KR20140013627A - Ultrasonic imaging system - Google Patents

Abstract

An ultrasonic imaging system is disclosed. The system of the present invention can analyze the pattern of an ultrasonic beam on a space from the two-dimensional array probe, when processing an ultrasonic image received from a two-dimensional array probe comprising a plurality of elements, to determine the maximum interval among focal points, can arrange the focal points at intervals less than or equal to the maximum interval among the focal points, wherein the distribution thereof gradually changes according to distances on the space, and can generate focusing delay, based on the positions of the elements of the two-dimensional array probe and the positions of the arranged focal points, thereby being applied to beamforming. [Reference numerals] (10) First beamforming unit; (20) Orthogonal demodulation unit; (30) Bandwidth sampling unit; (40) Second beamforming unit; (50) Interpolation unit; (60) Envelope detection unit; (70) Focal point setting unit; (80) Pixel point setting unit

Description

[0001] ULTRASONIC IMAGING SYSTEM [0002]

The present invention relates to an ultrasound imaging system, and more particularly, to a system for capturing ultrasound data to generate an image.

Ultrasound imaging has been developed as an effective tool for diagnosing a wide variety of disease states and conditions. The ultrasonic equipment market has been steadily growing over the years, and the image quality has been steadily improving.

Presently, a two-dimensional array probe is preferred for imaging ultrasound. When a two-dimensional array is used as compared with the case of a one-dimensional array, more scan lines can be obtained by one transmission. This is because a one-dimensional array can generate several beams simultaneously on one plane to obtain a plurality of scan lines in parallel, but in the case of a two-dimensional array, beams can be simultaneously generated in the upper and lower right and left spaces, This is because the number of lines is doubled as compared with the case of the one-dimensional array probe.

In the conventional hardware based beamforming, signals of many elements are collected by a predetermined number (for example, 64 x 64 = 4096 elements are collected into 128 signals) by sub-aperture beam forming in the probe, After that, it was sent to the system, which beamformed it inside the system. At this time, the beam forming in the probe is performed by an analog ASIC (Application Specific IC), and the beam forming inside the system is performed by a digital ASIC.

Software-based beamforming is a method of processing the beamforming processed by the digital ASIC in the conventional system by software in the system.

Of these software methods, the method of collecting two-dimensional array probe data and performing two-dimensional mapping is called a forward mapping method. However, this requires a large number of computations for signals having coordinates that are not necessary for obtaining one output, and therefore, there is a problem in that the amount of data operation is enormous.

In order to solve such a problem, a backward mapping method is proposed. This is a method of finding a necessary pixel for an output image and calculating the pixel. Therefore, the amount of computation is reduced.

However, in the case of a phased array probe radially arranged as shown in FIG. 1, the scan line becomes excessively dense at a close distance, resulting in an excessive amount of computation. However, There is a problem in that the image quality is deteriorated due to excessively roughening at a long distance.

An object of the present invention is to provide an ultrasound imaging system that minimizes the amount of computation required for a beamforming operation.

According to an aspect of the present invention, there is provided a system for processing an ultrasound image received from a two-dimensional array probe composed of a plurality of elements, the system comprising: analyzing a pattern of an ultrasonic beam on a space from the two- An analysis unit for determining a maximum interval of the focal points; A setting unit for arranging the focal points at intervals equal to or smaller than the maximum interval of the focal points so that the distribution gradually changes according to the distance in the space; And a generation unit that generates a focusing delay according to the position of the element of the two-dimensional array probe and the position of the focal point disposed.

In one embodiment of the present invention, the analysis unit may analyze the spatial frequency component from the ultrasound beam in space, determine the Nyquist sampling frequency in the space, and determine the spatial maximum focal point spacing therefrom.

In an embodiment of the present invention, the setting unit may uniformly arrange the focal points in a region where the beam pattern is dense, and arrange the focal points in accordance with the scan lines in the region where the beam pattern is sparse.

In one embodiment of the present invention, the apparatus may further include a first beamforming unit configured to receive a signal from a plurality of elements of the two-dimensional array probe and to perform sub-aperture beamforming combined with a predetermined number of signals.

In one embodiment of the present invention, the apparatus may further include a second beamforming unit that performs beamforming by applying a focal point to the beam pattern output from the first beamforming unit.

In an embodiment of the present invention, the second beamforming unit may perform beamforming such that a scan line is located at an arranged focal point.

In an embodiment of the present invention, the second beamforming unit may perform beamforming by applying a focusing delay.

