The present invention relates to a photoacoustic measuring device and method of measuring a photoacoustic wave.
Various proposals have so far been made for a technique of generating image data using light, and one of the proposals is a Photoacoustic Tomography (hereinafter “PAT”). PAT shows usability for diagnosis of skin cancer and breast cancer in particular, and receives an increasing expectation as a medical device in place of ultrasonic diagnostic devices, X-ray devices and MRI devices which were conventionally used for those diagnoses.
PAT visualizes in vivo information by measuring a photoacoustic wave, which is generated when a body tissues is irradiated with measuring beam such as visible light or near-infrared light and a light absorbing material inside the living body, particularly, the substance such as hemoglobin in blood, absorbs energy and instantaneously swell. This PAT technique enables quantitative and three-dimensional measurement of an optical energy absorption density distribution, that is, a density distribution of a light absorbing material in the living body.
Generally, benignancy and malignancy of breast cancer diagnosis in the department of mammary gland is comprehensively made based on a result of palpation or using a plurality of modalities as exemplified above. One of the critical grounds for this diagnosis is a diagnostic imaging result as to whether or not an angiogenesis generated by a cancer occurs. A photoacoustic image obtained from a breast cancer site, where the blood flow is increased compared to normal tissues due to the angiogenesis, potentially has better detectability than measurement using conventional ultrasonic diagnostic devices, X-ray devices and MRI devices. Further, since PAT uses light to generate diagnostic image data, it enables non-invasive diagnostic imaging without exposure to radiation, and consequently, it provides a greater advantage in terms of the burden of a patient, and it is expected for use in screening or early diagnosis of a breast cancer in place of X-ray devices of which repetitive use in diagnosis is seen to be difficult.
As for a technique of adequate detection of a photoacoustic wave, Patent Literature 1 and Patent Literature 2 propose techniques of identifying an attachment state of a device to an object. According to the technique disclosed in Patent Literature 1, by extracting the position of a body surface and the position of tissues in the living body from the resulting photoacoustic signal, it is possible to calculate the distance between the two extracted positions and decide an attachment state of a device to an object, based on this distance. Further, according to the technique disclosed in Patent Literature 2, by comparing the resulting photoacoustic signal and previous photoacoustic signals in a device which repeats photoacoustic measurement a plurality of times, it is possible to identify whether or not photoacoustic measurement is accurately performed, based on the change amount of a signal amplitude.
Generally, with a photoacoustic measuring device which generates three-dimensional photoacoustic image data by moving a light source and a probe along a holding plate to scan an object while holding the object by means of the holding plate, the rate that a scan time occupies in the time required for entire diagnosis is not small. When a scan area determined in the device is measured at a full size, a measuring operation of the entire scan area is conducted irrespectively of the presence of an object in a scanned area, and therefore a long time is uniformly required per diagnosis. At the same time, the object takes a load more than necessary. Therefore, there is a demand to reduce the scan time as much as possible. To reduce the scan time, it is effective to adapt the measuring operation to the object. Then, it is necessary to take a measure of identifying the presence of an object using, for example, an optical sensor or pressure sensor and controlling a scanning operation, or a measure of specifying an effective scan area in advance. However, when a method of using these measures is adotped, a new configuration is necessary, which makes the device larger. However, there is a request to remove these configurations as much as possible.
Patent Literatures 1 and 2 disclose methods using time out and a method of making identification by comparison with previous measurement results as a technique of identifying the presence of an object in generating photoacoustic image data. However, adaption of the measuring operation including scan to the presence of the object is not assumed. Further, the method using time out requires time to make identification, and the method of making comparison with previous measurement results requires multiple times of measurement for the identification. That is, it has been difficult to say that these related arts are sufficiently easy as techniques of identifying the presence of an object using a photoacoustic wave generated by irradiated light.
In light of the foregoing, features of the photoacoustic measuring device according to the present invention which measures a photoacoustic wave generated by radiating light include the following configuration. The photoacoustic measuring device has: a irradiating unit which irradiates an object with light; a holding unit which holds the object by a holding plate; a detecting unit which detects the photoacoustic wave generated by the light irradiated from the irradiating unit; and an analyzing unit which analyzes the photoacoustic signal generated as a result of detecting the photoacoustic wave in the detecting unit, in which the analyzing unit analyzes the photoacoustic signal to acquire information concerning a change of signal intensity of a component of a photoacoustic signal of the photoacoustic wave produced in at least one of an interface between the detecting unit and the holding plate and an interface between the holding plate and object, and identify a presence of the object.
