Diagnostic ultrasound apparatus

In tomographic image data, a reference region-setting unit (30) sets a body reference region for the body of a fetus and sets a cardiac reference region for the heart of the fetus. A body shift analysis unit (50) analyzes the movement of the fetus' body in the tomographic image data using the body reference region and obtains body shift information. A cardiac motion analysis unit (60) analyzes the movement of the fetus' heart in the tomographic image data using the cardiac reference region and obtains cardiac motion information. Once body shift information and cardiac motion information are obtained in this manner, a pulse information-processing unit (70) obtains fetal pulse information on the basis of the cardiac motion information from which the body shift information has been subtracted. The pulse information obtained by the pulse information-processing unit (70) is displayed on the display unit (80).

TECHNICAL FIELD

The present invention relates to an ultrasound diagnostic apparatus which diagnoses a fetus.

BACKGROUND ART

Ultrasound diagnostic apparatuses are being used in diagnosis of a tissue or the like in a living body, and are particularly important in diagnosis of a fetus. Under such a circumstance, various techniques related to diagnosis of the fetus by the ultrasound diagnostic apparatus have been proposed. For example, Patent Document 1 discloses an epoch-making technique that can measure a time difference of motion at each site of a cardiac muscle, for a heart or the like of the fetus.

However, for example, for a fetus of an early stage such as a fetus up to 10 weeks of pregnancy, the fetus itself is still small, and the heart is also very small. Thus, diagnosis of the heart by the ultrasound diagnostic apparatus is very difficult. For example, in the M-mode measurement or Doppler measurement of the ultrasound diagnostic apparatus, it is difficult to set the cursor or the like on the heart which is very small, and, even if the cursor or the like can be set, the overall fetus may move due to respiration of the mother or the like, causing the cursor or the like to be deviated from the heart, and making it difficult to maintain the precision of the measurement related to pulse information or the like.

Because of this, an improved technique is desired for the ultrasound diagnostic apparatus which can obtain, for example, pulse information for the fetus of early stage.

RELATED ART REFERENCE

Patent Document

DISCLOSURE OF INVENTION

Technical Problem

The present invention was made in view of the above-described background, and an advantage thereof is provision of an improved technique for an ultrasound diagnostic apparatus for obtaining pulse information of a fetus.

Solution to Problem

According to one aspect of the present invention, there is provided an ultrasound diagnostic apparatus comprising: a probe that transmits and receives ultrasound to and from a diagnosis region including a fetus; a transmitting and receiving unit that obtains a reception signal of the ultrasound from the diagnosis region by controlling the probe; a reference region setting unit that sets, in image data related to the diagnosis region obtained based on the reception signal, a body reference region for a body of the fetus and sets a cardiac reference region for a heart of the fetus; a shift analysis unit that analyses a motion of the body of the fetus using the body reference region in the image data to obtain shift information of the body; a cardiac motion analysis unit that analyzes a motion of the heart of the fetus using the cardiac reference region in the image data to obtain motion information of the heart; and a pulse information processor that obtains pulse information of the fetus based on the motion information of the heart from which the shift information of the body is subtracted.

In the above-described configuration, a preferred specific example of the image data related to the diagnosis region is, for example, data of a two-dimensional B-mode image (tomographic image), but data of a color Doppler image or a three-dimensional image may alternatively be used. In addition, the shape of the reference region (the body reference region and the cardiac reference region) may take various forms. For example, for two-dimensional image data, a reference region of a two-dimensional shape (rectangular, other polygons, circular, elliptical, or the like) may be used, and, for three-dimensional image data, a reference region of a three-dimensional shape may be used. The size of the reference region is set to a size corresponding to the body or the heart of the fetus, for example, and the body reference region is preferably larger than the cardiac reference region. In addition, for analysis of the motion of the body of the fetus and the motion of the heart of the fetus, tracking with the reference region as a template, a calculation of similarity targeted to the image data in the reference region, or the like, is employed.