According to an embodiment of the present invention, a demodulator may include: a demodulator for converting a beam output from the first beamformer to a complex number; And a sampling unit for performing bandwidth sampling on the output of the demodulation unit.

In one embodiment of the present invention, an interpolation unit performs interpolation with reference to a position of a pixel / voxel point preset for an output of the second beamforming unit. And a detector for detecting the envelope of the output of the interpolator.

According to the present invention as described above, the beam pattern according to the array probe is analyzed in advance, the focal point for the beam pattern is arranged, and the beam forming is performed using the focal point, thereby effectively reducing the amount of calculation required for beam forming It is effective.

Figure 1 is intended to illustrate the general arrangement of scan lines in a phased array probe.
2 is a block diagram of an ultrasound imaging system according to an embodiment of the present invention.
Fig. 3 is an example for explaining the relationship between the element, sub-aperture and aperture. Fig.
4 is a detailed configuration diagram of an embodiment of the focal point setting unit of FIG.
5 is an exemplary view for explaining focal points distributed according to the present invention.
FIG. 6 is an exemplary diagram illustrating a focusing delay generated by the focusing delay table generating unit of FIG. 5;

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that the invention is not intended to be limited to the particular embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

Terms including ordinals such as first, second, etc. may be used to describe various elements, but the elements are not limited by such terms. These terms are used only to distinguish one component from another.

When an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, but other elements may be present in between . On the other hand, when an element is referred to as being "directly connected" or "directly connected" to another element, it should be understood that there are no other elements in between.

The terminology used in this application is used only to describe a specific embodiment and is not intended to limit the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In this application, the terms "comprises", "having", and the like are used to specify that a feature, a number, a step, an operation, an element, a component, or a combination thereof, But do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof.

The present invention proposes a receive beamforming scheme as follows.

1. It is not necessary to place the point to be focused on the scan line. Or, conversely, it is not necessary to place the point to be focused on the pixel (or voxel) to be displayed. In the present invention, these points may or may not be included.

The present invention is characterized in that the spatial resolution is determined from the beam pattern, and the minimum number of points to be focused on the lattice most spaced at an interval satisfying the Nyquist rate of the spatial resolution is set. The lattice is, for example, a lattice on a Cartesian coordinate. However, the present invention is not limited to this, and it is possible to use a spherical coordinate system or a grid on a cylindrical coordinate system, or to arrange the grid freely in an arbitrary position. Or, if necessary, it may be arranged at a density equal to or less than the Nyquist rate.

2. After performing Rx focusing on these points (using, for example, a delay-and-sum method), interpolating the resulting received signal, (RF) data or IQ (Inphase / Quadrature) data or an envelope of the desired pixel (or voxel).

3. In addition, the present invention can perform quadrature demodulation or Hilbert transform at the same time while performing reception focusing so that the output of the reception focusing becomes a complex number. According to this, the amount of computation of the received signal interpolation can be greatly reduced, and the values of I / Q data or envelopes can be easily obtained thereafter.

Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

2 is a block diagram of an ultrasound imaging system according to an embodiment of the present invention.

As shown in the figure, an image system according to the present invention includes a first beamforming unit 10, a quadrature demodulator 20, a bandwidth sampling unit 30, a second beamforming unit 40, An interpolator 50, an envelope detector 60, a focal point setting unit 70, and a pixel point setting unit 80. The interpolator 50 includes an envelope detector 60, a focal point setting unit 70,

The first beamforming unit 10 receives a plurality of ultrasonic signals from an element of a two-dimensional array probe (not shown) and combines them into a predetermined number of signals (for example, 100) and performs subaperture beamforming on the sub-aperture. Sub-aperture beamforming, also referred to as microbeamforming, is known in the art to those skilled in the art.

Fig. 3 is an example for explaining the relationship between an element, a sub-aperture and an aperture, and shows an example of an aperture divided into sub-apertures.

The beam pattern obtained as a result of the beamforming performed in each subperifferer depends on how much delay is applied to the signal of each probe element. For example, the beam may be focused to a single scanline as much as possible, a beam close to a plane wave may be produced, or conversely may be defocused over a wide range. Each sub-aperture can generate an ultrasound beam directed towards the required space.

For example, if one transmission is intended to obtain one scan line, the transmit / receive beam pattern of each sub-aperture will be gathered on the scan line as much as possible. On the other hand, when a plurality of scan lines over a wide range are to be obtained by one transmission, the transmit / receive beam patterns of each sub-aperture will spread evenly throughout the range.

It is obvious that the first beamforming unit 10 of the present invention is a more efficient method in the latter case, but does not preclude the use of electrons.

