WO2016084720A1 - Appareil d'acquisition d'informations d'objet et procédé de commande de cet appareil - Google Patents

Appareil d'acquisition d'informations d'objet et procédé de commande de cet appareil Download PDF

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Publication number
WO2016084720A1
WO2016084720A1 PCT/JP2015/082638 JP2015082638W WO2016084720A1 WO 2016084720 A1 WO2016084720 A1 WO 2016084720A1 JP 2015082638 W JP2015082638 W JP 2015082638W WO 2016084720 A1 WO2016084720 A1 WO 2016084720A1
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WIPO (PCT)
Prior art keywords
light
wavelength
pulsed
wavelengths
information acquiring
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PCT/JP2015/082638
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English (en)
Inventor
Takao Nakajima
Yasufumi Asao
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Canon Kabushiki Kaisha
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Publication of WO2016084720A1 publication Critical patent/WO2016084720A1/fr

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/1702—Systems in which incident light is modified in accordance with the properties of the material investigated with opto-acoustic detection, e.g. for gases or analysing solids
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/0059—Measuring for diagnostic purposes; Identification of persons using light, e.g. diagnosis by transillumination, diascopy, fluorescence
    • A61B5/0062—Arrangements for scanning
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/0093—Detecting, measuring or recording by applying one single type of energy and measuring its conversion into another type of energy
    • A61B5/0095—Detecting, measuring or recording by applying one single type of energy and measuring its conversion into another type of energy by applying light and detecting acoustic waves, i.e. photoacoustic measurements
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
    • G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
    • G01N21/314—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry with comparison of measurements at specific and non-specific wavelengths
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/47—Scattering, i.e. diffuse reflection
    • G01N21/4795—Scattering, i.e. diffuse reflection spatially resolved investigating of object in scattering medium

Definitions

  • the present invention relates to an object information acquiring apparatus and a method of controlling the same .
  • a photoacoustic imaging technique is known as one of imaging techniques which use light.
  • an object is irradiated with a pulsed light generated from a light source.
  • the irradiation beam propagates through and diffuses into the object and the energy of the beam is absorbed by a plurality of portions inside the object, whereby an acoustic wave (hereinafter referred to as a photoacoustic wave) is generated.
  • a transducer receives the photoacoustic wave and the received signal is analyzed by a processing device, whereby information on optical
  • Patent Literature 1 improves resolution by focusing a pulsed light using lenses so that an object is disposed at a focal position of the beam.
  • a concentration distribution of a substance present inside an object can be obtained.
  • the oxygen saturation of the blood can be acquired based on the concentration of oxyhemoglobin HbO and deoxyhemoglobin Hb.
  • S0 2 can be acquired by Equation (1) .
  • ⁇ ⁇ represents an absorption coefficient at a wavelength ⁇ and ⁇ ⁇ represents an absorption coefficient at a wavelength ⁇ 2 .
  • B H bo Xl represents a molar absorption coefficient of oxyhemoglobin at the wavelength ⁇ ⁇ and s H l represents a molar absorption coefficient of deoxyhemoglobin at the wavelength ⁇ .
  • E H o represents a molar absorption coefficient of oxyhemoglobin at the wavelength ⁇ 2 and 8 Hb represents a molar absorption coefficient of deoxyhemoglobin at the wavelength ⁇ 2 .
  • Equation (1) The coefficients ⁇ ⁇ ⁇ > ⁇ ⁇ 1 / £nb l , ⁇ ⁇ ⁇ 3 ⁇ ⁇ 2 , and z Ri> X2 are known values.
  • r represents a position coordinate. As illustrated in Equation (1), the ratio of the absorption coefficients at two wavelengths is required to obtain the oxygen saturation of the blood.
  • the shorter the emission interval of the pulsed lights of two wavelengths that is, the shorter the interval between the time at which an object is irradiated with a pulsed light of a first wavelength and the time at which the object is irradiated with a pulsed light of a second wavelength
  • a method of performing alternate irradiation using one wavelength-variable mechanism such as a
  • wavelength-variable light source In order to prevent a positional shift due to pulsations or breaths, it is necessary to shorten the emission interval of the pulsed lights of the two wavelengths. Thus, a complex high-speed wavelength-variable control technique is required.
  • the present invention provides an object
  • a light source that emits a pulsed light of a first wavelength and a pulsed light of a second wavelength, which is different from the first wavelength, at different points in time; a delay optical system that delays the pulsed light of the first wavelength relative to the pulsed light of the second wavelength;
  • a conversion element that receives photoacoustic waves generated when the pulsed lights of the first and second wavelengths are radiated to an object and outputs reception signals
  • a photodetector that detects light quantities of the pulsed lights of each of the first and second wavelengths; and a processor that acquires characteristics information on the object based on the reception signals originating from the pulsed lights of each of the first and second wavelengths, which have been output from the conversion element, and the light quantities of the pulsed lights of each of the first and second wavelengths, which have been detected by the photodetector .
