CN110298915A - A kind of Fast Volume Rendering Algorithm three-dimensional ultrasonic image reconstruction algorithm introducing scattering model - Google Patents

A kind of Fast Volume Rendering Algorithm three-dimensional ultrasonic image reconstruction algorithm introducing scattering model Download PDF

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CN110298915A
CN110298915A CN201910534008.9A CN201910534008A CN110298915A CN 110298915 A CN110298915 A CN 110298915A CN 201910534008 A CN201910534008 A CN 201910534008A CN 110298915 A CN110298915 A CN 110298915A
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algorithm
scattering
light
data
sampling
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陈晓冬
邓惟心
盛婧
汪毅
蔡怀宇
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Tianjin University
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Tianjin University
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    • GPHYSICS
    • G06COMPUTING; CALCULATING; COUNTING
    • G06TIMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T17/00Three dimensional [3D] modelling, e.g. data description of 3D objects
    • GPHYSICS
    • G06COMPUTING; CALCULATING; COUNTING
    • G06TIMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T2210/00Indexing scheme for image generation or computer graphics
    • G06T2210/41Medical

Abstract

The present invention discloses a kind of Fast Volume Rendering Algorithm three-dimensional ultrasonic image reconstruction algorithm for introducing scattering model, this algorithm introduces phase function on the basis of light projecting algorithm to consider the influence of surrounding voxels.Since the scattering direction of light is theoretically unlimited item, calculate every ray tracing that operand is very big, therefore the energy scattered using random direction is calculated by the way of Monte Carlo sampling phase function.By the way that multiple sampling samples are averaged, three-dimensional reconstruction result closer to reality and smooth can be obtained.Traditional light projecting algorithm computational efficiency is lower, this algorithm pre-processes data by introducing bounding box and octree structure, using non-equidistant sample mode, accelerates the reconstruction speed of volume data.

