CN109559359A - Artifact minimizing technology based on the sparse angular data reconstruction image that deep learning is realized - Google Patents

Artifact minimizing technology based on the sparse angular data reconstruction image that deep learning is realized Download PDF

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CN109559359A
CN109559359A CN201811137448.2A CN201811137448A CN109559359A CN 109559359 A CN109559359 A CN 109559359A CN 201811137448 A CN201811137448 A CN 201811137448A CN 109559359 A CN109559359 A CN 109559359A
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CN109559359B (en
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胡轶宁
许强
谢理哲
王浩
王征
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Southeast University
Nanjing Medical University
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Abstract

The present invention provides a kind of artifact minimizing technology of sparse angular data reconstruction image realized based on deep learning, passes through acquisition sparse angular data for projection and complete Angles Projections data;It is rebuild respectively using sparse angular data for projection and complete data for projection;The neural network of artifact is gone in building;Using the image of reconstruction as training data;Trained neural network model is saved, and wherein by test image investment;The noise that obtained neural network forecast in step E is subtracted using test image, can be obtained clear image.The deep learning method having outstanding performance in computer vision at present is introduced into the artifact removal research of sparse angular projection analytic reconstruction image, the characteristics of using Inception-resnet network, the fine and various neural network of ability to express is constructed, the artifact suitable for sparse angular data analytic reconstruction image removes.

Description

Artifact minimizing technology based on the sparse angular data reconstruction image that deep learning is realized
Technical field
The present invention relates to a kind of artifact minimizing technologies of sparse angular data reconstruction image realized based on deep learning.
Background technique
CT scan (Computed tomography, CT) passes through development in more than 30 years, imaging speed Degree and image quality have significant progress, and as CT scan is using more and more extensive, people are for CT scan to human body Radiation increasingly pay attention to, medical research shows that x-ray bombardment may induce the diseases such as pathobolism, cancer, leukaemia Disease.In conventional CT examination, dose of radiation suffered by patient has arrived very important stage.However the reduction of CT scan dosage It is usually associated with the decline of image quality, research hotspot instantly is exactly to guarantee imaging while reducing CT scan dosage as far as possible Quality.
Sparse angular projection acquisition mainly realizes the purpose for reducing scanning dose, but its by reducing the CT scan time Analytic reconstruction can bring serious strip artifact, can be to scarce under the conditions of sparse sampling according to the redundancy of CT data for projection It loses data and repair and estimate to obtain complete data for projection collection, and rebuild with this, under this thinking, Li et al. utilizes dictionary learning The data for projection that method estimation is lost, and rebuild, achieve the result better than TV method.Zhang etc. utilizes S2etram's Direction difference approach carries out the missing data that difference removes acquisition projection data spatial to data for projection, then carries out related reconstruction, This method compares traditional linear difference and achieves preferable experiment effect.Based on compressed sensing (Compressed Sensing, CS) method in, Rudin is removed for the Gaussian noise in data for projection using full variational method, in mooring The noise of pine distribution then uses improved full variational method.Ma etc. is obtained using the local smoothing method of non-local mean as constraint More preferable than TV result.Hu etc. proposes a kind of 2 layers of progressive iterative model, by the prior-constrained introducing three dimensional CT weight of zero norm It builds, is obtained under conditions of height is sparse and be much better than the prior-constrained result of a norm.Furthermore iterative reconstruction algorithm is also dilute A solution of Angles Projections is dredged, but relative to parsing class algorithm for reconstructing, excessive calculation amount limits it and answers extensively With.
In existing all kinds of methods based on analytic reconstruction, there are still following problems:
One, the existing all kinds of methods based on analytic reconstruction thoroughly can not effectively inhibit structural large scale strip artifact, Iterative reconstruction approach takes long time.
Two, in the neural network of the non-resnet type of tradition, the gradient explosion and the gradient disappearance problem that occur.Generally For network it is deeper, the ability to express of network is stronger, but in practice, when the neural network number of plies is more than a fixed number Mesh, the ability to express that just will appear network are not further added by, and are even not so good as shallower network.This is because the gradient updating of network Rule be according to chain rule, the gradient of front layer from all layers of gradient below product, in this way after the number of plies increases, The gradient of front layer will be made to become very small or very big, referring to 0.9^100 ≈ 0.00002,1.1^100 ≈ 13781. In this way training when just will appear front layer and update that amplitude is too small or amplitude causes greatly very much can not finally restrain.
Three, the overall feeling open country of Inception-resnet-v2 network is still not big enough, can not capture strip artifact completely Feature.
Four, traditional neural network has full articulamentum, will lead to network parameter huge amount, and time consumption for training is very long, And it is easy over-fitting.