  • the present invention also provides an object information acquiring apparatus comprising:
  • a light source that emits pulsed lights having a plurality of wavelengths at different points in time
  • a delay optical system that delays the pulsed lights of the respective wavelengths by different delay periods for respective wavelengths
  • a conversion element that receives photoacoustic waves generated when the pulsed lights of respective wavelengths that have passed through the delay optical system are radiated to an object and outputs reception signals
  • a photodetector that detects light quantities of the pulsed lights of the respective wavelengths
  • a processor that acquires characteristics information on the object based on the reception signals originating from the pulsed lights of the respective wavelengths, which have been output from the conversion element, and the light quantities of the pulsed lights of the respective wavelengths, which have been detected by the photodetector, wherein
  • the delay optical system is configured such that optical paths through which the pulsed lights of the respective wavelengths pass have different optical path lengths.
  • the present invention also provides a method of controlling an object information acquiring apparatus, the method comprising:
  • the present invention also provides a method of controlling an object information acquiring apparatus, the method comprising:
  • the pulsed lights of the respective wavelengths pass though optical paths having different optical path lengths.
  • Fig. 1 is a schematic diagram illustrating a configuration of a photoacoustic apparatus.
  • Fig. 2 is a flowchart illustrating an example of the flow of acquiring object information.
  • Fig. 3 is a timing chart illustrating an example of measurement by a photoacoustic apparatus.
  • Fig. 4A is a graph illustrating light irradiation and reception signals of generated photoacoustic waves.
  • Fig. 4B is a partially enlarged graph illustrating light irradiation and reception signals of generated photoacoustic waves.
  • Fig. 4C is a partially enlarged graph illustrating light irradiation and reception signals of generated photoacoustic waves.
  • the present invention relates to a technique of detecting acoustic waves having propagated from an object, and generating and acquiring specific information on the interior of the object.
  • the present invention can be understood as an object information acquiring apparatus or a control method thereof, and alternatively, as an object information acquiring method and a signal processing method.
  • the present invention can be understood as a program for allowing an information processing apparatus having hardware resources such as a CPU to execute these methods and a storage medium having the program stored therein.
  • the present invention can be understood as an acoustic wave measurement apparatus and a control method thereof.
  • the object information acquiring apparatus includes an apparatus which uses a photoacoustic technique to irradiate an object with light (electromagnetic waves) to receive (detect) acoustic waves having propagated through the object after being generated inside or on the surface of the object according to a
  • Such an object information acquiring apparatus can be referred to as a photoacoustic imaging apparatus, a photoacoustic image apparatus, or simply a photoacoustic apparatus as characteristics information on the interior of the object is obtained in a format such as image data based on photoacoustic measurement.
  • photoacoustic apparatus indicates a generation source
  • the characteristics information include a blood component distribution such as oxyhemoglobin and
  • the characteristics information may be a fat concentration, a glucose concentration, a collagen concentration, a melanin concentration, and a volume fraction of fats and water.
  • the characteristics information may be obtained as distribution information relative to respective positions inside an object rather than as numerical data. That is, the characteristics information may be 2-dimensional or
  • 3-dimensional distribution information such as an absorption coefficient distribution or an oxygen saturation distribution.
  • Acoustic waves referred in the present invention are typically ultrasound waves, and include elastic waves called sound waves and acoustic waves.
  • the acoustic waves generated by the photoacoustic effect are referred to as photoacoustic waves or light-induced ultrasound waves.
  • Electrical signals converted from acoustic waves by a probe are also referred to as acoustic signals, and acoustic signals originating from photoacoustic waves are referred to as photoacoustic signals in particular.
  • a main object of the apparatus of the present invention is to examine blood diseases or malignant tumors of a person or an animal or to perform follow-up examination of chemotherapy.
  • the object may be a part of a living body, and specifically, the skin, hypodermic segments, breast, neck, and abdomen of a person or an animal may be the examination obj ect .
  • a segment within several millimeters from the surface of the skin is ideal as the examination object.
  • the object is not limited thereto, however, and other segments of a living body and non-living materials can be also measured.
  • Typical examples of the light absorber inside the object include oxyhemoglobin or deoxyhemoglobin inside a living body, a blood vessel that contains many oxyhemoglobins or deoxyhemoglobins , and a malignant tumor that contains many angiogenesis .
  • the light absorber preferably has a relatively high absorption coefficient inside the object. Besides this, melanoma, plaque on the carotid wall, or the like may be the light absorber .
  • Fig. 1 is a schematic diagram illustrating a configuration of a photoacoustic apparatus according to the present embodiment.
  • the photoacoustic apparatus according to the present embodiment includes a light source 100 including an oscillating unit 110 and a wavelength converting unit 120, a probe 200 including a conversion element 210, and a delay optical system 300 for delaying light emitted from the oscillating unit 110.
