JP4909131B2 - Optically assisted ultrasonic velocity change imaging apparatus and optically assisted ultrasonic velocity change image display method - Google Patents

Description

  In the present invention, a tomographic image (optical tomographic image) relating to a distribution of an ultrasonic velocity change inside an object is measured by using an ultrasonic wave to measure a change in sound velocity before and after irradiation when the inside of a subject is irradiated with light. The present invention relates to a light-assisted ultrasonic velocity change imaging apparatus and a light-assisted ultrasonic velocity change image display method.

  Ultrasound diagnostic devices used in the medical field transmit ultrasonic signals (ultrasound beams) oscillated from ultrasonic transducers into the living body and receive and detect ultrasonic echo signals from the living body. This is tomographic image. These ultrasonic diagnostic apparatuses have a function of imaging the intensity of the received ultrasonic echo signal by luminance modulation or the like, as in the so-called B mode or M mode. Various ideas have been made, such as calculation of blood flow and development of other application software. Recently, an apparatus for displaying a tomographic image in real time by adopting electronic scanning by an array type probe or the like has been widely used, and it exerts great power for noninvasive diagnosis in the body.

  As one of the new diagnostic methods using such an ultrasonic diagnostic apparatus, a mechanism for irradiating light to the observation area is provided, and the received signals (super It has been proposed to obtain a tomographic image (light-assisted ultrasonic velocity change image) by obtaining the distribution of the ultrasonic velocity change in the observation region due to light irradiation from the change of the sound echo signal) (see Patent Document 1).

  This optical tomographic image shows a tomographic image of a temperature change in the observation region due to absorption of the irradiated light. In other words, when light is irradiated into the living body, if the light absorption characteristics are different for each part in the living body, a temperature distribution is generated in the living body according to the light absorption characteristic of each part. Since the sound velocity of the ultrasonic wave propagating in the living body changes depending on the temperature, by calculating the sound velocity change of the ultrasonic echo signal before and after the light irradiation for each part and tomographic imaging, It can be displayed as a tomographic image of ultrasonic velocity change distribution, temperature change distribution, or light absorption distribution. Therefore, in the following description, the tomographic image related to the ultrasonic velocity change distribution includes tomographic images of the ultrasonic velocity change distribution, the temperature change distribution, and the light absorption distribution.

FIG. 7 is a diagram showing a device configuration for displaying an optical tomographic image described in Patent Document 1. As shown in FIG. The subject 100 is irradiated with light by a light source 40 composed of an infrared laser. On the emission side of the light source 40, a shutter 42 for intermittently irradiating the subject 100 with light is provided. The shutter 42 is controlled to be opened and closed by the light absorption analysis unit 60.
Transmission / reception of ultrasonic waves is performed by the linear array probe 50. The linear array probe 50 is excited by a drive signal from the transmission / reception unit 52 to generate an ultrasonic signal, and returns a reception signal (ultrasonic echo signal) from the inside of the subject with respect to the ultrasonic signal to the transmission / reception unit 52. The scanning control unit 54 scans a plurality of ultrasonic signals by sequentially switching transducers that transmit and receive waves.
The reception signal of the linear array probe 50 is input to the B-mode signal processing circuit 56 and the light absorption analysis unit 60. The B-mode signal processing circuit 56 performs a well-known B-mode tomographic image forming process on the received signal to form a tomographic image in the beam scanning range, and writes it in a DSC (digital scan converter) 58. Further, the light absorption analysis unit 60 analyzes the received signal and forms an image of the light absorption distribution (that is, the ultrasonic velocity change distribution) in the beam scanning range. This light absorption distribution is obtained by calculating the phase change of the received signal before and after the light irradiation.