According to the above-described configuration, there is provided an improved technique for an ultrasound diagnosis apparatus for obtaining the pulse information of the fetus. For example, because the pulse information of the fetus is obtained based on the motion information of the heart from which the shift information of the body is subtracted, the pulse information of the fetus can be obtained while reducing, or more preferably, completely removing, the influence of the shift due to the respiration of the mother or the motion or the like of the fetus itself. With this configuration, the pulse information of the fetus of an early stage up to about 10 weeks of pregnancy, for example, can be obtained with relatively high precision.

According to another aspect of the present invention, preferably, the shift analysis unit tracks the body reference region in the image data over a plurality of time phases, to form, as the shift information, a shift signal showing the motion of the body of the fetus over the plurality of time phases; the motion analysis unit tracks the cardiac reference region in the image data over a plurality of time phases, to form, as the motion information, a motion signal showing the motion of the heart of the fetus over the plurality of time phases; and the pulse information processor obtains the pulse information of the fetus based on a difference between the motion signal and the shift signal.

According to another aspect of the present invention, preferably, the shift analysis unit tracks the body reference region in the image data over a plurality of time phases, to obtain shift information which captures a motion of the body of the fetus over the plurality of time phases; the motion analysis unit moves the cardiac reference region in the image data over the plurality of time phases to follow the motion of the body of the fetus based on the shift information, and forms, as the motion information, a similarity signal showing a similarity of the image which changes over the plurality of time phases based on the image data in the cardiac reference region which is moved; and the pulse information processor obtains the pulse information of the fetus based on the similarity signal.

According to another aspect of the present invention, preferably, the reference region setting unit sets a relatively large body reference region including a boundary between the fetus and amniotic fluid, and sets a relatively small cardiac reference region including the heart of the fetus.

Advantageous Effects of Invention

According to various aspects of the present invention, an improved technique is provided for the ultrasound diagnostic apparatus for obtaining the pulse information of the fetus. For example, according to a preferred configuration of the present invention, the pulse information of the fetus can be obtained while reducing, or more preferably, completely removing, the influence of the shift due to the respiration of the mother or the motion or the like of the fetus itself. With this configuration, the pulse information of the fetus of an early stage up to, for example, about 10 weeks of pregnancy can be obtained with relatively high precision.

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1is an overall structural diagram of an ultrasound diagnostic apparatus preferable in practicing the present invention (“present ultrasound diagnostic apparatus”). A probe10transmits ultrasound to a diagnosis region including a fetus and receives ultrasound reflected from the diagnosis region. The probe10has a plurality of transducer elements which transmit and receive ultrasound, and the plurality of the transducer elements are transmission-controlled by a transmitting and receiving unit12, to form a transmission beam. In addition, the plurality of transducer elements receive the ultrasound reflected from the diagnosis region, a signal thus obtained is output to the transmitting and receiving unit12, and the transmitting and receiving unit12forms a reception beam.

The transmitting and receiving unit12outputs a transmission signal corresponding to each of the plurality of transducer elements provided in the probe10, to form a transmission beam of the ultrasound, and scans the transmission beam. In addition, the transmitting and receiving unit12applies a phasing and adding process or the like to a reception signal obtained from each of the plurality of transducer elements of the probe10, to form a reception beam corresponding to the transmission beam which is scanned, and outputs echo data (reception signal) obtained along the reception beam.

An image forming unit20forms image data of an ultrasound image over a plurality of time phases related to the diagnosis region including the fetus based on the echo data (reception signal) obtained over the plurality of time phases. The image forming unit20forms, for example, image data of a tomographic image (B-mode image) showing the fetus for each frame (for each time phase) and over a plurality of time phases. The image data of the tomographic image formed in the image forming unit20are output to a reference region setting unit30sequentially for each frame. The image data formed in the image forming unit20are also output to a display unit80such as a monitor, and a tomographic image corresponding to the image data is displayed on the display unit80.

