JP3643585B2 - Ultrasonic image forming apparatus using combination of linear scanning and sector scanning - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to an ultrasonic imaging system using phased array beam steering and focusing, and in particular, uses a combination of linear scanning and sector scanning to expand the field of view while maintaining the advantages of linear scanning. The present invention relates to a method and apparatus for ultrasound imaging.
[0002]
[Background Art and Problems to be Solved by the Invention]
In the phased array type ultrasonic imaging system, the ultrasonic transducer includes a conversion element array. The system includes a multi-channel transmitter and a multi-channel receiver. In the typical case where the number of channels is less than the number of transducer elements in the array, an electronic switch network connects a selected group of transducer elements to the transmitter and receiver channels. Each channel of the transmitter causes the selected transducer array to transmit an ultrasonic pulse into an object (typically a human body) to be imaged. This transmitted ultrasonic energy is steered and focused by providing an appropriate delay to the pulses transmitted from each transducer element, effectively adding the transmitted energy to the desired point. Some of these pulses are reflected back to the transducer array by various structures and tissues in the human body.
[0003]
The steering and focusing of the received ultrasonic energy is performed in the opposite manner to the transmission described above. The reflected ultrasonic energy from the object or structure reaches the array element at different times. The received signals are amplified and delayed on separate channels of the receiver and then summed in a receive beamformer. The delay for each channel is selected so that the received beam is focused at the desired point. These delays can be changed dynamically to focus the beam at progressively increasing depths along the scan line upon receipt of ultrasonic energy. The transmitted beam is scanned over a region of the human body and the signal generated by the beamformer is processed to generate an image of the region.
[0004]
Various scan patterns or scan formats are known in the art. In a linear scan pattern, ultrasonic energy is transmitted and received along a number of parallel lines starting at different points on the transducer array. These parallel lines can be perpendicular to the array and can be steered to a desired angle. This linear scan pattern produces a relatively high quality image. This is because all the scanning lines are incident on the structure to be image formed from the same direction. The field of view obtained with the linear scan pattern is the same at all depths.
[0005]
In the sector scanning pattern, ultrasonic energy is typically transmitted and received along a sector line starting from a common vertex located on the transducer array. This sector scan pattern has a field of view that expands with increasing depth. A disadvantage of the sector scan pattern is that its field of view is relatively narrow at shallow depths. A technique for expanding the field of view of the sector scan pattern at a shallow depth is well known, and this technique shifts the sector scan pattern from the virtual vertex located behind the transducer array. Is included. This virtual vertex scanning pattern does not have the advantage of linear scanning that produces a high quality image.
[0006]
A scanning technique using a combination of linear and sector scanning is disclosed in US Pat. No. 4,664,122 issued May 12, 1987 to Yano. In the disclosed conversion element array, the scanning format is realized by making the distance between the elements in the partial array at both ends of the conversion element array smaller than the distance between the elements in the central partial array. There is no disclosure of steering for linear scanning.
[0007]
[Means for Solving the Problems]
In accordance with the present invention, a method and apparatus for ultrasound imaging is provided. According to a first aspect of the present invention, a method for ultrasonic imaging in a system including an ultrasonic transducer array starts from different points on the ultrasonic transducer array and is normal to the transducer array. Transmitting ultrasonic energy by the transducer array along parallel lines oriented or steered at a variable angle θ with respect to the parallel lines defining a linear scan pattern, and 1 Transmitting ultrasonic energy by the array along sector lines defining a sector scan pattern starting from one vertex. A composite scan pattern is formed by adjoining the sector scan pattern and the linear scan pattern. The method further includes receiving ultrasonic echoes by the array along the parallel lines and the sector lines to provide a signal representative of an image along the parallel lines and the sector lines.
[0008]
The sector scan pattern can be used at one or both ends of the linear scan pattern. Typically, the apex of the sector scan pattern is located on the array at one end of the linear scan pattern. When the sector scan pattern is used at both ends of the linear scan pattern, the composite scan pattern has a substantially trapezoidal shape. The sector scan pattern extends between the desired maximum angle α with respect to the normal to the array and the angle θ of the parallel lines.