Further, in light of the foregoing, features of the photoacoustic measuring method according to the present invention of measuring a photoacoustic wave generated by radiating light include the following configuration. That is, the photoacoustic measuring method includes: irradiating an object held by a holding plate with light; detecting the photoacoustic wave generated by irradiating light using a detecting unit; and analyzing a photoacoustic signal generated as a result of detecting the photoacoustic wave, in which, in the analyzing, the photoacoustic signal is analyzed to acquire information concerning change of a signal intensity of a component of a photoacoustic signal of a photoacoustic wave produced in an interface between the detecting unit and the holding plate and an interface between the holding plate and the object, and identify a presence of the object.
According to the present invention, the photoacoustic measuring device which acquires a photoacoustic wave while holding an object by means of a holding plate identifies the presence of an object, based merely on signal characteristics of a photoacoustic signal to be detected, so that it is possible to easily make identification in a comparatively short time. Consequently, by, for example, adapting the measuring operation to the object according to a result of this identification, that is, controlling, for example, a scanning operation and an operation of processing a photoacoustic signal after photoacoustic measurement, it is possible to facilitate photoacoustic measurement.
Features of the present invention include analyzing a photoacoustic signal of a photoacoustic wave detected by a detecting unit to acquire characteristics of the photoacoustic signal seen in the interface between the detecting section and holding plate and/or an interface between the holding plate and object, that is, information concerning a change of a signal intensity, to thereby identify the presence of an object. Based on this idea, the photoacoustic measuring device and method according to the present invention employ the basic configuration as described above. With the present invention employing this configuration, the detecting unit which is an electromechanical transducer can use any system (for example, a converting device using piezoceramic, a capacitance type Capacitive Micro-Machined Ultrasonic Transducer (CMUT), a Magnetic Micro-Machined Ultrasonic Transducer (MMUT) using a magnetic film or a Piezoelectric Micro-Machined Ultrasonic Transducer (for example, PMUT) using a piezoelectric thin film).
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
The first embodiment using a photoacoustic measuring device or method according to the present invention will be described with reference to the drawings. As illustrated in
With the present embodiment, the presence determining unit 106 has an analyzing unit which analyzes a photoacoustic signal generated when the detecting unit detects a photoacoustic wave, and a control unit which controls the operation of performing photoacoustic measurement of an object according to the analysis result of the analyzing unit. The analyzing unit analyzes the photoacoustic signal to acquire information concerning signal intensity change of a component of the photoacoustic signal, which change being produced in at least one of the interface between the detecting unit and holding plate and the interface between the holding plate and object, to thereby identify the presence of an object. In the present invention, the presence of an object means whether or not there is the object in an area (the front face of the detecting unit) corresponding to the position of the detecting unit in a direction vertical to a detection face of the detecting unit (cephalocaudal axis direction, namely head-to-foot direction, when the object is a human body). That is, as illustrated in
In
The irradiating unit 103 which irradiates the object 101 with the measuring beam is a member for irradiating the object with light from a laser light source, and which includes, for example, a mirror which reflects light, a lens which condenses or expands light, and changes the shape of light, a prism which diffuses, refracts or reflects light, optical fibers which propagate light or a diffusing plate. Light irradiated from a light source can be guided to the object by an optical member such as a lens or mirror, and can be propagated by an optical member such as optical fibers. As long as these optical members can irradiate the object with a predetermined shape of light, any optical member may be used. The irradiating unit is provided with the scan unit to scan along the holding plate 102. The light source (not illustrated may be the one which emits pulse light (having the width equal to or less than 100 nsec) having the center wavelength in a near-infrared area of 530 nm to 1300 nm. For the light source, a solid-state laser which can emit a pulse having the center wavelength in the near-infrared area (for example, Yttrium-Aluminum-Garnet laser or Titan-Sapphire laser) is generally used. The wavelength of the measuring beam is selected between 530 nm and 1300 nm according to a light absorbing material (for example, hemoglobin, glucose or cholesterol) in the object 101 of the measurement target. For example, hemoglobin in a new blood vessel of a breast cancer of a measurement target generally absorbs light of 600 nm to 1000 nm and, by contrast with this, light absorption of water forming the living body becomes minimum at around 830 nm. Consequently, light absorption of the hemoglobin becomes relatively large at 750 nm to 850 nm. Further, the light absorption rate changes according to the state of hemoglobin (oxygen saturation), so that it may be possible to measure a functional change of the living body by comparing this change.