  • the photoacoustic apparatus further includes a guiding optical system 400 for guiding light having a plurality of wavelengths to an object, a photodetector 500, a water tank 600, a processor 700, a controller 800, a scanning mechanism 900, and a display unit 1000.
  • a pulsed light 1200 of a first wavelength emitted from the oscillating unit 110 is guided to the delay optical system 300.
  • the pulsed light 1200 of the first wavelength delayed by the delay optical system 300 and a pulsed light 1300 of a second wavelength excited by a pulsed light 1210 from the oscillating unit 110 and emitted from the wavelength converting unit 120 are guided to the same optical path by an optical element.
  • the optical element is a dichroic mirror 360, for example.
  • the pulsed light 1200 of the first wavelength arrives at a delay corresponding to the period, in which the pulsed light 1200 propagates through the delay optical system 300, relative to the pulsed light 1300 of the second wavelength.
  • the pulsed lights 1400 of the respective wavelengths guided to the same optical path are alternately radiated to an object 1100 through the guiding optical system 400 and reach a light absorber 1110 in the object 1100.
  • the light absorber 1110 absorbs the energy of the light of the respective wavelengths to generate photoacoustic waves of respective wavelengths.
  • the generated photoacoustic waves propagate through the object to reach the conversion element 210.
  • the conversion element 210 Upon receiving the photoacoustic waves, the conversion element 210 outputs time-sequential reception signals.
  • the conversion element 210 (the reception surface) of the probe 200 is immersed in water 610 as an acoustic matching material in the water tank 600. In this way, acoustic matching between the object 1100 and the conversion element 210 is realized.
  • the photodetector 500 detects a portion of the pulsed lights 1400 and outputs a reception signal.
  • the scanning mechanism 900 scans a measurement unit 1500 including the probe 200, a portion of the optical system 400, and the photodetector 500 during photoacoustic measurement.
  • the controller 800 controls respective constituent blocks in the photoacoustic apparatus by supplying necessary control signals and data to the constituent blocks.
  • the processor 700 sequentially receives the reception signals output from the conversion element 210 and the photodetector 500.
  • the processor 700 generates object information using the signals input from the conversion element 210 and the photodetector 500.
  • the processor 700 transmits data of the generated object information to the display unit 1000 to display images and numerical values of the object information.
  • the light source 100 includes the oscillating unit 110 and the wavelength converting unit 120.
  • the light generated by the oscillating unit 110 and the wavelength converting unit 120 is preferably a pulsed light on the order of nanoseconds to microseconds.
  • a specific pulse width is preferably
  • the wavelength of the light is preferably between approximately 300 nm and 1600 nm.
  • the visible wavelength region between 400 nm and 700 nm
  • light having a wavelength (700 nm or more and 1100 nm or smaller) in which the light is rarely absorbed in the background tissue of a living body is preferred.
  • light in the terahertz, microwave, and radio wave regions can be also used.
  • a solid-state laser such as a solid-state laser, a semiconductor laser, or a gas laser
  • a solid-state laser is particularly preferable.
  • a Nd:YAG laser a laser which uses the crystal structure of the neodymium-doped yttrium aluminum garnet
  • these lasers are preferably capable of generating second harmonics and third harmonics and emitting light of respective wavelengths.
  • Nd:YAG laser a laser which uses the crystal structure of the neodymium-doped yttrium vanadate
  • Nd:YLF laser a laser which uses the crystal structure of the neodymium-doped yttrium lithium fluoride
  • other lasers can be used.
  • One of the light beams such as a fundamental wave, a second harmonic, a third harmonic, and the like oscillated by the oscillating unit 110 is emitted from the oscillating unit 110 as the pulsed light 1200 of the first wavelength.
  • one of the laser beams such as a fundamental wave, a second harmonic, a third harmonic, and the like oscillated by the oscillating unit 110 is guided to the wavelength converting unit 120 as the pulsed light 1210 and becomes the pulsed light 1300 of the second wavelength different from the first wavelength of the pulsed light 1200.
  • the pulsed light 1200 and the pulsed light 1210 may have the same wavelength and different wavelengths.
  • a dye laser, a Ti:sa (titanium-sapphire) laser, an optical parametric oscillators (OPO) laser, or the like can be used as the wavelength converting unit 120.
  • the dye or crystal in these lasers is excited by the pulsed light 1210 to oscillate the pulsed light 1300 of the second wavelength different from the first wavelength of the pulsed light 1200.
  • Pyrromethene 597 for example, can be used as the dye.
  • a second harmonic of a Nd:YAG laser having a wavelength of 532 nm can be used as the pulsed light 1210.
  • a second harmonic of the Nd:YAG laser or a third harmonic having a wavelength of 355 nm is used as the pulsed light 1210 depending on the second wavelength of the pulsed light 1300.
  • the Ti:sa laser when used, the second harmonic of the Nd:YAG laser can be used as the pulsed light 1210.
  • a laser capable of changing an oscillating wavelength is more preferably used as the wavelength converting unit 120.