[0009]
Sector lines of the sector scan pattern are transmitted through the array's sector apertures, and parallel lines are transmitted through the array's linear apertures. According to another aspect of the present invention, the width of the sector aperture in the composite scan pattern using the linear scan pattern and the sector scan pattern is changed according to the depth of the target region. A full-width sector aperture is used for image formation of a relatively deep portion, and a narrow-width sector aperture is used for image formation of a relatively shallow portion, which is narrower than the full-width sector aperture. When the width of the sector aperture is narrowed for shallow image formation, it is preferable to provide a wide field of view by increasing the number of parallel lines in the linear scan pattern.
[0010]
In a preferred embodiment, the conversion element array is constituted by a linear array of conversion elements of the same size and spaced apart from one another. Preferably, the parallel lines are spaced from each other at equal intervals, and the sector lines are spaced from each other at equal angles.
[0011]
According to another aspect of the present invention, a system comprising an ultrasonic transducer array, a predetermined number of transmission channels and reception channels, and an electronic switch for selecting transducer elements connected to those transmission channels and reception channels. An ultrasonic image forming method using a sector scanning pattern is provided. This method determines the mapping of the transducer elements for the transmit and receive channels from the size of the sector aperture and the position of the sector aperture on the transducer array, and determines the focusing delay from the sector angle and focus for the sector scan pattern, The focus delay is converted into a mapped focus delay using the mapping, and ultrasonic energy is transmitted and received along the sector scan line of the sector scan pattern using the mapped focus delay. Providing a signal representative of the image along.
[0012]
【Example】
An ultrasonic image forming technique according to an embodiment of the present invention is shown in FIGS. The ultrasonic transducer array 10 typically includes a number of transducer elements in a linear configuration. The manufacturing technology of the ultrasonic transducer array is well known.
[0013]
The composite scanning pattern 12 includes a linear scanning pattern 14 and sector scanning patterns 16 and 18. The linear scanning pattern 14 can be steered at an angle θ with respect to the normal 20 to the array 10, and its ends are bounded by lines 22 and 24. The linear scanning pattern 14 is generated by a large number of parallel scanning lines 26, 28 and others starting from different points on the conversion element array 10. Each of these parallel scan lines can be directed or steered at an angle θ with respect to the normal 20 and can also be parallel to the normal 20. As used herein, the terms “parallel scan line” and “sector scan line” mean lines along which ultrasound energy is transmitted and received. These “scanlines” are the focal point and the center of the active aperture of the transducer array (more specifically, the center of mass of the apodization function for the active aperture of the transducer array). Can be defined as a line between.
[0014]
The sector scanning pattern 16 starts from a vertex 30 on the conversion element array 10, and the sector scanning pattern 18 starts from a vertex 32 on the conversion element array 10. The sector scanning pattern 16 extends from a line 34 that forms an angle α with the normal 20 to a line 22 that is located at the boundary of the linear scanning pattern 14. The sector scanning pattern 18 extends from a line 36 that forms an angle −α with respect to the normal line 20 to a line 24 that is located at the boundary of the linear scanning pattern 14. The sector scanning pattern 16 is obtained by transmitting and receiving ultrasonic energy along the sector scanning lines 33 and 35 extending from the vertex 30 to the lines 34 and 22 and others. Typically, sector scan lines are spaced equiangularly. Similarly, the sector scan pattern 18 is obtained by transmitting and receiving ultrasonic energy along a sector scan line (not shown) that extends between the lines 36 and 24 starting from the apex 32. Accordingly, the sector scanning pattern 16 is adjacent to the linear scanning pattern 14 at one end, and the sector scanning pattern 18 is adjacent to the linear scanning pattern 14 at the other end.
