JP2014233520A - Device for acquiring information on object to be examined - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technology to reduce the attenuation of an ultrasonic wave, and easily scan an ultrasonic probe.SOLUTION: A device for acquiring information on an object to be examined includes: a probe 31 for receiving an ultrasonic wave transmitted from an object to be examined 5; a holding unit 1 provided with a holding member 11 for holding the object to be examined 5 and a contact member 12 that the probe 31 contacts, the inside of which is filled with acoustic matching liquid 14; adjustment means 2 for adjusting a liquid amount of the acoustic matching liquid 14 in the holding unit 1: scanning means 32; and processing means 4 for calculating characteristic information in the object to be examined using the ultrasonic wave received by the probe. The probe 31 receives the ultrasonic wave transmitted from the object to be examined 5 through the holding unit 1. The scanning means 32 scans the probe 31 on the contact member 12. The adjustment means 2 adjusts the liquid amount so as to suppress the deformation of the contact member 12.

Description

  The present invention relates to a subject information acquisition apparatus.

  When an ultrasonic probe is used to irradiate a subject such as a living body with ultrasonic waves, an echo signal reflected from the living tissue is generated, and the echo signal is received by the ultrasonic probe to reconstruct a tomographic image. There is an ultrasonic diagnostic apparatus to configure. If the image is reconstructed while the ultrasonic probe is directly in contact with the living body and the subject is deformed, the obtained image may lose reproducibility. In addition, there is a disadvantage that a difference occurs in the images obtained depending on the individual skill of each engineer. Furthermore, in the case of an uneven part such as a nipple, a gap is generated between the ultrasonic probe and the surface of the living body, and air enters, so that an ultrasonic image can be obtained without propagating the ultrasonic wave to the body surface. There is a problem of disappearing. Therefore, there is a method using an ultrasonic diagnostic coupler in order to make a diagnosis without directly contacting an ultrasonic probe with a living body (for example, Patent Document 1).

  The ultrasonic diagnostic coupler is manufactured from a material whose acoustic impedance characteristics are adapted to a living body. A concave portion is formed on the surface of the ultrasonic diagnostic coupler that contacts the living body. Therefore, a gap between the living body surface can be eliminated by forming a water bag having a living body surface as a thin film in the recess and adjusting the amount of water in the water bag or by inserting an ultrasonic gel in the recess. Further, the surface with which the ultrasonic probe of the ultrasonic diagnostic coupler comes into contact is formed as a flat portion. Thereby, since the contact surface is stable, the scanning of the ultrasonic probe becomes easy, and the influence of the skill of the engineer is reduced.

JP 2006-247007 A

When the water bag is formed in the concave portion of the ultrasonic diagnostic coupler and the ultrasonic probe is scanned by the flat surface portion of the ultrasonic diagnostic coupler as in the configuration of Patent Document 1, the water in the water bag is adjusted. Thus, scanning can be easily performed without deforming the living body. However, when ultrasonic waves of several MHz are used for diagnosis, there is a problem that the ultrasonic attenuation is caused by the thickness of the concave portion and the flat portion of the ultrasonic diagnostic coupler, and the diagnosis cannot be made deep in the living body.
Therefore, in order to reduce the attenuation of the ultrasonic wave, a configuration in which the thickness of the concave portion and the flat portion of the ultrasonic diagnostic coupler is eliminated and the entire ultrasonic diagnostic coupler is used as a water bag is also conceivable. However, in this case, since the living body comes into contact with the water bag, the shape of the surface on which the ultrasonic probe comes into contact easily changes. As a result, the ultrasonic probe cannot be easily scanned.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a technique for reducing the attenuation of ultrasonic waves and easily scanning an ultrasonic probe.

The present invention employs the following configuration. That is,
A probe for receiving ultrasonic waves propagating from the subject;
A holding unit that holds the object, and a holding unit that contacts the probe, and a holding unit that is filled with an acoustic matching liquid;
Adjusting means for adjusting the volume of the acoustic matching liquid in the holding unit;
Scanning means;
Processing means for calculating characteristic information in the subject using ultrasonic waves received by the probe;
The probe receives ultrasonic waves propagating from the subject through the holding unit,
The scanning means scans the probe on the contact member,
The adjusting means is a subject information acquiring apparatus that adjusts the liquid amount so as to suppress deformation of the contact member.