Therefore the deep learning method having outstanding performance in computer vision at present is introduced into and sparse angular is parsed It is had a very important significance in the removal research of reconstruction image artifact.
Summary of the invention
The object of the present invention is to provide a kind of artifacts of sparse angular data reconstruction image realized based on deep learning to go Except method solves the problems, such as that current analytic reconstruction class method existing in the prior art can not effectively inhibit large scale strip artifact.
In the present invention, Inception indicates the Inception network basic module of Google, Inception-resnet table Show the new basic network module that Google combines residual error network and Inception network design to come out, specific structure such as Fig. 2 institute Show.
In the present invention, FDK algorithm is 3 D pyramidal CT algorithm for reconstructing very classical in CT image reconstruction field, three wounds The upper-case first letters of beginning name word are composed its name.
The technical solution of the invention is as follows:
A kind of artifact minimizing technology for the sparse angular data reconstruction image realized based on deep learning, is based on deep learning Constructing one combines the sparse angular reconstruction from projections imaging artifact of full convolutional network and Inception-resnet network module to disappear Except neural network, going artifact and noise to be predicted and remove it for sparse angular CT image specifically includes following step Suddenly,
Several pairs of S1, acquisition data for projection, each pair of data for projection includes sparse angular data for projection and complete Angles Projections Data;
S2, it is rebuild, will be rebuild respectively using the sparse angular data for projection and complete data for projection of step S1 acquisition Data set patchi (i=1,2,3,4,5 ...) afterwards is saved, and each pair of data set includes sparse angular backprojection reconstruction data set With complete backprojection reconstruction data set;
S3, building sparse angular reconstruction from projections imaging artifact eliminate neural network;
S4, using the image rebuild in step S2 as training dataset, complete backprojection reconstruction data set does contrasting data, Neural network is eliminated to the sparse angular reconstruction from projections imaging artifact constructed in step S3 to be trained, and it is preferable to save training effect Model, be denoted as model model;
The trained sparse angular reconstruction from projections imaging artifact that S5, obtaining step S4 are saved eliminates neural network model Model, and wherein by test image test_img investment, it finally predicts and saves test image test_img and corresponding puppet Shadow figure noise_img;
S6, obtained artifact figure noise_ in step S5 is subtracted using the test image test_img saved in step S5 Clear image clean_img can be obtained in img.
Further, in step S1, the acquisition angles interval of the sparse angular data for projection of acquisition is not less than 4 ° and not Greater than 8 °, complete Angles Projections data acquisition angles interval is not more than 0.5 °, i.e. the group number of data acquisition is in less than 90 Group is greater than in the range of 45 groups.
Further, in step S2 using FDK algorithm for reconstructing to the step S1 sparse angular data for projection acquired and complete Data for projection is rebuild respectively, specifically,
S21, institute's acquired projections data in two-dimensional projection's matrix, that is, step S1 are calculated with weighted factor and is multiplied, be modified So that it is met Central slice theorem, obtains revised data for projection;
S22, the revised data for projection of step S21 is done and is filtered line by line using slope filtering method;
S23, image is gone out as backprojection reconstruction to the filtered data of step S22.
Further, sparse angular reconstruction from projections imaging artifact is constructed in step S3 eliminate neural network specific structure are as follows:
Convolution -> BN layers -> relu- > convolution -> BN layers -> relu- > Resblock- > Res_inception_block1- > Res_inception_block2- > Res_inception_block3- > BN layers -> relu- > convolution;
Wherein, it is normalized for i.e. batch for BN layers, to sparse angular reconstruction from projections imaging puppet when neural metwork training The output data that shadow eliminates neural network middle layer carries out Z-score normalized, that is, subtracts mean value except variance;Relu is sparse Angles Projections reconstruction image artifact eliminates the activation primitive that neural network uses, and expression formula is relu (x)=max (0, x); Concat representing matrix splices layer, i.e., the input of multiple branches is stitched together as a whole in a certain specified dimension It is input to next layer;What Resblock was indicated is the basic module of a residual error network;Res_inception_block1,Res_ Inception_block2, Res_inception_block 3 respectively indicates the basic module of an Inception_resnet, The different internal structure of digital different expressions;
Further, in step S3,
The normal connection path of the Resblock: input -> convolution -> BN layers -> relu- > convolution -> sum layers, then its A parallel link is had more, is directly connected to sum layers from input, is added with the output of normal connection path, as next layer Input;
First connection path of the Res_inception_block1: input -> convolutional layer -> concat layers i.e. channel Splice layer;Article 2 connection path: input -> convolutional layer -> BN layers -> relu- > convolution -> BN layers -> relu- > convolution -> Concat layers;Third path: input -> convolutional layer -> BN layers -> relu- > convolution -> BN layers -> relu- > convolution -> concat Layer;Then the input of the output and parallel link path by above-mentioned three paths after concat layers of splicing passes through sum layers It is added, result is as next layer of input;
First connection path of the Res_inception_block2: input -> convolution -> concat layers;Article 2 Connection path: input -> convolution -> BN layers -> relu- > convolution -> BN layers -> relu- > convolution -> concat layers;It then will be above-mentioned Output of two paths after concat layers of splicing is added with the input in parallel link path at sum layers, result conduct Next layer of input;
First connection path of the Res_inception_block3: input -> convolution -> concat layers;Article 2 Connection path: input -> convolution -> BN layers -> relu- > convolution -> BN layers -> relu- > convolution;Then above-mentioned two paths are passed through Cross concat layers splicing after output be added under sum layers with the input in parallel link path, result is as next layer Input.