[0015]
The sector scanning patterns 16 and 18 and the linear scanning pattern 14 define the composite scanning pattern 12. The composite scanning pattern 12 has a substantially trapezoidal shape. The reason why the shape of the composite scanning pattern 12 is described as “substantially trapezoidal” is that the lower boundary 38 may not be a straight line. 1A and 1B, the lower boundary 38 includes curved portions 38a and 38b and a straight portion 38c. As an alternative, it is also possible to extend the sector scan lines of the sector scan patterns 16, 18 so that the entire lower boundary of the composite scan pattern is a straight line.
[0016]
Ultrasonic energy is transmitted and received along sector lines of sector scan patterns 16, 18 and parallel lines of linear scan pattern 14 through a partial array of transducer elements in transducer array 10 known as an "aperture". Is done. Apertures that are involved in transmitting and receiving ultrasound energy are known as active apertures. In FIGS. 1A and 1B, the sector scanning patterns 16 and 18 are formed by transmitting and receiving ultrasonic energy via the sector apertures 40 and 42 indicated by the hatched portions of the array 10, respectively. Each of the sector apertures 40 and 42 includes a sufficient number of conversion elements for generating a desired sector scan pattern. The vertex of each sector scan pattern is typically located at the center of the individual sector aperture. In the example described more fully below, the sector apertures 40, 42 each comprise 128 conversion elements.
[0017]
The linear scanning pattern 14 extends from the vertex 30 of the sector scanning pattern 16 at the center of the sector aperture 40 to the vertex 32 of the sector scanning pattern 18 at the center of the sector aperture 42. Each parallel line of the linear scanning pattern 14 has an associated linear aperture as described later.
[0018]
A typical scan of the composite scan pattern 12 can be performed as follows. First, the sector scanning pattern 16 is formed by transmitting and receiving ultrasonic energy by the conversion element in the sector aperture 40 along the sector lines 33, 35 and others starting from the vertex 30. These sector lines extend from a line 34 forming a desired maximum angle α to a line 22 forming an angle θ of the linear scanning pattern 14. In one example, the sector lines are separated by 1/2 degree. Accordingly, in the example of FIG. 1A, the sector lines of the sector scanning pattern 16 are from the line 34 forming 28.5 degrees to the line forming −9.5 degrees adjacent to the line 22 (this is because the line 22 is linear scanning pattern 14). Because it is the first line of). In this example, the sector scan pattern 16 has 76 sector lines. Alternatively, line 22 can be the last sector line of sector scan pattern 16 and the first line of linear scan pattern 14 can be a line adjacent to that line 22.
[0019]
Next, the linear scanning pattern 14 is formed by transmitting and receiving ultrasonic energy via the linear apertures of the array 10. The parallel lines of the linear scan pattern 14 are formed by electronically shifting the active linear aperture across the array 10, typically two transducer elements at a time. The first linear aperture used to form the line 22 is typically the same as the sector aperture 40. The linear aperture is then shifted by two transducer elements, and ultrasonic energy is transmitted and received along a second line parallel to the line 22. The process of moving the linear aperture by two transducer elements and transmitting and receiving ultrasonic energy along parallel lines is repeated until the linear scanning pattern 14 is completed at line 24. Therefore, the linear scanning pattern 14 is composed of a large number of scanning lines parallel to the lines 22 and 24 of the steering angle θ. Here, it will be understood that it is possible within the scope of the present invention to shift the linear aperture between parallel scan lines by only one transducer element or by two or more transducer elements.
[0020]
Finally, the sector scan pattern 18 is formed in the same manner as the sector scan pattern 16. That is, ultrasonic energy is transmitted and received by the conversion element of the sector aperture 42, and a sector line starting from the vertex 32 is formed. The sector line extends between a line 36 that forms the desired maximum angle and a line 24 at the boundary of the linear scan pattern 14. It will be appreciated that the sequence for scanning the sector scan pattern and the linear scan pattern is arbitrary and different sequences can be used. Preferably, however, the scans are performed sequentially from left to right or from right to left.