  ADVANTAGE OF THE INVENTION According to this invention, the technique for reducing the attenuation | damping of an ultrasonic wave and scanning an ultrasonic probe easily can be provided.

1 is a schematic diagram showing an example of an ultrasonic diagnostic apparatus. The schematic diagram which shows the example which performs a liquid quantity adjustment means by distortion | strain detection. The schematic diagram which shows the example of arrangement | positioning structure of the distortion | strain detection means of a liquid quantity adjustment means. The schematic diagram which shows the example which performs a liquid quantity adjustment means by pressure detection. The schematic diagram which shows the example which performs a liquid quantity adjustment means by a deformation | transformation detection. The schematic diagram which shows the example of an arrangement configuration of the deformation | transformation detection means of a liquid quantity adjustment means.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. However, the dimensions, materials, shapes, and relative arrangements of the components described below should be changed as appropriate according to the configuration of the apparatus to which the invention is applied and various conditions. It is not intended to limit the following description.

  The present invention can be applied when ultrasonic waves coming from a subject are received by an ultrasonic probe. The subject information acquisition apparatus of the present invention transmits ultrasonic waves to a subject, receives reflected waves (echo waves) reflected and propagated inside the subject, and acquires subject information as image data. Includes equipment using echo technology. Further, the present invention provides a device that irradiates a subject with light, receives an acoustic wave (also called a photoacoustic wave) generated and propagated in the subject by a photoacoustic effect, and obtains subject information as image data. Is also applicable.

  In the case of an apparatus using the ultrasonic echo technique, the acquired object information is characteristic information that reflects a difference in acoustic impedance of tissue inside the object. In the case of a device using the photoacoustic effect, the subject information includes the source distribution of acoustic waves generated by light irradiation, the initial sound pressure distribution in the subject, or the light energy absorption density distribution derived from the initial sound pressure distribution, This is characteristic information indicating the absorption coefficient distribution and the concentration distribution of substances constituting the tissue. The concentration distribution of the substance is, for example, an oxygen saturation distribution or an oxidized / reduced hemoglobin concentration distribution.

  In the following description, as a typical example of such an object information acquisition apparatus, an ultrasonic wave that irradiates a living body with ultrasonic waves, receives an echo signal reflected by the biological tissue with an ultrasonic probe, and reconstructs a tomographic image. A sonic diagnostic apparatus will be described.

(Overall configuration of the device)
FIG. 1 is a schematic diagram illustrating an example of the configuration of an ultrasonic diagnostic apparatus.
In broad terms, the apparatus includes a holding unit 1, a liquid amount adjusting unit 2, an ultrasonic scanning unit 3, and an arithmetic processing unit 4, and measures a subject 5.

The holding unit 1 includes a holding member 11 that faces the subject 5, an abutting member 12 that comes in contact with the ultrasonic probe, and a frame member 13 that fixes the holding member 11 and the abutting member 12. The holding unit 1 has a watertight structure, and an acoustic matching liquid 14 is sealed between the holding member 11 and the contact member 12.

  The liquid amount adjusting unit 2 adjusts the amount of the acoustic matching liquid 14 between the holding member 11 and the contact member 12. The liquid amount adjusting unit 2 includes a supply pipe 21, a discharge pipe 22, a tank 23, and a pump 24. The supply pipe 21 and the discharge pipe 22 are coupled to a tank 23 that stores the acoustic matching liquid 14 and further connected to the holding unit 1. The pump 24 serves as a power source for transporting the acoustic matching liquid 14.

  The ultrasonic scanning unit 3 includes an ultrasonic probe 31 and a scanning mechanism 32. Characteristic information can be acquired from a desired imaging range on the subject 5 by causing the scanning probe 32 to scan the ultrasound probe 31 with respect to the contact member 12. The ultrasonic probe 31 inputs an ultrasonic pulse to the subject, receives an echo wave in the subject, converts it into an electrical signal, and outputs it to the arithmetic processing unit 4.

  The arithmetic processing unit 4 controls each part in the apparatus such as signal processing output from the ultrasound probe 31 and driving of the pump 24. The arithmetic processing unit 4 generates characteristic information in the subject using the input electric signal, generates image data based on the characteristic information, and displays the image on a display unit (not shown).

