitable wavelengths, could calculate local organization oxygen saturation and blood oxygen concentration preferably and change.The measurement medium wavelength of different tissues is selected some difference, and muscle blood oxygen detects 700/880nm, the 780nm/840nm of head, and we use is 700/880, the 780nm/840nm component leds.For biological tissue is not produced any injury, the luminous power of LED should be less than 10mW.

Introduction by above-mentioned hardware configuration and principle of work, the system signal flow process can reduce: (1) microcontroller sends control signal to the LS driver element, 3 LED order luminous (2) light are connected to prime amplifier (4) 1 road sampling holders through tissue (5T1 among Fig. 2,6T2,7T3) from detection position outgoing (3) OPUS detection light intensity signal sampling are kept, A/D converter is changed, and by microprocessor controls transformation result is read in SRAM and preserves.(5) by calculating in the microcontroller and demonstration local organization oxygen saturation rSO2.

In microcontroller, calculate the OD value on 3 distances, utilize formula, calculate rSO2.

Experiment effect

The baby who utilizes the present invention to test normal infant and suffer from encephalopathic under rest state, the basic value of tissue oxygenation saturation; In the blood model outer tissue is arranged the time utilize the contrast of the method that blood oxygen saturation changing value that the present invention detects and publication number US005632273A use, the method that US005632273A uses is limited in measurement range, for 18%-98% as shown in Figure 8.

The effect that this patent invention brings after implementing can reduce: (1) it be can't harm, be again quantitative simultaneously, accurate reflection blood oxygen saturation when having outer tissue.(2) whether normally this parameter of the absolute value of tissue oxygenation saturation degree provided by the invention is can judge to organize blood fortune state leading indicator (comparing with the variable quantity of other blood oxygen index).

Main feature of the present invention:

1, proposed the detection method of local organization oxygen saturation, and provided to exist under the outer tissue condition and accurately detect tissue The empirical equation of oximetry value, the result is accurate, need not calibrate.

2, adopt 3 light sources and a photoelectric detector to detect according to 1 method, each light source linear array with photoelectricity On the different distance of detector. The signal to noise ratio height, the accuracy of detection height, system architecture is simple.

Claims (4)

1. comprise based on biological tissue's blood oxygen metabolism non-destructive monitoring method of diffused light and use the light source that is positioned at deep layer tissue surface to be measured and detect from the local step of organizing diffused light to be measured of deep layer, it is characterized in that: it make on three diverse locations and each all can send respectively two wavelength light LED successively in less than the time interval of 0.5ms order luminous, detect successively by a photoelectric detector that is positioned at above-mentioned three light emitting diode one sides again and pass through the deep structure tissue and the light intensity of diffusion bright dipping from above-mentioned three light emitting diodes, and thus by calculating the blood oxygen saturation that optical density value OD calculates the local tissue to be measured of deep layer, this non-destructive monitoring method contains following steps successively:

(1) utilizes the formula of optical density to detect the different optical density ODk that detect under the distance of photoelectric detector by computing machine, and preserve.

(1.1) three light sources are fixed on three diverse locations.

(1.2) it is luminous to drive each light source order under microprocessor controls, and according to the value of time-ordered measurement scattered light intensity correspondence.

(1.3) utilize following optical density formula to calculate from the different optical density OD that detect under the distance of photoelectric detector _k:

$O{D}_k=\log \frac{I_k}{I_{\mathrm{kr}}},$

Wherein, k=1,2,3, the footnote of three Different Light of expression;

I _KrThe light that sends for the light source of diverse location is through detecting reflective light intensity by photoelectric detector after the organization internal scattering,

I _kIt is the light intensity of three light source outgoing;

(2), calculate the oxygen saturation rSO of the local tissue to be measured of deep layer according to above-mentioned test result ₂, show and preservation;

(2.1) in the same sense cycle but different detect distance down detected optical density subtract each other and ask poor:

$\mathrm{\&Delta;O}{D}_2^{{\mathrm{\&lambda;}}_j}={\mathrm{OD}}_2^{{\mathrm{\&lambda;}}_j}-{\mathrm{OD}}_{{\mathrm{\&lambda;}}_j}^{{\mathrm{\&lambda;}}_j},$

$\mathrm{\&Delta;O}{D}_1^{{\mathrm{\&lambda;}}_j}={\mathrm{OD}}_3^{{\mathrm{\&lambda;}}_j}-{\mathrm{OD}}_2,$

Wherein, j=1,2, represent different wavelength respectively, i.e. λ ₁, λ ₂Represent the optical wavelength under the different wave length respectively:

Represent that its wavelength that the 2nd light source sends is λ _jThe optical density of light and its wavelength that the 1st light source sends be λ _jOptical density poor of light;

Represent that its wavelength that the 3rd light source sends is λ _jThe optical density of light and its wavelength that the 2nd light source sends be λ _jOptical density poor of light:

(2.2) calculate the oxygen saturation rSO of the local tissue to be measured of deep layer with computing machine with following experimental formula ₂:

${\mathrm{rSO}}_2=C{\left(\frac{\mathrm{\&Delta;}{\mathrm{OD}}_1^{{\mathrm{\&lambda;}}_1}}{{\mathrm{\&Delta;OD}}_1^{{\mathrm{\&lambda;}}_2}}\right)}^2+B_1\left(\frac{{\mathrm{\&Delta;OD}}_1^{{\mathrm{\&lambda;}}_1}}{{\mathrm{\&Delta;OD}}_1^{{\mathrm{\&lambda;}}_2}}\right)+B_2\left(\frac{{\mathrm{\&Delta;OD}}_2^{{\mathrm{\&lambda;}}_1}}{{\mathrm{\&Delta;OD}}_2^{{\mathrm{\&lambda;}}_2}}\right)+A$

Wherein: C:0.16～0.25; B ₁:-1.66～-2.5

B ₂：-0.13～-0.25；A：1.8～2.7。

2. the biological tissue's blood oxygen metabolism non-destructive monitoring method based on diffused light according to claim 1 is characterized in that described three light sources and photoelectric detector are on the same straight line.

3. the biological tissue's blood oxygen metabolism monitoring method based on diffused light according to claim 1, it is characterized in that: the centre distance of two adjacent light sources is between 5mm～10mm, and the centre distance of photoelectric detector and all light sources is between 30mm～50mm.

4. require 1 described biological tissue's blood oxygen metabolism monitoring method according to detection, it is characterized in that described all light sources are to send ruddiness and near infrared light respectively based on diffused light.

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