CN1190753C - Ultrasonic dynamic receiving apodization method based on delta-sigma transformation - Google Patents

Abstract

The present invention relates to an ultrasonic dynamic receiving apodization method based on delta-sigma transformation, which belongs to the technical field of digital medical ultrasound image processing and is characterized in that on the basis of non-uniform sampling and delta-sigma transformation, the present invention introduces a multi-storage page addressing method for a data store unit to realize the dynamic receiving apodization in order to suppress a diffraction lobe induced by an array hole diameter so as to improve the quality of an ultrasonic image. The present invention takes delta-sigma sampling data as the address input of an apodization storage unit, and the apodization data of a focus p, which is calculated according to the formula, is stored in the corresponding storage unit, wherein A#-i is the delta-sigma sampling output, W#-pi is the apodization coefficient, and k#-p is the proportionality factor. The apodization data of different focuses p is selected from the corresponding storage unit by page selection signals to form data stream output, and a composite wave beam is formed by low pass filtering and extraction. The method of the present invention has the same effect with the dynamic receiving apodization method based on common A/D transformation, but the method of the present invention has simpler line, and the image quality is better than that of a non-apodization delta-sigma transformation method.

Description

Ultrasonic dynamic receiving apodization method based on the delta sigma conversion

Technical field

Ultrasonic dynamic receiving apodization method based on the delta sigma conversion belongs to digitizing Medical Ultrasound Image Processing technology.

Background technology

The most critical of decision digitizing medical ultrasound image system picture quality partly is the design of front end.The digitizing front end of excellent in design can improve the quality of image in the burden that alleviates aftertreatment greatly.The digitizing front-end technology of multidigit mould/number conversion (ADC) sampling is comparative maturity, and the preferable image quality can be provided.This technology of the medium-to-high grade many employings of digitizing medical ultrasound image system.

The delta sigma conversion is called ∑-Δ conversion and feedback quantization again, is a kind of by improving sampling rate and increasing the technology that feedback element reduces quantization error.GE company has proposed the over-sampling beam-forming technology based on the delta sigma conversion first in 1993, and has obtained United States Patent (USP).The Freeman of Univ Michigan-Ann Arbor USA improves the design proposal of GE company, has obtained two United States Patent (USP)s in, calendar year 2001 in 1999.On the basis of the design of Freeman, osmanli Karaman proposed the design proposal based on nonuniform sampling and delta sigma conversion in 1999.

Compare with the multi-bit ADC Sampling techniques, the over-sampling beam-forming technology is fairly simple, can when guaranteeing picture quality, reduce the complicacy of circuit and the size of follow-up digital signal processing calculated amount, be suitable in portable and ultrasonic image-forming system, using based on PC.

Receive change mark technology and can suppress the diffraction lobe that array aperture causes, improve the quality of ultrasonoscopy.Existing digitalized ultrasonic beam-forming technology based on the delta sigma conversion can not realize that all ultrasonic echo receives the change mark.

Summary of the invention

The object of the present invention is to provide a kind of diffraction lobe that causes in order to the inhibition array aperture, improve the ultrasonic dynamic receiving apodization method based on the delta sigma conversion of ultrasonograph quality.Now be explained as follows:

In the ultrasound aperture array, when all array element is subjected to the excitation of onesize pulse simultaneously, be equivalent to infinitely-great transmitting aperture by space rectangular window weighting, its roomage response is sin (x)/x, and secondary lobe is bigger, has reduced the signal to noise ratio (S/N ratio) of ultrasonoscopy.With Hamming (breathing out bright), Hanning window functions such as (Chinese are peaceful) the emission driving pulse is weighted, can reduces secondary lobe, improve the signal to noise ratio (S/N ratio) of ultrasonoscopy.This by the emission driving pulse being weighted the method for the secondary lobe that suppresses launching beam, be called emission and become mark.

According to principle of reciprocity, with Hamming (breathing out bright), Hanning window functions such as (Chinese are peaceful) echoed signal that each array element on the receiving aperture receives is weighted, can reduce the secondary lobe of receiving aperture roomage response, improve the signal to noise ratio (S/N ratio) of ultrasonoscopy.Thisly be weighted, reduce the method for receiving aperture roomage response secondary lobe, be called to receive and become mark by the echoed signal that each array element on the receiving aperture is received.

By adopt little receiving aperture in the near field, adopt bigger receiving aperture in the far field, make F/Number (focus/array element number) keep constant technology to be called dynamic receiving aperture technology.Dynamically the receiving aperture technology can be improved the acoustic characteristic near field, improves the picture quality near field.When becoming mark in the dynamic aperture technology, when receiving aperture varied in size, receiving apodizing function also needed respective change.Receive apodizing function with the technology that receiving aperture changes, be called reception and dynamically become mark.