(Description of each component)
Hereinafter, preferred embodiments of each component will be described in detail. However, the types and forms of the components are not limited to the following descriptions, and may be any as long as the object of the invention can be achieved.

((Holding unit))
The holding member 11 included in the holding unit 1 includes a holding portion 11a that holds a subject and a holding frame portion 11b that attaches the holding portion 11a.
The holding unit 11a is preferably made of a material that matches the acoustic impedance of the subject 5 and the ultrasound probe 31. Moreover, it is also preferable that the material is a material with little attenuation of ultrasonic waves, or a material with high transmittance when irradiated with light. More preferably, the holding part 11a is desirably a thin and flexible elastic material for holding the subject. Examples of the material with low ultrasonic attenuation include polymethylpentene and silicone rubber.

  The holding frame portion 11b has a structure to which the holding portion 11a can be attached. For example, there are methods such as adhesive fixing, fixing with screws, and clamping by clamping between members. The material of the holding frame portion 11b is preferably a metal material that is not affected by corrosion by the acoustic matching liquid or is subjected to surface treatment by corrosion. An acoustic matching material such as an ultrasonic gel may be placed between the holding unit 11a and the subject 5.

  The contact member 12 includes a contact portion 12a that is scanned by an ultrasonic probe and a contact frame portion 12b that attaches the contact portion 12a. The material of the contact member 12 can be the same as that of the holding member 11. More preferably, the material of the contact portion 12a is desirably a material having a Young's modulus greater than that of the holding portion 11a.

  The frame member 13 needs to have strength to support the load of the subject. The frame member 13 is preferably a metal material that is not corroded by the acoustic matching liquid or has been subjected to surface treatment by corrosion. The frame member 13, the holding member 11, and the contact member 12 have a watertight structure. For example, the acoustic matching liquid can be sealed in a watertight manner by providing a groove for inserting an O-ring on the surface that contacts the frame member 13, the holding member 11, and the contact member 12.

The acoustic matching liquid 14 is a liquid in which the acoustic impedance with the subject 5 is matched. For example, water or oil is preferable.
As described above, the holding unit is configured by the holding member 11, the contact member 12, the frame member 13, and the acoustic matching liquid 14, thereby reducing the attenuation of ultrasonic waves between the subject 5 and the ultrasonic probe 31. it can.

((Liquid level adjusting means))
The liquid amount adjusting means 2 moves the acoustic matching liquid 14 between the tank 23 and the watertight structure of the holding unit 1 by driving the pump 24. Thereby, the size and shape of the holding unit 1 and the shape of the subject 5 can be controlled. Specifically, adjustment is performed so that the acoustic matching liquid 14 is sent to the holding unit 1 via the supply pipe 21 and the acoustic matching liquid 14 is discharged from the holding unit 1 via the discharge pipe 22.

((Ultrasonic scanning unit))
The ultrasound probe 31 included in the ultrasound scanning unit 3 has one or more elements that receive acoustic waves and convert them into electrical signals. Any element may be used as long as it can receive an acoustic wave and convert it into an electric signal, such as a transducer using a piezoelectric effect, a transducer using optical resonance, or a transducer using a change in capacitance. Preferably, by arranging a plurality of elements that receive an acoustic wave in a one-dimensional or two-dimensional manner, the acoustic wave can be received simultaneously at a plurality of locations. As a result, the time required for measurement can be shortened and the influence of vibration of the subject can be reduced. By moving one element, it is possible to obtain a signal similar to that obtained by arranging a plurality of elements in two dimensions or one dimension. Between the contact member 12 and the ultrasound probe 31, a material such as gel, oil, water, or the like whose acoustic impedance is matched with the subject may be interposed. It is preferable that an amplifier for amplifying an electric signal and a converter having an AD conversion function are provided between the ultrasonic probe 31 and the arithmetic processing unit 4.

  The scanning mechanism 32 causes the ultrasonic probe 31 to scan the contact portion 12 a of the contact member 12. Any scanning mechanism 32 may be used, but in the case of a linear motion, a linear motion mechanism such as a ball screw, a linear guide, a chain, or a timing belt is preferable. What is necessary is just to select combining a linear motion mechanism and a rotation mechanism according to the desired way of movement. The power transmission unit may be either electric or manual. In the case of electric operation, a DC motor or a brushless motor may be used, and in the case of manual operation, a handle or grip may be used.

