JP2004261245A - Ultrasonograph - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To measure a position or posture of an ultrasonic probe more precisely. <P>SOLUTION: A magnetic field generator 30 and a magnetic field detector 32 measure the three-dimensional coordinates and direction of the ultrasonic probe 10 at each of the respective moving positions of the ultrasonic probe 10 and utilize these measured values to calculate the acquisition position or image surface direction of each of tomographic images. A three-dimensional image forming part 38 utilizes the calculation result to combine tomographic image data to form a tree-dimensional image. The timing for generating/detecting the magnetic field by the magnetic field generator 30 and the magnetic field detector 32 is controlled by a timing control part 36. The timing control part 36 also controls the transmitting-receiving timing of ultrasonic waves by the transmission-reception part 12 to prevent the mutual interference of the transmitting-receiving operation of ultrasonic waves and the generation/detection operation of the magnetic field. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an ultrasonic diagnostic apparatus, and more particularly to an ultrasonic diagnostic apparatus that uses information on the position and orientation of an ultrasonic probe.
[0002]
[Prior art]
While moving the ultrasound probe on the patient's body surface, it transmits and receives ultrasonic waves to acquire two-dimensional tomographic images of the tissue inside the patient one after another, and three-dimensional tissue from multiple acquired two-dimensional tomographic images. 2. Description of the Related Art An ultrasonic diagnostic apparatus that forms a stereoscopic image is known. In such an ultrasonic diagnostic apparatus, generally, an ultrasonic probe is manually moved by an examiner. Therefore, it is desirable to form a three-dimensional stereoscopic image in consideration of the acquisition position and the image plane direction (normal direction of the image plane) of each two-dimensional tomographic image.
[0003]
For this reason, in the conventional ultrasonic diagnostic apparatus, the acquisition position and image plane direction of each two-dimensional tomographic image are calculated by measuring the position and orientation of the ultrasonic probe, and a three-dimensional stereoscopic image is calculated based on the calculation result. (For example, see Patent Document 1).
[0004]
[Patent Document 1]
JP-A-10-295691
[Problems to be solved by the invention]
As described above, in the conventional ultrasonic diagnostic apparatus, a three-dimensional stereoscopic image is formed based on the measurement results of the position and orientation of the ultrasonic probe. That is, accurate measurement of the position and orientation of the ultrasonic probe is the key to obtaining a good three-dimensional stereoscopic image.
[0006]
When measuring the position or orientation of the ultrasonic probe using a magnetic field, for example, by disposing a magnetic field generator near the patient and providing a magnetic field detector on the ultrasonic probe, the detected magnetic field The position and orientation of the ultrasonic probe are calculated based on On the other hand, the ultrasonic probe has a transmitting / receiving circuit for transmitting / receiving ultrasonic waves. For this reason, there is a concern that the magnetic field generated by the magnetic field generator causes electromagnetic induction in the transmission / reception circuit of the ultrasonic probe and gives noise to a reception signal obtained by transmission / reception of the ultrasonic wave. Conversely, the ultrasonic transmission / reception circuit applies a large-amplitude pulse-like voltage to the vibrator when transmitting an ultrasonic wave, so that the electromagnetic field caused by the pulse-like voltage becomes noise and causes a magnetic field detector. May be detected.
[0007]
As described above, there is concern about mutual interference between a positioning signal (for example, a magnetic field) for measuring the position and orientation of the ultrasonic probe and ultrasonic waves transmitted and received from the ultrasonic probe. Therefore, by reducing this mutual interference and desirably completely eliminating the mutual interference, it is expected that the accuracy of measuring the position and orientation of the ultrasonic probe can be improved.
[0008]
Therefore, an object of the present invention is to measure the position and orientation of an ultrasonic probe with higher accuracy.