Further, step S4 specifically,
S41, in step S2 rebuild after data set patchi (i=1,2,3,4,5 ...), carry out blocking processing, then It puts into sparse angular reconstruction from projections imaging artifact and eliminates neural network;
S42, it is eliminated by data set patchi (i=1,2,3,4,5 ...) investment sparse angular reconstruction from projections imaging artifact Data are normalized before neural network, i.e., training sample obtained in step S2 are normalized, i.e.,Wherein mean is the mean value of patchi, and std is its standard deviation;It will Patchi* investment sparse angular reconstruction from projections imaging artifact is eliminated neural network and is trained;And put into institute in step S3 The sparse angular reconstruction from projections imaging artifact of building is eliminated neural network and is trained, and training includes propagated forward and reversely passes It broadcasts;The final model model for saving training and obtaining, supplying step S5 test use.
Further, in step S42, sparse angular reconstruction from projections imaging artifact is eliminated specific in neural network training process It is to take mean square error mse as last loss function is trained to be corrected to network parameter, expression formula is as follows:
Wherein, n is the size of every a batch investment data volume Batch-size, and w, h are the length and width of each sample, D respectively It is the effect picture clean_ subtracted after sparse angular reconstruction from projections imaging artifact elimination neural network prediction artifact and noise Img, X are correlation datas, i.e. the sparse angular backprojection reconstruction data set rebuild in step S2 and complete Angles Projections rebuild number According to the error image of collection;In training process, sparse angular reconstruction from projections imaging artifact eliminates neural network according to loss function Numerical value successively calculates renewal amount by back-propagation algorithm and Adam optimization algorithm to update the parameter of network gradually to optimize mould Type model.
Further, step S5 specifically,
S51, the model model that training obtains in step S4 is saved;
S52, test image test_img is put into progress artifact figure noise_img prediction among model model, and saved The artifact figure noise_img of prediction.
Further, step S6 specifically,
The artifact figure noise_img and test image test_img predicted in S61, obtaining step S5.
S62, artifact figure noise_img is subtracted with test image test_img, required clear image can be obtained clean_img。
The beneficial effects of the present invention are:
One, the artifact minimizing technology for the sparse angular data reconstruction image that this kind is realized based on deep learning, will exist at present The artifact removal that the deep learning method having outstanding performance in computer vision is introduced into sparse angular projection analytic reconstruction image is ground In studying carefully, the characteristics of using Inception-resnet network, the fine and various neural network of ability to express can be constructed, Artifact suitable for sparse angular data analytic reconstruction image removes;
Two, the method for the present invention is replaced originally in the overall structure of Inception-resnet network using resnet Simple convolutional layer in Inception-resnet, to construct the neural network of deeper, so that the overall feeling of network is wild It is bigger, more meet the feature of strip artifact overall situation distribution.
Three, the present invention uses the mode of the full convolutional network of FCN, that is, convolutional layer is used only without the use of full articulamentum, due to The features such as weight of convolution is shared, part connects, the parameter of network greatly reduces, and greatly reduces the training time, also improves Anti- over-fitting ability, and designed image can be easier to the network of image by FCN, save many troubles.
Detailed description of the invention
Fig. 1 is the artifact minimizing technology for the sparse angular data reconstruction image that the embodiment of the present invention is realized based on deep learning Flow diagram.
Fig. 2 is the structural schematic diagram of the basic module of Inception-resnet in embodiment.
Fig. 3 is that the basic structure of the elimination neural network of sparse angular reconstruction from projections imaging artifact used in embodiment is shown It is intended to.
Fig. 4 is the structural schematic diagram of corresponding Resblock module in embodiment.
