JP2010516372A - Ultrasonic detection method and apparatus for motion using an adjustable fluid lens - Google Patents

Abstract

  To provide a practical and cost-effective way to detect motion in the human body using acoustic waves. The system 200 for detection of motion in the body includes acoustic probes 242, 100, a motion detection processor 270, a variable voltage source 290, and a controller. The acoustic probes 242,100 include acoustic transducers 244,20 and variable refractive acoustic lenses 242,10 coupled to the acoustic transducer. The variable refractive acoustic lens has at least one set of electrodes 150 adapted to adjust at least one characteristic of the variable refractive acoustic lens at least in response to a selected voltage applied across the electrodes. 160a and 160b. The motion detection processor executes an algorithm to detect motion of the target in response to acoustic energy coupled to and received by the acoustic transducer. The variable voltage source applies a selected voltage to a set of electrodes. The controller controls the variable voltage source to apply the selected voltage to the set of electrodes.

Description

  The present invention relates to an acoustic imaging method, an acoustic imaging device, and more particularly to a method and apparatus that uses an acoustic signal and an adjustable fluid lens to detect motion in the body.

  Detecting motion in the body is a technical goal in many medical imaging applications. Many imaging methods, such as computed tomography (CT), positron emission tomography (PET), or magnetic resonance imaging (MRI), can be used to obtain an imaging plane or imaging volume, the patient breath cycle, the cardiac It takes a sufficiently long time for movement or movement due to movement of the patient's muscle tissue to obtain a result that results in sub-standard image quality. In addition, there are many invasive or biopsy procedures that first determine the location of a disease state with previously acquired imaging data sets. When this procedure is performed, the placement of invasive devices (eg, radio-frequency removal needles, biopsy needles, etc.) is performed by alignment with external landmarks from a pre-collected data set. Movements that do not correlate with external landmarks, such as organ deformation due to expiratory motion, heart movement during the normal heartbeat pattern of the heart, and other sources of movement, reduce the placement accuracy of the invasive device.

  Many of these clinical problems can be solved by properly detecting motion in the body.

  To date, several methods have been used to detect motion in the body. For correction of expiratory motion, pressure sensors are sometimes used in a halter that is fixed to the patient's chest to measure the expiratory rate. At this time, in order to correct this motion, an anticipatory model that predicts the position of the patient's chest can be used.

  On the other hand, acoustic waves (specifically including ultrasound) are useful in many scientific or technical fields, such as medical diagnostics, non-destructive control of machine parts and underwater imaging. Since acoustic waves can travel through media that do not pass electromagnetic waves, acoustic waves allow for diagnostics and control that complement optical observation.

  Therefore, since ultrasound has the ability to detect deep structures and their corresponding motion, ultrasound has been proposed for measuring translational motion and deformation of internal organs. Several solutions have been explored, ranging from simple one-element transducers in Doppler or M-mode to more complex image-based approaches. For single-element acoustic transducers, the ability to detect motion is often only in the direction along the acoustic wave propagation line. This limits the measurable field of view. In this case, multiple sensors would be required to detect true deformation and 3D motion.

  An acoustic imaging device with multiple sensors includes devices that use conventional one-dimensional (“1D”) acoustic transducer arrays and fully sampled two-dimensional (“2D” using micro-electron radiation forming techniques. ") Includes both instruments that use acoustic transducer arrays.

  For instruments that use 1D acoustic transducer arrays, the acoustic transducer elements are often arranged so that the focus is optimized within a single plane. This makes it possible to focus the transmitted and received acoustic pressure waves in the axial direction (ie propagation direction) and lateral direction (ie 1D array direction). Out-of-plane (elevation) focusing is usually fixed by the geometry of the acoustic transducer. That is, the elevation height of the acoustic transducer element controls the natural focus of the array of elevation dimensions. For most medical applications, the out-of-plane (elevation) focus adds a lens that is fixed in front of the acoustic transducer array to focus most of the acoustic energy to the nominal depth of focus. It can only be changed by changing the geometry of the element at elevation height. Unfortunately, this compromise results in sub-optimal elevation focusing at different depths.

  In each of these solutions, it would be desirable to add the ability to advance the ultrasound beam in a direction not possible with existing transducer geometries.