Description

A kind of Fast Volume Rendering Algorithm three-dimensional ultrasonic image reconstruction algorithm introducing scattering model
Technical field
The present invention relates to three-D ultrasonic scope imaging fields, and in particular to a kind of Fast Volume Rendering Algorithm three for introducing scattering model Tie up ultrasonic image reconstruction algorithm.
Background technique
Probe with ultrasonic transducer is sent into human body by the biopsy channel of medical electric scope by endoscopic ultrasonography, is passed through Transmitting and reception ultrasonic wave simultaneously calculate echo signal processing, the tomoscan image of available human internal organs, thus Corresponding position lesion is detected.
Traditional two-dimensional ultrasonic imaging is only able to display the histology section information of a certain specific position of human body, can only pass through experience The three-dimensional structure for judging tissue is unfavorable for keeping the objective and accurate of diagnostic result;Three-D ultrasonic scope is by the rotation of ultrasonic transducer Turn scanning and axial movement combines acquisition three dimensional ultrasonic image data, then three-dimensional reconstruction is carried out to data, three-dimensional can be obtained Ultrasound image.Three-dimensional ultrasound pattern can be intuitively displayed the three-D space structure of test serum, to improve the accuracy rate of detection.
Common three-dimensional reconstruction algorithm can be divided into iso-surface patch algorithm and two kinds of volume rendering algorithm.Iso-surface patch algorithm passes through extraction The threshold value of a certain attribute of target object is determined to drawing data point, with tri patch connection contour surface carries out target object surface Drafting further according to normal direction setting color rendered.Although this method drafting speed is fast, can lose many in volume data The information of tissue key position, therefore it is not particularly suited for 3-D supersonic imaging field.
The volume rendering algorithm of mainstream is light projecting algorithm at present, i.e., from each pixel of image, sends out along fixed-direction The light for passing through whole image sequence is penetrated in this process to sample image sequence.Due to each sampled point Final display result has certain influence on the screen on the pixel for color and transparency, will be each according to light absorption model The color value and transparency of sampled point are overlapped the result finally rebuild.But this algorithm only considered observation road Voxel on diameter (radiation direction), the influence without the scattering in view of surrounding voxels to final three-dimensional image reconstruction result, Reconstruction effect has to be hoisted.It is traditional comprising many on being ultimately imaged point of the result without influence meanwhile in ultrasonic volume data Light projecting algorithm can repeatedly calculate these points, take a long time, reduce the operational efficiency of algorithm.
Summary of the invention
The purpose of the present invention is improve on traditional light projecting algorithm to further increase three-dimensional ultrasound pattern Reconstruction effect and rebuild speed.It is proposed a kind of Fast Volume Rendering Algorithm three-dimensional ultrasonic image reconstruction algorithm for introducing scattering model, light Line Projection algorithm only considers that the voxel on observation path, this algorithm introduce phase function on this basis to consider the shadow of surrounding voxels It rings.Since the scattering direction of light is theoretically unlimited item, it is very big therefore special using covering that operand is calculated to every ray tracing The mode of Carlow sampling phase function calculates the energy of random direction scattering.By the way that multiple sampling samples are averaged, can be obtained Closer to real and smooth three-dimensional reconstruction result.Traditional light projecting algorithm computational efficiency is lower, this algorithm is by introducing packet It encloses box and octree structure pre-processes data, using non-equidistant sample mode, accelerate the reconstruction speed of volume data.
The purpose of the present invention is what is be achieved through the following technical solutions:
A kind of Fast Volume Rendering Algorithm three-dimensional ultrasonic image reconstruction algorithm introducing scattering model, comprising the following steps:
Step 101, the volume data that 3-D supersonic imaging obtains is read;
Step 102, volume data is pre-processed, removes the noise spot in data;
Step 103, the hollow body element that suitable bounding box removal volume data China and foreign countries enclose is chosen;Projection on bounding box to image planes Region is the sampling area of light;
Step 104, the intensity profile situation for analyzing volume data, according to the difference of data point gray value be divided into air, The classifications such as tissue;
Step 105, color and transparency assignment, color sets itself as needed, transparency are carried out to different voxels Codomain be (0,1), wherein 0 indicate it is fully transparent, sight can pass through completely;1 indicates completely opaque, and sight can not be worn It crosses;
Step 106, according to color and transparence value construction Octree, separation hollow body element and effective voxel;
Step 107, a pixel according to the viewpoint of setting in sampling area emits light, passes through light entire Volume data field, volume data field are exactly distribution of the volume data in three-dimensional space;
Step 108, the radiation direction non-equidistant in step 107 across volume data field selects several sampled points to skip sky Voxel makes sample in effective node of Octree;
Step 109, it introduces phase function and considers the effectively influence of voxel around sampled point, by monte carlo method to phase letter Number multiple sampling is averaged;
Step 110, the transparency of obtained sampled point is synthesized, when the opacity of resulting pixel is greater than 1, is stopped It only samples, obtains the gray value that data fields surface is a little shown on the screen;
Step 111, all sampling areas, the 3-D image after being rebuild are traversed.
Further, the phase function introduced in step 109 is Henyey-Greenstein (H-G) phase function, formula Are as follows:
Wherein, θ is incident direction and the angle for scattering direction;G is dissymmetry factor, formula are as follows:
Monte carlo method angle of scattering sampling equation are as follows:
Wherein ξ is the uniform random number between 0 to 1.
Further, Data Synthesis formula in step 110 are as follows:
Wherein, L is the brightness value projected on screen, and x is the position of light starting point, and ω is the angle of the light direction of the launch Degree, p are the phase function in step 9, Li(x ', ω ') is the brightness value of sampled point surrounding voxels, and τ (x, x ') reflects dissipating for light It penetrates and attenuation, formula are as follows:
Wherein, σaFor absorption coefficient, σsFor scattering coefficient.
Compared with prior art, the beneficial effects brought by the technical solution of the present invention are as follows:
Inventive algorithm considers surrounding voxels by introducing scattering model in traditional light projecting algorithm, using phase function Influence to the voxel on observation path can reduce the calculation amount of scattering model by the Monte Carlo methods of sampling, after reconstruction Can be obtained surface it is more smooth, closer to actual three-dimensional ultrasound pattern;Volume data is pre-processed by introducing bounding box, it will Effective voxel is separated with invalid voxel, is only carried out light projection to effective voxel, is weakened the influence of invalid voxel in volume data, Reduce operand;It is sampled by Octree method storing data, in light projection process using non-equidistant, eliminates traditional algorithm Trigram Interpolation Process, improve the operational efficiency of algorithm.
Detailed description of the invention
Fig. 1 is the implementation flow chart of inventive algorithm.
Fig. 2 is the schematic illustration of inventive algorithm.
Fig. 3-1 and Fig. 3-2 is respectively throw light quantitative comparison's schematic diagram of traditional algorithm and OBBs algorithm.
Fig. 4-1 and Fig. 4-2 is respectively Octree data space structure and addressing system schematic diagram.
Traditional algorithm is respectively adopted in Fig. 5-1 and Fig. 5-2 and inventive algorithm carries out the contrast schematic diagram of resampling process.
Specific embodiment
The present invention is described in further detail below in conjunction with the drawings and specific embodiments.It should be appreciated that described herein Specific embodiment be only used to explain the present invention, be not intended to limit the present invention.
The implementing procedure of inventive algorithm is entire to flow as shown in Figure 1, Fig. 2 is the schematic illustration of this algorithm spatially Journey is embodied on the figure:
Step 1: carrying out helical scanning using three dimensional ultrasound probe, carries out the operations such as interpolation to the data of acquisition and forms three Tie up ultrasound image volume data, the volume data read.
Step 2: pre-processing three-D ultrasonic volume data, removes the noise spot in volume data, prevents noise spot counterweight It builds result and generates biggish interference and influence.
Step 3: the hollow body element outside bounding box removal volume data is chosen.It is typically chosen cuboid bounding box, each side and coordinate Axis is parallel, and inside surrounds all effective voxels.Bounding box is projected into imaging plane, the range of projection is exactly to carry out body rendering Light sample range.Traditional algorithm and the contrast schematic diagram such as attached drawing 3-1 and 3-2 for using OBBs algorithm, by utilizing encirclement Box removes hollow body element, reduces the amount of light for participating in calculating, to improve arithmetic speed.
Step 4: analyzing the intensity profile situation of volume data, according to the different by the body in volume data of data point gray value Element is divided into the classifications such as air, tissue.The gray value that all voxels in volume data are represented with set U is classified as n according to gray value A subset U not overlapped0, U1..., Un;Classification results need to meet:
Step 5: according in step 3 classify situation to each pixel carry out color and transparency assignment, color according to Sets itself is needed, the codomain of transparency is (0,1), wherein 0 indicates fully transparent, sight can pass through completely;1 indicates complete Opaque, sight can not pass through;
Step 6: according to pixel color, Octree storage organization is constructed.Set acceptable color similarity threshold value δ, c1、c2Indicate the color of pixel, color similarity determines as follows: using bounding box integrally as the root node of Octree, node There are three types of situations: interior pixels color completely similar (being labeled as F), color value part similar (being labeled as P) and empty node (label For E).If root node is in state F or E, Octree is had built up;Otherwise, root node is further subdivided into 8 small squares, It is respectively labeled as 0,1 ... ... 7, as first layer child node, then carries out above-mentioned processing, until the node there is no P-state is Only, such as Fig. 4-1 and Fig. 4-2.
Step 7: light is emitted according to a pixel of the viewpoint of setting into sampling area, makes light and bounding box Intersection;
Step 8: several sampled points are selected along radiation direction unequal steps.The intersection point of light and bounding box is found out first As the access point of sampling, then child node adjacent with access point on radiation direction is found as next sampled point.If the sampling Point is invalid voxel, then continually looks for next child node, otherwise writes down color value and transparency at sampled point.Traditional adopts Sample process such as Fig. 5-1 needs to determine sampled point using Tri linear interpolation method at this time if sampled point is not fallen at effective voxel Transparency calculates complicated;The sampling process of this method such as Fig. 5-2, passes through the sampling process of unequal steps, it is ensured that all samplings Point can be fallen on effective voxel, so as to avoid complicated interpolation arithmetic, improve operation efficiency.
Step 9: it introduces Henyey-Greenstein (H-G) phase function and constructs scattering model, consider around sampled point Effective influence of the voxel to the sampled point, phase function formula are as follows:
Wherein, θ is incident direction and the angle for scattering direction;G is dissymmetry factor, formula are as follows:
When constructing scattering model, calculation amount is reduced using the Monte Carlo methods of sampling.Monte carlo method is to angle of scattering The equation being sampled are as follows:
Wherein ξ is the uniform random number between 0 to 1.
Step 10: the color and transparence value of each sampled point surrounding pixel point are obtained according to above-mentioned sampling process, repeatedly Sampling is averaged to obtain the result of the sampled point;Sampled point all on this light is synthesized in the hope of volume data field surface again The gray value a little shown on the screen;
Step 11: all pixels on traverses screen repeat step 7 to step 10, and the three-dimensional after being rebuild is super Acoustic image.
The present invention is not limited to embodiments described above.Above the description of specific embodiment is intended to describe and say Bright technical solution of the present invention, the above mentioned embodiment is only schematical, is not restrictive.This is not being departed from In the case of invention objective and scope of the claimed protection, those skilled in the art may be used also under the inspiration of the present invention The specific transformation of many forms is made, within these are all belonged to the scope of protection of the present invention.