The invention is characterized in: it is on the basis of nonuniform sampling and delta sigma conversion, introduced by a data storage unit and realized dynamically receiving the change mark to suppress the diffraction lobe that array aperture causes with many memory pages addressing method, improve the quality of ultrasonoscopy, it contains following steps successively:

(1). when the analog channel number is N, the twice of symmetry in the analog echo signal are merged into together, it is consistent to make analog echo signal port number and the address wire that becomes the mark data storage cell count M, wherein:

(2). the signal on M the analog echo signal passage is done nonuniform sampling and carried out the conversion of second order delta sigma;

(3). the sampled signal that step (2) obtains, send into first in first out (FIFO) data-carrier store;

(4). the data A of delta sigma sampling _i(i=0 ..., M-1),, dynamically receive the change mark with many memory pages addressing method as the address input that becomes the mark data storage cell, draw data stream D successively ₀～D _Q-1, carry out low-pass filtering and extraction then and form synthetic wave beam; It contains following steps successively:

(4.1). according to following formula calculate receive focus p (p=1,2 ..., change mark data P), depositing corresponding size in is 2 ^MIn each storage unit of byte:

${\mathrm{DATA}}_p(A_0,{\mathrm{<figure-callout\; id="1"\; label="A"\; filenames="C0310476100073.png"\; state="\{\{state\}\}">A</figure-callout>}}_1,\&CenterDot;\&CenterDot;\&CenterDot;A_{M-1})=\mathrm{round}(k_p\&times;\underset{i=0}{\overset{M-1}{\mathrm{\&Sigma;}}}{A}_i{W}_p\left(i\right)),$

Wherein, W _p(i) being the trace-changing coefficient that receives focus p correspondence, is a kind of window function, and its width is relevant with the position that receives focus p, and when receiving focus p variation, the width of window function changes thereupon, W _p(i) also change thereupon;

Round is the computing that rounds up;

k _pBe the scale-up factor that receives focus p correspondence, when storage unit output data figure place is q, get k _pFor:

$k_p=\frac{2^q}{\underset{i=0}{\overset{M-1}{\mathrm{\&Sigma;}}}{W}_p\left(i\right)},$

(4.2). select signal A by the page _M..., A _M+L-2, A _M+L-1Select the change mark data of different focus p from respective memory unit, the described page is selected number of signals L=floor (log ₂P)+1;

Wherein, floor is a rounding operation.

Described W _p(i) be Hamming or Hanning window function.

Experimental results show that: the present invention has obtained the effect identical with the multi-bit ADC method.

Description of drawings

Fig. 1. use the synoptic diagram that forms synthetic wave beam based on the dynamic receiving apodization method of the digitalized ultrasonic of delta sigma conversion.

Fig. 2. the addressing of many memory pages realizes dynamically receiving the synoptic diagram that becomes mark.

Fig. 3. The simulation experiment result figure.

Embodiment

The present invention realizes receiving the change mark by a data storage unit.Become the result of calculation of mark, summation operation in the data storage cell for reception.When handling echo data in real time, result's (binary number of 1bit) that delta sigma is sampled imports as the address of storage unit, and the data stream of reading successively is the synthetic wave beam that becomes the mark weighting through receiving.

If the analog channel number is N, consider symmetry, the twice of symmetry in the analog echo signal can be merged into together, be (referring to Fig. 1) so become the address wire number of mark data storage cell:

Reception focus p (p=1,2 ..., P) receiving when becoming mark, the size of the storage unit that needs is 2 ^MByte.Data in the storage unit calculate by following formula:

${\mathrm{DATA}}_p(A_0,{\mathrm{<figure-callout\; id="1"\; label="A"\; filenames="C0310476100073.png"\; state="\{\{state\}\}">A</figure-callout>}}_1,\&CenterDot;\&CenterDot;\&CenterDot;A_{M-1})=\mathrm{round}(k_p\&times;\underset{i=0}{\overset{M-1}{\mathrm{\&Sigma;}}}{A}_i{W}_p\left(i\right)),$

Wherein, W _p(i) be the trace-changing coefficient that receives focus p correspondence, can be window functions such as Hamming, Hanning.

Round is the computing that rounds up.

k _pBe the scale-up factor that receives focus p correspondence, suitable k is set _p, can obtain higher reception and become the mark processing accuracy.When storage unit output data figure place is q, get k _pFor:

$k_p=\frac{2^q}{\underset{i=0}{\overset{M-1}{\mathrm{\&Sigma;}}}{W}_p\left(i\right)},$

During the change apodizing function, need recomputate the also interior DATA value of refresh of memory cells.

The present invention realizes receiving dynamically change mark (F/Number is constant in maintenance) by many memory pages addressing technique.Fig. 2 is that the addressing of many memory pages realizes receiving the synoptic diagram that dynamically becomes mark.