  • the first and second wavelengths of a wavelength-variable laser are selected, light having a wavelength in which the light is efficiently absorbed in oxyhemoglobin and deoxyhemoglobin is preferred.
  • a laser is preferred as the light source 100, a light-emitting diode, a flash lamp, or the like can be used instead of the laser.
  • the probe 200 includes one or more conversion elements 210 and a housing.
  • An arbitrary conversion element capable of receiving acoustic waves and converting the acoustic waves into electrical signals such as a piezoelectric element (for example, lead zirconate titanate (PZT) ) which uses a piezoelectric phenomenon, a conversion element which uses resonance of light, or a capacitive conversion element (for example, CMUT) can be used as the conversion element 210.
  • a piezoelectric element for example, lead zirconate titanate (PZT)
  • PZT lead zirconate titanate
  • CMUT capacitive conversion element
  • the probe 200 is preferably a focus-type probe. That is, an acoustic lens is preferably mounted on a reception surface of the conversion element 210.
  • the probe 200 is preferably mechanically movable in relation to the object 1100 by the scanning mechanism 900.
  • a portion (an irradiation position of the pulsed lights 1400) of the optical system 400 and the probe 200 are preferably moved in synchronism.
  • the probe 200 when the probe 200 is a handheld-type probe, the probe 200 has a holding portion with which a user holds the probe 200.
  • a plurality of conversion elements 210 is preferably provided in the probe 200.
  • the conversion elements are preferably disposed so as to be aligned in a flat surface or a curved surface referred to as a ID. 1.5D, 1.75D, or 2D array.
  • an amplifier for amplifying analog signals output from the conversion element 210 may be provided in the probe 200.
  • the delay optical system 300 is an optical system for delaying the pulsed light 1200 of the first wavelength in relation to the pulsed light 1300 of the second wavelength.
  • the delay optical system 300 includes an optical mirror 310, a lens 320, an optical fiber 330, a collimator lens 340, an optical mirror 350, and a dichroic mirror 360.
  • the pulsed light 1200 of the first wavelength emitted from the oscillating unit 110 is guided to the lens 320 by the optical mirror 310 and is concentrated and incident on the optical fiber 330.
  • a beam splitter is preferably disposed at the position of the optical mirror 310 so as to split the same light.
  • the delay optical system 300 requires an optical path length for delaying the pulsed light 1200 of the first wavelength by a desired period, an optical fiber having a large optical path length is used as the optical fiber 330.
  • the occurrences of the photoacoustic signals of the respective wavelengths are preferably separated by at least 1 ⁇ .
  • an optical delay of at least 1 is required. Since the velocity of light in an optical fiber is 200 ⁇ / ⁇ 3, it is preferable to use an optical fiber having a length of at least 200 m.
  • the optical fiber 330 is preferably used in a state of being wound around a bobbin.
  • the light having passed through the optical fiber 330 is collimated by the collimator lens 340 and is reflected by the optical mirror 350.
  • a mirror capable of reflecting the pulsed light 1200 of the first wavelength and transmitting the pulsed light 1300 of the second wavelength is used as the dichroic mirror 360.
  • the pulsed lights 1200 and 1300 of the first and second wavelengths are guided to the same optical path and become the pulsed lights 1400 which radiate the pulsed lights of the first and second wavelengths alternately.
  • another optical element for example, a deflecting mirror
  • the dichroic mirror may be used instead of the dichroic mirror as long as the element can couple the pulsed lights of the first and second wavelengths .
  • the pulsed light 1200 of the first wavelength reaches the dichroic mirror 360 with a delay of 2 ⁇ from the pulsed light 1300 of the second wavelength.
  • a set (the pulsed lights 1400) of the pulsed lights 1200 and 1300 of the first and second wavelengths with an interval of 2 ⁇ is emitted every 10 ms . That is, the object 1100 is irradiated with the set of the pulsed lights of the first and second wavelengths with an interval of 2 ⁇ at a repetition frequency of 100 Hz.
  • the pulsed lights of the first and second wavelengths preferably occur at an interval required for the object to be contracted.
  • the pulsed light 1200 of the first wavelength is delayed in relation to the pulsed light 1300 of the second wavelength so that the pulsed lights 1200 and 1300 of the first and second wavelengths are alternately radiated.
  • the pulsed light 1300 of the second wavelength may be delayed in relation to the pulsed light 1200 of the first wavelength.
  • the delay optical system is applied to the pulsed light 1300 of the second wavelength emitted from the wavelength converting unit 120.
  • the large optical path length may be obtained using the optical fiber 330, another method may be used.
  • the large optical path length may be obtained by repeatedly reflecting light using an optical mirror instead of using the lens 320, the optical fiber 330, and the collimator lens 340.
  • the guiding optical system 400 guides the pulsed lights- 1400 of the respective wavelengths guided to the same optical path by the dichroic mirror 360 to the object 1100 and the photodetector 500.
