JPH10179589A - Ultrasonic image processing method and device by higher harmonic wave - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce scattering to the outside of a shaft, and prevent scattering to a proximal area by transmitting an ultrasonic wave having a basic frequency in the body, receiving an echo having a higher harmonic wave frequency, and forming an ultrasonic wave-image from this echo. SOLUTION: A transmitting frequency control 117 transmits a desired transmitting frequency by a command of a central controller 120, and makes a converter 112 of an ultrasonic probe 110 transmit an ultrasonic wave of a basic frequency band. This ultrasonic wave enters the body, and its return echo is received by a converter array 112, and is transferred through a T/R switch 114, and is digitalized by an analog-digital converter 115. It is also processed by a beam forming unit 116 and a digital filter 118, and is formed as an echo signal having a higher harmonic wave frequency by excluding a basic frequency. A two-dimensional ultrasonic wave image is displayed on a display 50 through processing of a B mode processor 37 or a contrast signal detector 128. By this constitution, an echo or the like in multiple passages is reduced, and scattering to a proximal area can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic diagnostic method and a body image processing method, and more particularly to a novel ultrasonic diagnostic image processing method and apparatus using a response frequency different from a transmission frequency. This is based on a continuation-in-part application of U.S. Patent Application Serial No. 08 / 723,483, entitled "Ultrasonic Diagnostic Image Processing Method Using Contrast Agent", filed on March 27.

[0002]

2. Description of the Related Art An ultrasonic diagnostic image processing apparatus has been used for image processing of a body by improving the image quality by an ultrasonic contrast agent. Contrast agents are substances that are biocompatible and have specially selected acoustic properties that return readily identifiable echo signals in response to sonication. Contrast agents have several properties that allow for improved image quality of ultrasound images. One is the non-linear nature of many contrast agents. When irradiated with ultrasound at one frequency, the contrast agent is manufactured to exhibit a resonant mode that returns energy at another frequency, especially a harmonic frequency. When illuminated at the fundamental frequency, the harmonic contrast agent will
Returns the fourth and even higher order harmonics.

[0003] It has long been known that tissues and bodily fluids also have inherently nonlinear characteristics. Tissues and bodily fluids create and send back echo response signals at their own non-fundamental frequency, including harmonic signals at the fundamental frequency, even in the absence of contrast agents. Muir and Carstensen studied such a property of water in early 1980 and reported that Starritt et al.
Found these properties in human calf muscle and examined them in cut-out bovine liver.

[0004]

Although these non-fundamental frequency echo components of tissue and bodily fluids are typically not as large in amplitude as the harmonic components returned by harmonic contrast agents, they are not compatible with ultrasound imaging. 3 illustrates a number of features that can be beneficially used in processing. One of the present inventors (M. Averkiou) has conducted extensive research into these properties in the work described in her doctoral dissertation. In this and other studies, we saw that the main lobe of the harmonic beam was narrower than its fundamental frequency lobe, and they found that imaging through a narrow mouth, such as a rib. This is the possibility of the scattering reduction at the time. They saw that the side lobe levels of the harmonic beams were lower than the corresponding side lobe levels of the fundamental beam, and found a potential for off-axis scattering reduction. They also found that the return of the harmonics from the near region was relatively smaller than the return energy at the fundamental frequency, and found the possibility of preventing near-region scattering. As explained below,
These properties are utilized in the method and construction embodiments of the present invention.

[0005]

According to the present invention, there is provided an ultrasonic image processing apparatus and method for performing image processing of tissue and body fluid from a response frequency different from a transmission frequency returning from tissue or body fluid, in particular, a harmonic echo of a transmission fundamental frequency. Is provided. The image processing apparatus includes a unit for transmitting an ultrasonic wave of a fundamental frequency, a unit for receiving an echo of a harmonic frequency, and an image processor for creating an ultrasonic image from the harmonic frequency echo. In a preferred embodiment of the invention, the transmitting and receiving means comprises a single ultrasonic probe. Another feature of the present invention is that the probe utilizes a broadband ultrasonic transducer for both transmission and reception.

[0006] A further feature of the present invention is that a partially decorrelated component of the received harmonic echo is created and used to remove virtual images from the harmonic image, thereby providing an image of the endocardium, such as an endocardial image. The purpose is to provide a clearly identifiable image. In a preferred embodiment, partially decorrelated components are created from harmonic echoes in different passbands. The method of the invention involves the use of harmonic echoes to reduce proximity or multipath scatter in ultrasound images, for example, images created during image processing through narrow acoustic windows, such as ribs. . Additional features of the invention include blending harmonics and fundamental frequency echoes into a common image to reduce noise, image processing at significant depths, and overcome depth-dependent attenuation effects.

FIG. 1 is a block diagram illustrating an ultrasonic diagnostic image processing apparatus according to the present invention. FIG.
3, 4, and 5 describe some properties of harmonic echoes that can be beneficially applied to ultrasound imaging applications. 6 and 7 are passband characteristic curves used to describe the behavior of the example of FIG. FIG. 8 illustrates typical basic and harmonic frequency passbands of the inventive example.
FIG. 9 illustrates an FIR filter structure suitable for use in the example of FIG. FIG. 10 is a block diagram of a preferred embodiment of the present invention. FIG.
The operation of the normalization stage of the example will be described. FIG.
6 is a block diagram of one of the multiplier accumulators used in the example filter. FIG. 13 illustrates typical basic and harmonic frequency passbands for the example of FIG. FIG.
Describes the blending of basic and harmonic signal components into one ultrasound image. FIG. 15 illustrates the passband of the time-varying filter used for forming the blended image.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring first to FIG. 1, an ultrasonic diagnostic imaging apparatus constructed in accordance with the present invention is shown in block diagram form. Central controller 120
Commands the transmission frequency control 117 to transmit a desired transmission frequency band. The variable of the transmission frequency band, f _tr , is
The signal is sent to the transmission frequency control 117 and the ultrasonic probe 110
Of the transmitter 112 emits an ultrasonic wave in the fundamental frequency band. In the configuration example, a frequency band having a center frequency of approximately 1.67 MHz is transmitted. This is usually 2.
It is lower than the conventional outgoing image processing frequency, which was in the range of 5 MHz or more. However, 3 or 5 MH
The use of typical transmission frequencies of z is 6 and 10 MHz
Create harmonics of Because high frequencies are attenuated more during passage through the body than low frequencies, these high frequency harmonics will experience significant attenuation as they return to the probe. Since the harmonic signal is generated while the transmitted wave travels through the tissue, it does not decay as much as the fundamental frequency signal, which experiences attenuation due to round trip from the transducer, but this reduces the penetration depth, And it degrades image quality at larger image processing depths. To overcome this problem, the center oscillation frequency in the example described is 5
MHz or less, preferably 2.5 MHz or less, which allows lower frequency harmonics to be formed that are less susceptible to depth-dependent attenuation, and allows deeper harmonic imaging. The transmit fundamental frequency of 1.67 MHz creates a return signal of the second harmonic of 3.34 MHz in the example described. Of course, it will be appreciated that ultrasound of any frequency can be used, with due consideration of the desired penetration depth, transducer and sensitivity of the ultrasound device.

The array converter 112 of the probe 110
Transmits ultrasonic energy and receives echoes returned in response to the transmission. The response characteristics of the converter show two passbands, one around the fundamental oscillation frequency and one near the harmonic frequency in the reception passband. For harmonic image processing, a broadband converter having a passband that includes both the transmit fundamental frequency and the receive harmonic passband is preferred. Converter is adjusted manufactured to exhibit response characteristics as shown in FIG. 6, there kelp 60 having a lower response characteristic curve is is centered around outgoing fundamental frequency f _r, and higher kelp 62 is centered around the reception harmonic frequency f _r of the response passband. However, the transducer response curve of FIG. 7 is preferred, since a single primary characteristic curve 64 allows the probe to be suitable for both harmonic imaging and conventional broadband imaging. Characteristic curve 64 includes encompasses outgoing fundamental frequency f _t, and included between the frequency f _L and f _c, and also the reception passband of harmonics centered around the frequency f _r. As mentioned above, the low fundamental oscillation frequency of 1.67 MHz is 3.
A return echo signal of a harmonic having a frequency of 34 MHz is formed. A response characteristic 64 of approximately 2 MHz is appropriate for these fundamental and harmonic frequencies.

[0010] Tissues and cells of the body alter the fundamental frequency signal emitted during the course of the process, and the return echo
It contains harmonic components of the fundamental frequency originally transmitted. In FIG. 1, these echoes are received by a converter array 112, transferred through a T / R switch 114, and digitized by an analog-to-digital converter 115. The sampling frequency f _s of the A / D converter 115 is controlled by a central controller. The desired sampling rate (r
ate) is at least twice the highest frequency f _c of the received passband, in the frequency in the previous example, the at least 8MHz about. Sampling rates higher than the minimum required are also preferred.

The echo signal samples from the individual transducer elements are delayed and summed by beamformer 116 to form a coherent echo signal.
The in-phase digital echo signal is then filtered by digital filter 118. In this example, the transmission frequency ft is _independent of the receiver, so that the receiver is free to receive a frequency band different from the transmitted band. The digital filter 118 corresponds to FIG.
Can be bandpass filtered frequency f _L and the signal in the pass band separated by f _c of, and also to move the frequency band to a lower or baseband frequency range. The digital filter in the above example has a 1 MHz passband and may be a filter with a center frequency of 3.34 MHz. The preferred digital filter is a series of multipliers 70-73 and accumulators 80-83, as shown in FIG. This arrangement is controlled by the central controller 120 and provides multiplier weighting and decimation control for controlling the characteristic curve of the digital filter. Preferably, this arrangement is controlled to act as a finite impulse response (FIR) filter, performing both filtering and decimation. For example,
Only the first stage output 1 has a 4: 1 decimation ratio of 4
It can be controlled to work as a tap FIR filter. The temporally discontinuous echo sample S is transferred to the multiplier 70 in the first stage. As the samples S are transferred, they are multiplied by the weight given by the central controller 120. Each of these products is stored in accumulator 80 until four such products are accumulated (added). Next, an output signal is created at the first stage output 1. Since the accumulated sum consists of four weighted samples, this output signal is filtered by a 4-tap FIR filter. Since a time for four samples is required to generate an output signal, a 4: 1 decimation ratio is realized. One output signal is formed for every four input samples. The accumulator is cleared and the process is repeated. It can be seen that the higher the decimation ratio (the longer the interval between output signals), the greater the number of effective taps of the filter.

If desired, the time-divided samples are delayed by a delay element τ, applied to four multipliers 70-73, multiplied, and accumulated in accumulators 80-83. After each accumulator accumulates the two products, the four output signals are combined into one output signal. That is, the filter operates as an 8-tap filter having a 2: 1 decimation ratio. Without decimation, this arrangement can operate as a 4-tap FIR filter. The filter can also be operated by transferring the echo signal to all multipliers simultaneously and by selectively weighing the coefficients in time.
Under the control of the central controller, the entire range of the filter characteristic curve is possible by programming the filter weights and the decimation ratio. The use of digital filters has the advantage that it can be changed quickly and easily to provide different filter characteristic curves. The digital filter can be programmed to first pass the received fundamental frequency and then pass the harmonic frequencies. Thus, the digital filter can be operated to alternately create images or scan lines of the fundamental and harmonic digital signals, and the time interleaved sequence is simply changed by the filter coefficients during signal processing. Can be operated to alternately generate scanning lines of different harmonics.

Returning to FIG. 1, the digital filter 118 is controlled by the central controller 120 so that only the non-fundamental frequencies are image-processed. To process.
Harmonic echo signals from the tissue are detected and processed by either the B-mode processor 37 or the contrast signal detector 128 for display on the display 50 as a two-dimensional ultrasound image. The filtered echo signal from digital filter 118 is also forwarded to Doppler processor 130 for conventional Doppler processing to form a velocity and power Doppler signal. The output of these processors is 3D for 3D image creation.
Transferred to image creation processor 162, which stores them in 3D image memory 164. These three-dimensional representations are
It can be implemented as described in US Patent Application Serial No. 08 / 638,710, and US Patent Nos. 5,474,073 and 5,485,842, the latter two patents being three-dimensional power Doppler Describes an ultrasound image processing technique. The signals from the contrast signal detector 128, the processors 37 and 130, and the three-dimensional image signal are transferred to a video processor 140, where the signals are displayed on the image display 50 in two or three dimensions according to the instructions selected by the user. Selected for display.

It has been found that harmonic imaging of tissue and blood can reduce the scattering of nearby areas in ultrasound images. It is believed that the harmonic response effect of the tissue depends on the energy level of the transmitted wave. Close to the array transducer, which is focused deeper, the transmitted wave component is not focused, and there is insufficient energy to produce a detectable harmonic response in the adjacent area tissue. However, as the transmitted wave continues to penetrate the body, higher intensity energy produces harmonic effects as the ultrasound components begin to focus. While both the near and distant regions return a fundamental frequency response, the scatter from these signals is reduced by the digital filter 11 set in the harmonic frequency band.
8 passbands. Harmonic responses from the tissue are then detected and displayed, while scatter from the near-field fundamental frequency response is eliminated from the displayed image.

FIGS. 2, 3, 4 and 5 illustrate some characteristics of harmonic return signals that can be beneficially used in ultrasound imaging. These properties, and some of their interactions, are not yet fully and generally understood among scientists and are still considered for study and discussion. FIG. 2 illustrates the spatial response of the fundamental and harmonic signals received by the transducer array 112, particularly the main and side lobes. In this example, the array is instructed to image a body area behind the ribs, such as the heart, and the main lobe is
It is visible extending between ribs 10 and 10 '. Overlying the ribs are tissue boundaries 12, such as the fat layer between the skin and the ribs. The figure shows the main lobe of the basic signal FL1, and the side lobes F on both sides of the main lobe.
There is L2FL3. The figure also shows the main lobe HL1 of the harmonic of the fundamental frequency and the side lobe HL of the harmonic main lobe.
2 and HL3 are shown.

In this example, it can be seen that the main lobe of the basic echo is so large that it covers the ribs 10, 10 '. Therefore, the acoustic energy at the fundamental frequency reflects back to transducer 112, as indicated by arrow 9. On the other hand, some of the energy of this reflection returns to the transducer and is received directly, but in this example, some of the reflected energy is reflected back by the tissue boundary 12, as shown by arrow 9 '. This second energy reflection reaches another rib 10 ', where it reflects again, as shown by arrow 9 ", and
Return to and be received.

Since the intent of this image processing technique is to image the heart behind the ribs, these echoes reflected by the ribs are unwanted virtual images that contaminate the ultrasound image. Echo following the path of arrow 9, 9'9 "
Unwanted echoes that are reflected many times before reaching the transducer are called multipath artifacts. At the same time, these virtual images are called image "scattering" and obscure the nearby areas, and in some cases the entire image. This haze or scattering of the proximity region may obscure the structure of interest near the transducer. In addition, multipath virtual images may be regenerated in deeper images due to the lengthy multiple paths that these virtual images follow, causing noise and obscuring deeper regions of interest. There is. However, if only the harmonic return signal is used to create the ultrasound image, the scatter from this fundamental frequency will be filtered out. Since the main lobe HL1 of the received harmonic echo is narrower than the lobe of the fundamental frequency, in this example, it passes between the ribs 10, 10 'without crossing them. There is no return of harmonics from the ribs,
There are no multipath virtual images from the ribs. Thus, the harmonic image is an image that is significantly less scattered and less fogged than the fundamental frequency image, especially in the vicinity, in this example.

FIG. 3 shows a second example in which the main lobes of both the fundamental frequency and the return of the harmonics do not intersect the ribs and do not suffer from the problems discussed in FIG. But in this example,
Ribs 10, 10 'are applied to the skin surface and transducer 112,
Closer. The main lobe does not cross the ribs, but the fundamental frequency side lobe FL2 reaches the ribs and reflects the side lobe energy back to the transducer, as shown in reflection path 9. Again, this causes scattering in the fundamental frequency image.
However, the smaller and narrower sidelobe HL2 of the received harmonic energy does not reach the ribs. Again, the harmonic image is displayed with less scattering than the fundamental frequency image.

FIG. 4 traverses the lobes of FIGS. 2 and 3,
That is, the fundamental frequency and harmonic beam patterns in the perspective view, crossing the axis of the transducer, will be described. This figure illustrates the relative amplitude response of the fundamental frequency and the second harmonic beam shape. Dynamic response DRF between the main lobe (FL1) of the fundamental component of the acoustic beam and the first side lobe (FL2), and between the main lobe (HL1) and the first side lobe (HL2) of the second harmonic component Is described. If the response due to the main lobe is regarded as the desired signal response and the response due to the side lobes is scattered or noise, the signal to noise ratio of the harmonics is greater than that of the fundamental frequency. That is, the side lobe scattering is relatively smaller in the harmonic image than in the corresponding fundamental frequency image of the same transmission, or DRH> DRF.

FIG. 5 illustrates another comparison of the characteristics of the fundamental and harmonic signals, which show the energy exiting from a deeper location Z in the body at the fundamental and second harmonic frequencies (the acoustic pressure P). (In units). Fun
d. The curve labeled with indicates that the advanced acoustic energy at the fundamental frequency has been built up. You can see that the curve peaks at the focus of the array transducer,
It can be seen that there is still a perceptible amount of fundamental energy in the shallow part before the focal region. By comparison, at these harmonic frequencies that proceed to these shallow regions,
There is a relatively much smaller energy and a smaller energy boost. Thus, near-field scattering is less with harmonic imaging than with return imaging of the fundamental frequency echo from the same transmission, since less energy was used for multipath echoes and other anomalies.

FIG. 8 illustrates the digital filter and received signal bandwidth of the exemplary FIG. 1 example of the present invention for a transmitted signal of four cycles of a 1.67 MHz sound wave. Multi-cycle transmission reduces the bandwidth of the transmitted signal; the more cycles, the lower the bandwidth. In response to this transmission, converter 112 receives the basic signal in bandwidth 90,
It can be seen that it culminates at a transmission frequency of 1.67 MHz. It can be seen that as the fundamental frequency band decreases, the harmonic band 92 rises and peaks again at a harmonic frequency of 3.34 MHz. The received signal is transferred to the digital filter with a passband characteristic curve 94, which is 3.3
It can be seen that there is a center around the 4 MHz harmonic frequency.
As FIG. 8 shows, this pass band essentially passes harmonic signals for further processing and imaging, while
Suppress fundamental frequency signals. When imaging the heart in this manner, it can be seen that the harmonic response of the heart's intracardiac tissue is very substantial, and that the harmonic tissue image of the heart shows clearly identified boundaries in the heart. Was issued.

To separate and extract the harmonic signal from the received echo information, for example, by separating the fundamental frequency in the broadband signal and leaving only the harmonic frequency, other signal processing techniques other than filtering can be used. For example, U.S. Pat.
28,318] discloses a two-pulse technique, whereby
Each scan line is illuminated with a continuous fundamental frequency pulse of rapid succession in opposite phase. When the resulting echoes are received from two pulses and combined on a spatial basis, the fundamental frequency is removed and the non-linear or harmonic frequencies remain. Thus, the harmonic frequencies are separated from the broadband echo signal without the need for a filter circuit.

FIG. 10 is a block diagram showing a part of the preferred embodiment of the present invention, from the output of the beam former to the image display device. This example not only produces harmonic images of tissue and blood flow, but also overcomes the disadvantages of signal dropout of conventional imaging devices that occur when imaging patients who have difficulty imaging a medical condition. Moreover, in this example, the virtual image of the in-phase ultrasound image, known as speckle, is reduced. In FIG. 10, all the signals and data connected to the blocks of the block diagram are
The lines represent a multi-conductor digital data path.
Scan line echo data from beamformer 116 is sent in parallel to two channels 30a, 30b of the processor described in FIG. 10, one for the high frequency channel and the other for the low frequency channel. Each channel of the processor is normalized
Steps 32 and 132 are included to integrate the scan line data with a scale factor for each sample to form a different gain or attenuation depending on the depth of the body to which each sample returns.
The scale factor for each channel is provided by the normalized coefficients created or stored by coefficient circuits 32, 132, which are preferably digital memories. Since the integration factor varies along a series of scan line echoes,
A depth dependent gain or attenuation is created.

There are two functions in the normalization stage. one,
It is to compensate for the effect of the transducer aperture which is extended by the scanning depth. As the signal from an increasing number of transducers is used with increasing depth, the magnitude of the summed beamformed signal increases. This increase is offset by a decrease in gain (increase in attenuation) in the normalization stage, which is proportional to the rate at which circuits are added to the beamforming process,
The resulting echo sequence will not be affected by the changing aperture.

The second function of the normalization stage is to equalize the nominal signal amplitude of the two channels 30a, 30b. The nominal signal amplitudes of the passbands of the two channels are preferably equal, and the original relative signal levels are maintained after the passbands are summed to create the total harmonic passband. However, since ultrasonic signals have depth-dependent attenuation that changes with frequency, high-frequency signals have greater attenuation by depth than low-frequency signals. In view of this depth-dependent attenuation, the coefficients of the normalization stage provide a signal gain that increases with depth. Since the two channels use different frequency passbands, the depth-dependent gains of the two channels are different from each other. In particular, the rate of gain increase for the high frequency passband channel is greater than for the low frequency passband channel. This will be described with reference to FIG. 11. For the sake of description, a normalized gain characteristic curve of a high-frequency passband channel divided into two components is shown. Depth dependent characteristic curve 200
Cancels the effect of the increased aperture in the channel, and the depth-dependent characteristic curve 202 compensates for the depth-dependent signal attenuation. The low frequency passband channel also has a depth dependent gain characteristic, but results in a different characteristic curve 202 due to the different attenuation rates of the lower frequencies. The high frequency passband channel has a similar, but more rapidly increasing, depth dependent gain characteristic curve due to the faster rate of attenuation by higher frequencies. Each depth-dependent gain characteristic curve 20
2 is selected to offset the depth-dependent gain effect for the particular frequency passband used by the channel.

In a preferred embodiment, the coefficients of the coefficient circuit apply a gain or attenuation characteristic curve combining the two characteristic curves 200,202. Preferably, the coefficient memory 32,
132 stores a multi-coupling gain curve that changes with memory addressing to match scan head characteristics or the type of signal being processed (2D or Doppler). The rate of gain change can be controlled by the rate at which the coefficients change for the multipliers in the respective normalization stages 30,130.

The normalized echo signals of the channels are transferred to the quadrature bandpass filters (QBP) of each channel. The quadrature bandpass filter performs three functions: band limiting RF line data, creating in-phase and quadrature pairs of line data, and reducing digital sample rate. Each QBP consists of two separate filters, one to create an in-phase sample (I) and the other to create a quadrature sample (Q), each filter being a plurality of filters implementing an FIR filter. Multiplier-accumulator
(MAC). One such M
AC is shown in FIG. When the echo sample of scan line data is sent to one input of digital multiplier 210, the coefficients are sent to another multiplier input. The product of the echo sample and the weighting factor is stored in accumulator 212 and accumulated with the previous product. Other MACs receive echo samples of different phases and accumulate similarly weighted echo samples. The output accumulated by several MACs is combined, and the final accumulated product consists of the filtered echo data. The rate at which the accumulated output is taken sets the decimation ratio of the filter. The length of the filter is the product of the decimation ratio and the number of MACs used to form the filter, and determines the number of input echo samples used to create the accumulated output signal. The filter characteristics are determined by the coefficient value of the multiplication. Different coefficient sets for different filter functions are stored in coefficient memories 38, 138 and forwarded to the MAC multiplier,
The selected coefficient is applied. The MAC efficiently convolves the received echo signal with coefficients expressed in sine and cosine to create an output sample in quadrature.

The coefficients for the MAC that form the I filter are
Perform the sine function, while the coefficients for the Q filter perform the cosine function. For band pass filtering, the coefficients of the active QBPs are further frequency shifted to perform a low band pass filter function by means of a sine (for I) and cosine (for Q) functions to form a band pass filter for the quadrature sample. I do. In this example,
QBP _{1 in} channel 30a creates I and Q samples of the first, low frequency passband scan line data, and channel 3
OBP QBP ₂ creates I and Q samples of the second, high frequency passband scan line data. Therefore, the spectrum of the original broadband echo signal is divided into a high frequency band and a low frequency band. To complete the dropout and speckle removal step, the echo data in the passband created by QBP ₁ channel 30a is detected by the detector 40 _1, sensed signal to one input of summer 48 Will be transferred. In a preferred embodiment, the detection is performed by the following algorithm

(I ² + Q ² ) ^1/2

Is performed digitally by calculating Echo data in the complementary passband created by QBP ₂ channel 30b is detected by the detector 40 _2, these sensed signal summer 48
To the second input. When the signals in the two passbands are combined by summer 48, the decorrelated signal dropouts and speckle effects in the two passbands are at least partially removed, and the signal dropouts and specs in the 2D image created from the signals are removed. Reduce virtual images.

The multiplier 4 Following detector in each subchannel, the coefficient memory 42 _1, 42 ₂ from receiving a weighting factor
4 _1, there is a gain stage formed by 44 _2. The purpose of this gain stage is to balance analog and digital gain in the ultrasound system for best system performance. Some gains in the echo signal path are performed automatically by the ultrasound system, while other manual gain controls and TGC gains can be controlled by the user. The device distributes these gains and adjusts the analog gain of the beamformer before the ADCs (analog to digital converter) to optimize the dynamic input range of the ADCs. The digital gain is adjusted to optimize the brightness of the image. Both gains implement the change in gain adjustment made by the user.

[0032] In a preferred embodiment, the applied gain the scan line signal by the multiplier 44 _1, 44 ₂ is selected to cooperate with the previous gain normalization stage 34,134 in the channel. The gain of each normalization step is determined by the Q, as occurs when a strong signal from contrast agent or harmonic imaging is received.
It is chosen to prevent the achievement of saturation levels in BPs. To avoid saturation levels the maximum gain of the normalization stage is controlled, and any reduction that is loaded for the control is also restored by the gain of the subsequent multipliers 44 _1, 44 _2. The gain function implemented by these multipliers is
It can be performed anywhere along the digital signal processing path. It can be performed by changing the slope of the compression curve discussed below. It can also be performed, for example, in connection with the gain given in the normalization stage. However, this latter implementation eliminates the ability to perform the saturation control described above. We have found that the ability to perform this gain function, when provided after detection, is canceled, preferably by the use of a post-detection multiplier.

The signal generated by the gain stage 44 _1, 44 _2, generally exhibit greater dynamic range than is provided by the display 50. As a result, the scan line signal of the multiplier is compressed to an appropriate dynamic range by the look-up table. Generally, as shown by a logarithmic compression processor 46 _1, 46 _2, the compression is logarithmic compression. The output of each look-up table is proportional to the logarithm of the signal input value. These look-up tables are programmable so that the brightness and dynamic range of the compression curve and the scan line signal sent to the display can be varied.

The use of logarithmic compression in echo signal normalization can adversely affect low level signals near the baseline (black) level of the signal dynamic range due to the degradation in the degree and number of echoes of the black level component. The present inventors have discovered that the catastrophic failure resulting from the speckle effect of the coherent ultrasonic energy is manifested. When the echo signals are displayed, many of them are at the black level and will be undetected or missing from the image. The example of FIG. 10 illustrates this problem with two channels 30.
Mitigation is achieved by creating echo signals that are separated and partially decorrelated in a, 30b. In this example, as shown in FIG.
The echo signal version is partially decorrelated by splitting the echo signal component into two different passbands. The two passbands can be completely separated or can overlap, as shown in this example. In this example, the low pass band 300a is centered around the frequency of 3.1 MHz, the high pass band 300b is centered around the frequency of 3.3 MHz, and the center frequency is separated by 200 kHz.
It's just Even with this small separation, the signal components of the two passbands are sufficiently decorrelated so that the black level signal dropout in one passband is often not frequency aligned with its corresponding component in the other passband. It turned out to be enough to do. Thus, when these decorrelated replicas of the same echo signal are combined by summer 48, signal dropouts and speckle virtual images will be significantly reduced. This is particularly important when trying to image the fine structure of deep parts of the body, such as the endocardium. The harmonic image of the endocardium is significantly improved by the virtual image removing effect of the example of FIG.

As discussed above, the signal gains of the two passbands 300a, 300b of FIG. 13 can be adjusted to preserve the original signal level after summing. However, in a preferred embodiment, the low frequency pass band is processed with a smaller dynamic range than the high frequency pass band, as shown in FIG. This is a low frequency passband (it is
(Contains more fundamental frequency components than the high frequency band)
Has the effect of suppressing the contribution of the fundamental frequency. This, as a component of different compression characteristics, after separation into divided passband of the broadband signal, a logarithmic compression processor 46 _1, 46 _2, or channels 30a,, carried out in another stroke in 30b.

The processed echo signal output from the summer 48 is transferred to a low-pass filter 52. This low-pass filter, like QBPs, is formed by a multiplier-accumulator combination with variable coefficients arranged to implement an FIR filter and controls the filter characteristics. The low pass filter performs two functions.
One is to remove the sampling frequency and other unwanted high frequency components from the processed echo signal. The second function is to match the scan line data rate to the vertical line density of the display 50 to prevent aliasing in the displayed image. FIR filters perform this function by selectively decimating or interpolating scan line data. The filtered echo signal is then stored in the image memory 54. If the scan lines have not been scan converted yet, ie, they are r,
If the scan line has θ coordinates, the scan line is straightened by the scan converter and grayscale mapping processor 56 (re
scan converted to ctilinear) coordinates. If scan conversion has been performed in a previous step, or if scan conversion is not required for the image data, processor 56
The echo data is simply converted to the desired grayscale map by a look-up table process. The image data is then sent to a video display driver (not shown) for storage in the final image memory or for conversion to a display signal suitable for driving the display 50.

Due to the rapid programmability of the digital filter, the above processing is performed in a time-interleaved manner by alternately producing a row of signals for each of the two passbands, thereby allowing any one of the channels 30a, 30b to be created. It is understood that this can be performed in an embodiment in which echo data from a scan line is processed twice by using Eq. However, the use of two parallel channels allows for the creation of harmonic images at twice the frame rate of the real-time time multiplex example, since there is twice the processing speed.

A harmonic image created from a high-frequency signal may deteriorate due to depth-dependent attenuation as the echo signal returns deeper into the body. Lower frequency fundamental signals may exhibit better signal-to-noise ratio at deeper locations due to less attenuation. FIG.
Uses this characteristic by blending the fundamental frequency and harmonic image data into one image.
For example, a normal tissue image of the heart can be created from the fundamental frequency, and a harmonic tissue image of the heart can be superimposed on the fundamental frequency tissue image to more clearly identify intracardiac boundaries in the composite image. Can be. Two images, one from the fundamental frequency component and one from the harmonic frequency component, are obtained by alternately switching the digital filter 118 between the fundamental and harmonic frequencies. The harmonic images are formed separately by combining or using the two parallel filters of FIG. 10 having two pass bands, one set passing the fundamental frequency and the other set passing the harmonic frequencies. be able to. In FIG. 14, the filter for channel 30a is set to pass the fundamental signal frequency, and the echo signal that has passed this channel is stored in the fundamental image memory 182. Correspondingly, the harmonic signal frequency passes through channel 30b and is stored in the harmonic image memory. The fundamental and harmonic images are then blended by proportional combiner 190 under the control of blend control 192.
Blend control 192 automatically executes a pre-programmed blending algorithm or executes user instructions. For example, the proportional coupler 190 uses only echo data from harmonic images at a shallow depth,
Then, at intermediate depths, the echo data from both images are combined, and finally at deeper depths, a mixed image is created using only the echo data of the base image. This has the benefit of reducing the scattering of harmonic echo data at shallow sites, while achieving a smooth transition from one data type to the other at intermediate depths, as compared to fundamental frequency echoes received from deep sites. It combines high penetration capability and signal-to-noise ratio. For example, simply switch from one data type to another at a predetermined depth,
Or other combining algorithms are possible, such as delineating the displayed image area in one data type and displaying the remaining images using the other data type.

It is also possible to use two parallel filters to blend the components prior to image construction, thereby adding a controllable component of the harmonic echo signal to the fundamental frequency signal and improving the quality of the resulting image It is. In such an example, the need to store the fundamental and harmonic images in separate memories can be eliminated, and the signal components are processed directly into the blended image memory.

A third technique for creating a blend image is to receive each scan line of the image through a depth-dependent, time-varying filter. Such filters are known to improve the signal-to-noise ratio of the received echo signal in the presence of depth-dependent attenuation, for example, as shown in U.S. Pat. No. 4,016,750. For the purpose of creating the blended basic and harmonic images, the pass band 210 of the time-varying filter is designed to pass the harmonic frequency f _h as shown in FIG. Is set. When it becomes desirable to start supplementing the image with the fundamental signal component at a deeper part, the pass band 210 moves to a lower frequency,
As shown in the passband 212, eventually moving to the fundamental frequency f _f. In the digital filter as shown in FIG. 9, the change of the pass band frequency is executed by changing the filter coefficient with time. When the filter performs this shift, the passband passes only a few harmonic frequencies and many fundamental frequencies, if desired, until the passband eventually passes only the fundamental frequency at the deepest image depth. By receiving each scan line through such a time-varying filter, each line of the resulting image will have a harmonic frequency in the near region (shallow region), a fundamental frequency in the remote region (deepest region), and intermediate frequencies. Then, it will consist of a blend of both.

Fourth for Creating Blended Images
Is to transmit and receive twice along each scan line. One transmission is at the fundamental frequency, followed by the reception of the harmonic frequency echo. Other transmissions are at the fundamental frequency, followed by receipt of the fundamental frequency. The two fundamental frequencies are the same, but may be different if desired. The harmonic and fundamental frequency echoes are then combined along the scan line at the desired rate to form a blended scan line, and an image area of such a scan line is created to form a blended image . US Patent Application Serial No. 08 / 655,394 entitled "Medical Ultrasound Power Motion Image Processing Method", which is exercising by processing a received harmonic tissue echo signal with a processor. A harmonic tissue image of the tissue can also be formed.

Accordingly, the present invention provides a non-linear response of body tissues and fluids to ultrasound by transmitting a fundamental frequency signal and receiving echo signals from non-basic, preferably harmonic, frequency tissue. An ultrasonic image processing apparatus that detects an echo signal of a fundamental frequency and performs image processing by forming an image of tissue and body fluid from the non-fundamental frequency echo signal is included. Since the principles of the invention described herein are equally applicable to higher and subharmonic frequencies, the term harmonic as used herein is even higher than the second harmonic. Both the next harmonic frequency and the subharmonic are meant.

The present invention discloses an ultrasonic diagnostic image processing method using a response frequency different from the transmission frequency. The present invention provides an ultrasonic diagnostic image processing method for generating an ultrasonic image from a harmonic echo component of a transmission fundamental frequency. Apparatus and method. Preferably, a programmable digital filter is used to pass harmonic echo components to remove and image the fundamental frequency signal. In a preferred embodiment, the virtual image is removed by creating a decorrelated replica of the harmonic signal, which is then combined and used for image processing. To create an image in the presence of depth dependent attenuation of the high frequency echo signal, both the fundamental and harmonic echo signals are processed to create a blended image from the components of both the fundamental and harmonic echo signals Used for

The embodiments of the present invention are as follows. 1. An ultrasonic diagnostic image processing apparatus for performing image processing of a harmonic response of a body structure, means for transmitting ultrasonic energy into a body at a fundamental frequency; responding to the transmitted ultrasonic energy, using a harmonic frequency of the fundamental frequency. 1. An ultrasonic diagnostic image processing apparatus comprising: means for receiving an ultrasonic echo signal of the above; and means for generating an ultrasonic image from the harmonic echo signal. 2. The ultrasonic diagnostic image processing apparatus according to the first aspect, wherein the transmitting unit and the receiving unit each include an ultrasonic transducer probe. The ultrasonic diagnostic image processing apparatus according to claim 2, wherein the ultrasonic transducer probe transmits ultrasonic energy at a fundamental frequency and includes a plurality of transducer elements for receiving an ultrasonic echo signal at a harmonic of the fundamental frequency. 4. 4. The ultrasonic diagnostic image processing apparatus according to claim 3, wherein the transducer element exhibits a response characteristic including both the fundamental frequency and a harmonic of the fundamental frequency. The means for receiving an ultrasonic echo signal of a harmonic of the fundamental frequency comprises a filter having a pass band for identifying the harmonic frequency excluding the fundamental frequency.
5. The ultrasonic diagnostic image processing apparatus of 6. The ultrasound diagnostic image processing apparatus of claim 5, wherein the filter comprises a programmable digital filter; 7. the ultrasonic diagnostic image processing apparatus according to the first aspect, wherein the means for generating the ultrasonic image includes a B-mode processor; 8. The ultrasound diagnostic imaging apparatus of claim 7, wherein the B-mode processor has an amplitude detector for detecting an envelope of the harmonic echo signal; 9. The ultrasonic diagnostic image processing apparatus of claim 1, wherein the structure comprises a structure naturally existing in the body. 10. The ultrasonic diagnostic image processing apparatus according to the above item 9, wherein the naturally existing structure comprises a body tissue and cells; A method of creating an ultrasound image from a harmonic response inside a body, comprising: transmitting ultrasound energy into the body at a fundamental frequency; receiving an ultrasound echo signal at a harmonic frequency of the fundamental frequency; 11. A method of processing the wave echo signal to generate an ultrasonic image display signal; and displaying the ultrasonic image display signal to generate an ultrasonic image including the above steps; 12. The method of claim 11, wherein the transmitting and receiving steps comprise transmitting fundamental frequency ultrasonic energy and receiving harmonic echoes using an ultrasonic probe having a transducer array. 13. The method of claim 12, wherein the step of using an ultrasonic probe comprises transmitting fundamental frequency ultrasonic energy and receiving harmonic echo signals with the same transducer. The step of receiving an ultrasonic echo signal of a harmonic frequency of the fundamental frequency includes passing the received ultrasonic echo signal by a filter that excludes the fundamental frequency and passes the signal of the harmonic frequency of the fundamental frequency. The method according to the eleventh, comprising:
5. 11. The method of claim 11, wherein said processing comprises B-mode processing said harmonic echo signal. The B
16. The method of claim 15, wherein the mode processing step comprises the step of detecting the amplitude of the harmonic echo signal. An ultrasound diagnostic image processing apparatus for creating an ultrasound image of a harmonic response of a body structure with a reduced virtual image: means for transmitting ultrasound energy into the body at a fundamental frequency; Means for receiving an ultrasound echo signal at a harmonic frequency of the fundamental frequency; processing the harmonic ultrasound echo signal to form at least a partially decorrelated replica of the echo signal. Means for combining the decorrelated replicas to create a harmonic echo signal with reduced virtual image; and creating an ultrasound image using the harmonic echo signal with reduced virtual image. means,
17. an ultrasonic diagnostic image processing apparatus comprising: The ultrasonic diagnostic image processing apparatus according to the seventeenth aspect, wherein the virtual image is a dropped virtual image.
9. The virtual image further comprises a speckle virtual image.
20. An ultrasonic diagnostic image processing apparatus according to The ultrasonic diagnostic image processing apparatus according to the 17th aspect, wherein the means for processing comprises a band-pass filter that divides the component of the harmonic ultrasonic echo signal into two pass bands having different center frequencies.
1. 21. The ultrasonic diagnostic imaging apparatus of claim 20, wherein the means for processing further comprises a detector for detecting a harmonic ultrasonic echo signal in each of the passbands. 23. The ultrasonic diagnostic image processing apparatus of claim 21, wherein the means for processing further comprises a logarithmic compression processor that logarithmically compresses the detected harmonic ultrasonic echo signal. The processing means has two parallel channels each having an input connected to receive a harmonic ultrasound echo signal and an output connected to the combining means, wherein each of the channels is connected to the other. 23. The ultrasonic diagnostic image processing apparatus according to the above 17, which has a band-pass filter having a filter characteristic different from the filter characteristic of the channel. 23. The ultrasonic diagnostic image processing apparatus according to the above item 23, wherein the filter characteristic is a peak response frequency of the filter. 23. The ultrasonic diagnostic image processing apparatus according to the above item 23, wherein the filter characteristic is a center frequency of the filter. 23. The ultrasonic diagnostic imaging apparatus of claim 23, wherein each of the channels further comprises a detector. 28. The ultrasound diagnostic imaging apparatus of claim 26, wherein each of said channels further comprises a logarithmic compression processor. 27. The ultrasonic diagnostic image processing apparatus of claim 17, wherein said processing means comprises means for dividing said harmonic ultrasonic echo into two pass bands having unequal dynamic ranges. The two ultrasound diagnostic images wherein the two passbands comprise a low frequency passband and a high frequency passband, and wherein the dynamic range of the low frequency passband is less than the dynamic range of the high frequency passband. Processing device, 30. 30. The ultrasonic diagnostic imaging apparatus of claim 29, wherein said processing means further comprises means for differently mapping each dynamic range of said passband. A method of creating a harmonic ultrasound image with reduced virtual image, comprising: transmitting ultrasound energy at a fundamental frequency; receiving an ultrasound echo signal at a harmonic frequency at the fundamental frequency; decorrelating the signal. Processing the harmonic echo signal to create a replica; combining the decorrelated replicas to create a virtual image reduced harmonic echo signal; and the virtual image reduced harmonic echo signal 32. A method for creating a harmonic ultrasound image comprising the above steps, wherein an ultrasound image is created using 33. The method of claim 31, wherein processing the harmonic echo signal comprises dividing the components of the harmonic echo signal into two different passbands. 32. The method of claim 32, wherein processing the harmonic echo signal comprises splitting the harmonic echo signal component into two different passbands of two unequal dynamic ranges. Processing the harmonic echo signal divides the harmonic echo signal component into a high frequency passband with a given dynamic range and a low frequency passband with a smaller dynamic range than the given dynamic range. Said 3 consisting of
Method of 3, 35. An ultrasound diagnostic image processing apparatus for creating harmonic ultrasound images of internal body structures, comprising: means for transmitting ultrasound energy at a fundamental frequency into the body; responsive to the transmitted ultrasound energy, the fundamental frequency; Means for receiving an ultrasonic echo signal at a harmonic frequency of the fundamental frequency; and processing the received fundamental frequency echo signal and the harmonic frequency echo signal to form an ultrasonic echo signal formed from both components of the fundamental frequency and the harmonic frequency echo signal. 36. An ultrasonic diagnostic image processing apparatus comprising an image processor for creating an ultrasonic image,
35. The ultrasonic diagnostic imaging system of claim 35, wherein the means for receiving comprises means for creating split fundamental and harmonic frequency echo signals. 36. The apparatus of claim 36, wherein the receiving means includes a filter for creating a fundamental frequency echo signal excluding at least a portion of the harmonic frequency echo signal and creating a harmonic frequency echo signal excluding at least a portion of the fundamental frequency echo signal. 38. An ultrasonic diagnostic image processing apparatus of
35. The ultrasonic diagnostic imaging system of claim 35, wherein the image processor comprises means for using more of the harmonic echo signals in the near regions of the image and more of the fundamental frequency echo signals in the remote regions of the image. An ultrasonic diagnostic imaging apparatus for imaging harmonic response of a body structure exhibiting depth-dependent attenuation of ultrasonic energy, comprising: means for transmitting ultrasonic energy at a fundamental frequency of 5 MHz or less into the body; 10MHz in response to ultrasonic energy
40. An ultrasonic diagnostic image processing apparatus comprising: means for receiving an ultrasonic echo signal of a higher harmonic of the fundamental frequency or lower; and means for generating an ultrasonic image from the higher harmonic echo signal. The transmitting means transmits ultrasonic energy into the body at a fundamental frequency of 2.5 MHz or less; and the receiving means receives an ultrasonic echo signal at a harmonic frequency of the fundamental frequency of 5 MHz or less. 41. The ultrasonic diagnostic image processing apparatus according to the above 39, The transmitting means transmitting ultrasonic energy having a fundamental frequency of 2 MHz or less into the body; and the receiving means receiving ultrasonic echo signals having a harmonic frequency of the fundamental frequency of 4 MHz or less. Diagnostic image processing device, 42. The ultrasonic diagnostic imaging apparatus of claim 39, wherein the receiving means comprises a programmable digital filter programmed to pass the harmonic echo signal except for the fundamental frequency; 43. An ultrasonic diagnostic imaging apparatus for processing nonlinear response of a tissue, comprising: a transmitter for transmitting ultrasonic energy at a fundamental frequency into the body; A receiver for separating a signal representing the nonlinear response by ultrasound; and an image processor for creating an ultrasound image from the nonlinear response signal;
44. An ultrasonic diagnostic image processing apparatus comprising: The receiver is
43. The ultrasonic diagnostic image processing apparatus according to 43, further comprising a filter circuit for separating a signal representing the nonlinear response of the tissue by ultrasonic waves.
5. The receiver combines the multiple echo signals in response to receiving multiple echoes from the same spatial location in tissue;
43. The ultrasonic diagnostic image processing apparatus of claim 43, further comprising a signal processor that separates a signal representing the nonlinear response of the tissue by ultrasound,
46. 43. The ultrasonic diagnostic image processing apparatus according to 43, wherein the non-linear ultrasonic response of the tissue comprises a second or higher harmonic of the fundamental frequency. Non-linear ultrasonic response of tissue
43. The ultrasonic diagnostic image processing apparatus according to claim 43, which has a subharmonic of the fundamental frequency.

[0045]

According to the present invention, there is provided a method and apparatus for effectively using a harmonic frequency echo component other than the fundamental frequency for ultrasonic image processing. The use of harmonic beams reduces scattering when processing images through narrow mouths, such as ribs, and takes advantage of the fact that the side lobe levels of the harmonic beams are lower than the corresponding side lobe levels of the fundamental beam. To reduce off-axis scattering. In addition, since the return energy of the higher harmonic wave from the proximity region is relatively smaller than the return energy of the fundamental frequency, scattering of the proximity region can be prevented.

[Brief description of the drawings]

FIG. 1 is an illustration based on a block diagram of an image processing apparatus according to the present invention.

FIG. 2 is a diagram illustrating a main lobe and a side lobe of a harmonic echo signal.

FIG. 3 is an explanation of the main lobe and the side lobe of the harmonic echo signal under different conditions.

FIG. 4 is a diagram illustrating a beam pattern of a harmonic echo.

FIG. 5 is an explanation of another beam pattern of a harmonic echo.

FIG. 6 is a passband characteristic curve used to explain the behavior of the example of FIG. 1;

FIG. 7 is another passband characteristic curve used in FIG. 1;

FIG. 8 is an illustration of typical fundamental and harmonic frequency passbands.

FIG. 9 is an illustration of a FIR filter structure suitable for use in the example of FIG.

FIG. 10 is a block diagram of a preferred embodiment of the present invention.

FIG. 11 illustrates the operation of the normalization stage in the example of FIG.

FIG. 12 is a block diagram of a multiplier accumulator used in FIG.

FIG. 13 is an illustration of the basic and harmonic frequency pass bands of the example of FIG.

FIG. 14 illustrates blending of a fundamental frequency signal and a harmonic signal component.

FIG. 15 illustrates a pass band of a time change filter for forming a blend image.

[Explanation of symbols]

37 ... B-mode processor, 50 ... Display device, 110
... Ultrasonic probe, 112 ... Transducer, 114 ... T /
R switch, 115 ··· analog-digital converter,
116: Beamformer, 117: Transmission frequency control, 1
18 Digital filter, 70-73 Multiplier, 8
0-83: accumulator, 120: central controller, 128:
Contrast signal detector, 130 ... Doppler processor, 140 ... video processor, 162 ... 3D image creation processor, 164 ... 3D image memory.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Jeffrey E. Powers, USA 98110 Washington State, Bainbridge Island, West Blake Cree Ave No. 4054 (72) Inventor Peter N. Burns Canada M4K1B5 Langley Avenue, Toronto, Ontario, No. 22 (72) Inventor David N. Round Hill 28 drive S.E. Zinget Hwan East Maeser Way 7432, Maeser Island, Washington 98040 United States of America

Claims (47)

[Claims] 1. An ultrasonic diagnostic image processing apparatus for performing image processing on a harmonic response of a body structure, comprising: means for transmitting ultrasonic energy into a body at a fundamental frequency; An ultrasonic diagnostic image processing apparatus comprising: means for receiving an ultrasonic echo signal at a higher harmonic frequency; and means for generating an ultrasonic image from the higher harmonic echo signal. 2. The ultrasonic diagnostic image processing apparatus according to claim 1, wherein said transmitting means and said receiving means comprise an ultrasonic transducer probe. 3. The ultrasonic transducer probe of claim 2 wherein said ultrasonic transducer probe comprises a plurality of transducer elements for transmitting ultrasonic energy at a fundamental frequency and receiving ultrasonic echo signals at harmonics of said fundamental frequency. Ultrasound diagnostic image processing device. 4. The ultrasonic diagnostic image processing apparatus according to claim 3, wherein said transducer element exhibits a response characteristic including both said fundamental frequency and harmonics of said fundamental frequency. 5. The ultrasonic diagnostic apparatus according to claim 1, wherein said means for receiving an ultrasonic echo signal of a harmonic of said fundamental frequency comprises a filter having a pass band for identifying said harmonic frequency excluding said fundamental frequency. Image processing device. 6. An ultrasonic diagnostic imaging apparatus according to claim 5, wherein said filter comprises a programmable digital filter. 7. The ultrasonic diagnostic image processing apparatus according to claim 1, wherein said means for generating an ultrasonic image includes a B-mode processor. 8. An ultrasonic diagnostic imaging apparatus according to claim 7, wherein said B-mode processor has an amplitude detector for detecting an envelope of said harmonic echo signal. 9. The ultrasonic diagnostic image processing apparatus according to claim 1, wherein said structure is a structure naturally existing in a body. 10. The ultrasonic diagnostic image processing apparatus according to claim 9, wherein said naturally existing structure comprises a body tissue and cells. 11. A method of creating an ultrasound image from a harmonic response inside a body, comprising: transmitting ultrasound energy into the body at a fundamental frequency; and receiving an ultrasound echo signal at a harmonic frequency of the fundamental frequency. And a method for processing the harmonic echo signal to generate an ultrasonic image display signal; and displaying the ultrasonic image display signal to generate an ultrasonic image comprising the above steps. 12. The transmitting and receiving steps comprise:
12. The method of claim 11, comprising transmitting the fundamental frequency ultrasonic energy and receiving the harmonic echo using an ultrasonic probe having a transducer array. 13. The step of using an ultrasonic probe includes transmitting fundamental frequency ultrasonic energy with the same transducer element;
13. The method of claim 12, comprising receiving a harmonic echo signal. 14. The step of receiving an ultrasonic echo signal at a harmonic frequency of the fundamental frequency, wherein the step of filtering the received ultrasonic echo signal by a filter excluding the fundamental frequency and passing the signal at the harmonic frequency of the fundamental frequency. The method of claim 11, comprising passing a signal. 15. The method of claim 11, wherein said processing step comprises B-mode processing said harmonic echo signal. 16. The method of claim 15, wherein said step of B-mode processing comprises the step of amplitude sensing said harmonic echo signal. 17. An ultrasound diagnostic image processing apparatus for creating an ultrasound image of a harmonic response of a body structure with reduced virtual images, comprising: means for transmitting ultrasound energy into the body at a fundamental frequency; In response to the transmitted ultrasonic energy,
Means for receiving an ultrasonic echo signal at a harmonic frequency of the fundamental frequency; means for processing the harmonic ultrasonic echo signal to form at least a partially decorrelated replica of the echo signal; Combining the obtained replicas to create a harmonic echo signal with reduced virtual image; and using the harmonic echo signal with reduced virtual image to create an ultrasonic image. Ultrasound diagnostic image processing device. 18. The virtual image according to claim 1, wherein the virtual image is a dropped virtual image.
7 is an ultrasonic diagnostic image processing apparatus. 19. The ultrasonic diagnostic image processing apparatus according to claim 18, wherein said virtual image further comprises a speckle virtual image. 20. The means for processing comprises: converting the components of the harmonic ultrasonic echo signal into two signals having different center frequencies.
18. The ultrasonic diagnostic image processing apparatus according to claim 17, comprising a band pass filter that divides the pass band into two pass bands. 21. An ultrasonic diagnostic image processing apparatus according to claim 20, wherein said processing means further comprises a detector for detecting a harmonic ultrasonic echo signal in each of said pass bands. 22. The ultrasonic diagnostic image processing apparatus according to claim 21, wherein said processing means further comprises a logarithmic compression processor for logarithmically compressing the detected harmonic ultrasonic echo signal. 23. The processing means has two parallel channels each having an input connected to receive a harmonic ultrasound echo signal and an output connected to the combining means, wherein the two parallel channels have 18. The ultrasonic diagnostic image processing apparatus according to claim 17, wherein each of the apparatuses has a band-pass filter having a filter characteristic different from a filter characteristic of the other channel. 24. The ultrasonic diagnostic image processing apparatus according to claim 23, wherein the filter characteristic is a peak response frequency of the filter. 25. The ultrasonic diagnostic image processing apparatus according to claim 23, wherein said filter characteristic is a center frequency of the filter. 26. The ultrasonic diagnostic imaging apparatus of claim 23, wherein each of said channels further comprises a detector. 27. The apparatus of claim 26, wherein each of said channels further comprises a logarithmic compression processor. 28. An ultrasonic diagnostic imaging apparatus according to claim 17, wherein said processing means comprises means for dividing said harmonic ultrasonic echo into two passbands of unequal dynamic range. 29. The two passbands comprising a low frequency passband and a high frequency passband, wherein the dynamic range of the low frequency passband is less than the dynamic range of the high frequency passband. 28 ultrasonic diagnostic image processing apparatus. 30. The ultrasound diagnostic image processing apparatus of claim 29, wherein said processing means further comprises means for mapping each dynamic range of said passband differently. 31. A method for creating a harmonic ultrasound image with reduced virtual image, comprising: transmitting ultrasound energy at a fundamental frequency; receiving an ultrasound echo signal at a harmonic frequency at the fundamental frequency; Processing the harmonic echo signal to create a decorrelated replica of the signal; combining the decorrelated replicas to create a virtual image reduced harmonic echo signal; and reducing the virtual image. The method for creating a harmonic ultrasound image comprising the above steps, wherein the ultrasound image is created by using the obtained harmonic echo signal. 32. The method of claim 31, wherein processing the harmonic echo signal comprises splitting the components of the harmonic echo signal into two different passbands. 33. The method of claim 32, wherein processing the harmonic echo signal comprises dividing the harmonic echo signal component into two different passbands of two unequal dynamic ranges. 34. The step of processing the harmonic echo signal comprises converting the harmonic echo signal component to a high frequency passband with a given dynamic range and a low frequency passband with a smaller dynamic range than the given dynamic range. 34. The method of claim 33, comprising dividing into passbands. 35. An ultrasound diagnostic image processing apparatus for creating a harmonic ultrasound image of a structure in a body, comprising: means for transmitting ultrasound energy of a fundamental frequency into a body; responsive to the transmitted ultrasound energy; Means for receiving an ultrasonic echo signal of a fundamental frequency and a harmonic frequency of the fundamental frequency; and processing the received fundamental frequency echo signal and the harmonic frequency echo signal to obtain both the fundamental frequency and the harmonic frequency echo signal. An ultrasound diagnostic image processing apparatus comprising an image processor for creating an ultrasound image formed from components. 36. The ultrasonic diagnostic image processing apparatus according to claim 35, wherein said receiving means includes means for generating divided basic and harmonic frequency echo signals. 37. The receiving means creates a fundamental frequency echo signal excluding at least a part of the harmonic frequency echo signal, and creates a harmonic frequency echo signal excluding at least a part of the fundamental frequency echo signal. 37. The ultrasonic diagnostic image processing device of claim 36, comprising a filter. 38. The ultrasound diagnostic of claim 35, wherein said image processor comprises means for using more of the harmonic echo signals in a near region of the image and more of a fundamental frequency echo signal in a remote region of the image. Image processing device. 39. An ultrasonic diagnostic imaging apparatus for image processing the harmonic response of a body structure exhibiting depth dependent attenuation of ultrasonic energy: transmitting ultrasonic energy at a fundamental frequency of 5 MHz or less into the body. Means for receiving an ultrasonic echo signal of a harmonic of the fundamental frequency of 10 MHz or less in response to the transmitted ultrasonic energy; and means for generating an ultrasonic image from the harmonic echo signal. , An ultrasonic diagnostic image processing apparatus. 40. The transmitting means for transmitting ultrasound energy into the body at a fundamental frequency of 2.5 MHz or less; and the receiving means for transmitting an ultrasonic energy of a harmonic frequency of the fundamental frequency of 5 MHz or less. 40. The ultrasonic diagnostic image processing apparatus according to claim 39, which receives an ultrasonic echo signal. 41. The transmitting means transmits ultrasonic energy having a fundamental frequency of 2 MHz or less into the body; and the receiving means receives an ultrasonic echo signal having a harmonic frequency of the fundamental frequency of 4 MHz or less. An ultrasonic diagnostic image processing apparatus according to claim 39. 42. The ultrasound diagnostic imaging apparatus of claim 39, wherein said receiving means comprises a programmable digital filter programmed to exclude said fundamental frequency and pass said harmonic echo signal. 43. An ultrasonic diagnostic image processing apparatus for image-processing a nonlinear response of a tissue, comprising: a transmitter for transmitting ultrasonic energy of a fundamental frequency into the body; responding to an echo returned from the tissue after transmitting the ultrasonic energy. An ultrasonic diagnostic image processing apparatus comprising: a receiver for separating a signal representing the nonlinear response of the tissue by ultrasound; and an image processor for creating an ultrasound image from the nonlinear response signal. 44. The receiver according to claim 4, further comprising a filter circuit for separating a signal representing the nonlinear response of the tissue by ultrasound.
3. An ultrasonic diagnostic image processing apparatus. 45. The receiver, in response to receiving multiple echoes from the same spatial location in tissue, combining the multiple echo signals to separate a signal that is ultrasonically representative of the non-linear response of the tissue. The ultrasonic diagnostic image processing apparatus according to claim 43, further comprising a signal processor that performs the processing. 46. The ultrasonic diagnostic image processing apparatus according to claim 43, wherein the non-linear ultrasonic response of the tissue comprises a second or higher harmonic of the fundamental frequency. 47. The ultrasonic diagnostic imaging apparatus of claim 43, wherein the non-linear ultrasonic response of the tissue has a subharmonic of the fundamental frequency.