[0021]
The received ultrasonic echoes along each of the sector lines and parallel lines are converted into electrical signals by the conversion element of the active aperture. The electrical signal is processed as described below to provide an ultrasound image of an area within the composite scan pattern 12. The image is typically displayed on a display screen and has the shape of the composite scanning pattern 12 shown in FIGS. 1 (a) and 1 (b) and described above.
[0022]
The composite scanning pattern 12 described above shown in FIGS. 1 (a) and 1 (b) includes both a steered linear scanning pattern and one or more sector scanning patterns, and is superior to the conventional scanning pattern. It has several advantages. The steered linear scanning pattern 14 provides a high quality image of the structure of interest. This is because the angle θ of the linear scanning pattern 14 can be adjusted so as to be perpendicularly incident on the target structure. For example, as shown in FIG. 1B, when the blood vessel 50 to be investigated is oriented in the direction of the angle θ with respect to the conversion element array 10, the linear scanning pattern 14 is steered to the angle θ. The best image. Sector scanning patterns 16 and 18 greatly expand the field of view.
An example of the conversion element array 10 includes 288 conversion elements having an element pitch (inter-center distance) of 135 μm. The element pitch corresponds to 0.66 times the ultrasonic wavelength at 7.5 MHz and 0.44 times the ultrasonic wavelength at 5.0 MHz. With this configuration, it is possible to steer ultrasonic energy up to at least ± 30 degrees, and a smooth transition between the sector scan pattern and the linear scan pattern is realized. In the conversion element array 10 having 288 conversion elements and a length of 3.89 cm, the scanning width in the conventional linear scanning is 3.4 cm at all depths. When linear scanning is combined with sector scanning according to the present invention, the field of view expands with increasing depth. In the case of the above embodiment having a sector angle of 28.5 degrees and using a variable sector aperture as described below, the field of view at a depth of 4 cm is 6.8 cm, the field of view at a depth of 6 cm is 8.3 cm, and the depth The field of view at 8cm is 9.8cm.
It will be understood that many variations are included within the scope of the present invention. For example, it is not necessary to give sector scan patterns to both ends of the linear scan pattern. Alternatively, a single sector scan pattern can be provided at either end of the linear scan pattern. Further, when sector scan patterns are used at both ends of the linear scan pattern, the sector scan patterns can have different parameters. For example, the sector scan patterns can have different maximum angles and can be transmitted via different sector apertures. Further, the vertex of the sector scanning pattern does not necessarily have to be located on the conversion element array 10. Techniques for generating a sector scan pattern starting from a virtual vertex located behind or in front of the transducer array 10 can be used within the scope of the present invention. Furthermore, the parameters of the conversion element array, including the number of conversion elements and the pitch of the conversion elements, can be selected depending on the particular application.
As a further variation, a transmission splice technique can be used. According to this transmission splice technique, two scanning lines are sequentially transmitted in the same direction from the same starting point on the conversion element array, but the focal depths of these scanning lines are different from each other. This process is repeated for each scan line in the desired scan pattern.
According to another aspect of the present invention, the width of the sector apertures 40 and 42 is changed according to the depth of the target region. Typically, the depth of the image is selected based on the depth of the target area. As described above, the sector scan pattern has a relatively narrow field of view at shallow depths and a relatively wide field of view as the depth increases. The linear scan pattern has a constant field of view at all depths. Utilizing these features, a wide field of view is provided for both shallow and deep imaging. When the aperture is large, a detailed analysis of the deep tissue is possible. With a shallow image formation depth, the width of the sector aperture can be reduced, and the width of the linear scanning pattern can be increased by increasing the number of parallel lines. By expanding the width of the linear scanning pattern, the field of view at a shallow image formation depth is expanded.
Changes in the width of each sector aperture and the width of the linear scanning pattern are shown in FIGS. In FIG. 2 (a), the sector apertures 40 and 42 of the conversion element array 10 have a full width, and the linear scanning pattern extends between the vertices 30 and 32. In one embodiment of the present invention, the conversion element array 10 has 288 conversion elements, and the sector apertures 40, 42 each have 128 conversion elements. The linear aperture also has 128 transducer elements, and this linear aperture is typically shifted from vertex 30 to vertex 32, two transducer elements at a time, forming 81 parallel lines. Is done. The configuration shown in FIG. 2A is suitable for an image forming depth of about 8 cm or more.