  • An optical element such as a lens, a mirror, and an optical fiber can be used as the guiding optical system 400.
  • a light output portion of the guiding optical system 400 is preferably formed of a lens or the like so that the diameter of an irradiation light beam is focused.
  • the guiding optical system 400 may be moved in relation to the object 1100, whereby a large area of the object 1100 can be imaged.
  • the guiding optical system 400 includes an optical fiber 410, a lens 420, a collimator lens 430, a beam splitter 440, an axicon lens 450, and an optical mirror 460.
  • the optical mirror 460 is disposed so that the pulsed light 1400 guided in a ring form by the axicon lens 450 is focused at a target position of the object 1100.
  • a beam splitter having a reflectivity smaller than 5% at an inclination angle of 45° is preferably used as the beam splitter 440.
  • the light output portion of the guiding optical system 400 preferably radiates a light beam, with the diameter thereof being increased by a lens or the like .
  • a photodiode and an optical energy meter can be used as the photodetector 500.
  • a photodetector other than these elements may be used as long as the photodetector can detect a portion of the irradiation light guided by the beam splitter 440.
  • the water tank 600 is a container capable of storing the water 610 as an acoustic matching material.
  • the conversion element 210 provided in the probe 200 is immersed in the water 610.
  • acoustic matching between the object 1100 and the conversion element 210 can be realized by the water 610.
  • a surface of the tank in contact with the object 1100 is preferably formed of a film thinner than the wavelength of the photoacoustic wave so that the photoacoustic wave can easily pass from the film. More preferably, the contacting surface preferably has a thickness of 1/4 of the wavelength of the photoacoustic wave.
  • the acoustic matching material and the contacting surface are preferably formed of a material that rarely absorbs the pulsed light 1400.
  • a material that rarely absorbs the pulsed light 1400 For example, water, ultrasound gel, oil, or the like is ideally used as the acoustic matching material, andpolyethylene or the like is ideally used as the contacting surface.
  • acoustic matching is preferably realized between the object 1100 and the contacting surface by ultrasound gel or the like.
  • the processor 700 includes a photoacoustic signal collecting unit 710, a light quantity signal collecting unit 720, and a characteristics information calculating unit 730.
  • the photoacoustic signal collecting unit 710 performs signal processing of collecting time-sequential analog reception signals output from the conversion element 210, amplifying the reception signals, A/D converting the analog reception signals, and storing the digital reception signals.
  • a circuit generally called a data acquisition system (DAS) can be used as the photoacoustic signal collecting unit 710.
  • DAS data acquisition system
  • the photoacoustic signal collecting unit 710 includes an amplifier that amplifies reception signals and an A/D converter that digitalizes analog reception signals, for example.
  • the light quantity signal collecting unit 720 collects reception signals output from the photodetector 500.
  • the light quantity signal collecting unit 720 performs signal processing of amplifying reception signals, A/D converting analog reception signals, storing digital reception signals, and converting the obtained reception signals into light quantity values, as necessary.
  • the light quantity signal collecting unit 720 includes an amplifier that amplifies reception signals and an A/D converter that digitalizes analog reception signals, for example .
  • the characteristics information calculating unit 730 acquires characteristics information relative to the absorption coefficient inside an object and the concentration of substances that form tissues using the reception signals output from the photoacoustic signal collecting unit 710 and the light quantity signal collecting unit 720.
  • the characteristics information calculating unit 730 acquires information on the oxygen saturation.
  • the characteristics information relative to the oxygen saturation at respective positions in the object is also referred to as an oxygen saturation distribution inside an object.
  • the characteristics information on the absorption coefficient of light at respective positions inside an object is also referred to as an optical absorption distribution inside an object.
  • a processor such as a CPU or a graphics processing unit (GPU) or an arithmetic circuit such as a field programmable gate array (FPGA) chip can be used as the characteristics information calculating unit 730.
  • the characteristics information calculating unit 730 may be formed of one processor or arithmetic circuit and may be formed of a plurality of processors or arithmetic circuits. Moreover, the
  • characteristics information calculating unit 730 may include a memory that stores reception signals, generated distribution data, display image data, and various measurement parameters.
  • the memory is typically formed of at lease one storage media such as a ROM, a RAM, or a hard disk.
  • the controller 800 supplies necessary control signals or data to the respective constituent blocks. Specifically, a signal for instructing the light source 100 to emit light, a reception control signal for the conversion element 200, and a control signal for the scanning mechanism 900 are supplied. Further, the controller 800 controls signal amplification, AD conversion timing, and storage of reception signals, of the processor 700.
  • the controller 800 can be also formed of one or a plurality of processors, such as a CPU or a GPU, or circuits, such as a FPGA chip, in combination similarly to the processor 700. Moreover, the controller 800 may include a memory that stores various measurement parameters and the like. The memory is typically formed of at least one storage media such as a ROM, a RAM, or a hard disk. These elements may be shared by the processor 700.
