JPH02116356A - Ultrasonic system - Google Patents

Abstract

PURPOSE: To make it possible to optimize parameters important for ultrasonic imaging without increasing internal reflection of a probe, by optimizing attenuation of a combining fluid within a selected range without maximizing the transmissivity. CONSTITUTION: This ultrasonic system 101 is that to use a typical ring fused array transducer and is assembled with a transducer equipped with a comparatively large aperture for high sensitivity and selects an attenuating combining fluid for compensation of a nozzle problem generated by increasing the aperture dimensions. The aperture of a transducer 131 is about 3cm compared to a more typical 1.5cm aperture. The combining fluid 127 is a two components mixture of glycerol mainly containing 1-butanol (butyl alcohol). In a preferable example of the two components mixture, the ratio of 1-butanol to glycerol is about 27-37%. Both of speed and attenuation are decreased as the ratio of butanol is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ultrasound imaging system, and more particularly to a system and method for providing ultrasound for coupling between a transducer and a window of an ultrasound probe. It is something.

[Prior art and its problems] Ultrasonic imaging (ultrasonic i
mag-ing) is widely used to analyze the internal structure of living organisms. For example, ultrasound is often used to characterize the condition of a fetus inside a pregnant woman.

Ultrasonic imaging is based on the detection of ultrasound reflected waves from boundaries characterized by unequal impedance.

Such boundaries can represent boundaries between bones, organs, changes in tissue type, and the like.

Typically, ultrasound imaging is performed using an electron module and an electrically powered ultrasound probe. The probe generally has a handle.
an electro-acoustic transducer (electro-acoustic transducer);
acoustic transducer). An electronic module generates electrical pulses. This is converted into ultrasound pulses and propagated through a window into the patient's body to be observed.

A single ultrasound pulse has multiple impedance boundaries along its propagation path.
bou-ndaries) may cause multiple reflections.

These reflections are detected by a probe and converted into electrical signals by a transducer.

This electrical signal represents depth in time and impedance mismatch in amplitude. The electronic module can analyze this signal, reproduce the video information, and then perform display and/or recording as desired.

The quality of the image obtained is highly dependent on the sensitivity of possible reflection detection by the probe. A substantial portion of the energy of the ultrasound pulse is absorbed by the probe or body. The residual energy is distributed between multiple reflections. Only a small portion of each reflection is directed to the probe,
Most of that small portion is absorbed before reaching the transducer. The transducer must be able to detect the occurrence of these reflections and their amplitude, despite the minute amount of energy in each reflection.

Sensitivity is determined by the transducer's aperture or energy-gathering area.
It is a function of a). A transducer with a larger aperture can receive a larger portion of the reflected acoustic energy. On the other hand, a large aperture also means a shallow depth of focus. At a given time, the transducer is configured and/or operated such that a single depth is obtained that has the maximum depth resolving ability of the transducer. In practice, maximum resolution is not required, but some threshold resolution below this maximum resolution may be required in many imaging applications. When using a small aperture transducer, the depth range meeting or exceeding a given threshold value is greater than the corresponding depth range obtained when using a large aperture.

If the depth range of the observed object is greater than the depth of the probe field, the continuous depth focus (focus
1 points) to obtain imaging information. Larger apertures require finer steps between foci. In this specification,
While collecting images (during image
The process of changing the focal length of the probe is called "zooming".

Zooming allows for high resolution imaging along a single trajectory. Cross section of the observed object (sl
In order to obtain a two-dimensional image of the ice, it is necessary to pan the direction of ultrasound propagation. That is, it is necessary to perform a lateral sweep or "steering". It is due to this steering operation that many fan-shaped ultrasound images are provided. Zooming is collectively defined as scanning (5 scanning).

Scanning is performed separately with different probe types. Small aperture probes with spherical transducers can rely on fixed focal mechanical steering for imaging. In theory, a single element transducer could be mechanically deformed to allow zooming. Therefore, the aperture becomes larger. An annular array transducer (a
(nular array transducers)
is also being developed. Annular array transducers commonly use mechanical steering. Phased array used in radar
A rectangular array in which all scanning is done electronically, such as
) It is possible to realize an ultrasonic transducer. Such rectangular arrays are not widely used due to the considerable complexity involved in processing. Linear (I 1
(near) Phased arrays are easier to implement and allow for electronic zooming and steering;
vertical resolution (transverse to depth and pan) (e
levational resolution) is insufficient.

Although each probe design has advantages, annular arrays are superior in that they are capable of performing high-resolution imaging in all directions, but are less demanding in the process of generating images from received reflections. Not yet.