  A control procedure for obtaining a light absorption distribution image by the above apparatus will be described below. First, the light absorption analysis unit 60 closes the shutter 42 and stores the reception signal (the reception signal for the B-mode image) of the probe 50 in a state where the temperature of the subject 100 is not increased due to light absorption for one scan. . At this time, the light absorption analysis unit 60 distinguishes and stores the received signal for each scanning line (beam) based on the scanning information from the scanning control unit 54. Next, the light absorption analysis unit 60 opens the shutter 42 to irradiate the subject 100 with light, and a time during which a detectable temperature rise occurs in each part of the subject (this is obtained and set in advance by experiments). After the elapse of time, the reception signal of the probe 50 is again acquired for one scan. Then, the light absorption analysis unit 60 compares the received signals before and after the light absorption for each scanning line, and analyzes the change in the sound velocity of the ultrasonic wave from the phase change. The analysis result is written in the DSC 58. The DSC 58 displays a light absorption distribution image (that is, an ultrasonic velocity change distribution) that is an analysis result of the light absorption analysis unit 60 on the display device 62. At this time, the light absorption distribution image may be displayed in color by being superimposed on the B-mode image. For example, since the light absorption distribution corresponds to the temperature rise of each part of the subject, a warm color is used so that the higher the absorption rate (the greater the phase difference before and after irradiation), the higher the lightness. If an image such as this is taken, an image that can be easily grasped intuitively by a diagnostician can be obtained.

In this way, different from the ultrasonic echo signal intensity (reflection intensity) (B-mode image), it is possible to display a distribution of different physical quantities called a distribution of light absorption characteristics (that is, an ultrasonic velocity change distribution). A multifaceted understanding of the organization is possible.
JP 2001-145628 A

FIG. 8 is an example of a B-mode image created based on the ultrasonic echo signal observed by the array-type probe. This B-mode image is an image obtained by luminance-modulating 345 lines of ultrasonic echo signals. FIG. 9 shows an example of an ultrasonic echo signal for one line of the 345 lines. Ultrasound is reflected at the interface between tissues with different acoustic impedances. Therefore, as a reception signal (ultrasonic echo signal) when a pulsed ultrasonic signal is transmitted into the living body, echoes reflected at the boundary between the tissues appear as reflected pulses in the order closer to the probe.
The B-mode image is obtained by modulating the amplitude of the reflected pulse as luminance information, and is displayed in black as the amplitude increases. The received signals of all 345 lines are displayed and imaged, whereby a B-mode image as shown in FIG. 8 is obtained.

  Separately from this B-mode image, when an optical tomographic image showing the above-described light absorption distribution (ultrasonic velocity change distribution) is to be displayed, ultrasonic echo signals of each line before and after the light irradiation are acquired, Signal analysis before and after light irradiation is performed for each line.

  The signal analysis at this time will be described. As shown in FIG. 10, for each line of the ultrasonic echo signal, the waveform on the line is divided into equal intervals for about one wavelength, and the waveform before and after light irradiation in each interval. The cross correlation is calculated and the difference is detected. Based on the detected difference, the change in the sound speed of the ultrasonic wave in each section is calculated, and the same change in the sound speed is calculated for all lines. The calculated distribution of sound speed changes is displayed as an ultrasonic speed change image or a temperature distribution image (or a light absorption distribution image).

However, when the waveform data on one line is divided into equal intervals and the cross-correlation of each interval is calculated, a large error may occur in the calculated sound speed change value in some intervals.
In general, in a section including a large-amplitude ultrasonic echo signal (section in which the B-mode image is black), the signal and the artifact can be distinguished. Therefore, if the cross-correlation is calculated, a difference detection with a small error can be performed. However, in a section that includes only a signal having a small amplitude (a section in which the B-mode image is white), the S / N ratio is small, so that the signal and the artifact are difficult to be distinguished from each other. It is easy to include.

  FIG. 11 shows a B-mode image and a sound speed change distribution image obtained by creating a biological pseudo sample including a region where an ultrasonic echo signal with a small amplitude that makes it difficult to distinguish a signal from an artifact is obtained. FIG. This pseudo sample is prepared using agar, for example. FIG. 11A is a B-mode image of a biological pseudo sample having an ultrasonic echo signal area with a small amplitude at the center. The central part of the sample is made of a material that does not absorb the irradiation light. FIG. 11B is a diagram in which the distribution of changes in ultrasonic velocity before and after light irradiation is calculated and imaged. In the central part where the ultrasound echo signal with a small amplitude (the part where the B-mode image is white) cannot be distinguished from the signal and the artifact, the cross-correlation cannot be calculated accurately, resulting in an error. In the center of the image, a ghost image is generated as if there was a change in the sound speed despite no change in the ultrasonic velocity.

  In this way, when an ultrasonic velocity change distribution image is created by adopting a conventional signal processing method of dividing the ultrasonic echo signal of each line into equal intervals and calculating the cross-correlation of each interval, There has been a problem that an image in which an erroneous change in ultrasonic velocity appears is displayed in a region where the amplitude of the ultrasonic echo signal is small.