Fig. 5 is corresponding Res_inception_block1 basic structure schematic diagram in Fig. 3.
Fig. 6 is corresponding Res_inception_block2 basic structure schematic diagram in Fig. 3.
Fig. 7 is corresponding Res_inception_block3 basic structure schematic diagram in Fig. 3.
Fig. 8 is the schematic diagram of convolution mode in embodiment.
Wherein, Input table shows input, and Output indicates output;
The Inception network basic module of Inception expression Google;
Inception-resnet indicates that Google combines residual error network (resnet) and Inception network design to come out New basic network module;
Conv 1*1 indicates that it is a convolutional layer, and convolution kernel is having a size of 1*1;Conv 1*3 indicates that it is a convolution Layer, convolution kernel is having a size of 1*3;Conv 3*1 indicates that it is a convolutional layer, and convolution kernel is having a size of 3*1;Conv 3*3 indicates it It is a convolutional layer, convolution kernel is having a size of 3*3;Conv 1*7 indicates that it is a convolutional layer, and convolution kernel is having a size of 1*7;Conv 7*1 indicates that it is a convolutional layer, and convolution kernel is having a size of 7*1;
Relu is amendment linear unit, indicates that sparse angular reconstruction from projections imaging artifact eliminates one kind that neural network uses Activation primitive;
BN layers expression be batch normalization layer (Batch normalization);
Filter concat representing matrix splices layer, i.e., the input of multiple branches exists in a certain specified dimension splicing Next layer is input to together as an entirety;
What Resblock was indicated is the basic module of a residual error network;
Res_inception_block1, Res_inception_block 2, Res_inception_block 3 difference Indicate the basic module of an Inception_resnet, number is different to indicate different internal structure (convolution in general Combination it is different).
Specific embodiment
The preferred embodiment that the invention will now be described in detail with reference to the accompanying drawings.
Embodiment
A kind of artifact minimizing technology for the sparse angular data reconstruction image realized based on deep learning is sparse by acquiring Angles Projections data and complete Angles Projections data;Weight is carried out respectively using sparse angular data for projection and complete data for projection It builds;It constructs sparse angular reconstruction from projections imaging artifact and eliminates neural network;Using the image of reconstruction as training data;Save instruction The model perfected, and wherein by test image investment;Obtained sparse angular in step E, which is subtracted, using test image projects weight The noise that image artifacts eliminate neural network prediction is built, clear image can be obtained.It will be showed in computer vision at present prominent Deep learning method out is introduced into the artifact removal research of sparse angular projection analytic reconstruction image, utilizes Inception- The characteristics of resnet network, constructs the fine and various sparse angular reconstruction from projections imaging artifact of an ability to express and eliminates nerve Network, the artifact suitable for sparse angular data analytic reconstruction image remove.
A kind of artifact minimizing technology of sparse angular data reconstruction image realized based on deep learning of embodiment, is based on Deep learning constructs one and the sparse angular reconstruction from projections imaging artifact of full convolutional network and Inception-resnet is combined to disappear Except neural network, goes artifact and noise to be predicted for sparse angular CT image and remove it;Such as Fig. 1, specifically include Following steps:
Five pairs of S1, acquisition data for projection Ai (i=1,2,3,4,5), per internally comprising one group of sparse angular data for projection Ai_ Low and one group of complete Angles Projections data Ai_high.
The acquisition angles interval of the sparse angular data for projection acquired in step S1 is not less than 4 ° and no more than 8 °, complete Angles Projections data acquisition angles interval is not more than 0.5 °, i.e. the group number of data acquisition is to be in be greater than 45 groups less than 90 groups In range.
S2, it is rebuild using the five couples of data for projection Ai acquired in step S1, the data set after reconstruction is saved as five To S2i (i=1,2,3,4,5), each pair of data set is divided into sparse angular backprojection reconstruction data set S2i_low and complete Angles Projections Data set for reconstruction S2i_high, single layer image size is 512*512 in each pair of data set.
What reconstruction utilized in step S2 is FDK algorithm classical in analytic reconstruction algorithm, specifically,
S21, it calculates two-dimensional projection's matrix weighted factor and is multiplied, being modified, which makes it substantially meet center slice, determines Reason.
S22, it revised data for projection is done filters line by line, wherein using slope filtering mode.
S23, image is gone out as backprojection reconstruction to filtered data.
S3, building sparse angular reconstruction from projections imaging artifact eliminate neural network.
S31, constructed sparse angular reconstruction from projections imaging artifact elimination neural network overall structure specific structure are for example attached Fig. 3
Convolution -> BN layers (batch-normalization) layer -> relu- > convolution -> BN layers -> relu- > Resblock- > Res_inception_block1- > Res_inception_block2- > Res_inception_block3- > BN layers -> relu- > convolution.
