JPH0147754B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pulsed ultrasound imaging method and apparatus.

The use of arrays of phase transducers consisting of a plurality of adjacent transducer elements for beam focusing is well known in ultrasound imaging technology, as shown, for example, in U.S. Pat. No. 3,936,791. It is being It is also well known to operate individual transducer elements or groups of elements sequentially for beam scanning, as shown for example in US Pat. No. 4,164,213. Additionally, focusing means including separate tap-type delay lines for each element of the exemplary transducer is disclosed in U.S. Pat. No. 4,116,229. The taps are changed to provide fluid focusing from a minimum to a maximum range along the beam. Tap switching occurs during the signal reception period due to the generation of potentially harmful switching transients. Also, a large number of relatively expensive tapped delay lines are required for beam focusing and scanning provided by the prior art.

One object of the present invention is to use electronic beam focusing, scanning, and received signal processing means;
An object of the present invention is to provide an improved pulsed ultrasound imaging method and apparatus that provides high-resolution real-time images of a portion of the interior of an object.

Another object of the invention is to provide a pulsed ultrasound imaging device of the type described above, in which a relatively small number of fixed delay means are required for focusing and scanning the beam of the part to be imaged. It is about providing.

Another object of the invention is to provide a pulsed ultrasound B-scan in which a well-focused real-time image of the entire area being imaged is obtained using simple electronic focusing and scanning means. An object of the present invention is to provide a method and apparatus.

Briefly described, the above and other objects and advantages of the present invention are obtained by repeatedly transmitting pulses of ultrasonic energy into an object.
An ultrasonic transducer array consisting of a large number of adjacent transducer elements converts echo signals obtained from discontinuities (cuts) in the object into equivalent electrical signals. The range-gated signal processing means generate signals from transducer elements produced by reflected ultrasound waves obtained from within any one of a number of continuous range bands within the portion of the object being imaged. Can respond to electrical signals. The term "range band" here is a term indicating each area when the part of the object is divided into a plurality (for example, four) of areas parallel to the linear transducer row depending on the resolution ( (See Figure 2). The received signal processing device includes beam focusing and scanning means for focusing the transducer array elements and scanning the range band over which the processing device is range gated.

The term "range gating" means processing only echo signals received from discontinuities within one of the selected range bands. A single line is obtained by one transmit/receive pulse operation for each range band, and this is used as a "divided line part", that is, a total of four line segment signals from four bands to completely complete the part. You can get a single video. These line segments are fed into a cathode ray tube for visual display of the entire imaged portion. A digital scan converter can be used as a temporary storage for line segment signals from which the converter's overall video line signal can be obtained for display on a TV monitor.

The nature of the invention as well as other objects, features and advantages will become more apparent from the above detailed description taken in conjunction with the accompanying drawings.

Referring to FIG. 1, one embodiment of the novel ultrasound imaging system of the present invention is shown comprising a linear transducer array 10. Transducer array 10 is 64 for illustrative purposes.
adjacent conversion elements 10-1 to 10-64. Preferably, the transducer array 10 includes cylindrical lens focusing means 11 (see FIG. 2) for focusing the beam in a plane perpendicular to the plane of the portion 12 in the object 14 to be imaged. We are prepared. In the structure shown, the section 12 is located in the longitudinal plane of the transducer array.The use of cylindrical lenses for such beam focusing is well known and does not require further explanation. Probably not.

The transducer array 10 is incorporated within a pulsed ultrasonic B-scan imaging system, which consists of a pulser 16 supplied with repetitive timing pulses from a timing and control unit 18 for on-off control. Contains transmitter. When the pulser is turned on, a pulse of high frequency energy is generated which is sent to the switching matrix 22 via the transmit/receive switching unit 20. The signal delay unit 24 (consisting of seven fixed signal delay elements 24-1 to 24-7 in this embodiment) is connected to the seven transmit/receive switches 20-1 to 20-7 of the switching matrix 22, respectively. included in the section. Since one transmit/receive switch 20-8 is directly coupled to the switching matrix,
This interconnect does not include time delay means.

