JP2007307007A - Catheter system using photoacoustic effect - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a catheter system using a photoacoustic effect which quickly and temporally detects a light absorbing substance in blood by evanescent light or normal light with a simpler configuration than heretofore without forcing further burdens on a patient and accurately measures various kinds of characteristics of the blood and vascular walls in the catheter system having an optical fiber utilizing the evanescent light and the normal light. <P>SOLUTION: A control part 8 controls so that a laser beam is output from a light source 13, excitation waves suited to the light absorbing substance to be measures are formed by an excitation filter, and the excitation waves are introduced to a catheter. When the evanescent light is generated or the normal light is emitted from the distal end of the optical fiber and the light absorbing substance in the blood is irradiated, sound waves by the photoacoustic effect based on light absorption are detected by a sound gathering microphone 50; signal components are taken out; they are compared with reference data in the control part 8 and the various kinds of characteristic values of the blood are obtained. The evanescent light is utilized for detecting the light absorbing substance in plasma and on the surface of the vascular walls and the normal light is utilized for detecting the light absorbing substance in the entire blood and inside the vascular walls. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a catheter system using a photoacoustic effect used for blood measurement in intensive care and emergency care.

The applicant of the present application is a catheter system including an optical fiber using evanescent light as a system for selectively and quantitatively measuring a luminescent composition in blood in order to measure changes in the concentration of drugs and biological substances in blood. Has already been proposed (Patent Document 1).
Since normal light propagates through space (space propagation light) and penetrates into blood at a depth of mm, light in a wide wavelength band is absorbed by hemoglobin present in red blood cells. For this reason, when quantifying directly from blood, when detecting fluorescence by exciting a fluorescent substance (pharmaceuticals or the like) injected into blood, it is obstructed by light absorption of hemoglobin, making detection almost impossible. On the other hand, evanescent light (also referred to as near-field light) is present in the vicinity of several hundreds of nanometers near the surface where evanescent light is generated, and does not propagate through space like normal light. For this reason, in the blood, it is hardly influenced by the hemoglobin which exists in the red blood cell of about 8 micrometers in diameter, The fluorescent substance in plasma can be excited.
Patent Document 1 aims to provide a structure that can reliably measure the fluorescence intensity and the fluorescence spectrum of a substance around the distal end of the catheter using the characteristics of the evanescent light described above.

The above proposals are broadly divided into configurations in which the generation of evanescent light and the detection of fluorescence are performed using one optical fiber or different optical fibers.
In the former, as a configuration for generating evanescent light, a part of the cladding layer at the tip of the optical fiber is removed to expose the core, whereby the pumping light introduced into the optical fiber is totally reflected by the exposed core portion, thereby evanescent light. And the fluorescence generated by irradiating the fluorescent material present in the blood with the evanescent light is incident on the optical fiber from the tip of the optical fiber, guided outside the optical fiber, and measured by an external measuring instrument.
In the latter, one optical fiber generates evanescent light with the same structure as described above, and the fluorescence generated by the fluorescent material is guided to the outside by another one optical fiber and detected.

By the way, when attention is paid to the detection of fluorescence, a system constituted by one optical fiber performs transmission / reception of light, generation of evanescent light, and detection of fluorescence by a single optical fiber in a thin optical fiber. Therefore, it is difficult to reduce the fiber diameter and to construct the fiber. Further, since the fluorescence detection light is returned through the optical fiber, the weak light is further weakened and the blood measurement accuracy is limited.
When two optical fibers are used, the configuration of each optical fiber is not complicated. However, since the number of optical fibers is two, the cross-sectional area occupied by the optical fiber catheter is increased, and the diameter of the catheter is reduced. However, since the fluorescence detection light is returned through the optical fiber, there is a problem in common with the above that weak light is further weakened.

On the other hand, detection by a photoacoustic method can be considered as a means for measuring light absorption and spectrum in an opaque body and a scattering material.
As a method using the photoacoustic method, a photoacoustic spectroscopic analysis device and a photoacoustic spectroscopic analysis method have been proposed (Patent Document 2). This is to irradiate the sample with excitation light and detect photoacoustic waves from the sample. In the embodiment, the sample is inserted through the optical fiber from the body surface, and laser light is introduced into the optical fiber for irradiation. The substance to be measured is excited by absorbing this light. When the absorbed energy is released by a non-radiative process, a displacement due to thermal expansion, that is, an acoustic wave is generated, which is detected by a piezoelectric sensor. The sample is blood flowing through the blood vessels of the living body, the measurement target substance is glucose, and the glucose concentration in the blood is obtained.