The reference region setting unit30sets reference regions in the image data of the tomographic image formed by the image forming unit20. The reference region setting unit30sets a body reference region for the body of the fetus and sets a cardiac reference region for the heart of the fetus. The reference region setting unit30sets the body reference region and the cardiac reference region, for example, according to a user operation which is input through an operation device40. The user operates, for example, the operation device while viewing the tomographic image shown on the display unit80so that the body reference region and the cardiac reference region are set in desired positions. Alternatively, the reference region setting unit30may analyze the image state in the tomographic image, set the body reference region for the body of the fetus, and set the cardiac reference region of the heart of the fetus.

FIG. 2is a diagram showing an example setting of a body reference region55and a cardiac reference region65. The tomographic image25shows the fetus in the mother (womb), and the fetus is surrounded by the amniotic fluid in the mother.

The body reference region55is used for analyzing the overall motion of the body of the fetus. For this purpose, the body reference region55is desirably set at a location where the motion of the body of the fetus can be easily detected. More specifically, for example, the user designates the position of the body reference region55to include a boundary between the fetus and the amniotic fluid. Alternatively, the present ultrasound diagnostic apparatus may determine the boundary between the fetus and the amniotic fluid through an image analysis process such as, for example, binarization, and designate the position of the body reference region55. The body reference region55may alternatively be set at other locations where the motion of the body of the fetus can be easily detected.

The cardiac reference region65is used for analyzing a partial motion related to the heart of the fetus. For this purpose, the cardiac reference region65is preferably set at a location where the motion of the heart of the fetus can be easily detected. More specifically, for example, the user designates the position of the cardiac reference region65so that the heart portion of the fetus having a relatively high brightness is included. Alternatively, the present ultrasound diagnostic apparatus may determine the heart portion of the fetus having a relatively high brightness by an image analysis process such as, for example, binarization, and designate the position of the cardiac reference region65. Alternatively, the cardiac reference region65may be set at other locations where the motion of the heart of the fetus can be easily detected.

In the specific example shown inFIG. 2, the body reference region55and the cardiac reference region65both have a rectangular shape, but the shapes of these reference regions may alternatively be other polygons, circles, ellipses, or the like. In addition, as shown in the specific example ofFIG. 2, the cardiac reference region65is preferably relatively small to match the size of the heart of the fetus, and the body reference region55is preferably larger than the cardiac reference region65to match the size of the body of the fetus. The body reference region55and the cardiac reference region65may partially overlap each other. In addition, for example, a configuration may be employed in which only the position of the cardiac reference region65is designated, and the body reference region55is set to surround the cardiac reference region65.

Referring again toFIG. 1, when the reference region setting unit30sets the body reference region and the cardiac reference region in the image data of the tomographic image, a body shift analysis unit50analyzes the motion of the body of the fetus using the body reference region in the image data of the tomographic image, to obtain shift information of the body. In addition, a cardiac motion analysis unit60analyzes the motion of the heart of the fetus using the cardiac reference region in the image data of the tomographic image, to obtain motion information of the heart. When the shift information of the body and the motion information of the heart are obtained in this manner, a pulse information processor70obtains pulse information of the fetus based on the motion information of the heart from which the shift information of the body is subtracted. The pulse information obtained by the pulse information processor70is displayed on the display unit80.

The process from the setting of the reference regions to obtaining the pulse information will now be described in detail. For the structures (portions) already shown inFIGS. 1 and 2, the reference numerals thereof will be referred to also in the following description.

FIG. 3is a diagram showing a specific example 1 of a process in the ultrasound diagnostic apparatus ofFIG. 1. First, when the ultrasound is transmitted and received, and the image data of the tomographic image related to the diagnosis region including the fetus are obtained, the reference region setting unit30sets the reference regions in the image data of the tomographic image (S301). For example, the body reference region55and the cardiac reference region65are set in the tomographic image of a frame which forms a standard (refer toFIG. 2).