  Therefore, it would be desirable to provide a practical and cost-effective way to detect motion in the human body using acoustic waves. In particular, the use of an electronically controllable lens system consisting of an ultrasonic compatible fluid focus lens is employed in conjunction with a single or low element count transducer to detect motion with a simple low cost solution Is possible. In addition, it would be desirable to provide a device that uses acoustic waves to detect motion in the body. However, it would be desirable to require less electronics, require fewer elements, and potentially be driven much cheaper than existing devices.

  In one aspect of the invention, a system for detecting motion in the body includes an acoustic probe, a motion detection processor, a variable voltage source, and a controller. The acoustic probe includes an acoustic transducer and a variable refractive acoustic lens coupled to the acoustic transducer. The variable refractive acoustic lens has at least one pair of electrodes that adjust at least one characteristic of the variable refractive acoustic lens in response to a selected voltage applied to the electrodes. The motion detection processor is coupled to the acoustic transducer and executes an algorithm that detects motion of the target in response to the acoustic energy received by the acoustic transducer. The variable voltage source applies a selected voltage to a set of electrodes. The controller controls the variable voltage source to apply the selected voltage to the set of electrodes.

  In another aspect of the invention, a method for detecting motion using acoustic waves comprises: (1) applying an acoustic probe to a body; and (2) detecting the acoustic energy from a target region of the body. Controlling the variable refractive acoustic lens of the probe; (3) the acoustic transducer receives an acoustic wave returning from the target region from the variable refractive acoustic lens; and (4) an electric wave corresponding to the received acoustic wave. Output a signal from the acoustic transducer, (5) create acoustic data received from the electrical signal output by the transducer, and (6) whether to focus on other target areas of the body (7) When another target area is selected, the steps (1) to (6) are repeated for the newly selected target area, and (8) When no further target area is selected, Receiving Processing the sound data and outputs the number of images one or than indicating the motion in the body.

1 illustrates one embodiment of an acoustic probe including a variable refractive acoustic lens coupled to an acoustic transducer. 1 illustrates one embodiment of an acoustic probe including a variable refractive acoustic lens coupled to an acoustic transducer. 1 shows a block diagram of an embodiment of an acoustic imaging device. 2 shows a flowchart of an embodiment of a method for controlling an acoustic imaging device.

  The invention will be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. However, the invention can be implemented in different ways and should not be construed as limiting the invention to the embodiments described herein. Instead, these examples are provided as teaching examples of the present invention.

  As used in this application, the term “acoustic” refers to sonic action, particularly including ultrasound at frequencies that exceed the normal human hearing range. In the discussion that follows, an acoustic probe that includes an acoustic imaging device and a variable refractive acoustic lens is described. In the context of the term “variable refractive acoustic lens” as used in this application, the term “lens” directs (or possibly in addition to) radiation other than light, in particular acoustic radiation (eg ultrasound). Widely defined to mean a device that focuses on. A variable refractive acoustic lens can focus acoustic waves, but such focusing is not meant to be made using only the term “lens” in this context. In general, the variable refractive acoustic lens used herein is adapted to refract an acoustic wave and can deflect and / or focus the acoustic wave.

  The variable focus fluid lens technology is a solution originally invented for the clear purpose of allowing light focusing by variation of the physical boundary of a cavity filled with a fluid having a specific refractive index. Law (see Patent Cooperation Treaty (PCT) Publication WO2003 / 069380, all of which are incorporated herein by reference as if fully set forth herein) . A process known as electrowetting, in which the fluid in the cavity moves across the conductive electrode by applying a voltage, achieves movement of the surface of the fluid. This change in surface topology refracts the light so that the path of travel changes, thereby allowing the light to be focused.

  On the other hand, ultrasonic waves spread in the fluid medium. In fact, the human body is often referred to as a fluid that cannot support high frequency acoustic waves other than compression waves. In this sense, waves are sensitive to distortion due to differences in acoustic velocity of bulk tissue propagation, but also to distortion due to sudden changes in the speed of sound at the interface. This attribute is utilized in embodiments of the acoustic probe and acoustic imaging device disclosed below.