Claims (3)

1. a kind of Fast Volume Rendering Algorithm three-dimensional ultrasonic image reconstruction algorithm for introducing scattering model, which is characterized in that including following step It is rapid:
Step 101, the volume data that 3-D supersonic imaging obtains is read;
Step 102, volume data is pre-processed, removes the noise spot in data;
Step 103, the hollow body element that bounding box removal volume data China and foreign countries enclose is chosen;View field on bounding box to image planes is light Sampling area;
Step 104, the intensity profile situation for analyzing volume data is divided into air and tissue according to the difference of data point gray value Classification;
Step 105, color and transparency assignment, color sets itself as needed, the value of transparency are carried out to different voxels Domain is (0,1), wherein 0 indicates fully transparent, sight can pass through completely;1 indicates completely opaque, and sight can not pass through;
Step 106, according to color and transparence value construction Octree, separation hollow body element and effective voxel;
Step 107, a pixel according to the viewpoint of setting in sampling area emits light, and light is made to pass through whole number of individuals According to field;
Step 108, hollow body element is skipped in the radiation direction non-equidistant sampling in step 107 across volume data field, makes sample In effective node of Octree;
Step 109, it introduces phase function and considers the effectively influence of voxel around sampled point, it is more to phase function by monte carlo method Secondary sampling is averaged;
Step 110, the transparency of obtained sampled point is synthesized, when the opacity of resulting pixel is greater than 1, stops adopting Sample obtains the gray value that data fields surface is a little shown on the screen;
Step 111, all sampling areas, the 3-D image after being rebuild are traversed.
2. a kind of Fast Volume Rendering Algorithm three-dimensional ultrasonic image reconstruction algorithm for introducing scattering model according to claim 1, special Sign is that the phase function introduced in step 109 is Henyey-Greenstein (H-G) phase function, formula are as follows:
Wherein, θ is incident direction and the angle for scattering direction;G is dissymmetry factor, formula are as follows:
Monte carlo method angle of scattering sampling equation are as follows:
Wherein ξ is the uniform random number between 0 to 1.
3. a kind of Fast Volume Rendering Algorithm three-dimensional ultrasonic image reconstruction algorithm for introducing scattering model according to claim 1, special Sign is, Data Synthesis formula in step 110 are as follows:
Wherein, L is the brightness value projected on screen, and x is the position of light starting point, and ω is the angle of the light direction of the launch, p For the phase function in step 9, Li(x ', ω ') be sampled point surrounding voxels brightness value, τ (x, x ') reflect light scattering and Attenuation, formula are as follows:
Wherein, σaFor absorption coefficient, σsFor scattering coefficient.
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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN111540045A (en) * 2020-07-07 2020-08-14 深圳市优必选科技股份有限公司 Mechanical arm and three-dimensional reconstruction method and device thereof
CN111812956A (en) * 2020-06-12 2020-10-23 北京邮电大学 Volume data-based computer generated hologram method, device and electronic equipment
CN112001998A (en) * 2020-09-02 2020-11-27 西南石油大学 Real-time simulation ultrasonic imaging method based on OptiX and Unity3D virtual reality platforms

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN111812956A (en) * 2020-06-12 2020-10-23 北京邮电大学 Volume data-based computer generated hologram method, device and electronic equipment
CN111540045A (en) * 2020-07-07 2020-08-14 深圳市优必选科技股份有限公司 Mechanical arm and three-dimensional reconstruction method and device thereof
CN112001998A (en) * 2020-09-02 2020-11-27 西南石油大学 Real-time simulation ultrasonic imaging method based on OptiX and Unity3D virtual reality platforms

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