Also, a photoacoustic image forming apparatus that forms a photoacoustic image has been proposed as a method of creating an image of a living body of a human or a non-human animal or a part thereof (Patent Document 3).
This is to create an acoustic image from a pressure wave generated by administering a contrast agent to a living body and exposing it to radiation.
Furthermore, a cancer detection method using cell autofluorescence has been proposed as a method for detecting cell autofluorescence radiation (Patent Document 4).
The purpose of this is to detect cells that are newly formed or formed by measuring the autofluorescence of the cells. The cells are exposed to ultraviolet rays by an optical fiber inserted through an endoscope, and generate fluorescence. A wavelength indicating a tryptophan emission spectrum is measured. This proposal describes that it is applied to other techniques including the photoacoustic method as one of the measurement methods.

The above-mentioned Patent Document 2 uses excitation light of a laser beam and detects an acoustic wave generated from a sample by a piezoelectric element. However, since normal light is used, the influence of absorption by hemoglobin in blood is affected. It can only be used for glucose that has absorption in the near infrared region that is not received. Further, Patent Document 3 generates an acoustic image from a pressure wave generated by exposing a contrast agent with radiation, and cannot detect a sound wave due to a photoacoustic effect generated from a drug or a biological substance in blood.
Patent Document 4 discloses a specific example in which fluorescence is generated by exposure to ultraviolet light, and a wavelength indicating a tryptophan emission spectrum is measured therefrom, and there is a description that a photoacoustic method or the like can be applied, but a specific configuration is disclosed. There is no.
Patent Document 5 discloses a system that peels off a part of a clad layer of an optical fiber to generate evanescent light and measures an absorption spectrum in a living tissue, but does not use a photoacoustic method for the measurement. In addition, since the evanescent light and the normal light are not switched, it is impossible to measure whole blood and plasma, or the inside and the surface of the blood vessel wall separately.
Japanese Patent Application No. 2004-348482 JP-A-9-133655 Special table 2002-508760 gazette Special table 2003-533684 gazette JP 2002-214132 A

  The present invention has been made in view of the above-mentioned problems, and its purpose is to provide various light-absorbing substances in the blood and in the blood vessel wall in a catheter system including an optical fiber that utilizes light absorption without imposing a further burden on the patient. The volume is detected quickly and with high sensitivity with a simple configuration compared to the conventional configuration, and various characteristics of the whole blood or plasma and the inside of the blood vessel wall or on the surface of the blood vessel wall are separated and accurately detected. An object of the present invention is to provide a catheter system using a photoacoustic effect that can be measured.

In order to achieve the above object, claim 1 of the present invention is characterized in that the tip of an optical fiber is placed in a blood vessel to generate evanescent light, and plasma is detected by detecting a sound wave signal from a light absorbing material that has absorbed the evanescent light. And a catheter system for measuring a state of a blood vessel wall surface, the sound wave detecting element disposed on an external surface of a living body, detecting a sound wave generated by a photoacoustic effect based on the light absorption intensity, and converting the sound wave into an electric signal; A processing circuit that processes an electrical signal detected by a sound wave detection element and outputs a voltage or current signal corresponding to the sound wave signal, and compares the voltage or current signal of the processing circuit with a reference wave, thereby various blood and blood vessel walls And a control means for outputting a signal indicating the characteristic state.
A second aspect of the present invention is characterized in that, in the first aspect of the present invention, the tip end portion of the optical fiber removes the clad layer at the tip end of the cylindrical shape and exposes the core to generate evanescent light.
According to a third aspect of the present invention, a catheter system that measures the state of whole blood and the inside of a blood vessel wall by placing the optical fiber tip in a blood vessel to emit normal light and detecting the absorption of the normal light by a biological material. A sound wave detecting element disposed on an external surface of a living body for detecting a sound wave generated by a photoacoustic effect based on the light absorption intensity intensity and converting the sound wave into an electric signal, and processing the electric signal detected by the sound wave detecting element A processing circuit that outputs a voltage or current signal corresponding to the sound wave signal, and a control that outputs a signal indicating the state of various characteristics of blood and blood vessel walls by comparing the voltage or current signal of the processing circuit with a reference wave Means.
According to a fourth aspect of the present invention, in the invention according to the third aspect, the distal end portion of the optical fiber emits normal light from the distal end surface or the side surface portion, or the distal end surface and the side surface portion.
According to a fifth aspect of the present invention, in the invention according to the second or fourth aspect, the tip end portion of the optical fiber is provided with a mechanism capable of switching evanescent light or normal light alone or switching between evanescent light and normal light. And
According to a sixth aspect of the present invention, in the invention according to the first, second, third, fourth, or fifth aspect, the processing circuit obtains a signal component obtained by drawing a reference signal into a phase of an electric signal from the sound wave detecting element. It has a lock-in amplifier that outputs a DC voltage by averaging over time.
According to a seventh aspect of the present invention, in the invention according to the first, second, third, fourth, fifth or sixth aspect, the sound wave detecting element is a microphone, and the microphone is provided from a tip portion of the optical fiber in a blood vessel. It is made to face the target measured with evanescent light or normal light, and this measurement target is closely_contact | adhered to the outer surface of the biological body near.