The configuration shown in FIG. 2B is suitable for an intermediate image formation depth of about 6 cm. The width of the sector apertures 40a and 42a is narrower than the width of the sector apertures 40 and 42 shown in FIG. Ultrasonic energy is transmitted and received along sector lines starting from the vertices 30a and 32a. The vertices 30a and 32a are at both ends of the transducer array 10 as compared to the vertices 30 and 32 shown in FIG. It is displaced outward toward. The linear scanning pattern extends between the vertices 30a and 32a. In an example of the above-described conversion element array having 288 conversion elements, each of the sector apertures 40a and 42a has 96 conversion elements, and the linear scanning pattern includes 97 parallel lines.
A configuration for forming a shallow image at a depth of about 4 cm is shown in FIG. The widths of the sector apertures 40b and 42b are reduced to the minimum width, and the width of the linear scanning pattern is expanded to the maximum width. The sector scanning pattern starts from the vertices 30a and 30b, and these vertices 30a and 30b are displaced closer to both ends of the conversion element array 10. In an example of a conversion element array having 288 conversion elements, each of the sector apertures 40b and 42b has 64 conversion elements, and the linear scanning pattern has 113 parallel lines.
In the embodiment of FIG. 2 (a), the sector apertures 40 and 42 each have 128 conversion elements, and the linear aperture for transmitting parallel lines of the linear scanning pattern is 128 for each parallel line. It has the number of conversion elements. As shown in FIGS. 2B and 2C, when the width of the sector aperture is narrowed, the width of the linear aperture is preferably narrowed near both ends of the linear scanning pattern. In FIG. 2 (b), the linear aperture is narrowed to the width of the sector aperture in order to transmit and receive ultrasonic energy along a line starting from the vertex 30a. The linear aperture is then displaced along the transducer array by two transducer elements at a time, increasing its width by four transducer elements for each successive scan line, which is This is done until the aperture reaches the desired maximum width in the central portion of the transducer array 10. Next, when the linear aperture approaches the apex 32a, the width of the four elements is reduced for each successive scanning line, and ultrasonic energy is transmitted and received along the line starting from the apex 32a. The width of the sector aperture 42b for performing As the active linear aperture approaches the end of the linear scan pattern, the two apertures are removed from both the leading and trailing edges of the aperture for each successive scan line to symmetrically reduce the aperture. It is desirable to let them. Similarly, when the active linear aperture moves away from the end of the linear scan pattern, two on each leading and trailing edge of the aperture for each successive scan line until the aperture reaches its maximum width. Add a conversion element. This keeps the transmit beam parallel to the receive beam.
[0023]
Alternatively, an asymmetric linear aperture near the end of the linear scan pattern can be used, but the quality of the image away from the transmission focus will be somewhat degraded. In this case, when the active linear aperture reaches the end of the transducer array, its tip channel is not used because it attenuates that end.
[0024]
In the embodiment of FIG. 2 (b) in which the sector apertures 40a and 42a each have 96 conversion elements, the size of the linear aperture is determined from the 96 conversion elements at both ends of the linear scan pattern, and the central portion of the linear scan pattern. Changes up to 128 conversion elements. Similarly, in the case of the embodiment of FIG. 2 (c), the size of the linear aperture ranges from 64 conversion elements at both ends of the linear scanning pattern to 128 conversion elements at the central portion of the linear scanning pattern. Change.
[0025]
The number of conversion elements in the above-described conversion element array shown in FIGS. 2 (a) and 2 (c), the number of conversion elements in the sector aperture with a reduced width, and the number of conversion elements in the linear aperture It will be understood that this is merely exemplary and that other transducer element arrays and aperture sizes are within the scope of the present invention. Furthermore, the relative sizes of the linear and sector apertures are only a design choice. Depending on the relative width of the linear aperture and the sector aperture, it may not be necessary to reduce the width of the linear aperture near both ends of the linear scanning pattern as described above.