Zooming can be performed electronically at high speeds for each mechanically controlled pan position.

One of the challenges in designing large aperture, mechanically scanning ultrasound transducers, such as annular array transducers, is to couple the ultrasound transmission between the probe and the object under optimal conditions. For obvious reasons, including object comfort, a moving transducer cannot be brought into close contact with the object.

Instead, the close connection to the observed object is made by the window of the probe. The window material is
The choice is one that is safe, comfortable, rigid, and transparent to ultrasound energy. A more subtle criterion is that the acoustic index of refraction at ultrasound frequencies must closely match the object being imaged.

That is, the acoustic velocities of the window and the object to be observed must match. The purpose of this alignment is to minimize image distortion due to changes in beam direction at the boundary between the object and the window.

Additionally, it is desirable to match the ultrasonic impedance of the window to that of the object being observed, thereby minimizing reflections at its surface.

These reflections contain no useful information and cause reflections inside the probe, reducing image clarity and dissipating energy that would otherwise contribute to useful reflections. However, some compromises in impedance matching are allowed to accommodate other criteria, particularly window stiffness.

A mechanically panned transducer between the transducer and the window of the interlocking probe to enable steering operations and at the same time provide adequate ultrasonic coupling between the transducer, the window, and the object being observed. fluid-mediated intervention. Requirements for such coupling include transmission velocity and impedance matching between the fluid, window, and object for the same reasons as described above for aligning the window with the body. In addition, the use of fluids to balance the requirements for efficient transmission of ultrasound waves with the requirement to dampen reflections inside the probe that can generate artifacts and otherwise degrade image quality. Attenuation must be considered.

These requirements typically place constraints on the selection of liquid media materials sealed within the chamber defined by the probe body and window.

Many of these are proprietary patents.
As such, it is difficult to determine the range of coupling fluids used in mechanically scanned probes.

Conventionally, various organic liquids have been tried. Attempts are often made to mix materials and combine the properties of each component. However, most such combinations interact nonlinearly, making the results of the mixture unpredictable. Although attenuation and impedance relationship tables can be used, coupling fluid selection usually becomes a matter of trial and error.

One of the problems with conventional coupling fluids is that it is extremely difficult to vary important parameters, such as impedance, without being affected by other parameters such as velocity. It is often not possible to "tweak" a liquid mixture to obtain the desired properties. Furthermore, these properties must be maintained within acceptable tolerances over a range of operating temperatures.

Additionally, this eliminates binding fluids that would otherwise be acceptable.

For small aperture probes, a number of different materials have been successfully used as coupling fluids, such as silicone booth oil or mixtures of glycerol with propylene glycol. However, images produced by large aperture probes using the same fluid clearly suffered from artifacts caused by internal reflections. When using a large aperture probe, an ultrasound system (uitr
asound system) and methods are needed. Such systems and methods preferably use coupling fluids that allow adjustment of important parameters without significantly changing other parameters.

[Object of the Invention] The object of the present invention is to provide an ultrasonic system that solves the above-mentioned problems and optimizes balata, which is important for ultrasonic imaging, such as appropriate attenuation, without increasing internal reflection of the probe. and to provide a method thereof.

[Summary of the Invention] The present invention optimizes the attenuation of the coupling fluid within a selected range, rather than maximizing its transmission, so that the reflection to be measured reaches the transducer of the probe. This is to reduce the amplitude of internal reflection so that it has no effect. The coupling fluid between the transducer and the probe window includes a mixture of 1-butanol and glycerol (glyc-er-nl).

Appropriate amount of 2-hydroxyne ethyl ether (2-)iyd
By including Roxyethyl Ether) in the mixture, the attenuation can be adjusted in the downward direction. The present invention is most effectively used in mechanically scanning probes with large aperture transducers. However, it can also be applied to other ultrasound probes using coupling fluids.

The importance of coupling fluid attenuation is most critical in probes with large apertures. For small aperture probes, the length of the mean free path of ultrasound, such as acoustic energy with a frequency of about 20 kHz or higher, through the distance between the transducer and the window and its medium.
path of ultrasound) are both relatively short. As a result, there are relatively many reflections per unit time. Each reflection is accompanied by some attenuation due to transmission and some dissipation or loss, with reflections away from the transducer being particularly susceptible to attenuation. When the reflection to be measured reaches the transducer, a sufficient number of internal reflections occur so that
Reduce internally reflected energy to an acceptable level.

For large aperture probes, the mean free path is longer and there are fewer reflections per unit time.

In other words, the coupling fluid in the large aperture probe plays a relatively more important role in attenuating internal reflections. Therefore, the present invention provides a coupling fluid that is more attenuating than that used in conventional ultrasound probes.