According to the above configuration, the concentration of the drug or biological substance in the blood or blood vessel wall that absorbs evanescent light or normal light can be detected quickly and accurately over time without imposing a further burden on the patient.
The evanescent light is present in the vicinity of several hundreds of nanometers near the surface where the evanescent light is generated, and does not propagate through space like normal light. For this reason, the light-absorbing substance in plasma can be measured with little influence of hemoglobin present in red blood cells having a diameter of about 8 μm in blood. Moreover, the light-absorbing substance existing on the blood vessel wall surface can be measured by bringing the catheter into contact with the blood vessel wall.
On the other hand, since normal light propagates through space and penetrates into blood in units of several millimeters, light in a wide wavelength band is absorbed by hemoglobin present in red blood cells. Therefore, items involving hemoglobin such as blood oxygen partial pressure can also be measured. Further, by bringing the catheter into contact with the blood vessel wall, it is possible to measure the light-absorbing substance that penetrates into the blood vessel wall and exists inside.
Since light absorption is detected using the photoacoustic effect, it is not necessary to separate incident light and emitted light on the catheter proximal side. In fluorescence detection, since the wavelength of fluorescence is longer than that of excitation light, it is possible to separate incident light and emitted light relatively easily by using a filter or the like. Further, in light absorption by normal light, incident light and outgoing light can be easily separated by using separate optical fibers for the irradiation side and the light receiving side. However, in light absorption measurement using evanescent light, it is necessary to separate incident light and emitted light having the same wavelength with a single optical fiber, and the apparatus is likely to be complicated. However, in the photoacoustic method, the incident light and emitted light are separated. Is unnecessary.
Furthermore, a lock-in amplifier is used in the processing circuit, and the collected sound signal is converted into a digital signal to perform high-speed and high-precision digital processing, and various characteristics of blood and blood vessel walls can be measured with higher accuracy.
Moreover, since the cladding layer at the tip of the optical fiber is removed and the core layer is exposed, it is left in the blood, so that the intensity of the excitation light absorbed by the light-absorbing substance by efficiently generating evanescent light from the tip of the optical fiber Since the sound wave having a higher level can be received, blood measurement accuracy is improved.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a diagram showing a configuration example of a catheter system using a photoacoustic effect according to the present invention. This example is a configuration diagram of an optical system and a circuit system applied to the catheter system according to the present invention.
The control unit 8 sends a light source activation control signal to the light source control unit 11 based on an instruction from the console 12. The light source controller 11 activates a light source 13 such as a laser diode or LED. The excitation light from the light source 13 passes through the condenser lens 14 and the excitation filter 15 and is guided to the optical fiber end of the optical connector 1 by the condenser lens 2. Excitation light incident from the end of the optical fiber is transmitted to the tip of the evanescent catheter 3.

FIG. 2 is a view showing the structure of the distal end of the catheter used in the catheter system according to the present invention, and (a), (b), (c) and (d) show examples.
In either case, the protective layer 22 and the cladding layer 23 are removed from the entire circumference or part of the optical fiber near the distal end of the catheter 21. In addition, by disposing movable or fixed reflecting mirrors 27a to 27d at the tip of the optical fiber, high-intensity normal light is prevented from leaking out of the optical fiber during measurement with evanescent light.