Therefore, the inventors of the present invention have not yet performed signal waveforms of the non-irradiation ultrasonic echo signal received from the observation region and the post-light irradiation ultrasonic echo signal received from the observation region after light irradiation. The optical assist is designed to remove the influence of artifacts by extracting the envelope of the signal and extracting the signal section of interest based on the extracted envelope, and to reliably image the ultrasonic velocity change. An ultrasonic velocity change imaging apparatus (optical tomography apparatus) has been proposed (Japanese Patent Application No. 2006-230918).
Accordingly, it is possible to obtain an ultrasonic velocity change distribution image (or temperature change distribution image) in which a ghost image hardly appears as shown in FIG.

  By the way, this method is effective for eliminating the ghost image, but the light absorption amount of the subject with respect to the light irradiation does not change and is not affected. Therefore, if the amount of light absorption with respect to irradiation light (excitation light) does not change in the observation region, not only does the ghost image not appear in the distribution image of the ultrasonic velocity change, but the ultrasonic velocity change that is originally intended to be imaged Even if the distribution image itself is not displayed clearly, or even if the distribution image of the ultrasonic velocity change is displayed, the irradiation of the excitation light must be continued for a considerable time to sufficiently raise the temperature.

  As one method for clarifying the distribution image of the ultrasonic velocity change, injecting a contrast agent with an injector in order to promote the temperature rise due to light absorption of the tissue of interest in the subject is disclosed in Patent Document 1. Is disclosed. That is, if a substance having a high light absorption rate (photothermal conversion substance) as a contrast agent is injected into a site of interest tissue and then an image display of ultrasonic velocity change is performed, the temperature rise due to light absorption of the tissue of interest is higher than that of other parts. It is explained that a tomographic image in which the tissue of interest is emphasized can be formed because it becomes large.

  However, until now, a substance suitable as a photothermal conversion substance for a light-assisted ultrasonic velocity change imaging apparatus has not been specifically obtained. For example, in Patent Document 1, chicken is used as a living body pseudo sample, and a region with a high light absorption rate is formed by coloring a part thereof black. However, when a part of an animal is collected as a specimen, the collected specimen (subject) can be colored black, but when a living animal itself is used as a specimen, the inside of the living body is colored black. It is not possible.

Therefore, the present invention can obtain not only a distribution image of an ultrasonic velocity change in which a ghost image hardly appears, but also a clear distribution image of an ultrasonic velocity change by using an appropriate photothermal conversion substance. An object of the present invention is to provide an optically assisted ultrasonic velocity change imaging apparatus.
Another object of the present invention is to provide an optically assisted ultrasonic velocity change imaging apparatus capable of efficiently obtaining a distribution image of ultrasonic velocity change even if the irradiation time of excitation light to the observation region is shortened. To do.

  The optically assisted ultrasonic velocity change imaging apparatus of the present invention, which has been made to solve the above problems, transmits an ultrasonic signal to an observation region of a subject and receives an ultrasonic echo signal from the observation region. A photothermal conversion material including a gold nanorod distributed in a region of interest in an observation region, a transmission / reception mechanism, and a wavelength excitation that can be transmitted to the region of interest and is photothermally converted when irradiated to the photothermal conversion material. A light source that irradiates light toward the observation region, a non-irradiation ultrasonic echo signal received from the observation region when the excitation light is not irradiated, and a post-irradiation super-wave received from the observation region after excitation light irradiation Envelope data extraction unit that extracts the envelope of the signal waveform of each acoustic echo signal, and the non-irradiation ultrasonic echo signal and the post-irradiation ultrasonic echo signal based on the extracted envelope An interest signal interval extraction unit that extracts an interest signal interval in a signal waveform, and obtains an ultrasonic velocity change based on signals within each interest signal interval of the non-irradiation ultrasonic echo signal and the post-irradiation ultrasonic echo signal. An ultrasonic velocity analysis unit that displays a tomographic image relating to the distribution of the ultrasonic velocity change.