((Arithmetic processing unit))
As the arithmetic processing unit 4, a workstation or the like is typically used. The arithmetic processing unit 4 performs noise reduction processing on the electrical signal captured from the ultrasound probe 31 to reconstruct an image. By outputting the reconstructed image data to the display device, the characteristic information in the subject is visualized. The arithmetic processing unit 4 also performs overall processing for operating the ultrasonic diagnostic apparatus such as control of the ultrasonic scanning unit 3 and the liquid amount adjusting means 2.

<Example 1>
Hereinafter, specific examples will be described.
FIG. 2 is a schematic diagram showing an embodiment in which strain detecting means is used for adjusting the volume of the acoustic matching liquid. Reference numeral 25 denotes a strain detection means. For example, a strain gauge can be used as the strain detection means 25. The strain detection means 25 is not limited to this, and any strain detection means 25 may be used as long as the strain can be detected. More preferably, a small and flexible material that does not hinder the deformation of the contact member 12 is desirable. Further, not only a strain gauge but also a device that detects a load such as a piezoelectric element may be used.

FIG. 3 is a schematic diagram showing an example of the arrangement configuration of the strain detection means 25. FIG. 3A is a view of the holding unit 1 as seen from the direction in which the holding member 11 and the contact member 12 extend. FIG. 3B is a view of the holding unit 1 as viewed from the contact member side. The strain detection means 25 is installed outside the scanning region 33 scanned by the ultrasonic probe 31. The present invention is applicable regardless of the posture of the subject using the ultrasonic diagnostic apparatus. For example, in the prone position where the subject lies on his / her face down, the subject such as a breast can be hung down, or the subject can be sandwiched from above and below when the subject is in a sitting or standing position. Further, the present invention can be applied even when the subject is in a supine position in a supine state.

  FIG. 2A shows a schematic diagram in which an acoustic matching liquid is sealed in the holding unit. When the acoustic matching liquid 14 flows into the holding unit 1, the strain is detected by the strain gauge 25 because the weight of the liquid acts on the contact member 12. The acoustic matching liquid 14 is circulated by the pump 24 and filled in the holding unit so that bubbles are not mixed. Water pressure acts in the holding unit, and the weight of water acts on the contact member 12. At this time, the strain due to the water pressure and the weight of water can be detected by the strain detection means 25. The strain at this time is the initial strain.

  The deflection width of the contact portion 12a in the initial strain is desirably suppressed to 5 mm or less. One reason is that when an air layer enters between the ultrasonic probe 31 and the contact portion 12a, an acoustic wave is reflected, so that an acoustic matching material (not shown) such as water or oil can be held. This is because it is necessary to suppress the deflection width. As another reason, when the deformation of the contact portion 12a is large, the ultrasonic probe 31 may scan on the convex portion of the contact portion 12a (the portion protruding by the deformation). In this case, when the ultrasonic probe 31 pushes away the acoustic matching liquid 14 in the holding unit, the water pressure distribution in the holding unit changes, and force acts on the subject 5 to deform the subject 5. there is a possibility.

  FIG. 2B is a schematic diagram of a state in which the subject 5 is held by the holding unit 11 a of the holding member 11. When the subject 5 comes into contact with the holding unit 11a and a load is applied, the holding member tends to deform, and the water pressure in the holding unit increases. At this time, the subject 5 can be flattened by the rigidity of the holding unit 11a, but since the volume in the holding unit is constant, when the holding unit 11a is deformed, the water pressure in the holding unit rises, and the water pressure The contact portion 12a is deformed. Therefore, the amount of strain detected by the strain gauge 25 increases. If the deflection of the contact portion 12a is 5 mm or more, there is a possibility that it becomes difficult to hold the acoustic matching material and that the subject 5 is deformed when the ultrasonic probe 31 is scanned.

  FIG. 2C is a schematic diagram of a state in which the amount of the acoustic matching liquid 14 is controlled by the liquid amount adjusting unit 2 to reduce the distortion of the contact member 12. The arithmetic processing unit 4 discharges the acoustic matching liquid 14 in the holding unit by controlling the pump 24 so as to make the strain amount increased by holding the subject 5 asymptotically approach the strain amount detected in the initial state. At this time, the acoustic matching liquid 14 having a volume corresponding to the deformation of the holding portion 11 a due to the load of the subject 5 is discharged from the discharge pipe 22 and stored in the tank 23.