Then, the body shift analysis unit50and the cardiac motion analysis unit60obtain image data of a tomographic image of a frame to be processed through the reference region setting unit30(S302). For example, the image data of the tomographic images of frames after the tomographic image for which the reference regions are set (standard frame) are sent to the body shift analysis unit50and the cardiac motion analysis unit60sequentially for each frame.

The cardiac motion analysis unit60tracks the cardiac reference region65in the image data of the tomographic image over a plurality of frames which are sequentially sent, to form a motion signal showing a motion of the heart of the fetus over the plurality of frames (S303). The body shift analysis unit50tracks the body reference region55in the image data of the tomographic image over a plurality of frames which are sequentially sent, to form a shift signal showing a motion of the body of the fetus over the plurality of frames (S304). The pulse information processor70forms a pulse signal of the fetus based on a difference between the motion signal and the shift signal (S305), and calculates a pulse count of the fetus based on the pulse signal (S306).

FIG. 4is a diagram showing a signal obtained in the specific example 1.FIG. 4(A)shows a waveform of a motion signal formed by the cardiac motion analysis unit60. The horizontal axis represents time; that is, frame numbers of the frames which are sequentially processed, and the vertical axis represents a movement distance of the cardiac reference region65. The cardiac motion analysis unit60executes a matching process to set, as a template, the cardiac reference region65(FIG. 2) which is set in the tomographic image of the standard frame, to search an image portion, in the tomographic image of the frame to be processed, which is most similar (having high correlation) to the image in the template, and to set the searched portion as the movement position of the template. In the tomographic image of the plurality of frames to be processed, the cardiac motion analysis unit60sequentially searches and tracks the movement position of the template.

The cardiac motion analysis unit60tracks the cardiac reference region65(template) over a plurality of frames, and calculates the movement distance of the cardiac reference region65for each frame. In other words, the cardiac motion analysis unit60calculates, for each frame, a distance from the position of the cardiac reference region65in the tomographic image of the standard frame to the movement position of the cardiac reference region65in the frame to be processed.

For example, when a plurality of pixels forming the tomographic image are arranged by an xy orthogonal coordinate system and tracking is executed in the xy orthogonal coordinate system, for each frame, the movement distance d=√(dx2+dy2) is calculated based on an amount of movement dx in the x-axis direction and an amount of movement dy in the y-axis direction. In this manner, a waveform of a motion signal shown inFIG. 4(A)is obtained.

FIG. 4(B)shows a waveform of a shift signal formed by the body shift analysis unit50. The horizontal axis represents time; that is, the frame numbers of the frames which are sequentially processed, and the vertical axis represents the movement distance of the body reference region55. The body shift analysis unit50sets, as a template, the body reference region55(FIG. 2) which is set in the tomographic image of the standard frame, and sequentially executes tracking for searching the movement position of the template in the tomographic image of a plurality of frames to be processed. Similar to the formation process of the motion signal ofFIG. 4(A), the body shift analysis unit50calculates, for each frame, a distance from the position of the body reference region55in the tomographic image of the standard frame to the movement position of the body reference region55in the frame to be processed, and forms the shift signal shown inFIG. 4(B).

FIG. 4(C)shows a waveform of a pulse signal formed by the pulse information processor70. The pulse information processor70forms the pulse signal ofFIG. 4(C)based on a difference between the motion signal ofFIG. 4(A)and the shift signal ofFIG. 4(B). More specifically, for each frame, the pulse processor70calculates a movement distance obtained by subtracting the movement distance of the shift signal from the movement distance of the motion signal, and forms the pulse signal shown inFIG. 4(C). InFIG. 4(C), the waveform of the pulse signal is enlarged in the direction of the vertical axis and is translated.