[0009]
[Means for Solving the Problems]
(1) In order to achieve the above object, an ultrasonic diagnostic apparatus according to the present invention includes a portable transducer for transmitting and receiving ultrasonic waves to a living body and outputting a reception signal, a reference point, and the transmission and reception apparatus. A transmitter for providing a positioning signal for measuring at least one of the position and the attitude of the transducer, and a transmitter provided at one of the transducers and the other of the reference point and the transducer. A detector that detects the positioning signal, and a timing control unit that controls the operation timing of the transducer, the transmitter and the transmitter, and the detection of the transmission and reception of the ultrasonic wave and the generation of the positioning signal. And a timing control means for executing the processing in a time-division manner.
[0010]
According to the above configuration, since the timing control unit time-divides the transmission and reception of the ultrasonic wave and the detection of the generation of the positioning signal, noise generated by the operation of transmitting the ultrasonic wave has an adverse effect on the detection of the generation of the positioning signal. The effect can be suppressed, and the position and orientation of the transducer can be measured more accurately. In addition, it is possible to suppress a noise or the like generated by the detection of the occurrence of the positioning signal from adversely affecting the ultrasonic image, thereby obtaining a better ultrasonic image.
[0011]
Preferably, the timing control means executes the detection of the generation of the positioning signal for each ultrasonic beam. In the above configuration, the detection of the occurrence of the positioning signal is executed, for example, once for each ultrasonic beam. The detection of the generation of the positioning signal may be executed in units of a plurality of ultrasonic beams, for example, once for every two ultrasonic beams.
[0012]
Preferably, the timing control means performs the detection of the occurrence of the positioning signal in units of an ultrasonic frame. In the above configuration, the detection of the occurrence of the positioning signal is executed, for example, once for each ultrasonic frame. The detection of the occurrence of the positioning signal may be executed in units of a plurality of ultrasonic frames, for example, once every two ultrasonic frames.
[0013]
Preferably, the transmitter generates a positioning signal set including a plurality of positioning signals having different directions, and the detector is a detection signal set corresponding to the positioning signal set, and includes a detection signal set included in the positioning signal set. A position and orientation calculation unit that outputs a detection signal set including detection results for positioning signals having different directions and calculates at least one of a position and an orientation of the transducer with respect to the reference point based on the detection signal set; It shall have further. In the above configuration, the plurality of positioning signals having different directions are, for example, positioning signals having directions corresponding to the XYZ directions in a reference coordinate system using the transmitter as a reference point. The detection signal set includes, for example, a detection result of a positioning signal having a direction corresponding to the X direction, a detection result of a positioning signal having a direction corresponding to the Y direction, and a direction corresponding to the Z direction. It is a set of detection results of the positioning signals.
[0014]
Preferably, the position and orientation calculating means calculates at least one of the position and orientation of the transducer with respect to the reference point using a calibration detection signal calibrated based on a plurality of the detection signal sets. I do. According to the above configuration, a more appropriate detection result can be extracted based on a plurality of detection signal sets obtained within a time when the transducer does not substantially move (change in position or change in attitude), The measurement accuracy of the position and orientation of the transducer is further improved. A magnetic field is suitable as the positioning signal.
[0015]
(2) In order to achieve the above object, an ultrasonic diagnostic apparatus according to the present invention includes a portable transducer that transmits and receives ultrasonic waves to and from a target tissue and outputs a reception signal; A tomographic image forming means for forming a tomographic image of the target tissue based on the signal, a magnetic field generator provided at a reference point for generating a magnetic field for positioning, and a magnetic field generator provided at the transducer for detecting the magnetic field A magnetic field detector that performs, the transmitter / receiver, timing control means for controlling the operation timing of the magnetic field generator and the magnetic field detector, and time-divides the transmission / reception of the ultrasonic wave and the detection of the generation of the magnetic field. Based on the detected magnetic field, based on the detected magnetic field, position and orientation calculation means to calculate at least one of the position and orientation of the transducer with respect to the reference point and output a position and orientation calculation value, Transmission and reception Image forming means for forming a stereoscopic image of the target tissue by combining a plurality of the tomographic images obtained by moving the tomographic image, wherein acquisition position information and an image plane of each of the tomographic images obtained from the position and orientation calculation values Stereo image forming means for combining the plurality of tomographic images based on the direction information.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
[0017]
FIG. 1 shows a preferred embodiment of an ultrasonic diagnostic apparatus according to the present invention, and FIG. 1 is a block diagram showing the entire configuration. The ultrasonic diagnostic apparatus of FIG. 1 acquires a plurality of tomographic images of a tissue, and forms a three-dimensional image of the tissue by combining the acquired plurality of tomographic images.
