JP2013172900A - Subject information acquisition device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technology capable of easily optimizing compression conditions when a subject is compressed and held at the time of measuring a photoacoustic wave.SOLUTION: A subject information acquisition device having a plurality of members which compress and hold a subject for generating characteristic information in the subject based on an acoustic wave transmitted from the subject irradiated with light includes: a means for acquiring a first compression condition which is a reference value at the time of compressing the subject; a means for acquiring a second compression condition for representing a state in which the subject is compressed by the plurality of members; and an output means for outputting the information based on the first compression condition and the second compression condition.

Description

  The present invention relates to a subject information acquisition apparatus.

  In recent years, a technique for irradiating a living body with laser light to generate ultrasonic waves (photoacoustic waves) due to the photoacoustic effect, and analyzing the photoacoustic waves to visualize and analyze the structure and situation of the living body Has been devised (see Patent Document 1). This technique is also called photoacoustic measurement or photoacoustic tomography, and can be examined non-invasively. Therefore, there is a movement to divert medical care for examination inside the human body.

  For example, a photoacoustic measurement device for breast cancer screening has been developed (see Non-Patent Document 1). In such a photoacoustic measurement device, a compression holding mechanism for making the breast thin and flat in order to prevent the irradiated laser light and the generated photoacoustic wave from being attenuated in the living body and blurring the image. Many have

  On the other hand, X-ray mammography is currently used for the purpose of examination and diagnosis of breast cancer in medical institutions. In X-ray mammography, a device configuration having a compression holding mechanism for making a breast into a thin and flat shape is common. In X-ray irradiation, an image is obtained in which the mammary gland tissue and the tumor portion are white and the fat portion is black. If the breast tissue and the tumor part overlap, the presence of a small tumor part may be overlooked. Also, the radiation dose can be reduced as the tissue is thinner. That is, the purpose of the X-ray mammography having the compression holding mechanism is to reduce the overlap between the mammary gland tissue and the tumor portion and to reduce the radiation dose as much as possible.

In breast cancer screening, it is common to photograph the left and right breasts. When interpreting images, the left and right breast images are displayed side by side, and the presence or absence of a tumor is confirmed by comparing both images.
In order to make a proper diagnosis using the comparison image as described above, it is preferable that the comparison image is an image obtained by photographing a breast that is compressed in the same manner. However, at present, in order to position the breast so that the compressed state is uniform, it largely depends on the skill of the operator who operates the holding mechanism.

  In view of this, there has also been proposed an apparatus that improves the reproducibility of breast positioning by superimposing previously displayed breast outline information on the compressed breast outline information (see Patent Document 2). ).

US Pat. No. 5,843,0023 JP 2008-86389 A

S. A. Ermilov et al., Development of laser optoacoustic and ultrasonic imaging system for breast cancer utilizing handheld array probes, Photons Plus Ultrasound: Imaging and Sensing 2009, Proc. Of SPIE vol. 7177, 2009.

  However, in the conventional X-ray mammography, although the reproducibility of breast positioning is improved, the reproduction of compression conditions other than positioning, such as the thickness of the breast at the time of measurement and the compression force applied to the breast, has not been dealt with. This is because in the X-ray mammography, the thickness of the breast and the compression force do not greatly affect the diagnostic image.

  On the other hand, in the photoacoustic measurement, it is known that the thickness and compression force of the test site with respect to the laser irradiation direction, that is, the thickness of the breast and the compression force applied to the breast hold affect the image quality of the diagnostic image.

  In general, in photoacoustic measurement, if the area is not shallow to some extent with respect to the thickness direction of the region to be examined, the image quality of the diagnostic image tends to be lowered and the examination accuracy tends to be lowered. This is because the laser light applied to the living body is attenuated in the living body, and the photoacoustic wave generated in the living body is attenuated in the living body. For this reason, the compression holding mechanism is designed to deform the breast and reduce the thickness of the region to be examined with respect to the laser light incident path.