The direct masking unit 20 transforms the sub-aperture beam subjected to beamforming by the first beamforming unit 10 into a complex number using a quadrature demodulation or a Hilbert transform method.

The bandwidth sampling unit 30 samples the bandwidth with respect to the output of the direct masking unit 20.

The second beamforming unit 40 performs beamforming on the output of the bandwidth sampling unit 30 by setting the focal point setting unit 70. [ Hereinafter, the focal point setting unit 70 will be described first and the second beamforming unit 40 will be described.

The second beamforming unit 40 does not operate in real time but performs a preliminary one-time operation on a given two-dimensional probe (not shown) to create a focusing delay table. Then, the second beamforming unit 40 uses the corresponding table Beamforming is performed.

4 is a detailed configuration diagram of an embodiment of the focal point setting unit of FIG.

The focal point setting unit 70 is for reducing the number of focal points. In other words, you want to place a focal point only where it is absolutely necessary.

The ultrasound B-mode image is to image the distribution of the reflection coefficient within a section of the body (or a volume in the case of a three-dimensional ultrasound), wherein the focal point is an ultrasound beam (In practice, it is not always necessary to focus on all sampling points, but it is necessary to place the sampling point at the focal point for best performance).

However, since the ultrasonic beam has a certain volume due to the diffraction of the ultrasonic wave, the pulse length of the ultrasonic pulse, the incompleteness of the system and the medium, the reflection coefficient at one point can not be sampled, A value obtained by integrating reflection coefficients of a certain volume is obtained. That is, the reflection coefficient in the human body is not ideally sampled, but sampled while blurred by the volume of the ultrasonic beam.

Thus, for example, the width of the ultrasonic beam is wide (i.e., the lateral width of the ultrasonic beam is wide), and it is inefficient to place the focal point in the lateral direction too tightly. Likewise, it is also inefficient to arrange the focal points in the axial direction densely (i.e., the length of the beam in the axial direction is steady), although the ultrasonic pulse length is long.

This situation is equivalent to oversampling in sampling theory. Looking at this on the spatial frequency axis, the spectrum of the reflection coefficient in space is multiplied by the spectrum of the ultrasonic beam shape (which is the low frequency component), so that only low frequency components remain. An unnecessary space is generated in the sampled spectrum. Ideally, the number of samples (ie, focal points) is minimized by adjusting the sampling frequency to barely satisfy the Nyquist rate in the sampling theory. In the present invention, it is intended to arrange a focal point in space so as to satisfy such a bar.

The focal point setting unit 70 includes a beam pattern analyzer 71, a focal grid setting unit 72, and a focusing delay table generating unit 73, as shown in the figure.

The beam pattern analyzer 71 analyzes a pattern of an ultrasonic beam on a space from a two-dimensional array probe, analyzes its spatial frequency component, determines a Nyquist sampling frequency in space, Lt; / RTI >

The beam pattern can be obtained through actual measurement or through simulation. The beam pattern may vary depending on the axial and lateral coordinates. Generally, the front portion closer to the probe is narrower in the lateral width of the beam, and the lateral width becomes wider as it gets farther from the side or more toward the side. Since the axial width is similar to the pulse width, there is no significant change depending on the position.

Accordingly, the focal grid setting unit 72 arranges the focal points at intervals equal to or smaller than the maximum interval of the focal points determined by the beam pattern analyzer 71. [ Since the reflection coefficient sampled at the focal point must be interpolated and the image must be output, the distribution must be arranged so that the distribution gradually varies according to the distance while being evenly distributed in the space.

5 is an exemplary view for explaining focal points distributed according to the present invention. FIG. 5A shows a conventional forward mapping method, FIG. 5B shows a conventional backward mapping method, and FIG. 5C shows a conventional backward mapping method for describing a focal point arranged according to the present invention. will be.

As shown in the drawing, the focal grid setting section 72 of the present invention is a method of arranging focal points evenly in a region where the beam pattern is dense and arranging a focal point in accordance with the scan line in a region where the beam pattern is sparse Is applied.

When the focal points are arranged, the focusing delay table generating unit 73 calculates the focusing delay according to the positions of the array elements of the probes and the focal point positions as follows and stores them in a table format.

FIG. 6 is an exemplary diagram illustrating a focusing delay generated by the focusing delay table generating unit of FIG. 5;

는 포컬 포인트의 좌표이고,

는 어떤 엘리먼트의 좌표, 원점은 스캔라인과 프로브 표면의 교점이다.6,

Is the coordinates of the focal point,

Is the coordinate of an element, and the origin is the intersection of the scan line and the probe surface.