[0018]
The ultrasonic probe 10 is used, for example, in contact with a patient's body surface, and transmits and receives ultrasonic waves to and from a tissue in the patient's body while moving on the patient's body surface. However, the present invention can be applied to an ultrasonic probe inserted into a body cavity. The movement of the ultrasonic probe 10 may be manual or mechanical movement by an inspector. The ultrasonic probe 10 has a built-in array transducer in which a plurality of transducers are arranged and arranged. The array transducer is controlled by the transmission / reception unit 12 to form an ultrasonic beam.
[0019]
The transmission / reception unit 12 forms a scanning surface by electronically scanning the formed ultrasonic beam, acquires a reception signal in the scanning surface, and outputs the signal to the tomographic image forming unit 14. The tomographic image forming unit 14 determines each pixel value in the scanning plane based on the received signal and forms tomographic image data of a tissue in the scanning plane. The formed tomographic layer data is recorded in the data memory 16. The tomographic image data is also output to the display image forming unit 18, subjected to data processing for the display image, and displayed on the display 20 as a tomographic image of the tissue.
[0020]
The tomographic image data is generated for each moving position as the ultrasonic probe 10 moves, and the data memory 16 records tomographic image data acquired at each moving position one after another. The three-dimensional image forming unit 38 forms a three-dimensional image of the tissue by combining a plurality of tomographic image data recorded in the data memory 16. However, in each tomographic image data, an image forming position and a forming surface direction are different for each tomographic image data in accordance with a change in the position or posture of the ultrasonic probe 10 accompanying the movement. Therefore, the three-dimensional image forming unit 38 needs to combine the tomographic images in consideration of the acquisition position and the image plane direction of each tomographic image.
[0021]
In the ultrasonic diagnostic apparatus of FIG. 1, a magnetic field generator 30 and a magnetic field detector 32 are provided, and measure the three-dimensional coordinates and directions of the ultrasonic probe 10 at each moving position of the ultrasonic probe 10. Using these measured values, the acquisition position and image plane direction of each tomographic image are calculated, and the calculated results are used to combine tomographic image data.
[0022]
Known magnetic field generators 30 and magnetic field detectors 32 can be used. The magnetic field generator 30 is disposed near a patient, for example, on a bed on which the patient lies, and generates a magnetic field for positioning. The magnetic field generator 30 is provided with three magnetic field generating coils that are orthogonal to each other, and forms a fluctuating magnetic field having components in each of the XYZ directions with reference to the arrangement position of the magnetic field generator 30. For example, only the coils corresponding to the X axis and the Y axis are driven, then only the coils corresponding to the Y axis and the Z axis are driven, and then only the coils corresponding to the Z axis and the X axis are driven. A fluctuating magnetic field of different gender is formed.
[0023]
On the other hand, a magnetic field detector 32 is mounted on the outer surface of the ultrasonic probe 10 and detects a fluctuating magnetic field output by the magnetic field generator 30. The magnetic field detector 32 is provided with three magnetic field detection coils orthogonal to each other, detects a fluctuating magnetic field for each magnetic field detection coil, and outputs a detection result to the position calculation unit 34. Note that the magnetic field detector 32 may be provided inside the ultrasonic probe 10. The magnetic field detector 32 is fixedly arranged on the ultrasonic probe 10 and the magnetic field generator 30 is fixedly arranged at a specific position (reference point). The position and orientation of the ultrasonic probe 10 in the coordinate system described below can be known.
[0024]
The timing of generation / detection of a magnetic field by the magnetic field generator 30 and the magnetic field detector 32 is controlled by a timing control unit 36. The timing control unit 36 also controls the transmission / reception timing of the ultrasonic wave by the transmission / reception unit 12, and prevents the ultrasonic wave transmission / reception operation and the magnetic field generation detection operation from interfering with each other.