  Further, regarding the compression force, if the hardness inside the subject changes depending on the degree of pressure holding, the speed of the photoacoustic wave propagating through the inside changes. If the propagation speed of the photoacoustic wave inside the living body is accurately calculated and not reflected in the reconstruction calculation, the image quality of the diagnostic image will be affected. From the viewpoint of image comparison, the compression force is uniform for each measurement. It is preferable that

  On the other hand, since there is a difference among individuals in the degree of feeling a burden related to holding the breast, depending on the subject, it may be necessary to reduce the compression force, or it may not be able to withstand long-time compression fixation. In order to ensure the required test accuracy while reducing the burden on the subject, and to compare with the past measurement results, it is desirable to reproduce the holding status, but this requires a high level of operator skill. It has become a problem.

  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 easily optimizing a compression condition when a subject is pressed and held during photoacoustic measurement.

  The present invention employs the following configuration. That is, an object information acquisition apparatus that has a plurality of members that compress and hold a subject and generates characteristic information in the subject based on acoustic waves propagating from the subject irradiated with light. Means for acquiring a first compression condition, which is a reference value for compressing the subject, and means for acquiring a second compression condition indicating a state in which the subject is compressed by the plurality of members. And an output means for outputting information based on the first compression condition and the second compression condition.

  According to the present invention, it is possible to provide a technique for easily optimizing a compression condition when a subject is pressed and held during photoacoustic measurement.

The figure explaining the apparatus structure in a present Example. FIG. 6 is a diagram for explaining guide information display in the first embodiment. FIG. 6 is a diagram for explaining guide information display in the second embodiment.

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 relates to an apparatus using a photoacoustic effect that receives acoustic waves generated in a subject by irradiating the subject with light (electromagnetic waves) and acquires characteristic information in the subject as image data. . The characteristic information acquired at this time is the source distribution of acoustic waves generated by light irradiation, the initial sound pressure distribution in the subject, or the optical energy absorption density distribution or absorption coefficient distribution derived from the initial sound pressure distribution, tissue The concentration distribution of the substance which comprises is shown. The concentration distribution of the substance is, for example, an oxygen saturation distribution or an oxidized / reduced hemoglobin concentration distribution. Such characteristic information means information indicating the state of the subject, and can also be called subject information. Therefore, the photoacoustic measurement apparatus of the present invention can also be called a subject information acquisition apparatus.

  The acoustic wave referred to in the present invention is typically an ultrasonic wave, and includes an elastic wave called a sound wave, an ultrasonic wave, or an acoustic wave. An acoustic wave generated by the photoacoustic effect is called a photoacoustic wave or an optical ultrasonic wave.

First, the configuration of the photoacoustic measurement apparatus according to the present embodiment will be described with reference to FIG.
The photoacoustic measurement apparatus of the present embodiment includes a laser light source 100, an optical system 101, and a probe 104 as a basic hardware configuration. The apparatus further includes a compression plate 105 and a base plate 106, a handle 107, a linear scale 108, a load cell 109, and a controller unit 110. The subject 103 is a living body breast as a subject.

(Mechanism of light irradiation and photoacoustic wave acquisition)
The laser light emitted from the laser light source 100 is emitted to the subject 103 via the optical system 101. Various light sources such as light emitting diodes are used in addition to the laser. The wavelength of the irradiation light can be determined according to the light absorber inside the subject. For example, when near infrared light is used, it can be specifically absorbed into blood and blood vessels to generate photoacoustic waves. .

  The probe 104 receives a photoacoustic wave generated and propagated from the inside of the subject 103 due to the photoacoustic effect. As the probe 104, a piezoelectric element, a CMUT, or the like in which one or a plurality of elements that receive an acoustic wave and convert it into an electrical signal is used. The electrical signal is subjected to processing such as amplification and digitization as necessary.

The controller unit 110 analyzes a signal based on the photoacoustic wave acquired by the probe, and obtains characteristic information (subject information) of the subject. Furthermore, the subject information is converted into image data and output to a display device for display so that it can be used for diagnosis.
In the present embodiment, a living body such as a breast is a subject, but the measurement target of the photoacoustic measurement apparatus according to the present invention is not limited to this.