Because the pulse signal shown inFIG. 4(C)is a signal in which the shift information of the body is subtracted from the motion signal of the heart, the shift with respect to the body of the fetus is reduced, or more preferably, completely removed. Therefore, the pulse information processor70calculates the pulse count of the fetus, for example, based on the pulse signal. More specifically, for example, minimum values of the pulse signal are sequentially searched along the time axis direction which is the horizontal axis, and a time interval between adjacent minimum values is set as the time of one pulse. Because the time of one pulse may fluctuate in the time axis direction, for example, an average of times of one pulse obtained over a desired period is calculated. The pulse information processor70calculates the pulse count per unit time (heart rate) or the like, for example, based on the average of the time of one pulse.

In the calculation of the movement distances related to the signals ofFIG. 4, each of movement distances in the x-axis direction and the y-axis direction may be used. For example, as the movement signal ofFIG. 4(A), a waveform showing the movement distance in the x-axis direction over a plurality of frames and a waveform showing the movement distance in the y-axis direction over the plurality of frames may be formed. Similarly, for the shift signal ofFIG. 4(B), the waveforms for the x-axis direction and for the y-axis direction may be formed, and, as the pulse signal ofFIG. 4(C), a pulse signal related to the x-axis direction and a pulse signal related to the y-axis direction may be obtained. The pulse count may be calculated from each of the two pulse signals related to the x-axis direction and the y-axis direction. Alternatively, a combined movement distance d=√(x2+y2) may be calculated based on the movement distance x of the pulse signal related to the x-axis direction and the movement distance y of the pulse signal related to the y-axis direction, and a waveform corresponding toFIG. 4(C)may be formed based on a change with respect to time of the combined movement distance d, to calculate the pulse count. Moreover, the coordinate system is not limited to the xy orthogonal coordinate system, and, for example, the signals ofFIG. 4may be obtained using an rθ scanning coordinate system.

Referring again toFIG. 3, when the pulse count of the fetus is calculated by the pulse information processor70(S306), the value of the pulse count and the tomographic image of the fetus are displayed on the display unit80(S307). It is then determined whether or not the processes related to all frames to be processed are completed (S308), the processes from S302to S307are repeated until the processes for all frames are completed, and, when the processes for all frames are completed, the present flowchart is also completed.

FIG. 5is a diagram showing a specific example 2 of the process in the ultrasound diagnostic apparatus ofFIG. 1. First, when the ultrasound is transmitted and received and the image data of the tomographic image related to the diagnosis region including the fetus are obtained, the reference region setting unit30sets the reference regions in the image data of the tomographic image (S501). For example, in the tomographic image of a frame which forms a standard, the body reference region55and the cardiac reference region65are set (refer toFIG. 2).

Then, the body shift analysis unit50and the cardiac motion analysis unit60obtain the image data of the tomographic image of a frame to be processed through the reference region setting unit30(S502). For example, image data of the tomographic images of the frames after the tomographic image in which the reference regions are set (frame which forms the standard) are sequentially sent to the body shift analysis unit50and the cardiac motion analysis unit60for each frame.

The body shift analysis unit50tracks the body reference region55in the image data of the tomographic image over a plurality of frames which are sequentially sent, to obtain the shift information capturing the motion of the body of the fetus over the plurality of frames (S503). Based on the shift information, the cardiac motion analysis unit60moves the cardiac reference region65in the image data of the tomographic image over the plurality of frames which are sequentially sent, to follow the motion of the body of the fetus (S504). Further, the cardiac motion analysis unit60calculates similarity of the image which changes over the plurality of frames based on the image data in the cardiac reference region654which is moved, to form a similarity signal (S505). The pulse information processor70calculates the pulse count of the fetus based on the similarity signal (S506).