Wherein, it is normalized for i.e. batch for BN layers, to sparse angular reconstruction from projections imaging puppet when neural metwork training The output data that shadow eliminates neural network middle layer carries out Z-score normalized, that is, subtracts mean value except variance;Relu is sparse Angles Projections reconstruction image artifact eliminates the activation primitive that neural network uses, and expression formula is relu (x)=max (0, x); Concat representing matrix splices layer, i.e., the input of multiple branches is stitched together as a whole in a certain specified dimension It is input to next layer;What Resblock was indicated is the basic module of a residual error network;Res_inception_block1,Res_ Inception_block 2, Res_inceptio n_block 3 respectively indicate the basic mould of an Inception_resnet Block, number is different to indicate different internal structures;
Resblock described in S311, step S31 is as shown in Fig. 4, normal connection path: input -> convolution -> BN layers -> Relu- > convolution -> sum layers, then it has more a parallel link compared to common convolutional network, is directly connected to from input It sum layers, is added with the output of normal connection path, as next layer of input.
Res_inception_block1 specific structure described in S312, step S31 is as shown in figure 5, first link road Diameter: input -> convolutional layer -> concat layers of Filter (matrix splicing layer).Article 2 connection path: input -> convolutional layer -> BN Layer -> relu- > convolution -> BN layers -> relu- > convolution -> concat layers.Third path: input -> convolutional layer -> BN layers -> Relu- > convolution -> BN layers -> relu- > convolution -> concat layers.Then by above-mentioned three paths after concat layers of splicing Output and the input in parallel link path be added by sum layers, result is as next layer of input.
Res_inception_block2 specific structure described in S313, step S31 is as shown in fig. 6, first link road Diameter: input -> convolution -> concat layers.Article 2 connection path: input -> convolution -> BN layers -> relu- > convolution -> BN layers -> Relu- > convolution -> concat layers.Then the output by above-mentioned two paths after the splicing of concat floor and parallel link road The input of diameter is added at sum layers, and result is as next layer of input.
Res_inception_block3 specific structure described in S314, step S31 is as shown in fig. 7, first link road Diameter: input -> convolution -> concat layers.Article 2 connection path: input -> convolution -> S2N- > relu- > convolution -> S2N- > Relu- > convolution.Then the input of the output and parallel link path by above-mentioned two paths after concat layers of splicing exists Sum layers lower to be added, and result is as next layer of input.
Sparse angular reconstruction from projections imaging artifact eliminates the convolution mode of neural network using boundary extential form convolution, So that each layer of input is identical as Output Size.
S4, using the data set Bi_low (i=1,2,3,4,5) saved in step S2 as sparse angular backprojection reconstruction figure As the training dataset of artifact elimination neural network, data set Bi_high (i=1,2,3,4,5) does contrasting data, to step S3 The sparse angular reconstruction from projections imaging artifact of middle building is eliminated neural network and is trained, and the preferable model of training effect is saved, It is denoted as model.
S41, blocking processing is carried out to the data obtained Bi in step S2 (i=1,2,3,4,5), blocking will every figure Small block data collection patchi (i=1,2,3,4,5) as being divided into several 128*128 puts into sparse angular reconstruction from projections imaging puppet again Shadow eliminates neural network, to learn.
S42, it needs to carry out at Z-score normalization data before by data patchi (i=1,2,3,4,5) investment Reason, i.e.,Wherein mean is the mean value of patchi, and std marks for it It is quasi- poor;Patchi* investment sparse angular reconstruction from projections imaging artifact is eliminated neural network to be trained, and saves training effect Preferable model is denoted as model.
In step S42, it is specifically to take in neural network training process that sparse angular reconstruction from projections imaging artifact, which is eliminated, Square error mse is corrected network parameter as last loss function is trained, and expression formula is as follows:
Wherein, n is the size of every a batch investment data volume Batch-size, and w, h are the length and width of each sample, D respectively It is the effect picture clean_ subtracted after sparse angular reconstruction from projections imaging artifact elimination neural network prediction artifact and noise Img, X are correlation datas, i.e. the sparse angular backprojection reconstruction data set rebuild in step S2 and complete Angles Projections rebuild number According to the error image of collection;In training process, sparse angular reconstruction from projections imaging artifact eliminates neural network according to loss function Numerical value successively calculates renewal amount by back-propagation algorithm and Adam optimization algorithm to update the parameter of network gradually to optimize mould Type model.
Trained model in S5, obtaining step S4 will need to carry out the picture of artifact removal processing as test image Test_img puts into model, finally predicts and save the test_img and corresponding artifact figure noise_img.