The photoacoustic wave detecting unit 104 has a probe which has a plurality of acoustic wave detecting devices that receive and convert photoacoustic waves produced in the object 101 into electrical signals (photoacoustic signals), and a scan unit which moves the probe to scan along the holding plate. To improve the S/N ratio of the photoacoustic signal, preferably the object 101 is irradiated with the measuring beam in the front face of the probe. Hence, the same scan controlling is performed at the same time for both the irradiating unit 103 and optical acoustic unit 104 such that those units are arranged at opposing positions and this positional relationship is kept. The photoacoustic measuring unit 105 which amplifies the photoacoustic signal inputted from the photoacoustic wave detecting unit 104 and converts into a digital signal has the following sub-units. That is, the photoacoustic measuring unit 105 has a signal amplifying unit which amplifies the analog signal outputted from the photoacoustic wave detecting unit 104, and an A/D converting unit which converts the analog signal into a digital signal. The signal amplifying unit performs control of increasing and decreasing the amplification gain with respect to the time the photoacoustic wave takes to reach the probe after the measuring beam is irradiated, to obtain a photoacoustic image having a uniform contrast irrespectively of a measurement depth.
The presence determining unit 106 which identifies the presence of an object 101 based on signal characteristics of the measured photoacoustic signal outputs the identification result to the signal processing unit 107 and scan controlling unit 108. The method of identifying the presence of the object 101 will be described below. The signal processing unit 107 which performs correction processing, recording processing and accumulating processing of the photoacoustic signal measured by the photoacoustic measuring unit 105 performs the following processing. That is, the signal processing unit 107 performs correction of sensitivity variation due to an individual difference of the acoustic wave detecting device of a probe, complementary processing of devices which are physically or electrically defective, processing of recording the photoacoustic signal in a recording medium (not illustrated) and accumulating processing for reducing noise. The accumulating processing is performed by repeating measuring the same portion of the object 101, and it sums and averages the measurement results to reduce system noise and improve the S/N ratio of the photoacoustic signal. Further, according to the identification result of the presence determining unit 106, when there is no object 101, the above processing is not executed.
The scan controlling unit 108, which controls the positions of the irradiating unit 103 and photoacoustic wave detecting unit 104 on the holding plate 102, two-dimensionally scans the object 101 and measures the object 101 at each scan position to enable even a small probe to obtain a wide measurement range. For example, in a breast cancer diagnosis, it is possible to measure a photoacoustic image of a full breast. According to the identification result of the presence determining unit 106, scan controlling by the scan controlling unit 108 is adjusted.
An I/F 109 which transmits processed photoacoustic data to the image processing unit 120 which is an external unit and an I/F 121 of the image processing unit 120 function as an interface of performing data communication between the photoacoustic measuring device and image processing unit 120. It is preferable to employ a communication standard which can secure real time processing and enables large-capacity transmission. The image processing unit 120 as an external unit constructs and displays a photoacoustic image based on processed photoacoustic data received from the photoacoustic measuring device, and it has an I/F 121, an image constructing unit 122 and a displaying unit 123 which displays a photoacoustic image. The image constructing unit 122 constructs photoacoustic image data from processed photoacoustic data. Generally, a device such as a personal computer or work station is used which has a high computation function or graphic display function. The I/F 121 of the image processing unit 120 has the same function as the I/F 109 of the photoacoustic measuring device, and in conjunction with the I/F 109, it transmits and receives, for example, data and a control command of the device. The image constructing unit 122 converts information of a photoacoustic characteristics distribution of the object 101 into an image and constructs photoacoustic image data, based on the received processed photoacoustic data. The image constructing unit 122 can also construct information which is more suitable for diagnosis by, for the constructed image data, adjusting the brightness, correcting distortion and applying various correction processings such as clipping of an area of interest.