[0026]
A simplified block diagram of an example of an ultrasound imaging system suitable for implementation of the scanning technique described above is shown in FIG. Each conversion element of the conversion element array 10 is connected to the electronic switch network 60. The electronic switch network 60 defines an active sector aperture or an active linear aperture by selecting a group of transducer elements for transmitting and receiving ultrasonic energy. In the embodiment of FIG. 3, the conversion element array 10 has 288 conversion elements, and the maximum size of the aperture is 128 conversion elements. The electronic switch network 60 connects the selected conversion element to a transmitter 62 having one transmission channel for each conversion element in the selected aperture. The transmission channels have a programmable delay to steer and focus the transmitted ultrasonic energy. The transmitter 62 supplies appropriately delayed ultrasound pulses via the electronic switch network 60 to the selected transducer element of the sector aperture or linear aperture.
The selected transducer element of the aperture is also connected by an electronic switch network 60 to a receiver 64 having one receive channel for each transducer element in the selected aperture. The receiver 64 steers and focuses the received signal from each conversion element of the selected aperture, and combines the delayed signals to combine the delayed signals (see FIGS. 1A and 1B). ) To represent the images along the sector lines and parallel lines. Those signals are supplied to a display device 68 (typically a CRT) through a signal processing device 66, and an ultrasonic image is displayed. A suitable scan conversion technique used by the signal processor 66 is disclosed in U.S. Pat. No. 4,896,283 issued Jan. 23, 1990 to Hunt et al. It should be noted that the content of the disclosure is included in the present specification with this citation, and detailed description thereof is omitted. The display device 68 provides a display of the image space, as schematically shown in FIGS. 1 (a) and 1 (b). The control unit 70 supplies the control signal to the electronic switch network 60 for the selection of the conversion element, the control signal 70 to the transmitter 62 and the receiver 64 for the selection of the delay, and signal processing for the control of the image display Supply to device 66.
[0027]
The switch network 60 can be regarded as a multiplexer between the conversion element and the processing electronics. A preferred multiplexer is a “tractor treading” multiplexer. The tractor trading technology is disclosed in US patent application Ser. No. 07 / 191,999 filed May 9, 1988. It should be noted that the content of the disclosure is included in the present specification with this citation, and detailed description thereof is omitted. For phased array systems, each received signal of the transducer must be processed in an accurate manner, typically using a predetermined phase correction and delay tap selection within the processing electronics. These phase and tap variables are related to the relative position of the transducer elements in the selected aperture. A suitable technique for implementing a delay using a heterodyne means (mixer) and a tap delay line is disclosed in US Pat. No. 4,140,022, issued Feb. 20, 1979 to Maslak. Also, a delay factor generator for determining the delay factor to be used in performing dynamic focusing is disclosed in US Pat. No. 4,949,259, issued August 14, 1990 to Hunt et al. In addition, those disclosure contents are included in the present specification with the above citations, and detailed descriptions thereof are omitted. Known techniques for transmit apodization and dynamic receive apodization can be used in the system of FIG. A suitable system for implementing the scan pattern of the present invention is the Sonos 1000 system manufactured and sold by the Hewlett-Packard Company.
It will be appreciated that the present invention is not limited to implementation in an ultrasound imaging system of the kind shown in FIG. 3 and described above. For example, if the number of channels in the transmitter and receiver is equal to the number of conversion elements in the conversion element array, the electronic switch network 60 is not necessary. In this case, the selected transmit and receive channels are activated to generate the desired aperture. The scanning technique of the present invention can also be implemented with a digital receive beamformer that digitizes the received signal and then digitally delays it.