The model model saved in first obtaining step S42 is comprised the concrete steps that in step S5, will be carried out artifact and is handled Picture test_img investment model among carry out the prediction of artifact figure, and save the artifact figure noise_img of prediction.
S6, artifact figure noise_img is subtracted using the test image test_img saved in step E, it is clear to can be obtained Image clean_img.
S61, the noise_img and its test_img used predicted in the step E is obtained.
S62, its corresponding artifact figure noise_img is subtracted with test chart test_img, required clear effect can be obtained Fruit schemes clean_img.
It has been used in the elimination neural network of sparse angular reconstruction from projections imaging artifact constructed by embodiment many advanced The thought of neural network model, such as resnet, Inception-resnet, FCN etc..Specific structure is as matched shown in Fig. 2;
Sparse angular reconstruction from projections imaging artifact is eliminated neural network and is inspired by the thought of resnet in embodiment, uses The skill of " short connection " alleviates gradient disperse, the gradient explosion etc. that conventional depth network occurs as shown in the right one side of something of Fig. 2 Situation.Gradient disperse refers to, conventional network structure is stacked on after the network number of plies increases to a certain degree, sparse angular projection The performance that reconstruction image artifact eliminates neural network will not only improve, but also may be worse.Gradient disperse is depth nerve How a relatively conventional phenomenon in network is deepening network, while improving the ability to express of network, is evading gradient disperse Phenomenon is a hot spot in deep learning.Two non-conterminous hidden layers are directly connected with each other by parallel link, in this way in net In the case that network is very deep, even if going wrong in certain layers, but due to the presence of parallel link, so that the hidden layer knot of front Fruit can be input to below by short connection cross-layer, can't excessively influence whole effect.In Inception-resnet base In this module, this advantage of resnet is absorbed.
The characteristics of Inception is the parallel of a variety of convolution kernel combinations, that is, compared with " width ".Previous common net Network can only use a number of convolution kernel of like combinations mode when extracting different characteristic, and Inception structure is The extraction to different characteristic is carried out with several convolution kernels of several various combination modes, this structure schemes sparse angular CT Structural artifact, which differs larger feature with other noise characteristics and has, as in preferably agrees with.
Inception-resnet basic module combines the above resnet and Inception, as shown in Fig. 2, can be with The advantages of playing the two.It is eliminated in neural network structure in whole sparse angular reconstruction from projections imaging artifact, use is multiple Inception-resnet block combiner can construct deeper network and whole ability to express is promoted very much, and by It is more efficient for the mode of the extraction of different characteristic in the presence of Inception, and the problem that embodiment is studied, it is sparse Angle artifact mixes with noise, that is, the feature senior middle school low level to be predicted has, and agrees with very much with Inception-resnet base The network of this module building.As shown in table 1, it is trained and tests using several different networks, be followed successively by from top to bottom Simple residual error network, sparse angular reconstruction from projections imaging artifact eliminates mind in the convolutional network stacked merely and embodiment Through network, 9 layers of number of plies for referring to basic block that it is used, such as Resblock, Inception block.Using psnr and Ssim does evaluation index.
Sparse angular reconstruction from projections imaging artifact, which is eliminated, to be opened in neural network overall structure by the full convolutional neural networks of FCN The characteristics of hair, benefit are exactly to replace connecting entirely with convolution, and part connects, parameter sharing, so that the parameter of training subtracts significantly It is few, reduce the required hardware requirement of experiment and a possibility that certain levels reduce over-fitting.Full convolutional network is because take Disappeared full connection, thus its for input size also without rigid requirement, more suitable for field of image processing.
Sparse angular reconstruction from projections imaging artifact eliminates the convolution mode of neural network using boundary extential form convolution, As shown in Figure 8.So that each layer of input is identical as Output Size.Utilize sparse angular data reconstruction image and complete angle number Training data is done according to reconstruction image, enables sparse angular reconstruction from projections imaging artifact to eliminate neural network accurately pre- Measure the artifact and other noises in sparse angular image.