  As described above, by adjusting the amount of the acoustic matching liquid 14 in the holding unit while monitoring the strain of the contact portion 12a, the deflection of the contact portion 12a of the contact member 12 can be adjusted within a suitable range (for example, 5 mm or less).

<Example 2>
In Example 1, the amount of liquid was adjusted by a pump while referring to the detection result by a strain gauge or the like. In this embodiment, the amount of liquid is adjusted with reference to the detection result of pressure (particularly water pressure), not strain.

  FIG. 4 is a schematic diagram showing the configuration of this embodiment. Explanation of the same items as those in the first embodiment is omitted. Any pressure detecting means 26 may be used as long as the pressure can be measured. For example, in this embodiment, a pressure sensor that measures water pressure is used. As shown in FIG. 4, the pressure sensor is installed in the holding unit. In addition, as in the first embodiment, the present embodiment is not limited by the posture of the subject who uses the apparatus.

  FIG. 4A is a schematic diagram showing a state in which water pressure is applied when the acoustic matching liquid is sealed in the holding unit. The holding unit 1 is subjected to a water pressure corresponding to the installed height and a water pressure necessary to enclose the acoustic matching liquid 14 so that there are no bubbles. This pressure is the initial pressure.

  FIG. 4B is a schematic diagram illustrating a state in which water pressure is applied to the holding unit when the subject 5 is held by the holding unit 11a of the holding unit. If there is a difference in deformation between the holding part 11a and the contact part 12a when the load of the subject 5 is applied, the water pressure in the holding unit rises compared to the initial state.

  FIG. 4C is a schematic diagram illustrating a state in which the distortion of the contact portion 12 a is reduced by the liquid amount adjusting unit 2. The arithmetic processing unit 4 controls the pump 24 to discharge the acoustic matching liquid 14 in the holding unit so that the water pressure detected by the pressure detecting means 26 gradually approaches the initial pressure.

  As described above, the deflection of the contact portion 12a of the contact member 12 is adjusted to a suitable range (for example, 5 mm or less) by adjusting the amount of the acoustic matching liquid 14 while monitoring the water pressure in the holding unit. it can.

<Example 3>
In the present embodiment, the amount of liquid is adjusted with reference to the shape measurement result (deformation detection result) of the contact portion 12a of the contact member 12. FIG. 5 is a schematic diagram showing the configuration of the present embodiment. Explanation of the same items as those in the first embodiment is omitted. Any deformation detecting means 27 may be used as long as it can detect the deformation of the contact portion 12a. For example, a counter type photo interrupter, a range camera, a laser displacement meter, or the like can be used. In this embodiment, a counter type photo interrupter will be described. In addition, as in the first embodiment, the present embodiment is not limited by the posture of the subject who uses the apparatus.

  FIG. 6 is a schematic diagram showing the configuration of this embodiment, in particular, the arrangement configuration of photo interrupters that function as the deformation detection means 27. FIG. 6A is a view of the holding unit 1 as seen from the direction in which the holding member 11 and the contact member 12 extend. FIG. 6B is a view of the holding unit 1 as viewed from the contact member side. The photo interrupter is installed diagonally on the contact frame portion 12 b of the contact member 12. The initial position of the ultrasonic probe 31 is determined so as not to interfere with the optical path 28 of the photo interrupter.

  FIG. 5A is a schematic diagram showing the positional relationship between the deformation detection means 27 (photo interrupter) and the contact portion 12a when the subject 5 is held by the holding portion 11a of the holding unit 1. FIG. When the load of the subject 5 acts, the holding part 11a bends. Then, since the volume of the acoustic matching liquid 14 is constant, the contact portion 12a is also deformed. At this time, since the contact portion 12a blocks the optical path 28 of the photo interrupter, deformation can be detected. In order to suppress the deformation of the contact portion 12a as much as possible, it is preferable to install a photo interrupter in the vicinity of the contact portion 12a.

