CN104207801B - A kind of ultrasound detection image three-dimensional scaling method - Google Patents

Abstract

The present invention relates to a kind of ultrasound detection image three-dimensional scaling method, the method obtains the posture information of ultrasonic probe in real time by the receiver on ultrasonic probe, thus can be by arbitrfary point in template (including cotton thread intersection point) Coordinate Conversion to receiver coordinate system；By ultrasonic probe to the scanning of cotton thread intersection point in mesh template, it is thus achieved that the ultrasonoscopy of cotton thread intersection point；Space vector is built by cotton thread intersection point in template, according to the coordinate of cotton thread intersection point imaging point in computation of geometric property ultrasonoscopy between vector between template hollow, and then application homologous points Least squares matching calculates the relation between location receivers coordinate system Or and scanning probe image coordinate system Oi.Compared with prior art, the present invention calculates homologous points coordinate in image coordinate system by space vector relation, human factor impact when avoiding artificial captured image homologous points coordinate in previous methods, thus there is the advantages such as stated accuracy is high with reconstruction precision, demarcation speed is fast.

Description

A kind of ultrasound detection image three-dimensional scaling method

Technical field

The present invention relates to ultrasonic calibration technique field, especially relate to a kind of ultrasound detection image three-dimensional scaling method.

Background technology

Three-dimensional (3-D) ultrasonic demarcation is that ultrasonoscopy 3-D visualizes indispensable committed step, because hand-held ultrasound is visited Head Freehand sampling, obtain is a series of two dimension (2-D) ultrasonoscopys non-parallel, irregular, only from ultrasonic probe The 2-D image information obtained is set out, and calculates the geological information in the 3-D space of its correspondence, the more parallel figure of thus create-rule As sequence, follow-up three-dimensional reconstruction and Target Segmentation just can be carried out.This calibration calculates process and is referred to as the ultrasonic demarcation of 3-D, and it leads to Follow the tracks of equipment usually through stationary positioned on ultrasonic probe, calculate the position relation between this equipment and the ultrasonic probe plane of scanning motion Realize.Therefore this equipment can obtain for scanning with real time record ultrasonic probe with azimuth information during arbitrary orientation scanning target A series of non-parallel ultrasonoscopy provide corresponding direction in space and positional information.

Two kinds of the most conventional ultrasonic probe positioning and tracing methods are magnetic orientation and optical alignment, and this patent uses magnetic orientation Method.And positioning tracking device is once fixed, the position relation between itself and the ultrasonic probe plane of scanning motion is i.e. it has been determined that this conversion Relation typically can not be measured by physical method, but can be expressed as positioning tracking device coordinate relative to ultrasound image plane The conversion of pixel coordinate transfers the registration of Party membership, etc. from one unit to another (rotate, translate and proportionate relationship), and its mathematical form is 4 × 4 matrixes.This transfers the registration of Party membership, etc. from one unit to another square Battle array also known as calibration matrix, calculated by homologous points coordinate under different coordinates in calibration matrix in the past, applied least square Matching algorithm obtains the transition matrix between two coordinate systems.Wherein homologous points coordinate in image coordinate system relies on artificial from figure Pick up in Xiang, the most inevitably bring the human factor impact on stated accuracy.

Summary of the invention

The purpose of the present invention is contemplated to the defect overcoming above-mentioned prior art to exist, from homologous points coordinate in the picture The angle that can be automatically extracted from the image file is studied, and is unique in that the space vector characteristic relation of application homologous points carries out image The automatic calculating of coordinate, thus provide and reduce the impact of human factor in algorithm, it is achieved a kind of stated accuracy is high with reconstruction precision, Demarcate fireballing ultrasound detection image three-dimensional scaling method.

The purpose of the present invention can be achieved through the following technical solutions:

A kind of ultrasound detection image three-dimensional scaling method, location receivers is connected with location transmitters, and the method passes through mould Plate calculates the relation between the location receivers coordinate system Or and scanning probe image coordinate system Oi being fixed on ultrasonic probe, described Template be provided with the netted cotton thread of two-layer, netted cotton thread has n cotton thread intersection point on scanning plane, described scaling method include with Lower step:

1) the some I in ultrasound scan images is taken₁As datum mark, obtain I₁At the coordinate that scanning probe image coordinate is fastened, I₁Coordinate R in location receivers coordinate system₁For:

R₁=T_r←t·T_t←p·P₁

Wherein, P₁On the basis of put I₁Respective coordinates in template coordinate system Op, T_r←tFor location transmitters coordinate system Ot phase For the transition matrix of location receivers coordinate system Or, T_t←pFor template coordinate system Op relative to location transmitters coordinate system Ot's Transition matrix；

