GB2503760A

GB2503760A - A Method for Processing Scanner Signals from an Ultrasound Transducer

Info

Publication number: GB2503760A
Application number: GB201302053A
Authority: GB
Inventors: Franciscus Paulus Maria Budzelaar; Steven Antonie Willem Fokkenrood; Alexander Franciscus Kolen
Original assignee: Koninklijke Philips Electronics NV
Current assignee: Koninklijke Philips NV
Priority date: 2012-07-02
Filing date: 2013-02-06
Publication date: 2014-01-08
Also published as: GB201302053D0

Abstract

The invention relates to a method for processing scanner signals 201 from an ultrasound transducer, particularly for ultrasound transducers having a high scan frequency. The huge quantities of data from the ultrasound transducers put a high workload to the processing power of data processors. In order to reduce this workload an embodiment of the invention proposes to down sample the scanner signals 201, e.g. by performing a selection of some of the scanner signals and disregarding other non-selected scanner signals or by filtering scanner signals row by row so as to obtain a reduced number of scanner signals.

Description

A method for processing ultrasound signals

FIELD OF THE INVENTION

The invention relates to a method for processing ultrasound signals, particularly for processing high frame-rate ultrasound signals.

BACKGROUND OF THE INVENTION

In ultrasound acquisition signals from the ultrasound transducer can be acquired with high frame rates which results enormous amounts of data. These huge quantities of data put high workload to the processing power on data processors for running data processing algorithms such as image processing algorithms.

Accordingly, there is a need for improving the possibility for performing various data-processing on ultrasound signals such as A-mode signals from ultrasound transducers before further processing of the ultrasound signals, e.g. processing for generating M-mode images.

US 2011013488 discloses a multi-channel receiver circuitry for a sub-beam forming receiver of an ultrasound system in which digital filtering, down-sampling and successive data storage circuitry impose programmable fine and coarse time delays on received digital data signals.

The inventor of the present invention has appreciated that an improved method for processing data from ultrasound transducers is of benefit, and has in consequence devised the present invention.

SUMMARY OF THE INVENTION

It would be advantageous to achieve improvements of image processing of ultrasound signals. In particular, it may be seen as an object of the present invention to provide a method that solves the above mentioned problems related to processing high frame rates of ultrasound signals, or other problems, of the prior art.

To better address one or more of these concerns, in a first aspect of the invention an -ultrasound receiver for processing reflection signals from an ultrasound transducer is presented that comprises, -an input for receiving the reflection signals, where each reflection signal contains information obtained from reflections of an ultrasound wave emitted by the ultrasound transducer, and where different successive reflection signals arc separated in time corresponding to the time between successive ultrasound waves, -a sampling unit for down sampling the reflection signals so as to obtain a reduced number of down sampled reflection signals.

The information contained by the reflection signal may be amplitude information corresponding to an envelope signal, amplitude information derived as samples of an envelope signal or other values related to the original reflection signal.

By performing down sampling of the reflection signals so as to obtain a reduced number of reflection signals the amount of data to be processed in a subsequent processing step is advantageously reduced. The reduction of data may enable processing of the down sampled reflection signals, e.g. for creation of M-mode images with improved image quality, where the processing may be performed with less complex and expensive processing electronics as compared to processing of reflection signals which have not been down sampled. Other processing methods of the down sampled reflections signals may also have been made possible with a given available processing performance due to the fact that the amount of data to be processed have been reduced.

In an example the sampling unit may comprise a decimating unit for taking one reflection signal out of X reflection signals and discarding the other X-1 reflection signals. This may provide a particularly simple and effective method for achieving down sampling.

In an embodiment the sampling unit comprises a filtering unit for filtering a series of reflection signals. Use of filtering for achieving down sampling may advantageously improve the filtered and down sampled signals, reduce noise and/or provide an artifact reduction. The filtering unit maybe arranged to apply one of: mean filtering, median filtering, low-pass filtering, edge detection filtering and motion compensated filtering.

In an embodiment individual reflection signals are received at a given receiving rate, and the down sampling provides down sampled reflection signals at a rate which less than the receiving rate.

In an embodiment the information contained in each reflection signal provides values of the reflected signal for different propagation depths of the ultrasound waves, and the down sampled reflection signals arc obtained by down sampling values for a particular depth of each of the reflection signals.