  • An automated stage formed of a stepping motor and a servo motor, for example, can be used as the scanning mechanism 900.
  • the scanning mechanism 900 scans the measurement unit 1500.
  • the scanning mechanism 900 performs photoacoustic measurement while scanning measurement positions on the object 1100.
  • such a configuration is not essential , and measurement may be performed while scanning the measurement positions on the object 1100.
  • the irradiation light 1400 may be radiated to a large area of the object 1100 and the scanning mechanism 900 may scan the probe 200 only.
  • an acoustic focusing configuration in which a probe (for example, a single transducer or an array transducer having a wide focusing range) capable of receiving a photoacoustic wave in a wide range is fixed may be used.
  • the irradiation light 1400 is focused and radiated to the object 1100 and the scanning mechanism 900 scans only a portion of the guiding optical system 400, whereby the measurement positions are scanned.
  • liquid such as water
  • a gel member for example, polyurethane-based gel
  • the like may be used instead of the water tank 600 and the water 610.
  • a method of changing the position or the angle of a portion of the probe 210 or the guiding optical system 400 may be used as the scanning method of the scanning mechanism 900.
  • the scanning mechanism 900 may scan the detection position of photoacoustic waves and the irradiation position of the irradiation light 1400 by moving a mirror that reflects the photoacoustic waves and the irradiation light 1400.
  • a mirror that reflects the photoacoustic waves and the irradiation light 1400.
  • the mirror may be moved by changing the position or the angle of the mirror.
  • a galvanic mirror or a MEMS mirror may be used as the mirror capable of performing such an operation.
  • a display such as a liquid crystal display (LCD) , a cathode ray tube (CRT) , or an organic EL display can be used as the display unit 1000.
  • the display unit 1000 may be provided separately from the photoacoustic apparatus of the present embodiment and be connected to the photoacoustic apparatus .
  • the present invention can be applied to a handheld photoacoustic apparatus.
  • members surrounded by dot line 1600 may be stored in one housing.
  • the controller 800 reads a program which is stored in the processor 700 and in which an object information acquisition method is described and allows the photoacoustic apparatus to execute the following object information acquisition method.
  • the controller 800 instructs the respective constituent blocks to start photoacoustic measurement.
  • the oscillating unit 110 oscillates the pulsed light 1200 of the first wavelength using the signal as a trigger signal.
  • the photoacoustic signal collecting unit 710 collects the time-sequential analog reception signals output from the conversion element 210 at respective measurement positions.
  • the oscillating unit 110 preferably oscillates the pulsed light 1200 of the first wavelength using the signal output whenever the scanning mechanism 900 scans an equal distance as a trigger signal, whereby the photoacoustic signals are collected at equal intervals .
  • Fig. 3 illustrates an example of the timing chart of a photoacoustic measurement process.
  • a trigger signal during photoacoustic measurement is illustrated at the top
  • the timing at which the pulsed lights 1200 and 1300 of the first and second wavelengths are radiated to the object 1100 is illustrated at the middle
  • the timing at which the photoacoustic signals occurring due to the respective pulsed lights reach the conversion element 210 is illustrated at the bottom.
  • the oscillating unit 110 oscillates the pulsed light 1200 of the first wavelength at a pulse repetition frequency (PRF) of 100 Hz.
  • PRF pulse repetition frequency
  • the input interval 302 is 10 ms .
  • the oscillating unit 110 oscillates so that a pulsed light 303 of the second wavelength and a pulsed light 304 of the first wavelength are radiated to the object 1100 in that order.
  • the irradiation interval 305 between the pulsed light 303 of the second wavelength and the pulsed light 304 of the first wavelength is a delay period caused by the delay optical system 300, and the irradiation interval 305 is 2 ⁇ 3 when the optical fiber 330 having the length of 400 m is used, for example.
  • the set of the pulsed light 303 of the second wavelength and the pulsed light 304 of the first wavelength is radiated to the object 1100 at intervals of 10 ms .
  • a photoacoustic signal 307 occurring due to the pulsed light 303 of the second wavelength reaches the conversion element 210. Since the interval 306 is determined by the distance between the conversion element and the light absorber and the velocity of sound in a medium, the interval can be acquired by computation if these values are known.
  • a photoacoustic signal 308 occurring due to the pulsed light 304 of the first wavelength reaches the conversion element 210 with a delay of the interval 309.
  • the interval 309 is the same period as the irradiation interval 305.
  • the photoacoustic signal collecting unit 710 receives the photoacoustic signal using the pulsed light emitted by the light source 100 as a trigger signal .
  • the trigger signal can be created based on the photo detection result obtained by the photodiode.
  • the light quantity signal collecting unit 720 collects the reception signals output from the photodetector 500 at respective measurement positions.
  • Figs. 4A to 4C illustrate examples of reception signals received by the photoacoustic signal collecting unit 710 and the light quantity signal collecting unit 720.