More importantly, the present invention allows for more precise control over coupling fluid damping. Since the coupling fluid used in large aperture probes is a relatively important factor in attenuating internal reflections, the performance of ultrasound systems incorporating it is more sensitive to the degree of attenuation exerted by the coupling fluid. be influenced by. For this reason, it is important to precisely set the attenuation to an optimum level.

Determining this optimal level is difficult.

This optimal level exhibits as yet unpredictable variations depending on probe configuration and geometry. Furthermore, for a given probe, this optimal level may vary depending on the depth of the object to be measured and the structure of the tissue or other material being treated.

Therefore, the coupling fluid will typically be selected through a process of trial and error.

This process of trial and error is extremely monotonous and tedious. Generally, fluid mixture adjustments are made to change the damping, which in turn changes the velocity and/or impedance, which must be kept within a predetermined range.

Fluid properties usually do not combine linearly, so it is difficult to predict mixture values without testing.

Therefore, a mixture suitable for a particular probe and application may not be able to be modified for probes and applications that are only slightly different.

The present invention addresses this problem in the probe by allowing the attenuation of the coupling fluid contained therein to be precisely adjusted without compromising velocity and impedance matching. At a suitable ratio of 1-butanol to glycerol, a relatively damping fluid can be obtained. A reduction in attenuation can be achieved by adding 2-hydroxyethyl ether.

The ratio of 1-butanol to glycerol can be varied to compensate for small changes in velocity and impedance.

The present invention provides an economical and high performance ultrasound system. This savings is achieved by achieving various attenuations.
This is because the design time required to find the correct coupling fluid is significantly reduced. The fluid components are known as the proportions required to achieve a particular damping level. This greatly reduces the amount of experimentation required to obtain optimal probe performance. Larger aperture probes are more practical and can improve probe performance because the attenuation can be more closely matched to the probe characteristics and application. Further features and advantages of the above description will become more apparent from the detailed description of the embodiments in conjunction with the following drawings.

[Embodiment of the Invention] FIG. 1 shows an ultrasound system 101 that is an embodiment of the present invention. The ultrasound system 101 includes an electronic module 10
3 and probe 105. The electronic module 103 is
Includes transmit electronics 107 and receive electronics coupled via cable 111. cable 1
11 is a line for supplying power and ground potential to the probe, transmitting electronics 107 to probe 1
Line for transmitting pulses to 05, probe 105
A line is provided for transmitting signals received from the receiving electronics 109 to the receiving electronics 109.

Housing 113 of probe 105 includes a probe head 115, a probe back 117, and a probe handle 119. Probe head 115 is attached to probe handle 119 via handle bracket 121. Probe window 123
is fixed and attached to the probe head 115. Probe window 123, probe head 115, and probe back 117 collectively define a chamber 125 that contains coupling fluid 12.
7 is filled. The transducer 131 is attached to a spherical frame 133 and
is mounted to pivot within the probe head 115 with a bearing 129 . Motor 135 is mounted within probe handle 119 by motor mount 137. Motor 135 drives pinion 139 via shaft 141. Shaft seal 143 prevents leaked fluid 127 from entering probe handle 1.
19. drive band 1
45 transmits the binion motion and provides steering of the frame 133 and thus of the transducer 131.

Drive band 145 is secured to frame 133 by bolts 147, only one of which is shown.
mounted on. Optical encoder 149 provides information to receiving electronics 109 regarding the pan position needed to generate an ultrasonic image.

Ultrasound system 101 is an ultrasound system that uses a typical annular fused array transducer, but incorporates a transducer with a relatively wide aperture to provide high sensitivity, resulting from increased aperture size. The difference is that a damping coupling fluid is selected to compensate for noise problems. The aperture of transducer 127 is more typical 1.5
cm aperture, approximately 3 cm. Binding fluid 127 is essentially a binary mixture of glycerol containing 1-butanol (butyl alcohol). In a preferred embodiment of this binary mixture, the ratio of 2-butanol to glycerol is about 23% to 37%. This binary mixture has an impedance of 4.5 MHz with a speed of 1.7 Mray/s and a speed of 1.540 m/s.
It is characterized by having an attenuation value of 4.1 dB/am below. The temperature sensitivity is -2,4 m/s/°C velocity gradient and -
Given by an attenuation slope of 0,1 dB/cm/t. Both speed and damping decrease with increasing proportion of butanol.