FIG. 6is a diagram showing a signal obtained in the specific example 2.FIG. 6(A)shows the shift information formed by the body shift analysis unit50. The horizontal axis represents time; that is, the frame numbers of the frames which are sequentially processed, and the vertical axis represents the movement distance of the body reference region55. The body shift analysis unit50executes a matching process to set, as a template, the body reference region55which is set in the tomographic image of the standard frame (FIG. 2), to search, in the tomographic image of the frame to be processed, an image portion which is most similar (having high correlation) to the image in the template, and to set the searched portion as the movement position of the template. The body shift analysis unit50sequentially searches and tracks the movement position of the template in the tomographic images of the plurality of frames to be processed.

The body shift analysis unit50tracks the body reference region55(template) over a plurality of frames, and calculates the movement distance of the body reference region55for each frame. In other words, the body shift analysis unit50calculates for each frame a distance from the position of the body reference region55in the tomographic image of the standard frame to the movement position of the body reference region55in the frame to be processed.

For example, when a plurality of pixels forming the tomographic image are arranged in an xy orthogonal coordinate system and the tracking is executed in the xy orthogonal coordinate system, a movement distance dx in the x-axis direction and a movement distance dy in the y-axis direction are obtained for each frame. In this manner, a waveform of the shift information shown inFIG. 6(A)is obtained for each of the x-axis direction and the y-axis direction.

The cardiac motion analysis unit60moves the cardiac reference region65by the same distance as the movement distance of the body reference region55in the image data of the tomographic image over the plurality of frames which are sequentially sent. In other words, the cardiac motion analysis unit60moves, for each frame, the cardiac reference region65in the x-axis direction by the same distance as the movement distance dx in the x-axis direction of the body reference region55, and moves the cardiac reference region65in the y-axis direction by the same distance as the movement distance dy in the y-axis direction of the body reference region55. With this process, the cardiac motion analysis unit60moves the cardiac reference region65to follow the movement of the body reference region55; that is, the motion of the body of the fetus.

In the tracking of the body reference region55and the movement of the cardiac reference region65, the coordinate system is not limited to the xy orthogonal coordinate system, and alternatively, for example, the re scanning coordinate system may be employed.

The cardiac motion analysis unit60calculates similarity of the image which changes over the plurality of frames based on the image data in the cardiac reference region65which is moved, to form a similarity signal. In other words, the cardiac motion analysis unit60calculates for each frame a similarity (for example, correlation) between the image data in the cardiac reference region65in the tomographic image of the standard frame and the image data in the cardiac reference region65in the frame to be processed. In this manner, the waveform of the similarity signal shown inFIG. 6(B)is obtained.

In obtaining the similarity signal ofFIG. 6(B), because the cardiac reference region65is moved to follow the motion of the body of the fetus, the influence of the shift related to the body of the fetus is reduced or more preferably completely removed in the similarity signal. Thus, the pulse information processor70assumes the similarity signal as a pulse signal, and calculates, for example, the pulse count of the fetus based on the pulse signal.

More specifically, for example, as shown inFIG. 6(C), minimum values of the pulse signal are sequentially searched along the time axis direction which is the horizontal direction, and a time interval between adjacent minimum values is set as a time of one pulse. However, because the time of one pulse may fluctuate in the time axis direction, for example, an average of the time of one pulse obtained over a desired period is calculated. The pulse information processor70calculates, for example, a pulse count per unit time (heart rate) or the like based on the average of the time of one pulse.

Referring again toFIG. 5, when the pulse count of the fetus is calculated by the pulse information processor70(S506), the value of the pulse count and the tomographic image of the fetus are displayed on the display unit80(S507). It is then determined whether or not processes for all frames to be processed are completed (S508), processes from S502to S507are repeated until the processes for all frames are completed, and, when the processes for all frames are completed, the present flowchart is also completed.

A preferred embodiment of the present invention has been described. However, the above-described embodiment is merely exemplary in every aspect, and is not intended to limit the scope of the present invention. The present invention includes various modified forms within the scope and spirit of the present invention.

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