(Holding mechanism)
The subject 103 is pressed and held between the compression plate 105 and the base plate 106. The probe 104 is arranged so that a photoacoustic wave emitted from the subject 103 can be acquired through the base plate 106. The subject is held by the plurality of plate-like members.
The material of the base plate 106 is preferably PMP (polymethylpentene), but other resins can be substituted. The base plate preferably has a small difference in acoustic impedance from the subject in order to pass acoustic waves. The degree of matching can be increased by using an acoustic matching agent between the subject and the subject.

The compression plate 105 compresses and holds the subject between the compression plate 105 and the base plate 106. By adjusting the gap between the two, the compression holding state can be changed. As the compression plate, a material having high transparency and low attenuation characteristics with respect to irradiation light is preferable.
The handle 107 is connected to the drive mechanism of the compression plate 105, and the compression plate 105 can be moved by operating the handle 107 to compress and release the subject 103. In the present embodiment, the subject is held by driving only one side of the plate, but the subject may be pressed and held by driving the plates on both sides.

(Pressure condition measuring mechanism)
The linear scale 108 is installed to measure the compression distance, that is, the retention thickness of the compressed and retained breast. The linear scale 108 in this embodiment is installed on a member that supports both plates so that the distance between the compression plate 105 and the surface of the base plate 106 that is in contact with the breast can be measured. In this embodiment, a linear scale is used as the compression distance measuring means, but an alternative sensor such as a laser distance sensor that optically measures the thickness between the plates may be applied.

  The load cell 109 is a compression force measuring unit that measures the compression force applied to the compressed and held breast. The load cell 109 is a sensor that converts a compression force into an electrical signal. In the present embodiment, the compression force that is attached between the compression plate 105 and the member that supports the base plate 106 and is applied between the compression plate 105 and the base plate 106 is regarded as the compression force applied to the breast. To measure. In this embodiment, a load cell is used as the measuring means, but other sensors may be applied. The compression force may be a force directly applied to the breast by the holding mechanism, a reaction force from the subject due to the compression, or a force (stress) per unit area.

  The compression distance information and the compression force information acquired by the linear scale and the load cell are stored in a storage unit in the apparatus as a reference value when the subject is compressed. Even if either one of the distance and the compression force is used, the compression state can be reproduced to some extent, but the reproduction accuracy can be improved by using both. Hereinafter, this reference value is also referred to as a first compression condition. As the reference value, for example, a sample parameter for reproducing the degree of retention of breast compression based on a record obtained when the subject was previously measured can be used. Also, a recommended value based on physical characteristics such as the attributes of the subject such as the size of the measurement site such as the breast and the age of the subject and the characteristics of the measurement site is possible. As the storage means, a non-volatile storage device represented by flash memory or HDD can be used.

(Display guide information)
In addition, the photoacoustic measurement device of the present embodiment monitors the compression distance and compression force information during the breast holding operation as the second compression condition for the breast that is the current measurement target. Then, the guide information generating means compares the first and second compression conditions and generates guide information for the compression operation.

  The guide information generated and displayed is information that allows the operator who performs the compression operation to know what to do to realize the first compression condition. For example, when the compression distance of the breast is wider than the reference value, guide information is generated so that it can be understood that the compression operation should be continued. In other words, when the compression force is weaker than the first compression condition, the guide information that prompts the operation of the holding mechanism in the direction of increasing the compression is displayed. On the contrary, when the compression force is stronger than the first compression condition, guide information for notifying that the operation of the holding mechanism should be moved in the direction of loosening the compression is generated.

  In addition, what kind of compression operation the operator performs even if the first compression condition that is the reference value and the second compression condition that indicates the current compression state are displayed side by side or displayed alternately Therefore, the effect of the present invention can be obtained.