The transducer elements 10-1 to 10-64 of the transducer array are connected to a switching matrix 22 for coupling different numbers of sets to the pulser 16. Timing and control signals from the timing and control unit 18 are applied to a transducer array that is fed to a switching matrix 22 for selecting the transducer element or group of adjacent transducer elements to be activated during pulse transmitting and receiving operations. Signal delay unit 2 for delaying the supplied transmitter signal and the signal received from the transducer bank
4 provides focusing of the beam at different depths of the portion 12 of the object 14, the depth at which the transducer array is focused is the delay element used in the connection of the transducer element to the pulsed B-scan transmitter/receiver. 24-1~2
It depends on 4-7. The axis of the beam is the transducer row 10
along which the transducer element or set of adjacent transducer elements is used for the transmit and receive operations. The function of fixed signal delay unit 24 for beam focusing at different depth bands within imaged portion 12 will be explained in more detail later in the description of receive operations. For purposes of the present invention, when the pulse transmitter or pulser 16 is turned on, the transducer element or set of adjacent transducer elements is energized for pulse generation of ultrasound waves, which are imaged. is focused in one of a number of continuous range bands within section 12. The actuated transducer element or set of transducer elements is shifted along the transducer column in the direction of double arrow 25 to scan each of the range bands.

pulse - insonified
Ultrasonic waves reflected from discontinuities (cuts) in object 14 are received by transducer array 10 and converted into equivalent electrical signals by individual transducer elements. 1 of conversion elements 10-1 to 10-64
Output from one or more transmitting/receiving switching means 2
0 to a summing amplifier 26. The transmit/receive switches 20-1 through 20-8 serve only to isolate the transmitted signal pulses from the input to the summing amplifier. As will be appreciated, a preamplifier (not shown) may be provided at the connection of the transmit/receive switch to the summing amplifier 26 to preamplify the relatively low level signals from the transducer element. can.

If desired, the operation of the device can be such that no switching of the switching matrix 22 takes place between the pulse transmitting operation and the associated pulse receiving operation, in which case the beam focusing and positioning are the same as during a single transmit/receive cycle. Of course, different sets of delay elements may be used during transmit operations and associated receive operations, if desired. For example, sidelobe suppression can be increased by using slightly different focus patterns in transmit and receive. However, for simplicity, we will discuss operating with the same beam pattern during the transmit and receive cycles.

In the device of this embodiment, the output from one or more transducer elements is sent to the summing amplifier 2 during the receiving operation.
6. The output from the summing amplifier related to the sum of the inputs is a time-variable gain amplifier 2.
8, the gain amplifier 28 has a gain characteristic that varies as a function of time to compensate for the loss of signal amplitude that occurs as it traverses the tissue of the object 14. In the illustrated structure, the gain of gain amplifier 28 varies according to the output from range gate and gain function generator 30. The range gate and gain function generator 30 is a lamp detector having an output signal that operates to increase the gain of the gain amplifier 28 in proportion to the range to eliminate signal loss caused by sound aspiration within the object. It may also consist of a nerator.
The start-stop operation of generator 30 is controlled by timing and output from control unit 18. The output of the range gate and gain function generator, when turned on, is such that it disables the gain amplifier 28 from being range gated in the receiver before being triggered. In the illustrated configuration, range gating of receiver 70 in four consecutive range bands within the object occurs in the manner described below. Obviously, it is possible to range gate the received signal at other locations within the device, and the invention is not limited to the particular gating means including the combined range gate and gain function generator 30 shown. It's not something you can do.