(A) is generated on the surface around the core 24 where the evanescent light 25 is exposed when the excitation light 29 enters the optical fiber. When the evanescent light 25 is irradiated to the light absorbing material in the plasma or the blood vessel wall surface, a sound wave 30 is generated and emitted to the surroundings. The light that has not been absorbed by the reflecting mirror 27a at the tip of the optical fiber returns to the incident side, and nothing other than the evanescent light 25 leaks out of the optical fiber. When the reflecting mirror 27a is tilted by the reflecting mirror opening / closing wire 46a, the normal light 49 is emitted into the blood from the exit window 45 on the end face of the optical fiber, and is absorbed by the light absorbing substance in the blood or inside the blood vessel wall to generate the sound wave 30. Radiated to the surroundings.
In (b), the optical fiber at the distal end of the catheter is deformed from a linear shape to a curved shape by pulling or pushing the optical fiber at the distal end bending wire 46b or a piezoelectric actuator, so that only the evanescent light 25 is generated linearly. The normal light 49 is generated in addition to the evanescent light 25 from the curved portion.
In (c), an optical fiber having only a core is covered with a stretchable transparent plastic film 47 and the like, and a transparent liquid 48 is poured between the core 24 and the stretchable transparent plastic film 47 to be deformed. Each refractive index needs to have a relationship of core 24 ≦ transparent liquid 48 ≦ stretchable transparent plastic film 47. In the case of a straight line, only the evanescent light 25 is generated, but the normal light 49 is irradiated from a curved portion as the stretchable transparent plastic film 47 expands.
Since these catheter structures have a single optical fiber, they can be made smaller in diameter than the same size compared with catheters that measure oxygen saturation, etc., using ordinary two optical fibers. is there.
(D) is a structure in which two optical fibers for the evanescent light 25 and the normal light 49 are provided, and the incident light is switched to the optical fibers for the evanescent light 25 and the normal light 49 for measurement. (A), (b) and (c) have a simple structure with no moving parts. Since there is no moving part, it is possible to make it the same size as the catheter which measures the oxygen saturation etc. which use two normal optical fibers.

The light absorbing material that has absorbed the evanescent light 25 or the normal light 49 generates a sound wave 30 corresponding to the absorption intensity by the photoacoustic effect, and the sound wave 30 radiated to the surroundings is placed on the living body surface of the measurement target. It is detected by the sound collecting microphone 50.
The sound wave detected by the sound collecting microphone 50 is converted into an electric signal 50 a and input to the lock-in amplifier 51. In the lock amplifier 51, the reference wave is drawn into the frequency of the signal component and is time-averaged to output a DC voltage of the signal component.
The control unit 8 performs light source control and measurement operation by an arithmetic element such as a CPU based on a control program, and compares the DC voltage output from the lock-in amplifier 51 with reference data stored in advance in blood and blood vessels. Calculate the amount of light-absorbing substance in the wall.

The monitor 9 displays a menu screen for the measurement operation, and displays the measured light absorption intensity and the amount of the light absorbing substance. On the menu screen, specifications such as the output of the light source and the wavelength region are displayed, and the light emission wavelength and output of the light source can be adjusted by the console 12. It is also possible to adjust the calculation contents to be output.
The recorder 10 is engraved with a change in light absorption intensity by a light absorbing substance such as riboflavin in blood over time.

FIG. 3 is a block diagram showing an embodiment of a signal processing unit of the catheter system according to the present invention, and FIG. 4 is a waveform diagram showing an example of an output signal waveform of each circuit unit of FIG.
In the light source control unit 11, the oscillator 31 outputs a sine wave (in addition, a square wave or the like), and the light source driving circuit 32 is driven by the sine wave. From the light source 33 such as an LED or a laser diode, for example, as shown in FIG. An excitation wave having a predetermined frequency as shown is output. The excitation wave propagates through the optical fiber, and evanescent light is generated from the optical fiber tip or normal light is emitted and irradiated into the blood vessel 37. In the case of evanescent light, the light absorbed by the light absorbing material present in the evanescent light generation site 34a near the surface of the optical fiber tip is converted into a sound wave corresponding to the absorbed light intensity by the photoacoustic effect, and directed toward the surface of the skin 36. The emitted sound wave is detected by the microphone 35 and amplified by the amplifier 40. In the case of normal light, the light absorbed by the light-absorbing substance present in the normal light irradiation site 34b is converted into a sound wave corresponding to the absorbed light intensity by the photoacoustic effect, and is emitted toward the surface of the skin 36. Is amplified by the amplifier 40.