  FIGS. 1A-B show one embodiment of an acoustic probe 100 comprising a variable refractive acoustic lens 10 coupled to an acoustic transducer 20. The variable refractive acoustic lens 10 is adapted to condition at least one acoustic signal that processes its characteristics in response to at least one selected voltage applied thereto. For example, the variable refractive acoustic lens 10 changes the elevation focus of the acoustic wave along the propagation (“focus”) axis and / or perpendicular to this plane (“deflection”), as will be described in detail later. It is beneficial to include the ability to The variable refractive acoustic lens 10 includes a housing 110, a coupling element 120, first and second flow media 141 and 142, a first electrode 150, and at least one second electrode 160a. The housing 110 may have a cylindrical shape, for example. The top end and the bottom end of the housing 110 are acoustically substantially transparent, but preferably the acoustic waves do not ooze from the side walls of the housing 110.

  The acoustic transducer 20 is preferably coupled to the bottom of the housing 110 by one or more acoustic matching layers 130. The acoustic transducer 20 is a known type in acoustic wave technology. The acoustic transducer 20 preferably comprises a 1D array of acoustic transducer elements, but in some embodiments a single transducer element can be used in place of the 1D array.

  In one embodiment, acoustic probe 100 is adapted to operate in both transmit and receive modes. In this case, in the transmission mode, the acoustic transducer 20 converts an electrical signal input input thereto into an acoustic wave output from the electrical signal input. In the reception mode, the acoustic transducer 20 converts the acoustic wave it receives into the electrical signal it outputs.

  Alternatively, in alternative embodiments, the acoustic probe 100 may be adapted to operate in a receive-only mode. In this case, the transmission transducer is provided separately.

  The coupling element 120 is preferably provided at one end of the housing 110. The coupling element 120 is designed to form a contact area when pressed against a body, such as a human body. The coupling element 120 preferably comprises a flexible sealed pocket (ie, an acoustic window) or a plastic membrane that is filled with a bonded rigid material, such as a Mylar membrane, having an acoustic impedance substantially equal to the body.

  The housing 110 encloses a sealed cavity having a volume V in which a first fluid medium 141 and a second fluid medium 142 are provided. In one embodiment, for example, the volume V of the cavity in the housing 110 is about 0.8 cm in diameter and about 1 cm high (ie, along the axis of the housing 110).

  The speeds of sound in the first fluid medium 141 and the second fluid medium 142 are each different, i.e., acoustic waves propagate in the fluid medium 141 at a different speed than in the fluid medium 142. It is. Further, the first fluid medium 141 and the second fluid medium 142 are not mixed. Thus, they always remain as separate liquid phases within the cavity. The separation of the first fluid medium 141 and the second fluid medium 142 is a contact surface or meniscus that defines the boundary between the first fluid medium 141 and the second fluid medium 142 without any solid parts. It is also advantageous that one of the two fluid media 141, 142 is conductive and the other fluid media is substantially non-conductive or electrically insulating.

In one embodiment, the first fluid medium 141 consists primarily of water. For example, it may be a saline solution with a sufficient concentration of ions to make it electrically polar or conductive. In this case, the first fluid medium 141 can include, for example, potassium and chloride ions (both having a concentration of 1 mol / L). Alternatively, it can be a mixture of water and ethyl alcohol that is substantially conductive due to the presence of ions such as sodium or potassium (for example at a concentration of 0.1 mol / L). The second fluid medium 142 can include, for example, silicone oil that does not react to an electric field. Table 1 below lists some exemplary fluids that can be used as the first fluid medium 141 or the second fluid medium 142.

  In the example of FIGS. 1A and 1B, when the fluid medium 141 is mainly made of water, at least the lower wall of the housing 110 is preferably covered with a hydrophilic coating 170. Alternatively, in another example where the fluid medium 142 is primarily water, the top wall of the housing 110 can be covered with a hydrophilic coating 170.

  The first electrode 150 is preferably provided in the housing 110 so as to be in contact with one of the two fluid media 141 and 142 that are electrically conductive. In the example of FIGS. 1A-B, it is assumed that fluid medium 141 is a conductive fluid medium and fluid medium 142 is a substantially non-conductive fluid medium. However, it should be understood that the fluid medium 141 can be a substantially non-conductive fluid medium and the fluid medium 142 can be a conductive fluid medium. In this case, the first electrode 150 will be placed in contact with the fluid medium 142. Also in this case, the concave surface of the contact meniscus shown in FIGS. 1A-B will be reversed.