[0025]
Here, the control operation by the timing control unit 36 will be described with reference to FIG. In the following description, the portions described in FIG. 1 are denoted by the reference numerals in FIG. FIG. 2 shows a timing chart of various signals controlled by the timing control unit 36.
[0026]
The ultrasonic wave transmission signal 50 indicates the generation timing of the ultrasonic wave emitted from the ultrasonic probe 10, and the ultrasonic wave reception signal 52 indicates the ultrasonic wave returning to the ultrasonic probe 10. . The ultrasonic gate signal 54 is a signal indicating one period during which ultrasonic waves are transmitted and received, that is, a period for forming one ultrasonic beam, and the ultrasonic waves are transmitted and received during the period when the signal is at the Hi level.
[0027]
The transmission and reception of the ultrasonic wave is controlled by the transmission / reception unit 12. The timing control unit 36 outputs the ultrasonic gate signal 54 to the transmitting / receiving unit 12, and when the transmitting / receiving unit 12 detects a change in the ultrasonic gate signal 54 from Lo to Hi, the transmitting / receiving unit 12 controls the ultrasonic probe 10 to control the ultrasonic wave. The pulse-like ultrasonic wave indicated by the transmission signal 50 is transmitted. Immediately after the transmission of the ultrasonic wave, the reflected wave from the patient returns to the ultrasonic probe 10 as indicated by the ultrasonic wave reception signal 52. The transmission / reception unit 12 starts acquiring the received signal immediately after the transmission of the ultrasonic wave, and stops acquiring the received signal when detecting the change of the ultrasonic gate signal 54 from Hi to Lo. As shown in the ultrasonic wave reception signal 52, the level of the reflected wave from the inside of the patient gradually decreases as time passes from the transmission of the ultrasonic wave. Therefore, the ultrasonic gating signal 54 changes from Hi to Lo at a time when the level of the reflected wave becomes substantially zero.
[0028]
On the other hand, the timing controller 36 controls the magnetic field gate signal 60 output to the magnetic field generator 30 and the magnetic field detector 32 using the period when the ultrasonic gate signal 54 is Lo, that is, the period when the ultrasonic beam is not formed. To Hi. Generation / detection of a magnetic field is performed during a period when the magnetic field gate signal 60 is Hi. The magnetic field generation signal 56 indicates the timing at which the magnetic field generator 30 generates a fluctuating magnetic field. Three consecutive rectangular pulses of the magnetic field generation signal 56 indicate the generation timing of the X-directional magnetic field, the Y-directional magnetic field, and the Z-directional magnetic field in order from the left. As described above, when detecting the change of the magnetic field gate signal 60 from Lo to Hi, the magnetic field generator 30 generates an X-directional magnetic field, a Y-directional magnetic field, and a Z-directional magnetic field one after another.
[0029]
The magnetic field detection signal 58 indicates the timing of detecting the fluctuating magnetic field by the magnetic field detector 32. Three consecutive rectangular pulses of the magnetic field detection signal 58 are generated following each rectangular pulse of the magnetic field generation signal 56, and sequentially from the left, detection of an X-directional magnetic field, detection of a Y-directional magnetic field, and Z direction Each timing of the detection of the sexual magnetic field is shown. After the detection of the Z-directional magnetic field is completed, the magnetic field gate signal 60 changes from Hi to Lo. As described above, the detection of the generation of the magnetic field is executed by the magnetic field generator 30 and the magnetic field detector 32 during the period when the magnetic field gate signal 60 is Hi. The detection of the generation of the magnetic field may be executed a plurality of times during the period when the ultrasonic gate signal 54 is Lo. Since the detection of the generation of the magnetic field may be performed during a period in which no ultrasonic beam is formed, the detection may be performed once for each ultrasonic beam, or may be performed after several ultrasonic beams. Alternatively, it may be performed for each ultrasonic frame formed by a predetermined number of ultrasonic beams.