In addition, since it may be difficult to set the difference between the first compression condition and the second compression condition to zero, an allowable threshold for an error between the first compression condition and the second compression condition is set. Is preferred.
Moreover, it is preferable that the guide information of the holding operation is displayed only during the breast holding work. For example, the linear scale 108 detects that the compression plate 105 has started to move by operating the handle 107, and triggers notification of guide information using this as a trigger. On the other hand, if the value detected by the linear scale 108 does not change for a certain period of time, a method may be considered in which the notification of the guide information is terminated as the holding operation is completed.

<Example 1>
In this embodiment, the photoacoustic measurement apparatus further includes a display panel 200. The display panel 200 is installed to display information such as a device status even in a normal photoacoustic measurement device. The display panel 200 according to the present embodiment displays not only the apparatus status but also information that is useful for operation of the apparatus, such as a breast holding distance and a compression force applied to the breast, and specific guide information. Is done. In this embodiment, the display panel corresponds to output means.

FIG. 2 is an example of display of guide information for holding operation in the present embodiment. A frame 201 in the figure is a display screen of the display panel 200.
As shown in FIG. 2, during the holding operation, the display panel 200 displays both the target first compression condition 202 and the second measurement condition 203 that is the current measurement condition. The items displayed here are compression force (unit N) and compression distance information (unit mm).

  Further, in this embodiment, an operation necessary to bring the compression state closer to the first compression condition is displayed as the guide information 204 in characters. In this example, the holding distance and holding force are both lower than the reference value, and the pressure is not enough, so “Please press further” is displayed. If the compression distance and compression force fall within the allowable threshold values for the first compression condition, no further holding operation is required, such as displaying “Appropriate holding state”. Notify that.

In FIG. 2, the current measurement value and target value (reference value) are displayed regarding the compression force and the compression distance. However, the gist of the present invention is to present information that assists an operator's appropriate compression operation based on the current measured value and target value. Therefore, the display format may be the display of the difference value between the current value and the target value, or the difference value may be illustrated in a bar graph or the like.
The guide information may be expressed by a symbol such as an arrow. Alternatively, the operation direction of the handle may be used.

  It is also conceivable to set several allowable thresholds for the discrepancy between the current measured value (second compression condition) and the target value (first compression condition). Then, the degree of difference between the two is evaluated in several stages. If the display method is changed according to the degree of difference using the evaluation result, navigation until the operator reaches the target holding state can be performed.

  Such stepwise setting of the allowable threshold value can be combined with the display of guide information by arrows. For example, the display is such that the speed at which the arrow mark flows is faster as the difference between the first compression condition and the second compression condition is larger. By referring to this, the operator can intuitively perform the compression operation to approach the target compression condition by continuing the compression operation so that the speed at which the arrow mark flows is slowed down.

In this embodiment, the guide information is output to the display panel. However, the display screen may be projected and displayed on a place where the operator can easily see it using a projection display device such as a projector. The projection display location may be on a member of the apparatus main body such as a panel that is close to the user or on the compression plate 105, or may be a projection outside the apparatus such as the wall surface, floor, or ceiling of the examination room. Good.

<Example 2>
The photoacoustic measurement apparatus according to the present embodiment further includes an audio speaker, and displays the guide information by audio.

  A state of guide information display by voice is shown in FIG. In the figure, a speaker 300 is controlled by a photoacoustic measuring device via a connection line (not shown) or wirelessly. As specific guide information, when the compression force or the compression distance is insufficient, as shown in the figure, a notification “please compress further” is notified. If the pressure is too strong, notify “Please relax the pressure”, and if the first and second compression conditions are within the allowable threshold range, notify “Appropriate compression state”. In this embodiment, the speaker corresponds to the output means.

As a method of voice guidance, in addition to display by a language message, a method of changing a pronunciation pattern using a beep sound may be used.
Since the present embodiment is a voice notification, it is preferable to pay attention to the notification frequency and timing, such as guiding only during the holding operation, from the viewpoint of usability.
In FIG. 3, in addition to voice, guide information 204 by characters is also displayed, which makes it easier for the operator to understand.