Deep learning goes the whole concept of artifact that can be divided into two kinds, one is directly from the image with artifact and noise it is straight It connects and is mapped to original image, another kind is to be mapped to noise therein and artifact from the image with noise and artifact, then again The noise predicted is subtracted using the figure with noise and artifact and artifact obtains the raw information of image.And it is ground according to correlation Study carefully, goes the mode of artifact for second, network topology structure is than the first simpler namely artifact noise than normal tissue knot Structure is easier to be learned to, so this method uses the latter;
Sparse angular reconstruction from projections imaging artifact elimination neural network takes mse as last loss letter in embodiment Number, expression formula are as follows:
Wherein, n is the size of every a batch investment data volume Batch-size, and w, h are the length and width of each sample, D respectively It is the effect picture subtracted after sparse angular reconstruction from projections imaging artifact elimination neural network prediction artifact and noise, X is pair Than figure, i.e., corresponding complete angular image.In training process, sparse angular reconstruction from projections imaging artifact eliminates neural network root According to the numerical value of loss function, successively calculated according to back-propagation algorithm (Back Propagation, BP) and Adam optimization algorithm Renewal amount updates weight and biasing;
Sparse angular reconstruction from projections imaging artifact eliminates each parameter setting of neural network: the number of iterations is 150 times, and batch is big Small is 48, initial learning rate be 0.001, every 30 iterative attenuations be itself 60 percent, loss function use mse, optimization Device creates sparse angular reconstruction from projections imaging artifact elimination neural network for Adam with this and is trained and tests.Final 90 angle The test psnr of data for projection reconstruction image reaches 36.5915, ssim and reaches 0.8818, as shown in table 1.
1 embodiment of table and the training of different networks and test result
Explanation is made that the specific implementation of this method above, certain this method can also there are other a variety of specific embodiment parties Formula, those skilled in the art can make various changes and deformation, but this on the premise of without prejudice to spirit of the invention A little change should be contained in the required protection scope limited of the application patent with deformation.

Claims (9)

1. a kind of artifact minimizing technology for the sparse angular data reconstruction image realized based on deep learning, it is characterised in that: base The sparse angular backprojection reconstruction for combining full convolutional network and Inception-resnet network module is constructed in deep learning Image artifacts eliminate neural network, go artifact and noise to be predicted for sparse angular CT image and remove it, specifically Include the following steps,
Several pairs of S1, acquisition data for projection, each pair of data for projection includes sparse angular data for projection and complete Angles Projections data;
S2, it is rebuild respectively using the sparse angular data for projection and complete data for projection of step S1 acquisition, after reconstruction Data set patchi (i=1,2,3,4,5 ...) is saved, and each pair of data set includes sparse angular backprojection reconstruction data set and complete Standby backprojection reconstruction data set;
S3, building sparse angular reconstruction from projections imaging artifact eliminate neural network;
S4, using the image rebuild in step S2 as training dataset, complete backprojection reconstruction data set does contrasting data, to step The sparse angular reconstruction from projections imaging artifact constructed in rapid S3 is eliminated neural network and is trained, and the preferable mould of training effect is saved Type is denoted as model model;
The trained sparse angular reconstruction from projections imaging artifact that S5, obtaining step S4 are saved eliminates neural network model Model, and wherein by test image test_img investment, it finally predicts and saves test image test_img and corresponding puppet Shadow figure noise_img;
S6, obtained artifact figure noise_img in step S5 is subtracted using the test image test_img saved in step S5, Clear image clean_img can be obtained.
2. the artifact minimizing technology for the sparse angular data reconstruction image realized as described in claim 1 based on deep learning, It is characterized by: the acquisition angles interval of the sparse angular data for projection of acquisition is not less than 4 ° and no more than 8 ° in step S1, Complete Angles Projections data acquisition angles interval is not more than 0.5 °, i.e. the group number of data acquisition is to be in be greater than 45 less than 90 groups In the range of group.
3. the artifact minimizing technology for the sparse angular data reconstruction image realized as described in claim 1 based on deep learning, It is characterized by: using FDK algorithm for reconstructing to the step S1 sparse angular data for projection acquired and complete projection number in step S2 According to being rebuild respectively, specifically,
S21, institute's acquired projections data in two-dimensional projection's matrix, that is, step S1 are calculated with weighted factor and is multiplied, being modified makes it Meet Central slice theorem, obtains revised data for projection;
S22, the revised data for projection of step S21 is done and is filtered line by line using slope filtering method;
S23, image is gone out as backprojection reconstruction to the filtered data of step S22.
4. the artifact minimizing technology for the sparse angular data reconstruction image realized as described in claim 1 based on deep learning, It is characterized by: constructing sparse angular reconstruction from projections imaging artifact in step S3 eliminates neural network specific structure are as follows:
Convolution -> BN layers -> relu- > convolution -> BN layers -> relu- > Resblock- > Res_inception_block1- > Res_ Inception_block2- > Res_inception_block3- > BN layers -> relu- > convolution;
Wherein, it normalizes for i.e. batch for BN layers, disappears when neural metwork training to sparse angular reconstruction from projections imaging artifact Except the output data of neural network middle layer carries out Z-score normalized, that is, subtract mean value except variance;Relu is sparse angular Reconstruction from projections imaging's artifact eliminates the activation primitive that neural network uses, and expression formula is relu (x)=max (0, x);concat Representing matrix splices layer, i.e., the input of multiple branches is stitched together in a certain specified dimension and is input to as a whole Next layer;What Resblock was indicated is the basic module of a residual error network;Res_inception_block1,Res_ Inception_block2, Res_inception_block3 respectively indicate the basic module of an Inception_resnet, The different internal structure of digital different expressions.