The ultrasound receiver may be used for analyzing materials of various kinds.

According to an embodiment the ultrasound receiver is configured for use in clinical applications, ic. for scanning tissuc of human or animal bodies.

A second aspect of the invention relates to an ultrasound scanner system comprising, -an ultrasound receiver according to the first aspect, and -an ultrasound transducer for generating ultrasound reflection signals.

A third aspect of the invention relates to a method for processing reflection signals from an ultrasound transducer, the method comprises -rccciving the rcflcction signals, where cach reflcction signal contains information obtained from reflections of an ultrasound wavc emitted by thc ultrasound transducer, and where different successive reflection signals are separated in time corresponding to the time between successive ultrasound waves, -down sampling thc reflection signals so as to obtain a rcduccd numbcr of down sampled reflection signals.

A fourth aspect of the invention relates to a computer program containing program code for enabling a processor to cany out the mcthod steps of the third aspect. The computer program may be stored on a tangible media such as a DVD, a read-only memory such as flash memory or other media. Alternatively, the computer program may be downloaded or available from a central server or computer network such as the Internet.

In summary the invention relates to a method for processing scanner signals from an ultrasound transducer, particularly for ultrasound transducers having a high scan frcqudllcy. Thc hugc quantities of data from thc ultrasound transduccrs put a high workload to the processing power of data processors. In order to reduce this workload an embodiment of the invention proposes to down sample the scanner signals, e.g. by performing a selection of some of the scanner signals and disregarding other tion-selected scanner signals or by filtering scanner signals row by row so as to obtain a reduced number of scanner signals.

In general the various aspects of the invention may be combined and coupled in any way possible within the scope of the invention. These and other aspects, features and/or advantages of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will be described, by way of example only, with reference to the drawings, in which Fig. I shows an ultrasound receiver 100 and a scanner system 190, Fig. 2A shows the amplitude envelope of a reflection signal 201, Fig. 2B shows samples 204 of an amplitude envelope of a reflection signal Fig. 3 shows individual reflection signals 201, 32 1-324 and their samples 204 for different depths 202, and Fig. 4 shows an example of an M-mode image obtained from a plurality of reflection signals 201 or reflection signals which have been down sampled according to the mcthod of the invention.

DESCRIPTION OF EMBODIMENTS

Fig. I illustrates an ultrasound receiver 100. The receiver is configured to receive transducer signals from an ultrasound transducer 102 via an input 101. The ultrasound transducer is capable of emitting ultrasound waves into tissue of humans or animals. The ultrasound waves are reflected by the tissue (i.e. boundaries between tissue layers with different ultrasound impedance reflect an amount of the incoming ultrasound wave into outgoing waves) and received by the ultrasound transducer as reflected ultrasound signals. The output signal from the ultrasound transducer -which is transmitted to the input 101 via a wireless or wired connection -contains the measured reflected ultrasound signals in processed or unprocessed form. E.g. the output signal from the ultrasound transducer may be an envelope signal ofthe high frequency ultrasound signal. Irrespective of the output format of the output signal from the transducer 102, the output signal is referred to as a reflection signal 201 since it is directly related to the reflected ultrasound waves.

The ultrasound transducer 102 may have a single ultrasound emitter for generating a single wave, or the ultrasound emitter may contain an array of emitters for generating a plurality of waves.

The ultrasound receiver 100 comprises a processor, e.g. a digital data processor, or other electronic hardware or firmware, for processing the received reflection signals 201.

The ultrasound receiver 100 and the transducer 102 may constitute an ultrasound scanner system 190 which may additionally include a monitor 110 for displaying reflections signals from the receiver 100 in processed or unprocessed form and in various formats such as M-mode images.

Fig. 2A illustrates a reflection signal 201 representing the amplitude envelope of a reflected ultrasound wave. The reflection signal 201 is shown as a function of tissue depth 202 which depth is determined from the delay between the time of emission of the ultrasound wave and time of receipt of reflected waves from different tissue depths 202.

Different tissue characteristics at different depths generate different amplitudes 203 of the reflection signal 201. Accordingly, the reflection signal 201 contains information in the form of values 204 of characteristics of the reflected signal for different propagation depths of the ultrasound waves. The values contained by the reflection signal may have been obtained after some processing of the high frequency reflection signals received by the ultrasound transducer 102, e.g. analog filtering for determining the amplitude envelope, or analog filtering for removing noise or DC components. Such filters for preprocessing the reflection signal may be located in the ultrasound transducer 102, in the ultrasound receiver 100 or elsewhere in other device.