  • a Nd:YAG laser capable of outputting second and third harmonics was used as the oscillating unit 110
  • an OPO unit was used as the wavelength converting unit 120
  • an optical fiber having the length of 54 m was used as the optical fiber 410.
  • a pulsed light having the wavelength of 532 nm which is the second harmonic of the Nd:YAG laser was used as the pulsed light of the first wavelength and a pulsed light having the wavelength of 556 nm excited by the OPO unit with the third harmonic of the Nd:YAG laser was used as the pulsed light of the second wavelength.
  • a black body printed on a film was used as the light absorber.
  • a group of signals indicated by dot lines is the light intensity received by the light quantity signal collecting unit 720 and corresponds to the left axis.
  • a signal 401 is the reception signal of the pulsed light of the second wavelength
  • a signal 402 is the reception signal of the pulsed light of the first wavelength.
  • a group of signals indicated by -solid lines is the photoacoustic signal intensity received by the photoacoustic signal collecting unit 710 and corresponds to the right axis.
  • a signal 403 is a photoacoustic signal originating from the pulsed light of the second wavelength
  • a signal 404 is a photoacoustic signal originating from the pulsed light of the first wavelength.
  • the photoacoustic signals of the respective wavelengths are received with a delay from the irradiation time, corresponding to a period (in this example, approximately 7.5 ⁇ ) required for the generated photoacoustic waves reach the conversion element 210 from the light absorber.
  • Fig. 4B is an enlarged graph of the pulsed light signals of respective wavelengths received by the light quantity signal collecting unit 720 in Fig. 4A. It can be understood that the signal 402 is received with a delay of approximately 270 ns from the signal 401 corresponding to the optical path length of 54 m of the optical fiber.
  • Fig. 4C is an enlarged graph of the photoacoustic signals received by the photoacoustic signal collecting unit 710 in Fig. 4A. It can be understood that the signal 404 is received with a delay of approximately 270 ns from the signal 403 by reflecting the delay of light radiations between wavelengths.
  • the characteristics information calculating unit 730 calculates a photoacoustic signal intensity
  • acoustic pressure distribution (also referred to as an acoustic pressure distribution) of each wavelength based on the reception signals of respective wavelengths collected by the photoacoustic signal collecting unit 710.
  • the photoacoustic signal collecting unit 710 receives the photoacoustic signal using any one of the pulsed lights 1200 and 1300 of the first and second wavelengths as a trigger signal will be considered.
  • a photoacoustic wave originating from the pulsed light 1300 of the second wavelength and a photoacoustic wave originating from the pulsed light 1200 of the first wavelength delayed by an optical delay period are output from the photoacoustic signal collecting unit 710 as a series of photoacoustic signals.
  • the characteristics information calculating unit 730 may need to separate the photoacoustic wave originating from the pulsed light 1200 of the first wavelength and the photoacoustic wave originating from the pulsed light 1300 of the second wavelength.
  • a method of segmenting the reception signals by time to separate the reception signals, a pattern matching method, a threshold processing method, and the like can be used as the separating method. This process is not necessary when the photoacoustic signal collecting unit 710 receives photoacoustic signals using both the pulsed lights 1200 and 1300 of the first and second wavelengths as a trigger signal.
  • the characteristics information calculating unit 730 detects the envelope with time of the obtained photoacoustic reception signals of respective wavelengths, converts the time-axis direction of the pulsed light signals to a depth direction, and plots the photoacoustic reception signals on spatial coordinates. This process is performed for respective measurement positions (scanning positions) whereby acoustic distribution data is acquired.
  • the characteristics information calculating unit 730 reconstructs an image using the obtained photoacoustic reception signals of respective wavelengths. In this way, it is possible to acquire data on acoustic pressure corresponding to the positions on
  • An existing method such as universal back projection (UBP) or filtered back projection (FBP) may be used as the image reconstruction method.
  • UBP universal back projection
  • FBP filtered back projection
  • a delay and sum process may be used as the image reconstruction method.
  • the characteristics information calculating unit 730 calculates the light quantities of respective wavelength at respective measurement positions based on the reception signals of respective wavelengths collected by the light quantity signal collecting unit 720.
  • the characteristics information calculating unit 730 calculates the peak values the reception signals of respective wavelengths output from the photodiode at the respective measurement positions as the light quantities. Moreover, the integration value of the reception signals may be calculated as the light quantity . Further, it is preferable to convert the peak value and the integration value of respective wavelengths into the light quantity of light radiated to the object 1100. In this case, the characteristics information calculating unit 730 preferably stores such a conversion coefficient and a conversion formula.
  • the characteristics information calculating unit 730 calculates the optical absorption distributions of respective wavelengths based on the photoacoustic signal intensity distortions of respective wavelengths calculated in S140 and the irradiation light quantities of respective wavelengths at respective measurement positions calculated in S150.