Here, the gold nanorods refer to rod-shaped gold nanoparticles that exhibit large absorption in the wavelength range of 700 nm to 1000 nm.
According to this invention, the photothermal conversion substance including the gold nanorods is distributed to the region of interest of the subject by an injector or the like. The excitation light is not irradiated with the excitation light by using a light source that can transmit the excitation light having a wavelength that can be transmitted to the region of interest and is photothermally converted when the photothermal conversion substance is irradiated. The ultrasonic signal is transmitted to the observation region of the subject and the ultrasonic echo signal from the observation region is received in the two states of the irradiation state.
Then, the non-irradiation ultrasonic echo signal received from the observation region in the state where the excitation light is not irradiated and the post-irradiation ultrasonic wave received from the observation region in the state after the excitation light irradiation by the envelope data extraction unit The envelope data of the signal waveform of each echo signal is extracted. By extracting the envelope data, the true echo signal and the artifact included in the received echo signal can be distinguished.
Further, the interest signal section extraction unit extracts a section that is a true echo signal in the echo signal as the interest signal section based on the extracted envelope data. Then, the ultrasonic velocity analysis unit calculates the cross-correlation based on the signals in the interest signal section of the non-irradiation ultrasonic echo signal and the post-irradiation ultrasonic echo signal, and calculates the ultrasonic velocity change in the observation region. To do. As a result, a change in ultrasonic velocity is obtained based only on a true echo signal that does not include artifacts, and a tomographic image (light-assisted ultrasonic velocity change image) is created.

  According to the present invention, an image showing an erroneous ultrasonic velocity change is not displayed in a region where the amplitude of the ultrasonic echo signal is small, and furthermore, the region of interest can be obtained by the photothermal conversion material containing gold nanorods. Therefore, it is possible to effectively increase the optical absorptance of the image, so that it is possible to display an accurate ultrasonic velocity change image that is clear about the original ultrasonic velocity distribution and that hardly causes a ghost image to appear.

(Means and effects for solving other problems)
In the above invention, the photothermal conversion substance may be a drug labeling substance distributed to a site of interest by a drug delivery system.
As a result, when the drug is delivered to the site of interest and released by the drug delivery system, it is possible to observe whether the drug has reached the site of interest, for example, to accurately grasp the timing of releasing the drug from the drug carrier Can do.

  Moreover, in the said invention, it is desirable that a light source is a light source which irradiates at least one part wavelength light of the wavelength range of 700 nm-1000 nm as excitation light. By irradiating light in this wavelength range as excitation light, the photothermal conversion substance containing gold nanorods can effectively absorb light and raise its temperature.

In addition, the display method of the light-assisted ultrasonic velocity change image of the present invention made from another viewpoint is as follows: (a) a photothermal conversion material including gold nanorods is distributed to a site of interest in an observation region of a subject (excluding a human). And (b) using a light source that is transmissive to the region of interest and that irradiates the observation region with excitation light having a wavelength that is photothermally converted when irradiated to the photothermal conversion substance. The ultrasonic signal is transmitted to the observation region of the subject and the ultrasonic echo signal is received from the observation region in two states, i.e., the non-existing state and the excitation light irradiation state. Extract the envelopes of the signal waveforms of the non-irradiated ultrasonic echo signal received from the observation region in the unirradiated state and the post-irradiation ultrasonic echo signal received from the observation region in the state after the excitation light irradiation. , (D) on the extracted envelope Then, the signal section of interest in the signal waveform of each of the non-irradiation ultrasonic echo signal and the post-light irradiation ultrasonic echo signal is extracted, and (e) each of the non-irradiation ultrasonic echo signal and the post-light irradiation ultrasonic echo signal. An ultrasonic velocity change is obtained based on the signal in the interest signal section, and a tomographic image relating to the distribution of the ultrasonic velocity change is displayed.
With this display method, it is possible to display an accurate ultrasonic velocity change image that is clear about the original ultrasonic velocity distribution and that is unlikely to have a ghost image.

(Device configuration)
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a configuration of an optically assisted ultrasonic velocity change imaging apparatus according to an embodiment of the present invention.
Gold nanorods 110a are distributed as photothermal conversion substances in the region of interest 110 of the subject 100. As a method of distributing the gold nanorods 110a to the region of interest 110, the gold nanorods 110a may be distributed directly by an injector, or, if it is an animal body, using a drug delivery system (DDS) technique as a drug labeling substance. You may distribute to a region of interest.

  The optically assisted ultrasonic velocity change imaging apparatus 1 includes a linear array probe 2, a probe 5 including an infrared laser light source 3, a transmission / reception unit 6, a scanning control unit 7, an ultrasonic velocity analysis unit 8 (light absorption analysis unit), A control system 11 including an envelope data extraction unit 14, a signal of interest extraction unit 15, a B-mode signal processing unit 9, a DSC 10 (digital scan converter), and a display device 12 are provided.