A block diagram of a preferred embodiment of an ultrasound imaging system for practicing the present invention is shown in FIG. The basic architecture is based on the aforementioned Patent No. 4,140,022, which employs a so-called “mix and delay (fine delay added to coarse delay) mechanism” for steering and focusing. is there. A selection circuit 100 (corresponding to the above-described electronic switch network 60 shown in FIG. 3) connects the transmission channel and the reception channel of the ultrasonic imaging system to the conversion elements of the conversion element array 10. In the above embodiment, the system includes 128 channels and the transducer array 10 comprises 288 transducer elements. The selection circuit 100 performs tractor trading. Further, the ultrasonic imaging system shown in FIG. 4 includes both a sector focusing circuit and a linear focusing circuit to generate a sector scanning pattern and a linear scanning pattern as described above.
The digital controller 102 determines the operating mode (sector mode or linear mode) and the position of the active aperture on the array 10 for each scan line. In the sector mode, the digital controller 102 also determines the sector line angle α. The sector coefficient generator 104 generates a coefficient of a cubic polynomial when enabled in the sector mode at the time of transmission. The third order polynomial is a series approximation of the formula for the distance from the transform element for the selected focus and sector angle, as disclosed in the aforementioned patent 4,949,259. These coefficients are then rotated and aligned with the active aperture, as determined by the selection circuit 100, and sent to the MAC circuit 106 as a preset. The MAC circuit 106 generates a delay value for each channel, as disclosed in the aforementioned Patent No. 4,949,259. When enabled in linear mode during transmission, the linear coefficient generator 110 generates a delay for each channel for the selected focus and linear angle. The delay is then rotated and aligned with the active aperture as determined by the selection circuit 100. The transmission apodization generator 112 generates a transmission apodization characteristic for the selected transmission focus. The characteristic is then rotated and aligned with the active aperture as determined by the selection circuit 100. The transmission control circuit (TRIX) 114 loads the delay for each channel into the countdown counter. After that counter reaches the final count, TRIX 114 generates a transmit pulse when enabled by transmit apodization generator 112. The power supply 116 supplies a high voltage to the transmission driver 118.
[0028]
The received signal is supplied to the preamplifier 119 by the selection circuit 100. As is known in the art, TGC generator 120 provides a time gain control signal to variable gain amplifier 122 for each receive channel. The sector coefficient generator 104 is used to generate a reception coefficient preset for each focal area when enabled in sector mode upon reception. These coefficient presets are used in the MAC circuit 106 to generate a reception delay. The linear coefficient generator 110 is used to generate a reception delay for each focal area when enabled in linear mode upon reception. The TRIX 114 generates a mixer control signal for the mixer 124 of each reception channel at the time of reception. Receive apodization generator 130 provides dynamic receive apodization characteristics to variable gain amplifier 131. That characteristic is rotated and aligned with the active aperture as determined by the selection circuit 100 before being applied to the receive channel. The sector tap generator 132 generates a tap control signal for the selected focus and sector angle when enabled in the sector mode. This tap control signal is rotated and aligned with the active aperture as determined by the selection circuit 100. The linear tap generator 134 generates a tap control signal for the selected focus and linear angle when enabled in the linear mode. The tap control signal is then rotated and aligned with the active aperture as determined by the selection circuit 100. The tap selector 140 selects one tap on the addition delay line 142. Alternatively, the tap selector 140 can configure the delay line depending on the particular embodiment used to provide an appropriate delay to the scan line. The image detector / scan converter 144 scan-converts the detection signal using the scan conversion technique disclosed in the above-mentioned Patent No. 4,896,283, and displays an ultrasonic image on the video display screen.