  • the characteristics information calculating unit 730 corrects the acoustic pressure distribution data at respective measurement positions calculated in S140 using the light quantity values at respective measurement positions of respective wavelengths calculated in S150. By doing so, the optical absorption distribution data at respective measurement positions is obtained. For example, the acoustic pressure distribution data is divided by the light quantity value, whereby the optical absorption distribution data at respective measurement position of respective wavelengths is acquired.
  • the characteristics information calculating unit 730 calculates a light quantity distribution of respective wavelengths in the- object 1100 using the light quantity values at respective measurement positions of respective wavelengths calculated in S150.
  • the acoustic pressure distribution data of respective wavelengths calculated in S140 is divided by the light quantity distribution of respective wavelengths, whereby the optical absorption distribution data at respective measurement positions of respective wavelengths is calculated.
  • the light quantity distribution of respective wavelengths in the object 1100 can be calculated using a finite element method or a Monte Carlo method based on a light transport equation or a light diffusion equation .
  • the characteristics information calculating unit 730 calculates a distribution of concentrations of substances present inside an object using the optical absorption distribution data of respective wavelengths calculated in S160.
  • the oxygen saturation distribution of the blood is calculated based on the concentrations of oxyhemoglobin HbO and deoxyhemoglobin Hb.
  • the characteristics information calculating unit 730 transmits the data of the characteristics information calculated in S170 to the display unit 1000 so that the image of the object information is displayed on the display unit 1000.
  • the display unit 1000 may display various types of information such as the values of the object information or the figures or symbols indicating the tissues or functions inside the body instead of or together with images.
  • a set of pulsed lights having three wavelengths or more may be radiated using delay optical systems having different optical path lengths.
  • a delay optical system having a plurality of optical fibers having different lengths corresponding to the respective wavelengths may be ideally used. By doing so, the light of respective wavelengths passes through optical paths having different optical path lengths.
  • Embodiments of the present invention can also be realized by a computer of a system or apparatus that reads out and executes computer executable instructions recorded on a storage medium (e.g., non-transitory computer-readable storage medium) to perform the functions of one or more of the above-described embodiment (s) of the present invention, and by a method performed by the computer of the system or apparatus by, for example, reading out and executing the computer executable instructions from the storage medium to perform the functions of one or more of the above-described embodiment (s) .
  • the computer may comprise one or more of a central processing unit (CPU) , micro processing unit (MPU) , or other circuitry, and may include a network of separate computers or separate computer processors .
  • CPU central processing unit
  • MPU micro processing unit
  • the computer executable instructions may be provided to the computer, for example, from a network or the storage medium.
  • the storage medium may include, for example, one or more of a hard disk, a random-access memory (RAM) , a read only memory (ROM) , a storage of distributed computing systems, an optical disk (such as a compact disc (CD) , digital versatile disc (DVD) , or Blu-ray Disc (BD)TM), a flash memory device, a memory card, and the like.

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Abstract

La présente invention concerne un appareil d'acquisition d'informations d'objet, qui comprend : une source de lumière émettant une lumière pulsée qui a une première et une seconde longueur d'onde à un moment différent ; un système optique à retard retardant la lumière pulsée qui a la première longueur d'onde par rapport à la lumière pulsée qui a la seconde longueur d'onde ; un élément de conversion recevant des ondes photo-acoustiques générées par un objet, et émettant des signaux de réception ; un photodétecteur détectant des quantités de lumière de la lumière pulsée ; ainsi qu'un processeur acquérant des informations caractéristiques de l'objet sur la base des signaux de réception et des quantités de lumière.
PCT/JP2015/082638 2014-11-28 2015-11-13 Appareil d'acquisition d'informations d'objet et procédé de commande de cet appareil WO2016084720A1 (fr)

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EP3360467A1 (fr) * 2017-02-10 2018-08-15 Canon Kabushiki Kaisha Appareil d'acquisition d'informations d'objets et procédé d'affichage
CN111743548A (zh) * 2019-03-28 2020-10-09 株式会社爱德万测试 光声波测定装置
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JP6759032B2 (ja) * 2016-09-27 2020-09-23 キヤノン株式会社 光音響装置、情報処理方法、及びプログラム
JP7252887B2 (ja) * 2019-03-28 2023-04-05 株式会社アドバンテスト 光音響波測定装置
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EP3360467A1 (fr) * 2017-02-10 2018-08-15 Canon Kabushiki Kaisha Appareil d'acquisition d'informations d'objets et procédé d'affichage
CN108403084A (zh) * 2017-02-10 2018-08-17 佳能株式会社 被检体信息获取设备和显示方法
CN111743548A (zh) * 2019-03-28 2020-10-09 株式会社爱德万测试 光声波测定装置
CN111743548B (zh) * 2019-03-28 2023-08-29 株式会社爱德万测试 光声波测定装置
US11829048B2 (en) 2019-03-28 2023-11-28 Advantest Corporation Laser beam output apparatus
US11476629B2 (en) 2020-03-27 2022-10-18 Advantest Corporation Laser beam output apparatus

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