The range gate signal from the time-variable gain amplifier 28 is amplified by a variable gain amplifier 32, and the amplified output is sent to an envelope detector 34 consisting of a full-wave rectifier followed by a low-pass filter, for example.
Detected by a detector 34 associated with the envelope of the broadband high frequency signal from the gain amplifier 32;
The output of the ultrasonic image display device 3 consisting of a cathode ray tube
6. Generally, a compression amplifier (not shown) is used at the junction of the detector output signal and the cathode ray tube 36 to match the detected signal with the characteristics of the cathode ray tube for proper representation of the overall signal range. included in. The output of the detector is applied as an input to the control grid of the cathode ray tube for intensity (Z-axis) control of the electron beam.

For the illustrated B-scan display, the deflection of the cathode ray tube beam in the X or horizontal direction is proportional to the position of the ultrasound beam across the column scan path. An X-axis generator 38, triggered by synchronization and control signals from the timing and control unit 18, provides a step function signal output that is connected to the transducer bank 1.
The cathode ray tube 36 is used to shift the trace on the cathode ray tube according to the position of the ultrasonic beam axis at zero.
horizontal deflection system.

Vertical or Y-axis deflection of the cathode ray tube is provided by a lamp generator 40 which is triggered by the output from the timing and control unit 18 at selected times which follows the operation of the transmitter. The output of lamp generator 40 is fed to the vertical deflection system of cathode ray tube 36 for vertical scanning of the trace.
As mentioned above, a number of continuous range bands are
A large number of individual trace segments are used as required for generation of a complete video scan line. In the illustrated structure, four such range bands are used. As can be seen, a complete high-resolution B-scan ultrasound image of the object portion lying within the object portion 12 is provided on the surface of the cathode ray tube 36 by the display of multiple video line segments obtained from each of the range bands within the portion 12. provided.

In FIG. 2, transducer array 10 and attached cylindrical lens 11 are shown in contact with an object 14, such as soft tissue of the object. The portion 12 to be visualized is shown divided into a plurality of range bands, and for illustrative purposes, four range bands are shown, designated Band 1 through Band 4. The bands may be of equal or unique width (ie, range) as desired, and the number of range bands used depends, among other things, on the desired resolution for the overall operating range. As mentioned above, the signal delay unit 24 includes seven delay elements 2.
4-1 to 24-7, and in operation, in this embodiment, individual delay means sets ranging from zero to 7 are used for focusing in different range bands. ing. For operation in band 1, switching matrix 22
simply functions to couple a selected one of the 64 conversion elements directly to the summing amplifier 26 via the transmit/receive switch 20-8 without the signal passing through any of the delay elements. . The diagram in FIG. 2 labeled "DELAYS EMPLOYED" indicates that no delays are used for band 1 operation. In FIG. 2, a line is shown leading from a single transducer element (here elements 10-18) to the Band 1 portion of the diagram; for operation in Band 1, the transducer element is (1
represents the fact that they are operated (as a set). Additionally, during band 1 operation, the receiver is range gated so that processed signals are received from the motion conversion element only while time-reflected signals are received from inside the band.

In range band 1 (immediately adjacent to the transducer row), the best resolution is obtained by using a single transducer element. During the course of a complete scan cycle in which the entire section 12 is scanned, every transducer element in the transducer array is individually operated to provide a line segment information signal for each transducer element in band 1. There is. In the apparatus of FIG. 1, line segment signals are provided to a cathode ray tube 36 as they are produced for real-time images at that location. For 64 transducer elements in a column, a total of 24 line segments per band are obtained in the manner described above by using the illustrated apparatus. In FIG. 2, the beam direction pattern for band 1 operation provided by the operation of a single transducer element is represented by 44, and the beam direction pattern provided by the operation of a single transducer element (here elements 10-18)
The beam axis during operation is indicated at 46.

Signal delay elements included in signal delay unit 24 are employed for focusing the electron beam within range bands 2, 3 and 4. For example, for operation in band 4 furthest from transducer bank 10, a set of 15 transducer elements is used with a total of seven signal delay elements 24-1 through 24-7. The time delays provided by elements 24-1 to 24-7 increase as the sign index increases, with the smallest time delay provided by signal delay element 24-1.
and the maximum time delay is provided by delay means 2
4-7. In FIG. 3, a plot of the time delays used for signal delay elements 24-1 through 24-7 is shown.