[0029]
FIG. 5 shows steps included in the transmission and reception of ultrasonic waves along the sector lines of the sector scanning pattern starting from the sector aperture near one end of the conversion element array 10. In FIG. 4, the steps are performed by a digital controller 102, which can be a microprocessor, and the results are loaded into the sector coefficient generator 104, the apodization generators 112, 130 and the sector tap generator 132. . They can be equipped with random access memory. In step 150, the position of the sector aperture, i.e. one end of the transducer array 10, is determined from the sector angle and the linear angle. The sector aperture is on the left side of the array 10 when the sector line angle is greater than the linear line angle. Otherwise, the sector aperture is on the right side of the array 10. In step 152, the mapping of the transform elements to the transmission channel and the reception channel is determined from the size of the sector aperture and its position. The mapping is necessary because the tractor trading process causes rotation when matching the transducer elements with the system channels. In step 154, coefficient presets are generated according to the above-mentioned patent No. 4,949,259 for the transmit and receive focus and the required sector angle. In step 156, the coefficient preset is mapped according to the previously determined mapping to provide a mapped coefficient preset, which is stored in the sector coefficient generator 104 (see FIG. 4). In step 158, a tap control signal is determined for the indicated focus and the required sector angle. The tap control signal is mapped in step 160 to provide a mapped tap control signal, and the mapped tap control signal is stored in the sector tap generator 132. In step 162, a transmit apodization characteristic and a receive apodization characteristic are generated based on the apodization control signal. The unmapped apodization characteristics are mapped at step 164 and stored in the transmit apodization generator 112 and the receive apodization generator 130, respectively.
[0030]
The examples of the above-described ultrasound imaging system shown in FIGS. 4 and 5 are merely examples of systems suitable for the practice of the present invention, and it is understood that other embodiments can be used as described above. Let's be done.
[0031]
While the presently preferred embodiments of the invention have been illustrated and described, various changes and modifications can be made to the embodiments without departing from the scope of the invention as defined in the claims. It will be apparent to those skilled in the art that this can be done.
[0032]
【The invention's effect】
As described above, the present invention can provide a wide field of view while maintaining the advantages of linear scanning by using a combination of linear scanning and sector scanning.
[Brief description of the drawings]
FIGS. 1A and 1B are explanatory diagrams showing scanning patterns according to the present invention at different linear scanning angles.
FIGS. 2A to 2C are schematic views of a conversion element array showing changes in scanning patterns with respect to different image formation depths. FIGS.
FIG. 3 is a schematic block diagram showing an ultrasonic imaging system for implementing the present invention.
FIG. 4 is a block diagram illustrating a preferred embodiment of an ultrasound imaging system for implementing the present invention.
FIG. 5 is a flowchart illustrating steps associated with generating a sector scan pattern at one or both ends of a linear scan pattern in the system of FIG.
[Explanation of symbols]
10 Ultrasonic transducer array
12 Compound scan pattern
14 Linear scan pattern
16,18 sector scan pattern
20 Normal
26,28 parallel scan lines
30,32 vertex
33,35 sector scan lines
40,42 sector aperture

Claims (2)

An ultrasonic imaging apparatus in a system including an ultrasonic transducer array (10), the apparatus comprising:
Parallel lines starting from different points on the ultrasonic transducer array (10), oriented at a non-zero angle θ with respect to the normal (20) to the transducer array, and defining a linear scanning pattern (14) ( 26, 28), means for transmitting ultrasonic energy by the transducer array (10),
Via the sector aperture (40, 42) of the conversion element array (10) along the sector line (33, 35) starting from the vertex (30, 32) and defining the sector scanning pattern (16, 18) Means for transmitting ultrasonic energy, the sector scanning pattern (16, 18) and the linear scanning pattern (14) adjacent to form a composite scanning pattern (12);
An ultrasonic echo is received by the transducer array (10) along the parallel lines (26, 28) and the sector lines (33, 35), and the parallel lines (26, 28) and the sector lines ( 33, 35) and means for providing a signal representative of the image
Means for changing the width of the sector aperture (40, 42) and the width of the linear scanning pattern according to the depth of the target area;
An ultrasonic image forming apparatus comprising: The means for changing the width of the sector aperture and the width of the linear scanning pattern;
Means to provide wide sector aperture and narrow linear scan pattern for relatively deep image formation, and narrow sector aperture and wide linear scan pattern for relatively shallow image formation ,
The ultrasonic image forming apparatus according to claim 1, comprising:

Images