[0030]
Returning to FIG. 1, the position calculation unit 34 calculates three-dimensional coordinates (X, Y, Z) and rotation angles (θx, θy, θz) of the ultrasonic probe 10 based on the output of the magnetic field detector 32. . However, only one of the three-dimensional coordinates and the rotation angle may be calculated according to the moving state of the ultrasonic probe 10. If the ultrasonic probe 10 moves substantially in the XY plane, only the X and Y in the three-dimensional coordinates may be calculated. The three-dimensional coordinates and the rotation angle of the ultrasonic probe 10 calculated by the position calculation unit 34 are output to the three-dimensional image forming unit 38.
[0031]
The three-dimensional image forming unit 38 forms three-dimensional image data of a tissue by combining a plurality of tomographic image data recorded in the data memory 16. At this time, based on the three-dimensional coordinates and the rotation angle of the ultrasonic probe 10 at the time of acquiring each tomographic image data, the position and direction of each tomographic image data in the stereoscopic image are obtained, and the combination of the tomographic image data is obtained. Do. Further, stereoscopic image data is formed by performing data interpolation between tomographic image data and the like, and the formed stereoscopic image data is output to the display image forming unit 18.
[0032]
The display image forming unit 18 performs image processing for two-dimensional display on the stereoscopic image data. Examples of image processing for two-dimensional display include a rendering operation based on a volume rendering method. For the rendering operation based on the volume rendering method, for example, a method disclosed in Japanese Patent Application Laid-Open No. 10-33538 is suitable. The technique described in the above publication is as follows. A plurality of rays (e.g., coincident with an ultrasonic beam) are set for the three-dimensional space. The echo values are sequentially referred to for each ray, and the rendering operation is sequentially performed for each echo value. In parallel with this, integration of each opacity (opacity) is performed, and when the integrated value of the opacity becomes 1 or more, the rendering calculation for the ray is terminated. The rendering operation result at this point is determined as a two-dimensional display pixel value corresponding to the ray. By determining the two-dimensional display pixel value for each ray, a two-dimensional display image in which the tissue is transparently displayed is formed as a set.
[0033]
As described above, the display image forming unit 18 performs image processing for two-dimensional display on the stereoscopic image data output from the stereoscopic image forming unit 38 to form a two-dimensional display image. The formed two-dimensional display image is displayed on the display 20. Note that a tomographic image based on tomographic image data output from the tomographic image forming unit 14 may be juxtaposed, and a tomographic image and a two-dimensional display image of a stereoscopic image may be displayed on the display 20 at the same time. The main controller 40 is for centrally controlling each unit in the ultrasonic diagnostic apparatus of FIG. 1. To control the operation of each part.
[0034]
FIG. 3 shows a specific example regarding the arrangement of the magnetic field generator 30 and the magnetic field detector 32. In FIG. 3, a patient 70 is placed on a bed (not shown). The ultrasonic probe 10 transmits and receives ultrasonic waves 74 to and from a tissue inside the patient while moving on the body surface of the patient 70. The inspector 76 moves the ultrasonic probe 10 manually. In a diagnostic environment as shown in FIG. 3, for example, a stereoscopic image of a tissue located on the abdomen of the patient 70 is acquired.
[0035]
The magnetic field generator 30 is arranged near a patient, for example, under a bed, and generates a magnetic field 72 for positioning. On the other hand, the magnetic field detector 32 is mounted on the ultrasonic probe 10 and measures the position and orientation of the ultrasonic probe 10 by detecting the magnetic field 72. It is desirable that the magnetic field generator 30 and the magnetic field detector 32 are arranged close to each other in terms of detection sensitivity. However, the magnetic field generator 30 is not necessarily arranged below the bed, but may be fixedly arranged in the room where the diagnosis is performed.