  While the probe 5 is pressed against the subject 100, an ultrasonic signal is transmitted from the linear array probe 2, and infrared light (wavelength 809 nm) is appropriately irradiated as excitation light from the infrared laser light source 3. Is done. The infrared laser light source 3 is controlled to be turned on by the ultrasonic velocity analysis unit 8. The wavelength of the excitation light is not limited to this, and any wavelength may be used as long as the gold nanorod 110a can absorb light and can pass through the subject. Specifically, excitation light including light in the wavelength range of 700 nm to 900 nm is suitable.

The linear array probe 2 has a plurality of transducers arranged in a straight line, and each transducer is excited by a drive signal from the transmission / reception unit 6 to generate an ultrasound signal. An ultrasonic echo signal from the inside of the subject is returned to the transmission / reception unit 6. The scanning control unit 7 scans a plurality of (for example, 345) ultrasonic signals by sequentially switching transducers that transmit and receive waves.
The reception signal (ultrasonic echo signal) of the linear array probe 2 having such a structure is input to the B-mode signal processing circuit 9 and the ultrasonic velocity analysis unit 8. The B-mode signal processing circuit 9 performs a well-known B-mode tomographic image forming process on the received signal to form a tomographic image in the beam scanning range and writes it in the DSC 10.

  On the other hand, the ultrasonic velocity analysis unit 8 analyzes the received signal (ultrasonic echo signal) and forms an image of the distribution of ultrasonic velocity changes in the beam scanning range. At that time, the envelope data extraction unit 14. Control the interest signal section extraction unit 15.

  The envelope data extraction unit 14 performs a process of executing an envelope process for extracting an envelope for each waveform of the ultrasonic echo signal after light irradiation when the received signal is not irradiated. The envelope processing calculation itself is performed using known software. FIG. 2A is an example of envelope data, which is extracted from the ultrasonic echo signal shown in FIG.

  The interest signal section extraction unit 15 performs a process of extracting an interest signal section for calculating a change in ultrasonic velocity from the entire extracted envelope data. That is, a section including a signal peak on the envelope data is extracted as a signal section of interest. At this time, a processing time may be shortened by setting a threshold value in advance, extracting only signal peaks equal to or higher than the threshold value, and removing small peaks as artifacts.

  Specifically, the process of extracting the interest signal section from the envelope data is performed as follows. As shown in FIG. 3 (a), comparison is made with respect to each data (set as M = ± 160 points in FIG. 3) within a predetermined section M centered on one maximum point j on the envelope data. When the central maximum point is the maximum value in the predetermined interval M, the predetermined interval M centering on the maximum point j is extracted as one of the interest signal intervals. If the central maximum point j ′ is not the maximum value in the predetermined section M as shown in FIG. 3B, the section M is not extracted as an interest signal section, and the next maximum point is not extracted. Move the section so that becomes a new center, and repeat the same operation. For example, in the example of FIG. 2, four sections are extracted by this method. Except for the interest signal section, it is processed as an artifact.

  Then, the ultrasonic velocity analysis unit 8 performs ultrasonic echoes at the time of non-irradiation and after light irradiation for the portion of the ultrasonic echo signal (colored portion in FIG. 2B) corresponding to each extracted interest signal section. The signal cross-correlation ΔM is calculated. This cross-correlation calculation can also be performed using known software. The ultrasonic velocity analysis unit 8 performs the same analysis on the signal sections of interest of all the 345 ultrasonic beams that have been measured, and acquires the cross correlation data ΔM. The acquired cross-correlation data ΔM represents the waveform shift amount before and after the light irradiation of the ultrasonic echo signal, and ΔM / M represents a change in the ultrasonic velocity. Then, based on the calculated ΔM / M, a tomographic image (optical tomographic image) is created and displayed on the display device 12.

Although detailed explanation is omitted, when displaying as an image of a temperature change (ΔT) rather than an image of an ultrasonic velocity change before and after the light irradiation, the temperature correction term of the following equation (1) is added accurately. It is converted into an image with the collected data.

ΔT = (4.821−0.095124T + 0.00040623T ² ) ⁻¹ · (ν · ΔM / M) (1)
Here, T is temperature (° C.), and ν is sound velocity (m / s).