The signal light detected by the microphone 35 is a broadband signal as shown in FIG. 4B, and is a signal on which respiratory noise, pulse noise, blood flow noise, external noise, and the like are superimposed in addition to the light absorption signal. The superposed signal is extracted by the bandpass filter 41 in the vicinity of the absorption fluorescence signal as shown in FIG.
On the other hand, the sine wave output from the oscillator 31 is shaped by the waveform shaping circuit 38 and shifted by 90 ° by the 90 ° phase shift circuit 39.
By multiplying this 90 ° phase shifted signal and the signal of FIG. 4C by the multiplier 42, a multiplication signal as shown in FIG. 4D can be obtained.

The low-pass filter 43 can obtain a direct current component of the signal light intensity as shown in FIG. 4E by cutting the high frequency component of FIG. This direct current component is displayed on the display 44 (corresponding to the monitor 9 in FIG. 1), and the state of various characteristics of blood and blood vessels can be obtained by comparing with the reference data obtained and stored in advance by the control unit 8. it can.
The circuit portion including the waveform shaping circuit 38, the 90 ° phase shift circuit 39, the amplifier 40, the band pass filter 41, the multiplier 42 and the low pass filter 43 is a portion corresponding to the circuit functioning in the lock-in amplifier 51 of FIG. is there. Each circuit output waveform is displayed in an analog signal form, but is converted into a digital signal in advance and processed with the digital signal.

  The optical system for generating excitation light in FIG. 1 has a mechanism in which a plurality of semiconductor lasers and LEDs having different emission wavelengths are provided or an excitation filter is exchanged manually or automatically in order to select an excitation wavelength suitable for the light absorbing material to be measured. Can be attached. Further, when the light source is a semiconductor laser, since it is monochromatic light, a band-pass filter such as an excitation filter is unnecessary on the light source side. Furthermore, it is possible to attach an injection capillary, a balloon expansion pipe, or the like to the evanescent catheter.

Next, an example of the light absorbing material used in the embodiment of the present invention will be described.
Many in vivo substances and pharmaceuticals have light absorption in a specific wavelength range, so there are many substances that can be targeted. Examples include the following:
In vivo substances: bilirubin, vitamin Bs, hemoglobin, etc. Drugs: propofol, riboflavin, indocyanine green, etc. In many cases, the above drugs are injected into the living body by intravenous injection. There are also types that can measure changes in blood concentration by intramuscular injection or oral administration (drinking drugs).

  As the light that enters the optical fiber, that is, the light that generates evanescent light, excitation light of a target light-absorbing substance (vitamin B2, indocyanine green, etc.) is used. More specifically, vitamin B2 uses light around 450 nm, and indocyanine green uses light around 780 nm. The term “near” means the light in the absorption wavelength band. In addition, as light for normal light irradiation, light of 540 nm or 575 nm is used for hemoglobin in red blood cells, and light of 780 nm is used for indocyanine green.

FIG. 5 is a diagram showing a specific configuration example of the catheter system according to the present invention.
The catheter has a portion for inserting an optical fiber, a sampling port 55 and a liquid or drug administration port 54. A connector 56 is connected to the end of the optical fiber and is connected to a measuring device 57 that is a signal processing device. The lock-in amplifier is incorporated in the measuring device 57, but can be installed separately from the measuring device 57.
A sound collecting microphone 50 is brought into close contact with the skin 53 on the surface of the measurement target. The electric signal line (cord) 50 a is connected to the lock-in amplifier 51 by the connector 52, and the measured signal is input to the measuring device 57. The electric signal line 50a of the sound collection microphone 50 can be integrated with the cord of the catheter.

In FIG. 5, only one sound collecting microphone 50 is illustrated, but a plurality of sound collecting microphones 50 can be installed so as to surround the detection unit to improve detection sensitivity and reduce noise. When a plurality of sound collecting microphones are installed, it is difficult to make the distances (acoustic distances) between all the sound collecting microphones and the detection unit the same. If the distances are different, simply adding the signals does not necessarily enhance the signal depending on the phase of the sound wave.
In order to adjust the phase of the detected sound wave, as an example, a sound wave due to the photoacoustic effect is generated in a strong light absorption band near 415 nm of hemoglobin by normal light irradiation. This sound wave is measured with individual sound collecting microphones, the phase difference of each sound collecting microphone is measured with each sound collecting microphone, and the phase difference opposite to this is given at the time of addition to accurately add signals. , Improve detection sensitivity and reduce noise.