When the reception of P reception focus (being P kind receiving aperture) dynamically became mark, the storage unit capacity that needs was that single focus receives P times when becoming mark.The address is 0～2 ^MThe change mark data of-1 the put-focus point 1 of storage space internal memory; The address is 2 ^M～2 ^M+1The change mark data of-1 the put-focus point 2 of storage space internal memory; And the like, the address is (P-1) * 2 ^M～P * 2 ^M+1The change mark data of-1 put-focus some P of storage space internal memory.

Dynamically receive when becoming mark, select signal to come from storage unit, to select not confocal trace-changing coefficient by the page.When the reception of P reception focus dynamically became mark, the page that needs selected the number of signal to be:

L＝floor(log ₂P)+1，

Wherein, floor is a rounding operation.

Receive when dynamically becoming mark, receive the trace-changing coefficient W of focus p correspondence _p(i) width is relevant with the position that receives focus p, and it is far away more to receive focus p, and window function is wide more.For example, when apodizing function is the Hamming window, receive the trace-changing coefficient W of focus p correspondence _p(i) be:

Wherein, Number is an array element number.When receiving focus p change, Number needs to change thereupon, makes the ratio of focal position and array element number keep constant, W _p(i) value also correspondingly changes.

As the example of an enforcement, we have finished digitalized ultrasonic wave beam based on a delta sigma conversion focus in forming and have received the emulation experiment that becomes mark.The center probe frequency f ₀=3.5MHz, experimental data is the 16 road analog echo signals that real-time nonuniform sampling is gathered, the sampling rate of composite signal is f _s=20MHz.Apodizing function employing length is 16 Hamming window.Storage unit output data figure place is q=8, gets k=62.6.

Fig. 3 is the result of emulation experiment:

Fig. 3 (a) is 8 road analog echo signals (twice of symmetry are merged into together in the echoed signal in 16 roads).

Fig. 3 (b) be 8 ADC methods receive become the synthetic signal of marks and delta sigma converter technique receive become the synthetic signal of mark effect relatively.Waveform I is that 8 ADC methods receptions become the synthetic signal of mark, and for the ease of comparing, 8 ADC methods receive the synthetic signals of change mark and also taken advantage of k=62.6; Waveform II is that the delta sigma converter technique receives the synthetic signal of change mark.Waveform I and waveform II overlap fully.

Experiment has obtained success, has realized receiving in forming based on the digitalized ultrasonic wave beam of delta sigma conversion becoming mark.Method reaches set purpose.

Claims (2)

1. based on the ultrasonic dynamic receiving apodization method of delta sigma conversion, the step that contains nonuniform sampling and delta sigma conversion, it is characterized in that: it is on the basis of nonuniform sampling and delta sigma conversion, introduced by a data storage unit and realized dynamically receiving the change mark to suppress the diffraction lobe that array aperture causes with many memory pages addressing method, improve the quality of ultrasonoscopy, it contains following steps successively:

(1). when the analog channel number is N, the twice of symmetry in the analog echo signal are merged into together, it is consistent to make analog echo signal port number and the address wire that becomes the mark data storage cell count M, wherein:

(2). the signal on M the analog echo signal passage is done nonuniform sampling and carried out the conversion of second order delta sigma;

(3). the sampled signal that step (2) obtains, send into the first in first out data-carrier store;

(4). the data A of delta sigma sampling, i=0 ..., M-1, the address input as becoming the mark data storage cell with many memory pages addressing method, dynamically receives the change mark, draws data stream D successively ₀～D _Q-1, carry out low-pass filtering and extraction then and form synthetic wave beam; It contains following steps successively:

(4.1). calculate reception focus p according to following formula, p=1,2 ..., p, change mark data, depositing corresponding size in is 2 ^MIn each storage unit of byte:

$\mathrm{DAT}{A}_p(A_0,A_1,\&CenterDot;\&CenterDot;\&CenterDot;,A_{M-1})=\mathrm{round}(k_p\&times;\underset{i=0}{\overset{M-1}{\mathrm{\&Sigma;}}}{A}_i{W}_p\left(i\right))$

Wherein, W _p(i) being the trace-changing coefficient that receives focus p correspondence, is a kind of window function, and its width is relevant with the position that receives focus p, and when receiving focus p variation, the width of window function changes thereupon, W _p(i) also change thereupon;

Round is the computing that rounds up;

k _pBe the scale-up factor that receives focus p correspondence, when storage unit output data figure place is q, get k _pFor:

$k_p=\frac{2^q}{\underset{i=0}{\overset{M-1}{\mathrm{\&Sigma;}}}{W}_p\left(i\right)}$

(4.2). select signal A by the page _M..., A _M+L-2, A _M+L-1Select the change mark data of different focus p from respective memory unit, the described page is selected number of signals L=floor (log ₂P)+1;

Wherein, floor is a rounding operation.

2. the ultrasonic dynamic receiving apodization method based on the delta sigma conversion according to claim 1 is characterized in that: described W _p(i) be that Hamming is the hamming code window function, or Hanning is the Hanning window function.

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