(Operation example)
Next, an operation example by the optically assisted ultrasonic velocity change imaging apparatus 1 will be described using the flowchart of FIG.
The photothermal conversion substance 110a containing gold nanorods is distributed and labeled in the region of interest of the subject (S101).
The probe 5 is set toward the observation area of the subject and observation is started. A control signal for irradiating light to the infrared laser light source 3 is sent (S102). Thereby, the subject 100 is irradiated with infrared light from the infrared laser light source 3.

Then, after a lapse of a predetermined time from the start of irradiation, the scanning control unit 7 sequentially sends a signal to the transmission / reception unit 6 to drive the linear array probe 2 to transmit a pulsed ultrasonic signal and to the subject 100. An ultrasonic echo signal that is a received signal from the receiver is received (S103). Here, the predetermined time from the start of light irradiation to the start of ultrasound transmission / reception is the time required for the region of interest 110 in which the gold nanorods of the subject 100 are distributed to absorb sufficient light energy, and is observed in advance through experiments or the like. And set in a storage unit (not shown) of the control system 11. The scanning control unit 7 refers to this and adjusts the transmission / reception timing.
And the waveform of the ultrasonic echo signal (reception signal) acquired in the light irradiation state is memorize | stored as an ultrasonic echo signal after light irradiation (S104).

When storage of the received waveform of the ultrasonic echo signal after light irradiation ends, a control signal for stopping light irradiation is sent (S105). Thereby, the light irradiation with respect to the subject 100 is stopped.
When the temperature of the subject 100 is sufficiently lowered after a lapse of a predetermined time from the stop of the irradiation, the scanning control unit 7 sends a signal to the transmission / reception unit 6 to drive the linear array probe 2 and transmit an ultrasonic signal. At the same time, an ultrasonic echo signal is received from the subject 100 (S106). Then, the waveform of the ultrasonic echo signal (reception signal) acquired in the light irradiation stop state is stored as a non-irradiation ultrasonic echo signal (S107).

  Subsequently, envelope data is extracted with respect to the ultrasonic echo signals after light irradiation and during non-irradiation (S108). Further, a signal peak equal to or greater than a predetermined threshold is extracted from the envelope data, and an interest signal section is extracted based on the signal peak (S109). Subsequently, with respect to the ultrasonic echo signals after light irradiation and during non-irradiation, the cross-correlation between the signals in the interest signal section is calculated, and the change in the ultrasonic velocity due to the presence or absence of light irradiation in the signal section of interest is analyzed (S110). . The distribution of the ultrasonic velocity change of the analysis result is imaged and displayed on the display device (S111).

(Observation example)
Fig.5 (a) is a B mode image about an animal sample (chicken), FIG.5 (b) is the ultrasonic velocity distribution image by this invention in the same site | part about the same sample. However, a semiconductor laser having an excitation light wavelength of 809 nm is used as the light source, and the irradiation time is observed at intervals of 10 seconds from 10 seconds to 50 seconds. In this sample, gold nanorods are distributed at a depth of about 20 mm from the surface.
The image with the shortest irradiation time of 10 seconds is still unclear because the temperature change is still small, but with the image after 20 seconds, the temperature change becomes sufficiently large, the positions where the gold nanorods are distributed become black, and the surroundings It can be identified. Also, almost no ghost image appears.

(Comparative example)
Similarly, FIG. 6A is a B-mode image for an animal sample (chicken), and FIG. 6B is an ultrasonic velocity distribution image according to the present invention at the same site for the same sample. As this light source, a semiconductor laser having an excitation light wavelength of 532 nm is used, and observation is performed by changing the irradiation time from 10 seconds to 50 seconds at intervals of 10 seconds. Also in this sample, gold nanorods are distributed in the vicinity of a depth of 20 mm from the surface.
In this comparative example, no signal appears at a position where gold nanorods are distributed for any irradiation time of 10 seconds to 50 seconds. This is because light with an excitation light wavelength of 532 nm is absorbed near the surface and is not excited because the excitation light does not reach the position of the gold nanorod, and no temperature change occurs at the position of the gold nanorod.

  As described above, when gold nanorods are used as a photothermal conversion substance, the excitation light wavelength is a wavelength range of 700 nm to 1000 nm in which the gold nanorods can absorb light, thereby obtaining a clear ultrasonic velocity distribution image in the living body. Can do.