  On the other hand, the second electrode 160 a is provided along the side wall (side surface) of the housing 110. Optionally, two or more second electrodes 160a, 160b, etc. may be provided along the side wall (or walls) of the housing 110. Electrodes 150 and 160a are connected to two outputs of a variable voltage source (not shown in FIGS. 1A-B).

  In operation, the variable refractive acoustic lens 10 operates in conjunction with the acoustic transducer 20 as follows. In the exemplary embodiment of FIG. 1A, when the voltage applied between the electrodes 150 and 160a by the variable voltage source is zero, the contact surface between the first fluid medium 141 and the second fluid medium 142 is the meniscus M1. It is. In a known manner, the shape of the meniscus is determined by the surface properties inside the lateral walls of the housing 110 and the attributes of the first fluid medium 141 and the second fluid medium 142. In particular, when the density of the first fluid medium 141 and the second fluid medium 142 is substantially equal, the shape is substantially a part of a sphere. Since the acoustic wave W has different propagation speeds in the first fluid medium 141 and the second fluid medium 142, the volume V filled with the first fluid medium 141 and the second fluid medium 142 operates as a lens for the acoustic wave W. . Therefore, the diffusion of the acoustic wave W entering the probe 100 changes when it intersects the contact surface between the first fluid medium 141 and the second fluid medium 142. The focal length of the variable refractive acoustic lens 10 is the distance from the acoustic transducer 20 to the acoustic wave source point at which the acoustic wave is planarized by the lens variable refractive acoustic lens 20 before it strikes the acoustic transducer 20.

  When the voltage applied by the variable voltage source between the electrodes 150 and 160a is set to a positive or negative value, the shape of the meniscus changes depending on the electric field between the electrodes 150 and 160a. In particular, a force is applied to the side of the first fluid medium 141 adjacent to the contact surface of the first fluid medium 141 and the second fluid medium 142. Due to the polarity effect of the first fluid medium 141, depending on the polarity of the applied voltage and the relative surface tension of the fluid, it tends to move closer or further away from the electrode 160a. In the example of FIG. 1B, M2 indicates the shape of the contact surface when the voltage is set to a value other than zero. This change in the shape of the electrically controlled contact surface is called electrowetting. When the first fluid medium 141 is conductive, the change in shape of the contact surface between the first fluid medium 141 and the second fluid medium 142 when a voltage is applied is the same as described above. Since the shape of the contact surface changes, the signal processing characteristics of the variable refractive acoustic lens 10 change when the voltage is not zero.

  PCT Publication WO 2004-051323 is about tilting the meniscus of a variable refractive fluid lens (assuming that it is fully incorporated herein by reference as if it were fully described herein). Explains in detail.

  FIG. 2 is a block diagram of one embodiment of an ultrasonic motion detection system 200 that uses an acoustic probe that includes a variable refractive acoustic lens coupled to an acoustic transducer that detects motion within the body. The ultrasonic motion detection system 200 includes a processor / controller 210, a transmission signal source 220, a transmission / reception switch 230, an acoustic probe 240, a filter 250, a gain / attenuation stage 260, a motion detection processor 270 and a variable voltage source 290. On the other hand, the acoustic probe 240 includes a variable refractive acoustic lens 242 coupled to an acoustic transducer 244.

  As described above with respect to FIG. 1, the acoustic probe 240 can be implemented as the acoustic probe 100. In this case, the two fluids 141 and 142 of the variable refractive acoustic lens 242 have matching impedances, but it is beneficial that the speed of sound is different. This will allow maximum forward propagation of the acoustic wave while allowing control of the beam direction. The fluids 141, 142 preferably have a sound velocity selected to maximize acoustic wave focusing and refraction flexibility.

  The acoustic transducer element 244 preferably comprises a 1D array of acoustic transducer elements (in another embodiment it may comprise a single transducer element).