2) according to the position of cotton thread intersection point pickup point I in scan image in template₂, it is thus achieved that vectorDirection, I₂? Respective coordinates in template coordinate system Op is P₂, according to P₁With P₂Distance d₁₂WithDirection calculating I₂At scanning probe image Coordinate on coordinate system, I₂Coordinate R in location receivers coordinate system₂For:

R₂=T_r←t·T_t←p·P₂；

3) according to the position of cotton thread intersection point pickup point I in scan image in template₃, I₃Right in template coordinate system Op Answering coordinate is P₃, vectorBetween angle be θ, according toDetermine with θDirection, according to P₁With P₃Distance d₁₃WithDirection calculating I₃At the coordinate that scanning probe image coordinate is fastened, I₃Coordinate R in location receivers coordinate system₃ For:

R₃=T_r←i·T_t←p·P₃；

4) repeat step 2), 3), it is thus achieved that on scanning plane, n cotton thread intersection point is at location receivers coordinate system and scanning probe figure As the coordinate in coordinate system, and carry out homologous points principle of least square coupling according to below equation, it is thus achieved that calibration matrix T_r←t:

$T_{r\←i}=\underset{R.p}{\min }\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{\left|\right|R_i-({\mathrm{sRI}}_i+p)\left|\right|}^2$

Wherein, R_iFor i-th cotton thread intersection point coordinate in location receivers coordinate system, I_iVisiting for i-th cotton thread intersection point Coordinate in head scanning image coordinate system, s is proportionality coefficient, and R is rotation relationship matrix, and p is translation vector；

5) gather m width ultrasound scan images, repeat step 1)-4), calculate m calibration matrix T_r←iMean value as Whole calibration result.

Described datum mark I₁For the some imaging point in ultrasonoscopy of the centre of the superiors' intersection point in netted cotton thread.

DescribedDirection depend on I₂Along datum mark I₁Direction.

Described T_t←pBe calculated by template scaling method, described template scaling method particularly as follows:

Template both sides are provided with multiple through hole, and through hole coordinate is it is known that contact logical successively by the probe tip of location receivers Hole, according to position relationship and the T of needle point location receivers the most thereon_r←tObtain these through holes at location transmitters coordinate system Coordinate on Ot, obtains T according to homologous points principle of least square coupling_t←p。

Compared with prior art, the invention have the advantages that

1, calculate homologous points coordinate by the method for space vector, be that used method is not adopted in research in the past.In the past Method in generally use the method for direct captured image homologous points coordinate or applications similar triangle to calculate homologous points coordinate.

2, homologous points number is few, by building space vector, obtains three pairs of homologous points and can complete calibration algorithm, demarcate letter Single quick.

3, datum mark selects heart position in the picture, experiment to prove that this position is affected little by supersonic beam sector effect weakening, Stated accuracy and reconstruction precision can be improved.

4, datum mark selects in image position on the upper side, and experiment proves that this position is little by supersonic beam effect of depth, can improve mark Determine precision high with reconstruction precision.

5, in ultrasonoscopy, other 2 homologous points select, in the position near picture centre line, to reduce supersonic beam fan-shaped Effect weakening affects, and improves stated accuracy and reconstruction precision.

6, the computational methods using homologous points principle of least square coupling and multi collect ultrasonoscopy to average again, come Calculate final calibration matrix, can revise in single operation due to probe align, image imaging point pickup etc. is because of introducing mutually Error.

Accompanying drawing explanation

Fig. 1 is the principle schematic of the present invention；

Fig. 2 is template scanning plane schematic diagram；

Fig. 3 is ultrasound scan images reconnaissance schematic diagram.

Detailed description of the invention

The present invention is described in detail with specific embodiment below in conjunction with the accompanying drawings.The present embodiment is with technical solution of the present invention Premised on implement, give detailed embodiment and concrete operating process, but protection scope of the present invention be not limited to Following embodiment.

A kind of ultrasound detection image three-dimensional scaling method, uses NDI magnetic orientation mode, location receivers and location transmitters Connecting, the method need to be aided with template and complete, the location receivers coordinate system Or being fixed on ultrasonic probe by formwork calculation And the relation between scanning probe image coordinate system Oi, described template is provided with the netted cotton thread of two-layer, and netted cotton thread is at scanning plane On have n (n is 10) individual cotton thread intersection point.

Scanning probe image coordinate system Oi needed for calibration process is self-defined, and location receivers coordinate system Or is that NDI is public Department's definition, location transmitters coordinate system Ot is the definition of NDI company, and template coordinate system Op is self-defined.