For beam focusing in the range band 4 shown in FIG. 2, the outermost conversion elements (here conversion elements 10-11 and 10-
25) is directly connected to the transmit/receive switch 20-8 by the switching matrix 22 without delay. Conversion element 10-18 at beam axis 46
is connected by a switching matrix to a signal delay element 24-7 for maximum delay of transmitted and received signals. As is well understood, beam focusing is provided by using progressively larger time delays from the outermost transducer elements to the middle transducer element of the set being used. In FIG. 2, conversion elements 10-11 to 1
0-25 are used for focusing in band 4 along beam axis 46, transducer elements 10-17 and 10-19 are time delay elements 2
4-6 to a summing amplifier 26. Similarly, elements 19-16 and 10-20,
Elements 10-15 and 10-21, Element 10-1
4 and 10-22, elements 10-13 and 10
-23, and elements 10-12 and 10-24
are connected to the inputs of summing amplifier 26 via signal delay elements 24-5, 24-4, 24-3, 24-2 and 24-1, respectively. In operation, different sets of 15 transducer elements are coupled by a switching matrix 22 for scanning the range band 4 on which they are focused. Adjacent to both ends of the transducer array, the beam is formed using fewer transducer elements, and imaging therein is also correspondingly reduced. For the illustrated configuration, 64 range gated line segment signals are obtained for each range band, including range band 4, and these signals are processed by the receiver for display on cathode ray tube 36.
In FIG. 2, points 50-- in range bands 2, 3 and 4, respectively, along beam axis 46 are shown.
a focused ultrasound beam 48-2, for focusing at 2, 50-3 and 50-4;
Wavefront 52- to which 48-3 and 48-4 relate
2, 53-3 and 52-4.

As is clear from Figure 2, range band 3
For operation in range band 4, fewer sets of conversion elements and associated delay elements are used than in the case of range band 4. Similarly, the set of transducer elements for focusing in range band 2 includes fewer transducer elements and associated delay elements than the set for operation in range band 3. In the illustrated structure, operation in range bands 3 and 2 involves the use of 11 and 7 conversion elements and 5 and 3 signal delay elements, respectively. In addition, signal delay elements 24-1 to 24-7 are used to perform focusing in a large number of different range bands.
It will be seen that at least some of these are used. In this particular configuration, signal delay element 24-1 is used for focusing in range bands 3 and 4, and signal delay element 24-2
is used for focusing in range bands 2 and 4, and signal delay element 24-3 is used for focusing in range bands 2 and 4.
and 4, signal delay element 24-4 is used to focus in range bands 2, 3 and 4, and signal delay element 24-4 is used to focus in range bands 2, 3 and 4.
4-5 is used for focusing in range bands 2, 3 and 4, and a signal delay element 24-
6 is used for focusing in range bands 3 and 4.

Once the number of conversion elements to be included in each set for operation in different range bands is determined in a manner as described below, the various foci 50-2, 50-3, The delay required to focus at 50-4 can be calculated.
Now looking at Figure 3 again, the focal point 50-2,50
Plots of calculated delay times for focusing at -3 and 50-4 are shown. As can be seen from this plot, the delay times are grouped along the time delay axis. Looking at the desired accuracy at the highest expected return frequency, one can determine the required accuracy of the time delay used. Merely by way of example, for 0.1 wavelength accuracy at a frequency of approximately 15 MHz, a time delay within an accuracy of approximately ±6.7 nanoseconds is required. the result,
A group of time delays falling within the range of 13.4 nanoseconds will be satisfied by the use of a single delay means. Obviously, the possible groupings depend on the physical dimensions of the columns as well as the required operating frequency and accuracy. In FIG. 3, seven sets of time delays, including one set of one delay, provide the necessary delays for focusing in all four range bands.