In another embodiment of the invention, 2-hydroxyethyl ether is added to the mixture to reduce damping. This 2
- Effect on the addition of hydroxyethyl ether in the second
As shown in the figure. At the starting point, the speed indicated by line 201 is 15
00m in 7 seconds, line 202 shows an attenuation of 4.1 dB/
1-butanol/glycerol mixture with cm. When adding 8% by weight of 2-hydroxyethyl ether, there is no significant change in the attenuation and the speed changes only slightly to 1526 m/s. , the damping is
It rapidly drops to 2.9 dB/cm. However, the speed increases only by 1530 m/s. When 2-hydroxyethyl ether is 15% by weight based on the mixture,
The attenuation drops to 2.3 dB/cm while the speed increases to 1534 m 7 seconds.

Looking at it another way, when reducing the proportion of 2-hydroxyethyl ether in the mixture from 15% to 8%, a 78% increase in damping is observed while at the same time only a 2% decrease in speed. Therefore, significant damping control is possible while maintaining the speed within a narrow range. It should be noted that only a few fluids have the desired quality of changing damping without inducing unacceptable velocities. For comparison purposes, by varying the ratio of glycerol to 1-butanol to obtain the same attenuation level, an acceptable speed is approximately 1400 m 7
Seconds.

FIG. 3 shows a flowchart illustrating the invention in detail. In the first step 301, 1-butanol is mixed with glycerol and the velocity and impedance are adjusted to matching levels. In the next step 302, if necessary, 2-hydroxyethyl ether is added,
Reduce attenuation to an appropriate level. Step 303
In this case, the fluid is enclosed within the probe head of the ultrasound probe. In step 304, the probe
The window is pressed against the object and, in step 305, the transducer of the probe is mechanically scanned with respect to the object. In step 306, an ultrasound pulse is sent from the transducer through the fluid;
It is transmitted to the observation object through the window. At least a portion of the ultrasound reflected waves from the observed object are transmitted through the fluid through the window and converted into electrical signals by the transducer in step 307. These electrical signals are analyzed in step 308;
Generates an image that characterizes the observed object.

The above description relates to preferred embodiments of the invention. Additionally, different probe sizes and geometries can be accommodated. A variety of transmitting and receiving electronics are possible, including both digital and analog signal-based electronics. Different transducer types and geometries are also provided. The support body of a transducer can have a myriad of shapes and characteristics. A variety of enclosures and window types and materials are provided. The drive system for the transducer steering basin can take on a variety of configurations. In addition to the above-mentioned components, the coupling fluid also has critical character-acteri
It is possible to dilute the compounds (sticks) or include other components that leave these properties unaffected and perform auxiliary functions. It will be apparent to those skilled in the art that the present invention may include other modifications and variations.

[Effects of the Invention] As explained above, the present invention provides ultrasonic waves whose speed and/or impedance matching can be easily adjusted, and whose attenuation can be increased or decreased without significantly changing the speed or impedance matching. You can get the system. These adjustments can be easily made by changing the proportions of the fluid components.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an ultrasound system that is an embodiment of the present invention. FIG. 2 is a diagram showing the characteristics of a coupling fluid used in an embodiment of the present invention. FIG. 3 is an explanatory diagram of the operation of one embodiment of the present invention. 101: Ultrasound System, 103: Electronic Module, Probe, 107: Transmitting Electronics, Receiving Electronics, 113: Housing, Probe Head, Probe Back, Probe-Handle, Handle Bracket, Probe Window, Transducer, 135: Motor , optical encoder. FIG. 2

Claims (5)

[Claims] (1) transmitting electronics for supplying electrical pulses; receiving electronics for receiving electrical signals; and a transducer for converting electrical pulses into ultrasound energy and ultrasound energy into electrical signals; the transducer is connected to the transmitting electronics; a body that receives the electrical pulses, connects with the receiving electronics, provides the electrical signals, and supports the transducer; the vertical position of the transducer is controlled by moving the body, and the body encloses the transducer; container means fixedly mounted with the body and defining a chamber in which a fluid comprising the transducer is enclosed, the container means also comprising a window attached to the body; the window substantially transmitting the ultrasonic energy, drive means for moving the transducer relative to the body, and the ultrasonic energy emitted from the transducer being scanned relative to the body; An ultrasound system comprising a fluid contained within. (2) The ultrasonic system according to claim 1, wherein the fluid includes a mixture of 1-butanol and glycerol. (3) The ultrasonic system according to claim 2, characterized in that the ratio of 1-butanol to glycerol is between 23% and 37%. (4) In the ultrasonic system according to claim 2 or 3, the fluid further contains 2-hydroxyethyl ether. (5) The ultrasonic system according to claim 2, characterized in that 2-hydroxyethyl ether is added to the fluid mixture in order to obtain a desired degree of attenuation.