The reflection signal 201 may be generated from a single ultrasound emitter or a plurality of ultrasound emitters.

The reflection signal 201 may be in the form of an analog signal as shown in Fig. 2A or as a digitized signal as shown in Fig. 2B where the reflection signal 201 is represented by samples 204 of the analog reflection signal 201 or values 204 derived from the analog reflection signal 201 and where each sample or value corresponds to a distinct depth 205.

Fig. 3 illustrates a plurality of reflection signals 201 arranged as columns of samples or values 204 at distinct times 305 as a ifinction of time 301. Different samples 204 in a single column or equivalently in a single reflection signal 201 correspond to different reflection depths 202 of the ultrasound wave.

Successive reflection signals 201, such as first and second reflections signals 321, 322 are separated in time by a value which may correspond to the time 306 between successive ultrasound wave emissions from the transducer 102.

The reflection signals 201 may be arranged, as illustrated by Fig. 3, to form a 2D image, a so-called M-mode image, where the vertical dimension shows characteristics such as amplitude characteristics of the reflection signal 201 as a function of depth 202 and the horizontal dimension shows changes of the reflection signal characteristics as a function of time. Thus, the M-mode image may be used for monitoring and analyzing e.g. motion of parts of the heart, for monitoring lesion progression in ablation interventions, or generally for image guided imaging during interventions.

However, ultrasound waves must be emitted with a very high frequency and the reflection signals must be received and recorded with the same high frequency, e.g. more than I kHz. The high frequency results in huge amounts of data that need to be processed and therefore requires a high performance processor 103 in order to maintain real-time or close to real-time performance. Such high performance processors or electronics may be complex, expensive and have high power consumption.

In an embodiment the ultrasound receiver 100 comprises a sampling unit 113 configured to down sample the reflection signals 201. The sampling unit 113 may be configured as or comprise a decimating unit 114 for performing the down sampling. The down sampling may be canied out by performing a selection of the reflection signals for further processing and disregarding other non-selected reflection signals, e.g. by taking one reflection signal out of X reflection signals and discarding the other X-1 reflection signals.

This could be performed e.g. by selecting a first reflection signal 321, disregarding a second subsequent reflection signal 322, selecting a third subsequent reflection signal 323, disregarding a fourth subsequent reflection signal 324 and so forth in order to dowm sample by a factor two. Clearly, other down sampling factors may be chosen. E.g. a 1 kHz receiving rate of the reflection signals (i.e. 1000 reflection signals each containing signal characteristics from different depths or containing multiple sample values 204 are received per second) may be down sampled to a receiving rate of 200, 100, 40Hz or 20 Hz. The receiving rate may be equal to the scan frequency of the ultrasound transducer, i.e. the frequency by which ultra sound waves are emitted by the ultrasound transducer 102.

In an alternative embodiment, the sampling unit 113 may be configured as or comprise a filtering unit 115 for performing the down sampling. The down sampling may be carried out by filtering a series of reflection signals 321-324. The filtering of the reflection signals may be performed in groups of overlapping or non-overlapping blocks of reflection signals, where a block contains a certain number of reflection signals, or the filtering may be performed by continuously processing newly incoming reflection signals. Thus, filtering of reflection signals 321-324 could generate a reduced number of reflection signals 321, 323 from a group containing a larger number of reflection signals 321 -324. Thus, a plurality of reflections signals may be down sampled by the filtering unit 115 to one or more reflection signals. In addition to providing down sampling, the filtering unit 115 may provide signal improvement, noise reduction, and/or artifact reduction.

Different filtering methods may be utilized for filtering the reflection signals 201 such as mean filtering, median filtering, low-pass filtering, edge detection filtering, motion compensated filtering, or other suitable filtering methods.

As an example mean filtering may be carried out according to the formula:

N xi 1=1

where x1 represents selected samples 204 such as samples 331, 332 of a row 330, N is the number of samples 204 which are averaged and is the resulting mean value.