<Example 3>
Each said Example was the structure which sets a predetermined value as 1st compression conditions. By setting the compression condition to a predetermined value, it is possible to perform photoacoustic measurement with almost the same compression condition when measuring any patient. However, in actual measurements, there are individual differences in resistance to pressure retention. There are also individual differences in the size and flexibility of the measurement site (such as the breast). Therefore, it is desired to measure by changing the compression condition for each subject. Moreover, when following the pathology of the same patient (subject), it is preferable that the compression condition when the patient is measured before can be set as the first compression condition.

Therefore, in this embodiment, a photoacoustic measurement apparatus that sets a first compression condition for each patient will be described.
Here, as a precondition, it is assumed that at least the compression distance and the compression force are recorded as the compression condition in the past measurement data for each patient.

  In order to use the guide information in the breast compression operation by the operator, it is necessary to set the first compression condition of the patient to be inspected before starting the procedure. In the apparatus of the present embodiment, it is assumed that the ID of a patient to be examined and past measurement data are associated with each other and stored in a storage device (not shown).

  The setter inputs the ID of the patient to be examined into the device console by key operation. The setter may be the operator himself or another person. Then, a list of past measurement data associated with the input patient ID is displayed as a list. The measurement data list is preferably displayed together with information that serves as a reference for specifying data used as a reference for the compression condition, such as the measurement date and time and the operator in charge.

When the setter selects a desired item from the list of measurement data, compression condition data is extracted from the selected measurement data, and is stored in a storage device in the apparatus in association with the patient ID.
The compression condition data for each patient stored in the above procedure is specified using the patient ID input by the operator as a key. The identified compression condition data is referred to as the first compression condition and is used to generate guide information.

  As described above, according to the photoacoustic measurement apparatus according to each embodiment of the present invention, when a subject is compressed and held, a guide based on a reference value that is a target for a compression force and a compression distance and a current measurement value. Information can be displayed to the operator using a display panel. As the reference value, a compression condition in the past measurement or a general value is used. The guide information is comparison information between the measurement value and the reference value, and an operation instruction based on the comparison information. Therefore, the operator can perform the holding operation easily and appropriately by referring to the guide information and adjusting the compression holding distance and the compression force.

  100: Laser light source, 104: Probe, 105: Compression plate, 106: Base plate, 200: Display panel

Claims (9)

A subject information acquisition apparatus that has a plurality of members that compress and hold a subject and generates characteristic information in the subject based on acoustic waves propagating from the subject irradiated with light,
Means for acquiring a first compression condition that is a reference value when compressing the subject;
Means for acquiring a second compression condition indicating a state in which the subject is compressed by the plurality of members;
Output means for outputting information based on the first compression condition and the second compression condition;
A subject information acquisition apparatus characterized by comprising: The subject information acquiring apparatus according to claim 1, wherein the first compression condition is a compression force on the subject. The object information acquiring apparatus according to claim 1, wherein the first compression condition is a thickness of the compressed object. The output means provides guide information related to the operation of the plurality of members to bring the compression state of the subject close to the first compression condition based on the first compression condition and the second compression condition. The object information acquiring apparatus according to claim 1, wherein the object information acquiring apparatus outputs the object information. The object information acquiring apparatus according to claim 4, wherein the guide information is information indicating whether the compression of the object by the plurality of members is increased or decreased.   6. The subject information acquisition apparatus according to claim 1, wherein the first compression condition acquisition unit acquires a past compression condition related to the subject. The subject is a living body measurement site,
The object information acquiring apparatus according to claim 1, wherein the means for acquiring the first compression condition acquires a value based on a characteristic of the measurement site. The object information acquiring apparatus according to claim 1, wherein the output unit outputs information based on the first compression condition and the second compression condition to a display panel. . The object information acquiring apparatus according to claim 1, wherein the output unit outputs information based on the first compression condition and the second compression condition by voice.

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