In the illustrated embodiment, a single scan line segment is obtained from one of four range bands for each transmit/receive cycle. One sequence of transmit and receive gating operations followed when scanning an image is shown in the timing diagram of FIG. 4, which will now be described. Repeated transmission pulse T
1, T2, T3, T4, T5, following which the receiver is range gated for operation in range bands 1, 2, 3, 4 and 1, respectively. If the device uses four range bands, and 64 scan line segments are acquired for each band, a total of 256 scan line segments will be acquired and displayed over the course of a complete scan cycle.

It should be understood that the invention is not limited to any particular scan order. Such a scanning order is illustrated by reference to FIGS. 5A, 5B and 5C, which are diagrams showing three different scanning orders out of a substantially unlimited number of possible orders. In these figures, the four line segments forming one line are shown with a space between them to facilitate their identification. In reality, such gaps do not exist, and the segments forming a line are continuous. The order in which line segments are obtained and displayed is represented by the underlined numbers 1-256, only some of which are shown. In FIG. 5A, a total of four line segments of a line are sequentially obtained and displayed before stepping the beam axis to adjacent positions. For this operation, the receiver will be range gated in the manner shown in FIG.

In the scanning sequence of FIG. 5B, all range bands are beam scanned before the receivers are range gated in adjacent range bands. In the pattern shown, range bands 1, 2, 3 and 4 are scanned sequentially.

If desired, a substantially random scan order can be utilized, for example as shown in FIG. 5C. In all
After 256 line segments have been obtained and displayed, the sequence is repeated. When performing any sequence of operations, it is a simple matter to synchronize the display of line segments with the range gating and beam position of the receiver.

The number of transducer elements to be included in each set for focusing in different range bands is determined by calculating the resolution within each range band by using different numbers of adjacent transducer elements within the set. You can decide accordingly. The set that provides the best lateral resolution for the depth of the band will be used.
In the illustrated configuration, only sets containing an odd number of transducer elements are used, and the beam axis extends from the center of the transducer elements. As is clear, a system using an even number of conversion elements may also be used;
In this case the beam axis extends from a point between adjacent conversion elements. Also, by using odd and even transducer elements in sets, the number of lines that can be obtained is essentially doubled without increasing the number of transducer elements included in the column.

Although the foregoing description has presented the invention in detail in accordance with the requirements of the patent laws, various modifications and changes will become apparent to those skilled in the art. For example, the display on the surface of cathode ray tube 36 can be converted by a scan converter responsive to such display into a signal usable by a conventional television type monitor or display. In another variation of the invention, shown in FIG. 6, the electrical line segment signal from the envelope detector 34 is converted to a composite video signal that can be displayed on a conventional television monitor 62 by a digital scan converter 60. supplied to Digital scan converters for such applications are well known and often include a gray scale generator for generation of a multi-bit digital signal that is temporarily stored in a read-write memory. Timing and control means 1
The timing signal from 8' is supplied to a digital scan converter for its control. A complete video line is read out from the digital scan converter for display on monitor 62. By using 24 element columns, 64 lines of video information are provided, so each line can be repeated eight times to create a 512 line display if desired. Also, rather than simple repetition, each synthetically generated scan line can be interpolated by appropriately mixing the signals from two adjacent actual scan lines. Such details of signal processing to provide a more pleasant display are well known and do not form part of the present invention. However, the temporary storage of line segment signals required for digital scan conversion does not preclude real-time imaging by the device.