Median filtering may be performed by determining the numerical value which separates the higher half of a sample, a pcn1tn, or a prohabiUt distribution, from the lower half Low pass filtering may be carried out according to the formula: = ax1 + (1 -where x1 represents selected samples 204 in a row for a given depth, i is the sample number and a is a value between 0 and 1.

Edge detector filtering maybe performed according to the formula: V=[-1/2 0 1/21*1 Motion compensated mean filtering is a filtering technique in which sleight displacement of features in consecutive lines are tracked and aligned before the lines are averaged.

Different filters can be combined to adapt the signal even better to the application.

It is understood that that each of the reflection signals 201 contains samples 204 for different distinct depths 205 and that these distinct depths are the same for each reflection signal 201 so that the reflections signals 201 can be down sampled (by decimation or filtering) row by row, i.e. by down sampling values for a particular depth 205 of each of the reflection signals.

Thus, as an example, down sampling may be performed by filtering rows 330, 340 of samples of columns 321-324 row by row, i.e. by down sampling samples 204 of a first row 330, by down sampling samples 204 of a second row 340, and so forth. The rows 330, 340 may be down sampled simultaneously, i.e. real time, or consecutively depending on the capabilities of the sampling unit 113.

The down sampling of reflection signals could be performed directly on the analog or digital reflection signals 201 as they are received by the input 101 or the down sampling may be performed on processed reflection signals, e.g. after the received reflection signals have been digitized by an analog-to-digital converter.

Fig. 4 shows an example of an M-modc image obtained from down sampled reflection signals where individual reflection signals showing amplitude characteristics of the reflected ultrasound waves are displayed vertically as a function of the horizontal time axis.

The generation of the M-mode image may be performed by further processing of the down sampled reflection signals. Since the number of reflection signals have been reduced such further processing may be performed by less complex and less power consuming processor electronics or electronic hardware.

While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description arc to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiments.

Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invcntion, from a study of the drawings, the disclosure, and the appcndcd claims. In the claims, thc word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. A single processor or other unit may fulfill the functions of several items recited in the claims.

The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. A computer program may be stored/distributed on a suitable medium, such as an optical storage medium or a solid-state medium supplied together with or as part of other hardware, but may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunication systems. Any reference signs in the claims should not be construed as limiting the scope.

Claims

CLAIMS: 1. An ultrasound receiver (100) for processing reflection signals (201) from an ultrasound transduccr (102), the rcceivcr comprises, -an input (101) for receiving the reflection signals, where each reflection signal contains information obtained from reflections of an ultrasound wave emitted by the ultrasound transducer, and where different successive reflection signals are separated in time corresponding to the time between successive ultrasound waves, -a sampling unit (113) for down sampling the reflection signals so as to obtain a reduced number of down sampled reflection signals.
2. An ultrasound receiver according to claim 1, wherein the sampling unit comprises a decimating unit (114) for taking one reflection signal out of X reflection signals and discarding the other X-1 reflection signals.
3. An ultrasound receiver according to claim 1, wherein the sampling unit comprises a filtering unit (115) for filtering a series of reflection signals.
4. An ultrasound receiver according to claim 3, wherein the filtering unit (115) is arranged to apply one of: mean filtering, median filtering, low-pass filtering, edge detection filtering and motion compensated filtering.
S. An ultrasound receiver according to claim 1, where individual reflections signals (201) are received at a given receiving rate, and where the down sampling provides down sampled reflection signals at a rate which less than the receiving rate.
6. An ultrasound receiver according to claim 1, where the information contained in each reflection signal provides values of the reflected signal for different propagation depths (205) of the ultrasound waves, and where the down sampled reflection signals are obtained by down sampling values for a particular depth (205) of each of the reflection signals.
7. An ultrasound receiver according to claim 1, where the ultrasound receiver (100) is for use in clinical applications.
8. An ultrasound scanner system (190) comprising, -an ultrasound receiver (101) according to claim 1, and -an ulftasoundtransducer(102).
9. A method for processing reflection signals (201) from an ultrasound transducer (102), the method comprises -receiving the reflection signals, where each reflection signal contains information obtained from reflections of an ultrasound wave emitted by the ultrasound transducer, and where different successive reflection signals are separated in time corresponding to the time between successive ultrasound waves, -down sampling the reflection signals so as to obtain a reduced number of down sampled reflection signals.
10. A computer program containing program code for enabling a processor to early out the method of claim 9.