With the photoacoustic measuring system employing the above configuration, by generating image data based on the photoacoustic effect, it is possible to convert the photoacoustic characteristics distribution of the object 101 into an image, and present the photoacoustic image. In addition, although, in
In
With the measuring method according to the present embodiment, in
Next, illustrated in
There is no object 101 and nothing which blocks the measuring beam 201, and the measuring beam 201 irradiated from the irradiating unit 103 directly reaches the probe of the opposing photoacoustic wave receiving unit 104. In
In
As described above using
Focusing upon the scan line 402 in measurement of the full breast, there is at least a scan area in which there is no object 101 and which does not contribute to photoacoustic measurement, and the rate this scan area occupies in the entire scan area is not small. Therefore, when a measuring operation of the entire scan area is finished irrespectively of the presence of the object 101, a long time is uniformly required per photoacoustic measurement, and the subject has to take an unnecessary burden in proportion to this time. Hence, in the first embodiment, measurement control described below is performed. In
In
A scan position C indicates the position at which the device-of-interest 403 moves from an area in which there is the object 101 to an area in which there is no object 101. At the scan position C, the device-of-interest 403 misses the object 101 in addition to the device-of-interest 404, and hence, it is assumed that the scan position C is not an effective area for photoacoustic diagnosis, and the recording operation and signal processing after photoacoustic diagnosis are disabled again. In addition, since the devices-of-interest 403 and/or 404 reach the area in which there is no object 101 after passing the area in which there is the object 101 during one horizontal scan, this one horizontal scan is finished without performing subsequent horizontal scanning.
Since the device-of-interest 405 recognizes the object 101 during horizontal scan from the scan positions B to C, it is assumed that the object 101 has an expansion in the vertical direction and, consequently, vertical scan is performed. A scan position D indicates a position at which the device-of-interest 403 moves from an area in which there is no object 101 to an area in which there is the object 101, and, since it is assumed that the scan position D is an effective area for photoacoustic diagnosis, the same measurement control as in the scan position B is performed. A scan position E indicates a position at which the device-of-interest 404 moves from an area in which there is the object 101 to an area in which there is no object 101. The device-of-interest 404 misses an effective area for photoacoustic diagnosis, and therefore finishes horizontal scan similar to the scan position C, and if an expansion of the object 101 in the horizontal direction is recognized, it performs vertical scan.
A scan position F indicates the position at which the device-of-interest 404 moves from an area in which there is no object 101 to an area in which there is the object 101. Since it is assumed that the scan position F is an effective area for photoacoustic diagnosis, the same control as in the scan position B is performed. A scan position G indicates the position at which the device-of-interest 403 moves from an area in which there is the object 101 to an area in which there is no object 101. Since the device-of-interest 403 misses an effective area for photoacoustic diagnosis, horizontal scan is finished similar to the scan position C. At the scan position G, since the device-of-interest 405 does not recognize the object 101 during horizontal scan from the scan position F to G, a further expansion of the object 101 in the vertical direction is not recognized. Hence, full scan for generating photoacoustic image data is finished then.
According to the above photoacoustic measurement control, the presence of the object is identified based on the photoacoustic signals detected by a plurality of acoustic wave detecting devices, thereby performing scan controlling and skipping a measuring operation in the scan area which does not contribute to photoacoustic diagnosis. Therefore, it is possible to reduce the entire measurement time.
In step 503, the probe of the photoacoustic wave detecting unit 104 detects the photoacoustic wave produced as a result of the irradiation of the measuring beam in step 502, i.e. sampling. Further, the photoacoustic measuring unit 105 amplifies and A/D converts the photoacoustic signal detected by the photoacoustic wave detecting unit 104, and outputs this signal to the presence determining unit 106. In step 504, the presence determining unit 106 compares the signal intensities of the devices-of-interest 403, 404 and 405 with the threshold 261 set in advance for the photoacoustic signal inputted from the photoacoustic measuring unit 105, and identifies the presence of the object 101 at the position of each device. In the first embodiment, it is decided that there is no object 101 when the signal intensity exceeds the threshold 261.
In step 505, the presence determining unit 106 determines whether or not a current measurement position is an effective measurement position for photoacoustic diagnosis, based on the result of identifying the presence of the object 101 in step 504. When the measurement position is an effective measurement position, step 506 will follow. When the measurement position is not an effective measurement position, the presence determining unit 106 commands the scan controlling unit 108 to finish horizontal scan or full scan, and step 509 will follow. In step 506, the presence determining unit 106 identifies whether or not the photoacoustic measuring unit 105 detects the number of samples of photoacoustic signals required for one measurement. When detection of the required number of samples is finished, step 507 will follow. When detection is not yet finished, step 503 will follow and sampling is repeated to obtain photoacoustic signals aligned on the time axis. In step 507, the signal processing unit 107 performs correction of sensitivity variation of the acoustic wave detecting devices of the probe, complementary processing of devices which are physically or electrically defective, processing of recording the photoacoustic signal in a recording medium and accumulating processing of reducing noise.
In step 508, the scan controlling unit 108 identifies whether or not horizontal scan is finished. In this step, when a command to finish horizontal scan is received from the presence determining unit 106 or scan of the scan area at full size is finished, the scan controlling unit 108 identifies that horizontal scan is finished. When horizontal scan is finished, step 509 will follow. When horizontal scan is not finished, processing transitions to step 501 and photoacoustic measurement is repeated at the next measurement position. In step 509, the scan controlling unit 108 identifies whether or not full scan is finished. In this step, when a command to finish full scan is received from the presence determining unit 106 or full scan of the scan area at a full size is finished, the scan controlling unit 108 identifies that full scan is finished. When full scan is finished, a series of photoacoustic wave measuring operations will be finished. When full scan is not finished, processing transitions to step 510. In step 510, the scan controlling unit 108 simultaneously controls vertical scan of the irradiating unit 103 and photoacoustic wave detecting unit 104 to move a horizontal scan line to the next horizontal scan line, and continues the measuring operation.
According to the above processing, it is possible to provide capability of identifying the presence of the object based on the detected photoacoustic signal, and adapt the photoacoustic measuring operation to the shape of object 101. According to the present embodiment, in photoacoustic measurement for performing measurement with a configuration in which the light source and probe oppose to each other across the object while holding the object by means of the holding plate, it is possible to identify the presence of the object, based on change information of signal characteristics of the photoacoustic signal resulting from the presence of the object. Further, a new configuration such as an optical sensor or contact sensor for identifying the presence of the object are not necessary for realizing capability of identifying the presence of the object in one measurement. In addition, by adapting the photoacoustic measuring operation to the object based on the presence of the object, it is possible to reduce the entire photoacoustic measurement time.
Next, a second embodiment for realizing the present invention will be described. According to the first embodiment, with a configuration where the light source and probe are arranged to oppose to each other across the object 101, and the probe is irradiated with the measuring beam 201 from the opposite side, the presence of the object 101 is identified. In contrast to this, features of the second embodiment include identifying the presence of an object similar to the first embodiment in a configuration where a light source and probe are arranged in the same direction and a measuring beam is irradiated from the same side, the side on which there is the probe. Further, by extracting a photoacoustic signal in the interface required to identify the presence of the object using signal characteristics of the photoacoustic signal, an accidental detection signal such as noise is removed. The second embodiment will be described mainly concerning the above features.
The summing unit 602 which sums photoacoustic signals of a plurality of acoustic wave detecting devices forming the probe of the photoacoustic detecting unit 104 performs summarization to generate and extract an interfacial photoacoustic signal. The details will be described below. The scan controlling unit 603 controls the positions of the irradiating unit 601 and photoacoustic wave detecting unit 104 on the holding plate 102A. In this embodiment, the same scan controlling is simultaneously performed while keeping the positional relationship of the irradiating unit 601 and photoacoustic wave detecting unit 104 on the holding plate 102A. With a configuration of irradiating the measuring beam from the same side as the probe, the photoacoustic measuring system employing the above configuration can convert an optical characteristics distribution of the object 101 into an image and present a photoacoustic image by performing measurement based on the photoacoustic effect.