When ultrasonic probe scan templates as shown in Figure 1, certain some P that delivery plate is in field of view_ρ= [x_ky_kz_k1]^T, its imaging point coordinate in coordinate system Oi is designated as P_i=[s_u·u_ks_v·v_k01]^T, s_u、s_vFor ultrasonoscopy two The resolution ratio (proportionality coefficient, unit mm/pixel) in individual direction, generally: s_u=s_v, then the transformational relation between Op and Oi with Homogeneous coordinate transformation matrix table is shown as:

$\left(\begin{array}{c}{x}_k\\ y_k\\ z_k\\ 1\end{array}\right)=T_{p\←t}\·T_{t\←r}.T_{r\←i}.\left(\begin{array}{c}{s}_u.u_k\\ s_v.x_v\\ 0\\ 1\end{array}\right)---\left(1\right)$

It is abbreviated as: P_p=T_p←t·T_t←r·T_r←i·P_i (2)

Wherein, T_t←rFor the location receivers coordinate system Or transition matrix relative to location transmitters coordinate system Ot, determine magnetic The location algorithm that device is followed the tracks of intrinsic in position can be calculated；T_p←tFor the conversion relative to template coordinate system Op of transmitter coordinate system Ot Matrix, is calculated by template scaling method.(2) formula is expressed as the most in the matrix form:

T_p←i=T_p←i·T_t←r·T_r←i (3)

T_r←i=T_t←r ^-1·T_p←t ^-1·T_p←i (4)

T_r←iIt is the final goal of calibration algorithm.

Described T_t←pBe calculated by template scaling method, described template scaling method particularly as follows:

Template both sides are provided with multiple through hole, and through hole coordinate is it is known that contact logical successively by the probe tip of location receivers Hole, according to position relationship and the T of needle point location receivers the most thereon_r←tObtain these through holes at location transmitters coordinate system Coordinate on Ot, obtains T according to homologous points principle of least square coupling_t←p。

As in figure 2 it is shown, owing to the size of stencil design is it is known that so P in template₁, P₂, P₂, d₁₂、d₁₃, vectorWithBetween angle theta be can be calculated, all as known conditions.

As shown in Figure 1-Figure 3, this scaling method comprises the following steps:

1) the some I in ultrasound scan images is taken₁As datum mark, I₁For the centre of the superiors' intersection point in netted cotton thread a bit, Obtain I₁At the coordinate that scanning probe image coordinate is fastened, I₁Coordinate R in location receivers coordinate system₁For:

R₁=T_r←t·T_i←p·P₁

Wherein, P₁On the basis of put I₁Respective coordinates in template coordinate system Op, T_r←tFor location transmitters coordinate system Ot phase For the transition matrix of location receivers coordinate system Or, t_t←pFor template coordinate system Op relative to location transmitters coordinate system Ot's Transition matrix；

2) according to the position of cotton thread intersection point pickup point I in scan image in template₂, I₂Optional datum mark upper strata of closing on is left A bit of side,Direction depend on I₂Along datum mark I₁Direction, the x-axis direction can being parallel in template coordinate system, I₂? Respective coordinates in template coordinate system Op is P₂, by P₁With P₂Distance d₁₂Be converted to pixel, calculate I₁With I₂Distance: | I₁I₂| =s d₁₂, s is proportionality coefficient, and unit is: pixel/mm, and namely every millimeter represents how many pixels, according to distance and direction Calculate I₂At the coordinate that scanning probe image coordinate is fastened, I₂Coordinate R in location receivers coordinate system₂For: R₂=T_r←t· T_t←p·P₂；

3) according to the position of cotton thread intersection point pickup point I in scan image in template₃, I₃Optional datum mark lower floor of closing on is left A bit of side, I₃Respective coordinates in template coordinate system Op is P₃, vectorBetween angle be θ, according toAnd θ DetermineDirection, according to P₁With P₃Distance d₁₃WithDirection calculating I₃Coordinate in scanning probe image coordinate system: $\stackrel{\‾}{I_1{I}_2}\stackrel{\‾}{I_1{I}_3}=\left|I_1{I}_2\right|\·\left|I_1{I}_3\right|\cos \mathrm{\θ}=s\·d_{12}\·s\·d_{13}\cos \mathrm{\θ}.$ I₃Coordinate R in location receivers coordinate system₃For: R₃= T_r←t·T_t←p·P₃；

4) repeat step 2), 3), it is thus achieved that on scanning plane, 10 cotton thread intersection points are at location receivers coordinate system and scanning probe Coordinate in image coordinate system, and carry out homologous points principle of least square coupling according to below equation, it is thus achieved that calibration matrix T_r←i:

$T_{r\←i}=\underset{R.p}{\min }\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{\left|\right|R_i-({\mathrm{sRI}}_i+p)\left|\right|}^2$

Wherein, R₁For i-th cotton thread intersection point coordinate in location receivers coordinate system, I_iVisiting for i-th cotton thread intersection point Coordinate in head scanning image coordinate system, R is rotation relationship matrix, and p is translation vector；

5) gather 10 width ultrasound scan images, repeat step 1)-4), calculate m calibration matrix T_r←iMean value as Whole calibration result.