  This is a catheter system in which an optical fiber is introduced into a living tissue for clinical examination and drug monitoring, and a blood concentration change is measured using a sound collecting microphone utilizing a photoacoustic effect as a detector.

It is a figure which shows embodiment of the catheter system using the photoacoustic effect by this invention. It is a figure which shows the structure of the Example of the catheter front-end | tip used for the catheter system by this invention. It is a block diagram which shows embodiment of the signal processing part of the catheter system by this invention. FIG. 4 is a waveform diagram illustrating an example of an output signal waveform of each circuit unit in FIG. 3. It is a figure which shows the specific structural example of the catheter system by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical connector 2 Condensing lens 3 Evanescent catheter 8 Control part 9 Monitor 10 Recorder (XY plotter)
11 Light source control unit 12 Console 13, 33 Light source (semiconductor laser, LED, xenon lamp, etc.)
DESCRIPTION OF SYMBOLS 15 Excitation filter 21 Catheter 22 Protective layer 23 Clad layer 24 Core 25 Evanescent light 30 Sound wave 31 Oscillator 32 Light source drive circuit 34a Evanescent light generation part 34b Normal light irradiation part 35, 50 Sound collection microphone 36, 53 Skin 37 Blood vessel 38 Waveform shaping circuit 39 90 ° Phase Shift Circuit 40 Amplifier 41 Band Pass Filter 42 Multiplier 43 Low Pass Filter 44 Display 45 Exit Window 46a Reflector Mirror Opening Wire 46b Tip Bending Wire 47 Stretch Transparent Plastic Film 48 Transparent Liquid 49 Normal Light 51 Lock In-amp

Claims (7)

A catheter system for measuring the state of plasma and the surface of a blood vessel wall by generating an evanescent light by placing an optical fiber tip in a blood vessel and detecting absorption of the evanescent light by a biological material,
A sound wave detecting element that is disposed on the external surface of the living body, detects a sound wave generated by the photoacoustic effect based on the light absorption intensity, and converts the sound wave into an electrical signal;
A processing circuit that processes an electrical signal detected by the sound wave detection element and outputs a voltage or current signal corresponding to the sound wave signal;
Control means for outputting a signal indicating the state of various characteristics of blood by comparing the voltage or current signal of the processing circuit with a reference wave;
A catheter system using a photoacoustic effect.   2. The catheter system using the photoacoustic effect according to claim 1, wherein the distal end portion of the optical fiber removes the cylindrical cladding layer at the distal end and exposes the core to generate evanescent light. A catheter system for measuring the state of whole blood and the inside of a blood vessel wall by placing the optical fiber tip in a blood vessel to emit normal light and detecting absorption of the normal light by a biological material,
A sound wave detecting element that is disposed on the external surface of the living body, detects a sound wave generated by the photoacoustic effect based on the light absorption intensity, and converts the sound wave into an electrical signal;
A processing circuit that processes an electrical signal detected by the sound wave detection element and outputs a voltage or current signal corresponding to the sound wave signal;
Control means for outputting a signal indicating the state of various characteristics of blood by comparing the voltage or current signal of the processing circuit with a reference wave;
A catheter system using a photoacoustic effect.   The catheter system using the photoacoustic effect according to claim 3, wherein the distal end portion of the optical fiber radiates normal light from the distal end surface or the side surface portion, or the distal end surface and the side surface portion.   The catheter system using the photoelectric effect according to claim 2 or 4, wherein the tip portion of the optical fiber is a mechanism capable of switching evanescent light or normal light alone or switching between evanescent light and normal light.   The processing circuit includes a lock-in amplifier that time-averages a signal component obtained by drawing a reference signal into a phase of an electric signal from the sound wave detection element and outputs a DC voltage. A catheter system using the photoacoustic effect according to 2, 3, 4 or 5. The sound wave detection element is a microphone,
The microphone is made to face a target to be measured with evanescent light or normal light from a tip portion of the optical fiber in a blood vessel, and the measurement target is brought into close contact with a near outer surface of a living body. A catheter system using the photoacoustic effect described in 1, 2, 3, 4, 5 or 6.

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