In
A configuration has been employed with the second embodiment where the measuring beam 701 is irradiated from the same side as the probe, so that, in
Next, the difference from the photoacoustic signal in case where there is no object 101, as illustrated in
In
A case has been described with
As described above, depending on the presence of the object 101, there is a substantial difference in characteristics of photoacoustic signals outputted from the photoacoustic wave detecting devices 203. In the second embodiment, the presence determining unit 106 identifies the presence of the object 101, based on change information of these signal characteristics.
The above identification may be made based on information concerning change of characteristics of the interfacial photoacoustic signal outputted from one acoustic wave detecting device 203, or interfacial photoacoustic signals may be extracted from outputs of a plurality of acoustic wave detecting devices.
In
Although cases have been described here where, for ease of description, photoacoustic signals of the two acoustic wave detecting device 901 and acoustic wave detecting device 902 are used, actually, by using signals of a greater number of detecting devices, more precise extraction of an interfacial photoacoustic signal is enabled. Further, in such a configuration it is possible to cancel noise which is accidentally produced in one device and, consequently, it prevents error determination due to noise and it provides capability of stably identifying the presence of an object. In the present embodiment, the above method of identifying the presence of an object is applied to the extracted interfacial photoacoustic signal.
As described above, by taking an advantage of characteristics that the photoacoustic wave produced in the interface is a planar wave, and extracting only a component of the interfacial photoacoustic signal required to identify the presence of an object and identifying the presence of an object, it is possible to reduce the influence of accidental noise and to provide capability of stable identification.
The photoacoustic detecting unit 104 starts scanning from original point of scan (scan position A). At the scan position A, since there is no object 101 (all device groups-of-interest 1002 do not recognize the object 101), the recording operation and signal processing of the photoacoustic signal are skipped and the scan speed is increased. Between the scan positions A to B after horizontal scan is started, the device group-of-interest 1002 does not recognize an object, and hence the above horizontal scan is continued. The scan position B indicates the position at which the device group-of-interest 1002 transitions from an area in which there is no object 101 to an area in which there is the object 101. From the scan position B, since the device group-of-interest 1002 enters an area in which there is the object 101, it is assumed that the scan position B is an effective area for photoacoustic diagnosis, and the recording operation and signal processing of a photoacoustic signal are executed and the scan speed is decreased to a suitable speed for photoacoustic wave measurement.
The scan position C indicates the position at which the device group-of-interest 1002 transitions from an area in which there is the object 101 to an area in which there is no object 101. From the scan position C, since the scan position B misses the object 101, it is assumed that the scan position C is an effective are for photoacoustic diagnosis, and the recording operation and signal processing of a photoacoustic signal are skipped and the scan speed is increased to perform the same scan controlling as the scan position A. At the scan position D, since the device group-of-interest 1002 transitions from an area in which there is no object 101 to an area in which there is the object 101, it is assumed that the scan position D is an effective area for photoacoustic diagnosis, and the same measurement control as the scan position B is performed. Hereinafter, scan controlling and control such as signal processing are repeated based on an identification of the presence of the object 101 at each position to scan all scan areas 401.
According to the above photoacoustic measurement control, the presence of the object 101 is identifyied and the scan speed in the scan area which does not contribute to, photoacoustic diagnosis as in this embodiment, is increased, and thereby it is possible to reduce the entire measurement time. It should be noted that, since the device group-of-interest 1002 does not fully overlap the object 101 at the boundary part of the object, there is an area in which only part of devices forming the device group-of-interest 1002 recognize the object 101. In this case, since the extracted interfacial photoacoustic signal decreases as a result of sum, the above threshold 761 or 762 needs to be set while considering to which extent the boundary parts of the object are made an effective scan area.
In step 1001, the presence determining unit 106 sums a photoacoustic signal of each acoustic wave detecting device forming the device group-of-interest 1002 to extract the interfacial photoacoustic signal. In step 1002, since it is decided in step 505 that there is no object at the current measurement position and the area is not effective for photoacoustic diagnosis, the scan speed is increased. In step 1003, since it is decided in step 505 that there is an object at the current measurement position and the area is effective for a photoacoustic diagnosis, the scan speed is controlled to a suitable scan speed for measurement of photoacoustic wave. According to the above processing, it is possible to provide capability of identifying the presence of the object based on the detected photoacoustic signal, and to adapt the photoacoustic measuring operation to the object 101.