이고,

이다. 송신신호의 경우, 초음파가 원점을 통과하는 시간을 0초라 하면,

점에 위치한 엘리먼트의 송신시간은

로 주어진다. 또한, 수신신호의 경우도 거의 마찬가지로, 초음파가 원점에 도달하는 시간을 기준으로 할 때,

점에 위치한 엘리먼트의 신호의 시간지연은

이다. 이때, c는 초음파의 음속으로, 관습적으로 인체 내 연부조직(soft tissue)의 평균음속은 1540m/s라고 가정한다.At this time,

ego,

to be. In the case of a transmission signal, when the time for the ultrasonic wave to pass through the origin is 0 second,

The transmission time of the element at the point is

. In the case of the received signal, similarly, when the time when the ultrasonic waves reach the origin is taken as a reference,

The time delay of the signal of the element at the point is

to be. In this case, c is the sound velocity of the ultrasonic wave, and it is customarily assumed that the average sonic velocity of the soft tissues in the human body is 1540 m / s.

That is, the focusing delay table generating unit 73 stores the time delay and applies the corresponding time delay during beamforming in real time operation.

The second beamforming unit 40 of FIG. 2 performs a secondary beamforming by applying a set focal point to a bandwidth-sampled ultrasonic beam transmitted in real time. In other words, the beam forming is performed by determining the direction of the beam so that the scan line is located at the arranged focal point (see FIG. 5C), and the focusing delay of the probe element is applied Can be performed.

The interpolation unit 50 performs RF interpolation on the ultrasonic beam with reference to the position of the pixel point, and outputs the RF data . At this time, the output frequency is preferably 1 to 10 MHz.

The envelope detector 60 detects the envelope of the output RF data and outputs the final pixel value.

In the above description, the two-dimensional image processing method is performed, but the three-dimensional image processing method will not be different. That is, a two-dimensional image can be converted into a three-dimensional image from a known technique such as using a voxel point instead of the pixel point of the pixel point setting unit 80.

According to the present invention, the amount of computation can be reduced as compared with the conventional method. 5 (a), a frame rate of 10 times as much as that of the forward mapping method of FIG. 5 (a) can be realized by only the amount of computation required for beamforming, Can be implemented.

While the invention has been shown and described with reference to certain preferred embodiments thereof, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined by the appended claims. Accordingly, the true scope of the present invention should be determined by the following claims.

10, 40: beam forming section 20:
30: Bandwidth sampling unit 50: Interpolation unit
60: Envelope detection unit 70: Focal point setting unit
80: Pixel point setting unit 71: Beam pattern analyzing unit
72: focal grid setting unit 73: focusing delay table generating unit

Claims (9)

1. A system for processing ultrasound images received from a two-dimensional array probe comprising a plurality of elements,
An analyzer for analyzing a pattern of an ultrasonic beam on a space from the two-dimensional array probe to determine a maximum interval of the focal points;
A setting unit for arranging the focal points at intervals equal to or smaller than the maximum interval of the focal points so that the distribution gradually changes according to the distance in the space; And
And a generator for generating a focusing delay according to the position of the element of the two-dimensional array probe and the position of the focal point disposed.
The system according to claim 1, wherein the analyzing unit analyzes a spatial frequency component from a spatial ultrasonic beam, determines a Nyquist sampling frequency in space, and determines a spatial maximum focal point spacing therefrom.
The system according to claim 1, wherein the setting unit disposes the focal points evenly in the area where the beam pattern is dense, and arranges the focal point in accordance with the scan line in the area where the beam pattern is sparse.
The method according to claim 1,
Further comprising a first beamforming portion that receives signals from a plurality of elements of the two-dimensional array probe and performs sub-aperture beamforming combined with a predetermined number of signals.
5. The method of claim 4,
And a second beamforming unit for applying beamforming to the beam pattern output from the first beamforming unit by applying a focal point.
6. The system of claim 5, wherein the second beamforming portion performs beamforming such that a scan line is located at an arranged focal point.
6. The system of claim 5, wherein the second beamformer performs beamforming by applying a focusing delay.
6. The method of claim 5,
A demodulator for converting a beam output from the first beamformer into a complex number; And
And a sampling unit for performing bandwidth sampling on the output of the demodulation unit.
6. The method of claim 5,
An interpolator for performing interpolation with reference to a position of a pixel / voxel point preset for the output of the second beamforming unit; And
And a detector for detecting the envelope of the output of the interpolator.

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