Last T_r←iBeing 4 × 4 matrixes, first three is classified as rotation relationship R, and last is classified as translation vector p:

$T_{r\←i}=\left[\begin{array}{cccc}{P}_{11}& P_{12}& P_{13}& P_{14}\\ P_{21}& P_{22}& P_{23}& P_{24}\\ P_{31}& P_{32}& P_{33}& P_{34}\\ 0& 0& 0& 1\end{array}\right].$

Claims (2)

1. a ultrasound detection image three-dimensional scaling method, location receivers is connected with location transmitters, it is characterised in that the party Method is set up homologous points space vector by template and is calculated the location receivers coordinate system Or and probe being fixed on ultrasonic probe Relation between scanning image coordinate system Oi, described template is provided with the netted cotton thread of two-layer, and netted cotton thread has n on scanning plane Cotton thread intersection point, described scaling method comprises the following steps:

1) the some I in ultrasound scan images is taken₁As datum mark, described datum mark I₁For the superiors' intersection point in netted cotton thread Middle some imaging point in ultrasound scan images, obtains I₁At the coordinate that scanning probe image coordinate is fastened, I₁Connect in location Receive the coordinate R in device coordinate system₁For:

R₁=T_r←t·T_t←p·P₁

Wherein, P₁On the basis of put I₁Respective coordinates in template coordinate system Op, T_r←tFor location transmitters coordinate system Ot relative to The transition matrix of location receivers coordinate system Or, T_t←pFor the template coordinate system Op conversion relative to location transmitters coordinate system Ot Matrix；

2) according to the position of cotton thread intersection point pickup point I in ultrasound scan images in template₂, it is thus achieved that vectorDirection, The x-axis direction being oriented parallel in template coordinate system, I₂Respective coordinates in template coordinate system Op is P₂, according to P₁With P₂ Distance d₁₂WithDirection calculating I₂At the coordinate that scanning probe image coordinate is fastened, I₂In location receivers coordinate system Coordinate R₂For:

R₂=T_r←t·T_t←p·P₂；

3) according to the position of cotton thread intersection point pickup point I in ultrasound scan images in template₃, I₃For closing on the left of datum mark lower floor A bit, I₃Respective coordinates in template coordinate system Op is P₃, vectorBetween angle be θ, according toTrue with θ FixedDirection, according to P₁With P₃Distance d₁₃WithDirection calculating I₃At the coordinate that scanning probe image coordinate is fastened, I₃Coordinate R in location receivers coordinate system₃For:

R₃=T_r←t·T_t←p·P₃；

4) repeat step 2), 3), it is thus achieved that on scanning plane, n cotton thread intersection point is at location receivers coordinate system and scanning probe image seat Coordinate in mark system, and carry out homologous points principle of least square coupling according to below equation, it is thus achieved that calibration matrix T_r←i:

$T_{r\←i}=\underset{R,p}{\min }\underset{i=1}{\overset{n}{\Σ}}\left|\right|R_i-({\mathrm{sRI}}_i+p)|{|}^2$

Wherein, R_iFor i-th cotton thread intersection point coordinate in location receivers coordinate system, I_iSweep at probe for i-th cotton thread intersection point Retouching the coordinate on image coordinate system, s is proportionality coefficient, and R is rotation relationship matrix, and p is translation vector；

5) gather m width ultrasound scan images, repeat step 1)-4), calculate m calibration matrix T_r←iMean value as final mark Determine result.

A kind of ultrasound detection image three-dimensional scaling method the most according to claim 1, it is characterised in that described T_t←pLogical Cross template scaling method to be calculated, described template scaling method particularly as follows:

Template both sides are provided with multiple through hole, and through hole coordinate is it is known that by the probe tip of location receivers successively contact through hole, root Position relationship and T according to needle point location receivers the most thereon_r←tObtain these through holes on location transmitters coordinate system Ot Coordinate, obtains T according to homologous points principle of least square coupling_t←p。