According to the present embodiment, in a photoacoustic measurement of performing measurement with a configuration in which the light source and probe are arranged on the same side while holding the object by means of the holding plate, it is possible to identify the presence of the object based on the difference in signal characteristics of a photoacoustic signal produced depending on the presence of the object. Further, by utilizing characteristics included in an optical acoustic wave that a photoacoustic wave produced in the interface is a planar wave, to extract only an interfacial photoacoustic signal required to identify the presence of the object, it is possible to reduce the influence of accidental noise, and to provide capability of stably identifying the presence of the object.
The purpose of the present invention can also be achieved by the following embodiment. That is, a storage medium (or recording medium) which stores a program code of software for realizing the function (particularly, the function of the presence determining unit forming an analyzing unit or control unit) of the above embodiments, is supplied to a system or device. Then, a computer (or Central Processing Unit (CPU) or Micro Processing Unit (MPU)) of the system or device reads and executes a program code stored in the storage medium. In this case, the read program code from the storage medium itself realizes the function of the above embodiments, and the storage medium which stores this program code configures the present invention.
Further, by executing the program code read by the computer, the operating system (OS) operating on the computer performs a part or all of actual processings based on the command of this program code. A case where the function of the above embodiments is realized by such processing is also included in the present invention. Further, the program code read from the storage medium can be written into a memory provided in a function extension unit connected to a computer or in a function extension card inserted in the computer. Then, the present invention includes that, based on the command of this program code, a CPU provided in this function extension card or function extension unit performs part or all of actual processings, and the function of the above embodiments are realized by these processings. When the present invention is applied to the above storage medium, the program code corresponding to the flowchart described above is stored in the storage medium.
One of ordinary skill in the art can easily arrive at configuring a new system by adequately combining various techniques of the above embodiments, and, consequently, the system of these various combinations also belongs to the scope of the present invention. For example, examples described in the first and second embodiments are related to the cases where the present invention is applied to the photoacoustic measuring system in which the light source is arranged only on one side of the object and a measuring beam is only irradiated from one side to perform measurement. However, a configuration where light sources are arranged on both sides of the object and measurement is performed using measuring beams from the both sides is also possible for improving a measurement depth and obtaining a high contrast photoacoustic image. With this configuration, the change of characteristics of a photoacoustic signal due to the presence/absence of an object is represented by a combination of changes of signal characteristics according to the first embodiment and second embodiment, and this information of change can be used to identify the presence of the object. Consequently, a configuration of irradiating measuring beams on an object from both sides also belongs to the scope of the present invention. Further, a light guiding unit can be arranged by providing optical fibers so as to penetrate the photoacoustic detecting unit, and an object can be irradiated with a measuring beam from this light guiding unit to identify the presence of the above object, which embodiment also belongs to the scope of the present invention. Still further, although a configuration of identifying the presence of an object based on a photoacoustic signal digitized by A/D conversion has been described, if a photoacoustic signal having a sufficient S/N ratio can be detected, detection may be made based on an analog signal before the A/D conversion.
Further, examples of photoacoustic measurement control have been described in the first and second embodiments where recording and signal processing of a photoacoustic signal are skipped according to the presence of the object, and the scan direction or scan speed is controlled. In addition to the configurations, a measurement position or measurement interval (frame rate in photoacoustic measurement) can be controlled to adapt a measuring operation to a shape of an object. Further, a diagnostic device which has a plurality of modality functions which enable, for example, ultrasonic measurement and photoacoustic measurement simultaneously may employ a configuration of controlling other diagnostic functions according to a photoacoustic identification of the presence of an object.
This application claims the benefit of Japanese Patent Application No. 2010-258498, filed Nov. 19, 2010, which is hereby incorporated by reference herein in its entirety.
Number | Date | Country | Kind |
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2010-258498 | Nov 2010 | JP | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/JP2011/076127 | 11/8/2011 | WO | 00 | 4/17/2013 |