  In operation, the ultrasonic motion detection system 200 operates as follows. The processor / controller 210 controls the voltage applied to the electrodes of the variable refractive acoustic lens 242 by the variable voltage source 290. As described above, this sequentially changes the refraction of the variable refractive acoustic lens 242.

  When the meniscus surface defined by the two fluids of the variable refractive acoustic lens 242 reaches the correct topology, the processor / controller 210 controls the transmit signal source 220 to apply to the acoustic transducer 244. To generate a desired acoustic wave. In some cases, transmit signal source 220 is controlled to enable short time (broadband) signals operating in M-mode (perhaps pulse wave Doppler or other related signals for other imaging techniques). (Short tone-burst) can be generated. A typical use would be to image a surface with a fixed elevation focus that is adjusted to an area of clinical interest. The acoustic signal can be a normal echo, a time domain resolution signal such as M-mode or PW Doppler, or even a non-time domain resolution signal such as CW Doppler. Another typical use may be to adjust the focus of the ultrasound transducer to maximize the signal associated with tissue movement.

  The processor / controller 210 preferably executes an algorithm to scan the volume (eg, scan one surface at a time) for a time interval that is short enough to resolve the motion that occurs in the volume. . That is, the data for the three-dimensional volumetric view includes a series of energy applied to the acoustic transducer 244 and the electrodes of the variable refractive acoustic lens 242 to properly advance the acoustic wave in at least one direction. It is obtained by appropriately controlling the voltage. This controls the refraction of the acoustic wave in the second direction and / or depth of focus of the acoustic wave. The acoustic data received by the acoustic probe 240 for a series of measurements at different planes and / or depths is passed to the motion detection processor 270. The motion detection processor 270 processes the received acoustic data to provide motion in the region being scanned by the ultrasonic motion detection system 200, such as motion due to patient expiration cycles, heart motion or patient muscle tissue motion. An image and / or other output representing or indicating is generated.

  In the embodiment of FIG. 2, the acoustic probe 240 is adapted to operate in both transmit and receive modes. As described above, in another embodiment, the acoustic probe 240 can alternatively be adapted to operate in a receive-only mode. In this case, a transmission transducer can be provided separately and the transmission / reception switch 230 can be omitted.

  FIG. 3 shows a flowchart of one embodiment of a method 300 for controlling the operation of the ultrasonic motion detection system 200.

  In a first step 305, the acoustic probe 240 is coupled to the patient.

  Next, at step 310, the processor / controller 210 controls the voltage applied to the electrodes of the variable refractive acoustic lens 242 by the variable voltage source 290 to begin sweeping the desired volume measurement region.

  Next, in step 315, the processor / controller 210 controls the transmission signal source 220 and the transmission / reception switch 230 to apply a desired electrical signal to the acoustic transducer 244. The variable refractive acoustic lens 242 operates in conjunction with the acoustic transducer 244 to generate an acoustic wave and deflect the acoustic wave and / or focus the acoustic wave to the target area of the patient.

  Subsequently, at step 320, the variable refractive acoustic lens 242 operates in conjunction with the acoustic transducer 244 to receive acoustic waves returning from the patient's target area. At this time, the processor / controller 210 controls the transmission / reception switch 230 to connect the acoustic transducer 244 to the filter 250, and outputs an electrical signal from the acoustic transducer 244 to the filter 250.

  Next, in step 330, the filter 250, the gain / attenuator stage 260 and the acoustic signal processor 270 together condition the electrical signal from the acoustic transducer 244 and create the acoustic data received therefrom.

  Next, at step 340, the received acoustic data is stored in a memory (not shown) of the motion detection processor 270 of the ultrasonic motion detection system 200.

  Next, at step 345, the processor / controller 210 determines whether to scan in other directions, depths and / or planes as well. If so, at step 350, a scan area is selected and this processing step 310 is repeated. If not, then in step 355, motion detection processor 270 processes the received acoustic data (perhaps in conjunction with processor / controller 210) to produce a patient expiration cycle, heart motion or An image and / or other output is created that represents or shows motion within the region being scanned by the ultrasonic motion detection system 200, such as motion due to movement of patient muscle tissue.

  Finally, at step 360, the ultrasonic motion detection system 200 outputs an image representing the detected motion and / or other output.