[0036]
The magnetic field detector 32 is preferably provided inside the ultrasonic probe 10 in consideration of the operability of the ultrasonic probe 10. In the ultrasonic diagnostic apparatus according to the present embodiment, the transmission and reception of the ultrasonic wave and the detection of the generation of the magnetic field are time-divisionally performed. Avoid interference, for example, deterioration of an ultrasonic image due to noise given to the ultrasonic transmission / reception circuit by a magnetic field for positioning, and deterioration of positioning accuracy due to noise given to the magnetic field detector 32 by a pulse current at the time of ultrasonic transmission. This is suitable for a design in which the magnetic field detector 32 is built in the ultrasonic probe 10.
[0037]
【The invention's effect】
As described above, the ultrasonic diagnostic apparatus according to the present invention can more accurately measure the position and orientation of the ultrasonic probe.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an overall configuration of an ultrasonic diagnostic apparatus according to the present invention.
FIG. 2 is a diagram showing a timing chart of various signals controlled by a timing control unit.
FIG. 3 is a diagram showing a specific example regarding the arrangement of a magnetic field generator and a magnetic field detector.
[Explanation of symbols]
Reference Signs List 10 ultrasonic probe, 14 tomographic image forming unit, 30 magnetic field generator, 32 magnetic field detector, 34 position calculating unit, 38 stereoscopic image forming unit.

Claims (7)

A portable transducer that transmits and receives ultrasonic waves to and from the living body and outputs a received signal,
A transmitter that is provided at one of a reference point and the transducer, and that generates a positioning signal for measuring at least one of the position and the attitude of the transducer;
A detector provided at the other of the reference point and the transducer, and detecting the positioning signal;
Timing control means for controlling the operation timing of the transducer, the transmitter and the detector, and a timing control means for performing time division on the transmission and reception of the ultrasonic wave and the detection of the occurrence of the positioning signal, and ,
An ultrasonic diagnostic apparatus comprising: The ultrasonic diagnostic apparatus according to claim 1,
An ultrasonic diagnostic apparatus, wherein the timing control means executes the detection of the occurrence of the positioning signal for each ultrasonic beam. The ultrasonic diagnostic apparatus according to claim 1,
The ultrasonic diagnostic apparatus, wherein the timing control unit performs the detection of the occurrence of the positioning signal in units of an ultrasonic frame. The ultrasonic diagnostic apparatus according to any one of claims 1 to 3,
The transmitter generates a positioning signal set including a plurality of positioning signals having different directions,
The detector is a detection signal set corresponding to the positioning signal set, and outputs a detection signal set including detection results for different positioning signals having different orientations in the positioning signal set,
Based on the detection signal set, further comprising a position and orientation calculation means for calculating at least one of the position and orientation of the transducer with respect to the reference point,
An ultrasonic diagnostic apparatus, comprising: The ultrasonic diagnostic apparatus according to claim 4,
The position and orientation calculating means calculates at least one of the position and the orientation of the transducer with respect to the reference point using a calibration detection signal calibrated based on the plurality of detection signal sets. Ultrasound diagnostic equipment. The ultrasonic diagnostic apparatus according to any one of claims 1 to 5,
An ultrasonic diagnostic apparatus, wherein the positioning signal is a magnetic field. A portable transducer that transmits and receives ultrasound to and from the target tissue and outputs a received signal,
Based on the received signal, tomographic image forming means for forming a tomographic image of the target tissue,
A magnetic field generator that is provided at a reference point and generates a magnetic field for positioning;
A magnetic field detector provided in the transducer, for detecting the magnetic field;
Timing control means for controlling the operation timing of the transducer, the magnetic field generator and the magnetic field detector, the timing control means performing time-divisionally executing the transmission and reception of the ultrasonic wave and the detection of the generation of the magnetic field When,
Based on the detected magnetic field, position and orientation calculation means for calculating at least one of the position and orientation of the transducer with respect to the reference point and outputting a position and orientation calculation value,
A three-dimensional image forming unit that forms a three-dimensional image of the target tissue by combining a plurality of the tomographic images obtained by moving the transducer, and an acquisition position of each of the tomographic images obtained from the position and orientation calculation values Stereoscopic image forming means for combining the plurality of tomographic images based on information and image plane direction information,
An ultrasonic diagnostic apparatus comprising:

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