  The present invention can be used in a light-assisted ultrasonic velocity change imaging apparatus that displays a tomographic image of a change in a subject before and after light irradiation.

1 is a block diagram showing a configuration of a light-assisted ultrasonic velocity change imaging apparatus that is an embodiment of the present invention. The figure which shows an example of an envelope. The figure explaining the example of extraction of an interest signal area. The flowchart which shows the operation | movement procedure of observation by the optically assisted ultrasonic velocity change imaging apparatus which is one Embodiment of this invention. The figure which shows the example of the B mode image by an animal sample, and an ultrasonic velocity change image. The figure which shows the example of the B mode image by an animal sample, and an ultrasonic velocity change image. The block diagram which shows the structure of the conventional optically-assisted ultrasonic velocity change imaging apparatus. The figure which shows an example of a B mode image. The figure which shows an example of the received waveform of an ultrasonic echo signal. The figure explaining the example of extraction of an interest signal area. The figure explaining the signal processing implemented with the conventional optical assist ultrasonic velocity change imaging apparatus. The figure which shows the example of the B mode image and ultrasonic velocity change image by a biological pseudo sample. The figure which shows the example of an ultrasonic velocity change image by this invention.

Explanation of symbols

1: Optically assisted ultrasonic velocity change imaging device 2: Linear array probe 3: Infrared laser light source 5: Probe 8: Ultrasonic velocity analysis unit 12: Display device 14: Envelope data extraction unit 15: Interest signal segment extraction Part 110a: Gold nanorod (photothermal conversion material)

Claims (4)

An ultrasonic transmission / reception mechanism for transmitting an ultrasonic signal to the observation region of the subject and receiving an ultrasonic echo signal from the observation region;
A photothermal conversion material containing gold nanorods distributed in a region of interest in the observation area;
A light source that is transmissive to the region of interest and that irradiates the observation region with excitation light having a wavelength that is absorbed when the light-to-heat conversion substance is irradiated;
Extracts the envelopes of the signal waveforms of the non-irradiated ultrasonic echo signal received from the observation region and the post-irradiation ultrasonic echo signal received from the observation region when the excitation light is not irradiated. An envelope data extraction unit,
An interest signal interval extraction unit that extracts an interest signal interval in the signal waveform of each of the non-irradiation ultrasonic echo signal and the light irradiation ultrasonic echo signal based on the extracted envelope;
Ultrasonic velocity analysis that displays the tomographic image of the distribution of the ultrasonic velocity change by obtaining the ultrasonic velocity change based on the signals in the respective interest signal sections of the non-irradiation ultrasonic echo signal and the post-irradiation ultrasonic echo signal. And an optically assisted ultrasonic velocity change imaging apparatus.   The light-assisted ultrasonic velocity change imaging apparatus according to claim 1, wherein the photothermal conversion substance is a drug labeling substance distributed to a site of interest by a drug delivery system.   The light-assisted ultrasonic velocity change imaging apparatus according to claim 1, wherein the light source is a light source that irradiates at least a part of wavelength light in a wavelength range of 700 nm to 1000 nm as excitation light. (A) Distributing a photothermal conversion substance containing gold nanorods to a site of interest in an observation region of a subject (excluding a human),
(B) A light source that irradiates the observation region with excitation light having a wavelength that can be transmitted to the region of interest and that is absorbed when the light-to-heat conversion substance is irradiated is not irradiated with the excitation light. In two states, the state and the state irradiated with excitation light, an ultrasonic signal is transmitted to the observation region of the subject and an ultrasonic echo signal from the observation region is received,
(C) Signal waveforms of the non-irradiation ultrasonic echo signal received from the observation region in the state where the excitation light is not irradiated and the post-light irradiation ultrasonic echo signal received from the observation region in the state after the excitation light irradiation Extract the envelope of
(D) extracting a signal section of interest in the signal waveform of each of the non-irradiation ultrasonic echo signal and the post-light irradiation ultrasonic echo signal based on the extracted envelope;
(E) Light for obtaining a tomographic image relating to the distribution of the ultrasonic velocity change by obtaining the ultrasonic velocity change based on the signals in the respective interest signal sections of the non-irradiation ultrasonic echo signal and the post-irradiation ultrasonic echo signal. Display method of assist ultrasonic velocity change image.