5. the artifact minimizing technology for the sparse angular data reconstruction image realized as claimed in claim 4 based on deep learning, It is characterized by: in step S3,
The normal connection path of the Resblock: input -> convolution -> BN layers -> relu- > convolution -> sum layers, then it has more One parallel link, is directly connected to sum layers from input, is added with the output of normal connection path, as next layer of input;
First connection path of the Res_inception_block1: input -> convolutional layer -> concat layers of i.e. channel splicing Layer;Article 2 connection path: input -> convolutional layer -> BN layers -> relu- > convolution -> BN layers -> relu- > convolution -> concat layers; Third path: input -> convolutional layer -> BN layers -> relu- > convolution -> BN layers -> relu- > convolution -> concat layers;Then will Output of above-mentioned three paths after concat layers of splicing is added with the input in parallel link path by sum layers, is tied Fruit is as next layer of input;
First connection path of the Res_inception_block2: input -> convolution -> concat layers;Article 2 connection Path: input -> convolution -> BN layers -> relu- > convolution -> BN layers -> relu- > convolution -> concat layers;Then by above-mentioned two Output of the path after concat layers of splicing is added with the input in parallel link path at sum layers, and result is as next The input of layer;
First connection path of the Res_inception_block3: input -> convolution -> concat layers;Article 2 connection Path: input -> convolution -> BN layers -> relu- > convolution -> BN layers -> relu- > convolution;Then above-mentioned two paths are passed through Output after concat layers of splicing is added under sum layers with the input in parallel link path, and result is defeated as next layer Enter.
6. the artifact of the sparse angular data reconstruction image as described in any one in claim 1-5 realized based on deep learning is gone Except method, it is characterised in that: step S4 specifically,
S41, to the data set patchi (i=1,2,3,4,5 ...) after being rebuild in step S2, carry out blocking processing, then put into Sparse angular reconstruction from projections imaging artifact eliminates neural network;
S42, data set patchi (i=1,2,3,4,5 ...) investment sparse angular reconstruction from projections imaging artifact is being eliminated into nerve Data are normalized before network, i.e., training sample obtained in step S2 are normalized, i.e.,Wherein mean is the mean value of patchi, and std is its standard deviation;It will Patchi* investment sparse angular reconstruction from projections imaging artifact is eliminated neural network and is trained;And put into institute in step S3 The sparse angular reconstruction from projections imaging artifact of building is eliminated neural network and is trained, and training includes propagated forward and reversely passes It broadcasts;The final model model for saving training and obtaining, supplying step S5 test use.
7. the artifact minimizing technology for the sparse angular data reconstruction image realized as claimed in claim 6 based on deep learning, It is characterized by: it is specifically to take in neural network training process that sparse angular reconstruction from projections imaging artifact, which is eliminated, in step S42 Mean square error mse is corrected network parameter as last loss function is trained, and expression formula is as follows:
Wherein, n is the size of every a batch investment data volume Batch-size, and w, h are the length and width of each sample respectively, and D is to subtract Sparse angular reconstruction from projections imaging artifact is gone to eliminate effect picture clean_img, X after neural network prediction artifact and noise It is correlation data, i.e. the sparse angular backprojection reconstruction data set rebuild in step S2 and complete Angles Projections data set for reconstruction Error image;In training process, sparse angular reconstruction from projections imaging artifact eliminates neural network according to the numerical value of loss function, borrows Back-propagation algorithm and Adam optimization algorithm is helped to calculate renewal amount successively to update the parameter of network gradually with Optimized model model。
8. the artifact of the sparse angular data reconstruction image as described in any one in claim 1-5 realized based on deep learning is gone Except method, it is characterised in that: step S5 specifically,
S51, the model model that training obtains in step S4 is saved;
S52, test image test_img is put into progress artifact figure noise_img prediction among model model, and saves prediction Artifact figure noise_img.
9. the artifact of the sparse angular data reconstruction image as described in any one in claim 1-5 realized based on deep learning is gone Except method, it is characterised in that: step S6 specifically,
The artifact figure noise_img and test image test_img predicted in S61, obtaining step S5.
S62, artifact figure noise_img is subtracted with test image test_img, required clear image clean_ can be obtained img。
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