FIG. 5B is a schematic diagram in which the distortion of the contact portion 12 a is reduced by the liquid amount adjusting means 2. The arithmetic processing unit 4 controls the pump 24 to discharge the acoustic matching liquid 14 in the holding unit until the photo interrupter does not detect the state where the contact portion 12a is deformed.

  As described above, by adjusting the amount of the acoustic matching liquid 14 in the holding unit while monitoring the deformation of the contact portion 12a, the deflection of the contact portion 12a of the contact member 12 can be adjusted within a suitable range ( For example, it can be adjusted to 5 mm or less.

  As described above, according to the ultrasonic diagnostic apparatus of the present embodiment, attenuation of ultrasonic waves between the ultrasonic probe and the subject can be reduced, and the ultrasonic probe can be easily scanned. Deformation of the member in contact with the ultrasonic probe can be suppressed.

  Conventionally, there has been a case where a plate having a hardness of a certain level or more is used in order to compress and fix a subject or to stretch it thinly. Specifically, the subject is pressed against the plate, or the subject is held between two plates. Then, the ultrasonic probe is scanned on the surface of the plate, and the wide range of the subject is set as the imaging region. In this case, since the difference in acoustic impedance between the plate and the subject is large, even if an acoustic matching agent is used, some acoustic waves transmitted from the probe are subject to multiple reflections at the interface between the plate and the subject. There is. As a result, artifacts due to multiple reflections increase, and noise enters the acoustic wave signal generated from the inside of the subject.

  Here, in the holding unit of the present invention, a material (preferably a thin flexible elastic material) having high acoustic impedance matching with the subject is used. Therefore, an effect is obtained that artifacts due to multiple reflections are less likely to occur than when the subject is fixed by a plate.

  In the above, the example which applied this invention to the subject information acquisition apparatus which performs an ultrasonic diagnosis was demonstrated. However, the present invention can be applied to any apparatus that scans an ultrasonic probe and receives ultrasonic waves from a subject. For example, it is a subject information apparatus that receives an acoustic wave generated by the photoacoustic effect.

  1: holding unit, 11: holding member, 12: contact member, 14: acoustic matching liquid, 2: liquid amount adjusting means, 31: ultrasonic probe, 32: scanning mechanism, 4: arithmetic processing unit

Claims (11)

A probe for receiving ultrasonic waves propagating from the subject;
A holding unit that holds the object, and a holding unit that contacts the probe, and a holding unit that is filled with an acoustic matching liquid;
Adjusting means for adjusting the volume of the acoustic matching liquid in the holding unit;
Scanning means;
Processing means for calculating characteristic information in the subject using ultrasonic waves received by the probe;
The probe receives ultrasonic waves propagating from the subject through the holding unit,
The scanning means scans the probe on the contact member,
The subject information acquisition apparatus that adjusts the liquid volume so that the adjustment means suppresses deformation of the contact member. The subject information acquiring apparatus according to claim 1, wherein the contact member is deformed when the holding member holds the subject. The subject information acquiring apparatus according to claim 2, wherein the deformation of the contact member occurs when the scanning unit scans the probe. The object information acquiring apparatus according to claim 1, wherein the contact member is made of a material having a Young's modulus greater than that of the holding member. The subject information acquiring apparatus according to claim 4, wherein a deflection width of the contact member is 5 mm or less in a state where the holding member does not hold the subject. A strain detecting means for detecting strain of the contact member;
The object information acquiring apparatus according to claim 1, wherein the adjusting unit adjusts the liquid amount based on an output of the strain detecting unit. The object information acquiring apparatus according to claim 6, wherein the strain detecting unit is provided outside a region of the contact member that is scanned by the probe. A pressure detecting means for detecting the pressure in the holding unit;
The object information acquiring apparatus according to claim 1, wherein the adjusting unit adjusts the liquid amount based on an output of the pressure detecting unit. It further has a deformation detecting means for detecting the deformation of the contact member,
The object information acquiring apparatus according to claim 1, wherein the adjustment unit adjusts the liquid amount based on an output of the deformation detection unit. The object information acquiring apparatus according to claim 1, wherein the ultrasonic wave propagated from the subject is a reflection of an ultrasonic wave transmitted from the probe to the subject. The subject information acquiring apparatus according to claim 1, wherein the ultrasonic wave propagating from the subject is generated by a photoacoustic effect when the subject is irradiated with light.

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