  While preferred embodiments are disclosed herein, many variations are possible within the concept and scope of the invention. Such modifications will become apparent to those skilled in the art after review of the specification, drawings, and claims. Accordingly, the invention is not limited without exception within the spirit and scope of the appended claims.

Claims (15)

A system for detecting motion in the body,
An acoustic transducer and a variable refractive acoustic lens coupled to the acoustic transducer, wherein the at least one set adjusts at least one characteristic of the variable refractive acoustic lens in response to a selected voltage applied to an electrode. An acoustic probe comprising: a variable refractive acoustic lens having an electrode;
A motion detection processor coupled to the acoustic transducer and executing an algorithm for detecting motion of the target in response to the acoustic energy received by the acoustic transducer;
A variable voltage source for applying a selected voltage to the set of electrodes;
A controller for controlling the variable voltage source to apply the selected voltage to the set of electrodes;
A system comprising: A transmission signal source; and
A transmit / receive switch that selectively couples the acoustic transducer to the transmit signal source and the motion detection processor;
The system of claim 1 further comprising: The variable refractive acoustic lens is
The cavity,
A first fluid medium and a second fluid medium disposed within the cavity;
A first electrode and a second electrode;
The speed of the acoustic wave sound of the first fluid medium is different from the speed of the acoustic wave sound of the second fluid medium,
The first fluid medium and the second fluid medium are immiscible with each other and the first fluid medium has a substantially different electrical conductivity than the second fluid medium;
The system of claim 1.   The system of claim 3, wherein the first fluid medium and the second fluid medium have substantially equal densities.   The variable refractive acoustic lens includes a housing defining the cavity, and a first electrode of the electrode pair is provided at a bottom of the housing, and a second electrode of the electrode pair is The system of claim 3, provided on a lateral side of the housing.   A first electrode of the electrode pair is provided in contact with one fluid medium having a higher electrical conductivity of the first and second fluid media, and a second electrode of the electrode pair; 4. The system of claim 3, wherein a plurality of electrodes are isolated from said one fluid medium having greater electrical conductivity of said first and second fluid media.   The system of claim 1, wherein the variable refractive acoustic lens is coupled to the acoustic transducer by at least one acoustic matching layer.   The at least one characteristic of the variable refractive acoustic lens that is adjusted in response to the selected voltage applied across the electrode comprises a focal point and elevation of the variable refractive acoustic lens. system. A method for detecting motion using acoustic waves,
(1) Apply an acoustic probe to the body,
(2) controlling the variable refractive acoustic lens of the acoustic probe to detect acoustic energy from the target region of the body;
(3) The acoustic transducer receives the acoustic wave returning from the target area from the variable refractive acoustic lens,
(4) An electrical signal corresponding to the received acoustic wave is output from the acoustic transducer,
(5) creating acoustic data received from the electrical signal output by the transducer;
(6) Decide whether to focus on other target areas of the body,
(7) When another target area is selected, the steps (1) to (6) are repeated for the newly selected target area.
(8) when no further target area is selected, process the received acoustic data and output one or more images showing motion in the body;
Method.   The method of claim 9, further comprising storing the received acoustic data in a memory.   Further comprising applying an electrical signal to the acoustic transducer coupled to the variable refractive acoustic lens to generate an acoustic wave and direct it to the target region prior to step (3). Item 9. The method according to Item 9.   Controlling the variable refractive acoustic lens to detect acoustic energy from the target region of the body causes the two fluids to move through the variable refractive acoustic lens such that the two fluids have different acoustic wave propagation velocities. The method of claim 9, comprising applying a voltage to an electrode of the variable refractive acoustic lens for placement in a housing.   The method of claim 9, wherein controlling the variable refractive acoustic lens to detect acoustic energy from a target region of the body includes at least one signal processing characteristic of the variable refractive acoustic lens.   14. The method of claim 13, wherein at least one signal processing characteristic of the variable refractive acoustic lens that is adjusted is a focal point of the variable refractive acoustic lens.   The method of claim 13, wherein at least one signal processing characteristic of the variable refractive acoustic lens to be adjusted is a deflection angle of the variable refractive acoustic lens.

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