As mentioned above, other modifications include using different delay means for the associated transmit and receive scans for different beam focusing operations. It is also clear that the invention is not limited to the use of four range bands. A method and apparatus embodying the invention using eight range bands was constructed and tested. In addition to it,
The apparatus may use range bands of different sizes if desired, with the size of each band depending on the desired resolution through the total depth of the portion being imaged. These and other such modifications and variations are intended to be included within the spirit and scope of the invention as defined in the following claims.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an ultrasound imaging device embodying the invention; FIG. 2 is a diagram showing the transducer arrays in different range bands and the beam focusing of the time delay means associated with each band; Figure 3 is a graph showing the distribution of time delays required for focusing in different range bands;
5A, 5B and 5C are timing diagrams illustrating range gate operation of the received signal processor for operation in different range bands; FIGS. a schematic diagram showing the spatial morphology of different video frames;
Figure 6 is a block diagram similar to Figure 1, but
FIG. 6 is a diagram illustrating a portion of a modification of the present invention embodying a digital scanning converter. 10... linear transducer row, 10-1 to 10-
64... Conversion element, 12... Portion, 14... Object, 16... Pulser, 18... Timing and control unit, 22... Switching matrix, 24
...Signal delay unit, 24-1 to 24-7...
Signal delay element, 26...Summing amplifier, 28...Gain amplifier, 32...Gain amplifier, 36...Ultrasonic image display device (cathode ray tube), 60...Digital scanning converter, 62... ...TV monitor.

Claims (1)

Claims: 1. A pulsed ultrasound imaging method for imaging an interior portion 12 of an object 14 in real time from reflections of discontinuities within portions of repeatedly transmitted pulses of ultrasound energy, comprising: A linear transducer array 10 consisting of a plurality of adjacent transducer elements 10-1 to 10-64 transmits repeated pulses of ultrasonic energy into the portion 12 to be visualized, and the transmitted ultrasonic energy is visualized. electronically focusing on one of a plurality of continuous range bands within the section 12, said focusing being in the plane of the section 12, and receiving reflected wave pulses by said linear transducer array 10; , and converting the reflected wave pulses into electrical signals, the electrical signals from said transducer array 10 being range gated to obtain a line segment signal from a unique range band on which the associated transmitted ultrasound energy is focused; The electrical signals from the linear transducer array are passed through fixed signal delay elements 24-1 to 24-7, and at the same time, the transducer array 10 is electronically controlled in a range band where the electrical signals are range gated. scanning said portion 12 by scanning each range band to receive a focusing pulse and obtain a plurality of separate line segment signals from each range band for use in imaging said portion; The transducer array 10 is focused on a single range band for each pulse transmission and associated reception of ultrasound energy, and the line segment signals from each range band are used to complete the complete A pulsed ultrasound imaging method characterized by displaying an image. 2 Fixed signal delay elements 24-1 to 24 identical to those used to electronically focus the transducer array by which the transmitted ultrasonic energy pulses are used during associated receive operations. 2. The pulsed ultrasound imaging method according to claim 1, wherein the pulsed ultrasound imaging method is electronically focused by using -7. 3. A pulsed ultrasound imaging device for imaging a portion 12 within an object 14, the device comprising: a linear transducer array 10; 10 conversion elements 10-
A pulser 16 that energizes signals 1 to 10-64, and a plurality of fixed signal delay elements 24-1 to 24.
-7, on which the transmitted beam is focused on a plurality of continuous range bands 1-4 within the portion to be imaged 12; and beam scanning means for scanning the portion to be imaged; responsive to the output from the linear transducer bank 10;
range-gated signal processing means for processing signals received only from the range band on which the transmitted beam is focused; At least some of the signal delay elements 24-1 to 24-7 are used for focusing in a plurality of range bands, and furthermore, the part to be imaged is focused by the focusing means. means 18 for controlling said focusing means and said range gated signal processing means for providing line segment signals from each range band for use in visual display, said line segment signals corresponding to a single range band being provided; obtained by the transmitting/receiving operation of the apparatus, and further comprising visual display means for displaying a single image of said portion in response to line segment signals from each of said continuous range bands. A pulsed ultrasound imaging device. 4. The same fixed signal delay elements 24-1 to 24-7 used to focus said linear transducer array during receive operations are used for beam focusing during said associated transmit operations. A pulsed ultrasound imaging device according to claim 3, characterized in that: