CN104463828A - CT image evaluation device and CT image evaluation method - Google Patents
CT image evaluation device and CT image evaluation method Download PDFInfo
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- CN104463828A CN104463828A CN201310429626.XA CN201310429626A CN104463828A CN 104463828 A CN104463828 A CN 104463828A CN 201310429626 A CN201310429626 A CN 201310429626A CN 104463828 A CN104463828 A CN 104463828A
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Abstract
The invention provides a CT image evaluation device and a CT image evaluation method. The quality of a CT image can be evaluated objectively by using a known reference object device arranged in a scanning region, and reconstruction parameters for CT image reconstruction are set objectively. The CT image evaluation device comprises a CT image input unit used for inputting a CT image at least including a reference object region, an evaluation index calculation unit used for calculating evaluation indexes for CT image evaluation according to reconstruction data of the reference object region in the CT image and known CT data of the reference object device, and a CT image evaluation unit used for evaluating the CT image according to the evaluation indexes. In addition, the CT image evaluation device may also comprise a reconstruction parameter determining unit used for doing statistical analysis on the optimal values of the evaluation indexes, and determining the optimal reconstruction parameters for CT image reconstruction based on the corresponding relationship between the evaluation indexes and the reconstruction parameters.
Description
Technical field
The present invention relates to CT image evaluation apparatus and CT image evaluation method, particularly relate to and utilize reference substance device to provide CT image evaluation apparatus and the CT image evaluation method of the objective evaluation index of CT picture quality.
Background technology
X ray computer fault imaging (CT) technology has been widely used in checking human body, CT image as to medical diagnosis on disease according to the history of existing 30 years, CT image reconstruction technique studied to reduce radiation dose, improves CT picture quality, reduce image artifacts be research always with clinical in hot issue.
Therefore, in the prior aries such as non-patent literature 1, propose a variety of CT image rebuilding method, and these methods have much been applied in actual CT product.Because various CT product employs different CT image rebuilding methods, the picture quality of generation is also variant.The fine or not grade (quality grade) of existing CT picture quality is all provide conclusion according to the judgement of experienced radiologist.Because different doctor's experiences is different, require difference to the individual of picture quality, therefore the method for this assess image quality has subjectivity.Such as the grade of a certain CT image under the evaluation of doctor A can be used in diagnosis incipience cancer, but may think under the evaluation of doctor B picture quality too low be not enough to for diagnosis.
Non-patent literature 1:Medical Image Reconstruction, Gengsheng Zeng, ISBN-10:364205367X, Springer, 1st Edition (April26,2010)
But, along with remote diagnosis and PACS(image archiving and communication system) development, the breadth and depth of the clinical practice of CT image all day by day reaches unprecedented height, under this new situation background, has all had new, higher requirement to the evaluation criterion of CT picture quality.Subjective determination methods is difficult to satisfied new demand.
For demand new above, the evaluation method of some " objective " is suggested and studies.Basic thinking finds the good region of consistance in CT image to carry out statistical study.But be applied to the CT image in medical treatment, choosing Uniform Domains in the human body tangent plane of scanning is a problem.First be that the comparison of coherence in region is difficult to ensure card, the border of its sub-region is also difficult to determine, cannot be obtained the evaluation index of edge fog degree in CT by these regions.Finally, choosing of these regions also still has subjectivity.
Therefore, when prior art is evaluated CT picture quality, cannot subjective factors be avoided, be difficult to evaluate CT picture quality objectively.
In addition, CT manufacturer, when arranging the reconstruction parameter of CT image reconstruction, is equally also according to the evaluation of doctor to CT picture quality, weighs the noise intensity in control CT image and edge fog degree.As mentioned above, when prior art is evaluated CT picture quality, be difficult to evaluate CT picture quality objectively.Therefore, CT manufacturer, when arranging the reconstruction parameter of CT image reconstruction, also cannot avoid subjective factors, is difficult to the reconstruction parameter arranging CT image reconstruction objectively.
Summary of the invention
Based on above background, the object of the invention is to, a kind of CT image evaluation apparatus and CT image evaluation method are provided, utilize the known reference substance device be arranged in scanning area, can evaluate CT picture quality objectively, and the reconstruction parameter being used for CT image reconstruction is set objectively.
In order to achieve the above object, the invention provides a kind of CT image evaluation apparatus, by X ray, scanning area is scanned and the CT image generated for evaluating, it is characterized in that, possess: CT image input units, the CT image at least comprising reference substance region that input generates according to the data separate CT image reconstruction of described scanning gained, described reference substance region is the regulation region being provided with reference substance device in described scanning area; Evaluation index computing unit, according to the data reconstruction in the described reference substance region in described CT image and the known CT data of described reference substance device, calculates the evaluation index for evaluating described CT image; And CT picture appraisal unit, according to described evaluation index, described CT image is evaluated.
According to CT image evaluation apparatus of the present invention, the data reconstruction in reference substance region in the known CT data of reference substance device arranged according to the regulation region in scanning area and the CT image that will evaluate, Calculation Estimation index is also evaluated CT image.Thereby, it is possible to according to objective appraisal index, objectively CT picture quality is evaluated.
In CT image evaluation apparatus of the present invention, also can be, described evaluation index computing unit calculating noise intensity is used as described evaluation index, described noise intensity is: the absolute noise intensity of the data reconstruction in described reference substance region, calculates according to the difference between the data reconstruction in the described reference substance region in described CT image and the known CT data of described reference substance device; Or the relative noise intensity of the data reconstruction in described reference substance region, when the known CT data of described reference substance device are consistent in whole reference substance region, calculate according to the difference between the data reconstruction in the described reference substance region in described CT image and the mean value of the data reconstruction in described reference substance region.
At this, utilize noise intensity as the evaluation index of CT picture quality.And the known CT data by reference to thing device carry out calculating noise intensity with the data reconstruction in reference substance region in the CT image that will evaluate, and can provide objective appraisal index, evaluate objectively to CT picture quality.
In CT image evaluation apparatus of the present invention, also can be, described CT picture appraisal unit, based on the predetermined corresponding relation between described noise intensity and image quality level, determines the image quality level of described CT image according to described noise intensity, thus evaluates described CT image.
At this, between noise intensity and image quality level, be provided with predetermined corresponding relation.The corresponding relation predetermined according to this, when certain as the noise intensity of objective appraisal index, the image quality level of CT image is certain.That is, in the past such subjective factor can be avoided completely, provide objective and unified evaluation criterion for CT image.
In CT image evaluation apparatus of the present invention, also can be, multiple CT images that described CT image input units input utilizes CT image reconstruction respectively based on many group reconstruction parameters and generates; The data reconstruction of described evaluation index computing unit according to described multiple CT image described reference substance region separately and the known CT data of described reference substance device, calculate described multiple CT image described evaluation index separately; Described CT image evaluation apparatus also possesses: reconstruction parameter determining means, for the optimal value of evaluation index described in described multiple CT image statistics, and based on the corresponding relation between described evaluation index and described reconstruction parameter, determine the optimum reconstruction parameter being used for CT image reconstruction.
At this, many group reconstruction parameters are utilized to generate multiple CT image, and for the optimal value of the above-mentioned objective appraisal index of the plurality of CT image statistics.And then, set up the corresponding relation between evaluation index and reconstruction parameter, determine the reconstruction parameter of the optimum being used for CT image reconstruction.Thereby, it is possible to arrange the reconstruction parameter being used for CT image reconstruction objectively.And, can realize depending on the inter-process of artificial reconstruction parameter selection course by equipment in the past, therefore such as by various means such as interpolation, greatly can also improve the accuracy of reconstruction parameter, and save the workload paid when in the past a large amount of CT image being selected by doctor to improve the accuracy of reconstruction parameter.
In CT image evaluation apparatus of the present invention, also can be, described reconstruction parameter determining means is for described multiple CT image, the number of times being selected as optimum CT image using each CT image is weighted on average as the described evaluation index of weight to CT image, thus adds up the optimal value of described evaluation index.
At this, provide a mode of the optimal value of the statistical appraisal index when determining reconstruction parameter.Thus, when being selected as optimum CT image more than 1 CT image, can comprehensively these CT images evaluation index and count the optimal value of evaluation index, and determine optimum reconstruction parameter.Greatly can improve objectivity and the accuracy of reconstruction parameter, and save the workload paid when in the past a large amount of CT image being selected by doctor to improve the accuracy of reconstruction parameter.
In CT image evaluation apparatus of the present invention, also can be that described evaluation index computing unit edge calculation blur level and/or noise intensity are used as described evaluation index.
In CT image, there is the relation of balance mutually in edge fog degree and noise intensity.Some as evaluation index by with in edge fog degree and noise intensity, and determine optimum reconstruction parameter according to the optimal value of this evaluation index, the edge fog degree in the CT image generated based on this reconstruction parameter and noise intensity can be weighed, obtain the CT image that final resultant effect is good.
In CT image evaluation apparatus of the present invention, also can be, described edge fog degree is edge gradient, sum and the border width corresponding with each marginal point of the marginal point included by the data reconstruction in the described reference substance region in described CT image calculate, described noise intensity is: the absolute noise intensity of the data reconstruction in described reference substance region, calculates according to the difference between the data reconstruction in the described reference substance region in described CT image and the known CT data of described reference substance device; Or the relative noise intensity of the data reconstruction in described reference substance region, when the known CT data of described reference substance device are consistent in whole reference substance region, calculate according to the difference between the data reconstruction in the described reference substance region in described CT image and the mean value of the data reconstruction in described reference substance region.
At this, provide the concrete calculating means of evaluation index.That is, by edge calculation gradient as edge fog degree, or calculate relative noise intensity or absolute noise intensity as noise intensity, can be objective and calculate evaluation index exactly.
In CT image evaluation apparatus of the present invention, also can be, a certain in multiple circles of the rectangle of the annular that the reference substance device arranged in described reference substance region is integrated, one, multiple rectangles of split, split, the sweep object configuration that will scan in described scanning area equably.
At this, specifically list several preferred configuration of the reference substance device in reference substance region.Thereby, it is possible to grasp the allocation position of reference substance device in scanning area more easily, thus grasp the CT data of reference substance device better.
In addition, by performing CT image evaluation method with each step corresponding to each unit of the CT image evaluation apparatus of above-mentioned each technical scheme, also the present invention can be realized.In addition, by reflecting the computer program of each step of CT image evaluation method or describing the recording medium of this computer program, also the present invention can be realized.
As mentioned above, the present invention is by based on reference substance device calculating noise intensity or the edge fog degree evaluation index as CT image, and based on the quality grade of the noise intensity evaluate CT image as evaluation index, or the reconstruction parameter being used for CT image reconstruction is set based on as the noise intensity of evaluation index and/or edge fog degree, can evaluate CT picture quality objectively, and the reconstruction parameter being used for CT image reconstruction is set objectively.
Accompanying drawing explanation
Fig. 1 is the key diagram of the technical matters existed in CT image quality evaluation.
Fig. 2 is the key diagram of the balance in CT image reconstruction between noise intensity and edge fog degree.
Fig. 3 is the structural drawing of the CT image re-construction system possessing CT image evaluation apparatus of the present invention.
Fig. 4 A is the schematic diagram of an example of the allocation position of reference substance device.
Fig. 4 B is the schematic diagram of several configuration of reference substance device.
Fig. 5 is the structural drawing of the CT image evaluation apparatus involved by the first embodiment of the present invention.
Fig. 6 is the process flow diagram of the CT image evaluation method involved by the first embodiment of the present invention.
Fig. 7 is the key diagram based on reference substance device calculating noise intensity.
Fig. 8 is the key diagram based on noise intensity assess image quality grade.
Fig. 9 is the structural drawing of the CT image evaluation apparatus involved by the second embodiment of the present invention.
Figure 10 is the process flow diagram of the CT image evaluation method involved by the second embodiment of the present invention.
Figure 11 A is the key diagram based on reference substance device edge calculation blur level.
Figure 11 B is at the schematic diagram based on the border width utilized during reference substance device edge calculation blur level.
Figure 12 is the key diagram determining reconstruction parameter based on noise intensity or edge fog degree.
Embodiment
Below in conjunction with the drawings and the specific embodiments, the present invention will be described in more detail.In addition, be accompanied by same Reference numeral to same or considerable part in the accompanying drawings, the repetitive description thereof will be omitted.
First, the technical matters existed during evaluate CT picture quality in prior art is described in detail.Fig. 1 is the key diagram of the technical matters existed in CT image quality evaluation.As shown in Figure 1, can produce the CT image of different quality under x-ray doses different in figure, even the identical CT image under identical x-ray dose, different doctors often makes different quality grade of evaluations.Doctors can cause some problems in modern CT diagnostic imaging to the different definition of image quality evaluation result.Under cooperation medical treatment and tele-medicine development trend, there is the situation that different doctors diagnoses patient according to same width CT image, different doctors is different thus diagnostic result may be caused different because of the reason of picture quality own to the definition of the quality of identical image, in this case, the quality definition standard of an objective measurement is needed.
Then, before explanation CT image evaluation apparatus of the present invention and CT image quality evaluating method, the trade-off relationship between noise intensity and edge fog degree in CT image reconstruction is described.Fig. 2 is the key diagram of the balance in CT image reconstruction between noise intensity and edge fog degree.As shown in Figure 2, in CT image reconstruction, determining under reconstruction algorithm and given dose, there is trade-off relationship in the image noise intensity that X ray is rebuild and edge fog degree.Such as, determining under reconstruction algorithm and given dose, along with reconstruction parameter is different, in CT image A, CT image B, CT image C after reconstruction, edge fog degree reduces successively and noise intensity increases successively.Therefore, can consider to utilize noise intensity or edge fog degree as the evaluation index of CT picture quality, reflect the CT picture quality after reconstruction.
The following detailed description of the CT image re-construction system possessing CT image evaluation apparatus of the present invention.Fig. 3 is the structural drawing of the CT image re-construction system possessing CT image evaluation apparatus of the present invention.As shown in Figure 3, CT image re-construction system mainly comprises CT scan device 301, CT image processing apparatus 302 and CT image output device 303.
CT scan device 301 mainly comprises basic X-ray scanning device 304 and reference substance device 305.X-ray scanning device 304 is scanned the sweep object in scanning area by X ray, and at this, sweep object is such as human body etc.Reference substance device 305 will specifically describe in Fig. 4 A, Fig. 4 B.
CT image processing apparatus 302 is such as realized by general processor or special integrated circuit, mainly comprises the CT video generation device 306 for image reconstruction and the CT image evaluation apparatus 307 for image quality evaluation.The scan-data that CT video generation device 306 exports according to CT scan device 301, utilizes CT image reconstruction to generate CT image.CT image evaluation apparatus 307 is waited until aftermentioned as principal character of the present invention.
CT image output device 303 is typically CT image display device, and screen shows the CT image exported by CT image processing apparatus 302.Certainly, CT image output device is not limited to CT image display device, also can be to be sent the data transmission interface of the CT image exported by CT image processing apparatus 302 by network, printed the printer etc. of the CT image exported by CT image processing apparatus 302.
Illustrate reference substance device 305.The present invention has increased reference substance device 305 newly in CT scan device 301.Fig. 4 A is the schematic diagram of an example of the allocation position of reference substance device.As shown in Figure 4 A, in the existing X-ray scanning device 304 of CT scan device 301, swing-around trajectory 401 is swing-around trajectories of x-ray source 402 and detecting device 403.As the example with reference to thing device 305, reference substance 404 is arranged on around the body scans region 405 as sweep object.Here reference substance can be made up of any solid-state high-purity material, such as be made up of the organic material such as nonmetallic materials, synthesized polymer material or the metal materials such as iron, copper etc. such as silicon, and the purity of material and consistance are more high better, contributing to CT data corresponding to reference substance is like this constant, the CT data that the reference substance that each material produces is corresponding can obtain by experiment test in advance, are known.Fig. 4 B is the schematic diagram of several configuration of reference substance device.As shown in Figure 4 B, what be distributed in multiple circles of annular that body scans region (elliptic region of figure immediate vicinity) reference substance 404 around can be one, the rectangle of one, multiple rectangles of split, split is a certain, equably round the body scans area configurations as sweep object.At this, the shape of reference substance 404 is not limit, and distributing position is not limit, but needs to know the position of reference substance 404 in scanning area, thus obtains the pixel region (also referred to as reference substance region) corresponding to reference substance in CT image.At this, preferred reference substance is evenly distributed in around the body scans region as sweep object, will using annular as schematic view illustrating in the present invention.
(the first embodiment)
Below, the CT image evaluation apparatus involved by the first embodiment of the present invention and CT image evaluation method is illustrated.CT image evaluation apparatus involved by first embodiment of the present invention and CT image evaluation method are used for evaluating CT picture quality objectively.
Fig. 5 is the structural drawing of the CT image evaluation apparatus involved by the first embodiment of the present invention.As shown in Figure 5, CT image evaluation apparatus 307 involved by first embodiment of the present invention is scanned scanning area by X ray and the CT image generated for evaluating, and possesses CT image input units 501, evaluation index computing unit 502 and CT picture appraisal unit 503.CT image input units 501 inputs the CT image generated by CT video generation device 306.As mentioned above, this CT image is data separate CT image reconstruction according to scanning gained and the CT image at least comprising reference substance region that generates, and reference substance region is the regulation region being provided with reference substance device 305 in scanning area.Evaluation index computing unit 502, according to the CT data of the data reconstruction in the reference substance region in CT image and the known of reference substance device 305, calculates the evaluation index being used for evaluate CT image.CT picture appraisal unit 503, according to the evaluation index calculated, is evaluated CT image, and is exported evaluation result.
Fig. 6 is the process flow diagram of the CT image evaluation method involved by the first embodiment of the present invention.As shown in Figure 6, CT image evaluation method involved by first embodiment of the present invention is scanned scanning area by X ray and the CT image generated for evaluating, and comprises CT image input step 601, evaluation index calculation procedure 602 and CT picture appraisal step 603.The CT image at least comprising reference substance region that CT image input step 601 inputs the data separate CT image reconstruction according to scanning gained and generates.Evaluation index calculation procedure 602, according to the CT data of the data reconstruction in the reference substance region in CT image and the known of reference substance device 305, calculates the evaluation index being used for evaluate CT image.CT picture appraisal step 603, according to evaluation index, is evaluated CT image.
As mentioned above, noise intensity can be adopted as evaluation index.Fig. 7 is the key diagram based on reference substance device calculating noise intensity.As shown in Figure 7, evaluation index computing unit 502, in evaluation index calculation procedure 602, utilizes the actual value I of the known CT data of reference substance device 305
r701 and the image value of data reconstruction in reference substance region
702 carry out calculating noise strength S D
noise.
As noise intensity SD
noiseone example, the absolute noise intensity of the data reconstruction in reference substance region can be adopted, calculated according to the difference between the data reconstruction in the reference substance region in CT image and the CT data of the known of reference substance device 305 in evaluation index calculation procedure 602 by evaluation index computing unit 502.Such as, the absolute noise intensity of the data reconstruction in this reference substance region can by the image value of the data reconstruction in reference substance region
with the actual value I of the known CT data of reference substance device 305
rbetween the mean value of square of difference represent, and obtained by following formula, wherein N is the pixel sum in reference substance region.
Or, as noise intensity SD
noiseone example, when the known CT data of reference substance device 305 are consistent in whole reference substance region, also can adopt the relative noise intensity of the data reconstruction in reference substance region, be calculated according to the difference between the data reconstruction in the reference substance region in CT image and the mean value of the data reconstruction in reference substance region in evaluation index calculation procedure 602 by evaluation index computing unit 502.Such as, the relative noise intensity of the data reconstruction in this reference substance region can by the image value of the data reconstruction in the reference substance region in CT image
with the image value of the data reconstruction in reference substance region
mean value between the mean value of square of difference represent, and obtained by following formula, wherein N is the pixel sum in reference substance region.
In addition, when the evaluation index based on such as noise intensity carrys out assess image quality grade, CT picture appraisal unit 503 is in CT picture appraisal step 603, based on the predetermined corresponding relation between noise intensity and image quality level, determine the image quality level of CT image according to noise intensity, thus CT image is evaluated.Fig. 8 is the key diagram based on noise intensity assess image quality grade.As shown in Figure 8, by noise intensity SD
noisedetermine the quality grade L of image
quality, that is:
L
quality=f (SD
noise) (formula 3)
Such as, the quality grade being defined as the larger then image of noise intensity is lower, otherwise quality grade is higher, and the quality grade of image increases along with noise intensity and reduces.Therefore, optional multiple decreasing function as relation function, as:
The parameter lambda, β etc. of these decreasing functions are such as determined by the manufacturer of CT image re-construction system, according to SD
noisecalculate f (x), be finally divided into several grades according to the scope of f (x).
According to first embodiment of the invention CT image evaluation apparatus, the data reconstruction in reference substance region in the known CT data of reference substance device arranged according to the regulation region in scanning area and the CT image that will evaluate, Calculation Estimation index is also evaluated CT image.Thereby, it is possible to according to objective appraisal index, objectively CT picture quality is evaluated.
In addition, utilize noise intensity as the evaluation index of CT picture quality.And the known CT data by reference to thing device carry out calculating noise intensity with the data reconstruction in reference substance region in the CT image that will evaluate, and can provide objective appraisal index, evaluate objectively to CT picture quality.
In addition, predetermined corresponding relation is provided with between noise intensity and image quality level.The corresponding relation predetermined according to this, when certain as the noise intensity of objective appraisal index, the image quality level of CT image is certain.That is, the subjective factor of in the past such appraiser can be avoided completely, provide objective and unified evaluation for CT image.
(the second embodiment)
Below, the CT image evaluation apparatus involved by the second embodiment of the present invention and CT image evaluation method is illustrated.CT image evaluation apparatus involved by second embodiment of the present invention and CT image evaluation method are used for arranging the reconstruction parameter being used for CT image reconstruction objectively.
Fig. 9 is the structural drawing of the CT image evaluation apparatus involved by the second embodiment of the present invention.As shown in Figure 9, the difference of the CT image evaluation apparatus 307' involved by the second embodiment of the present invention and the CT image evaluation apparatus 307 involved by the first embodiment is, CT image input units 901 is different with the function of evaluation index computing unit 902, and has added reconstruction parameter determining means 903.Specifically, CT image input units 901 input utilize CT image reconstruction respectively based on many group reconstruction parameters and generate multiple CT images, namely from multiple CT images that CT video generation device 306 inputs.The data reconstruction of evaluation index computing unit 902 according to multiple CT image reference substance region separately and the known CT data of reference substance device 305, calculate multiple CT images evaluation index separately.Reconstruction parameter determining means 903 for the optimal value of multiple CT image statistics evaluation index, and based on the corresponding relation between evaluation index and reconstruction parameter, determines the optimum reconstruction parameter being used for CT image reconstruction.
Figure 10 is the process flow diagram of the CT image evaluation method involved by the second embodiment of the present invention.As shown in Figure 10, the difference of the CT image evaluation method involved by the second embodiment of the present invention and the CT image evaluation method involved by the first embodiment is, CT image input step 1001 is different with the action of evaluation index calculation procedure 1002, and has added reconstruction parameter deciding step 1003.In CT image input step 1001, input and utilize CT image reconstruction respectively based on many group reconstruction parameters and multiple CT images of generating.In evaluation index calculation procedure 1002, according to the data reconstruction in multiple CT image reference substance region separately and the known CT data of reference substance device 305, calculate multiple CT images evaluation index separately.In reconstruction parameter deciding step 1003, for the optimal value of multiple CT image statistics evaluation index, and based on the corresponding relation between evaluation index and reconstruction parameter, determine the optimum reconstruction parameter being used for CT image reconstruction.
As reconstruction parameter determining means 903 concrete example for the optimal value of multiple CT image statistics evaluation index in reconstruction parameter deciding step 1003, can for multiple CT image, the number of times being selected as optimum CT image using each CT image is weighted on average as the evaluation index of weight to CT image, thus the optimal value of statistical appraisal index.
As mentioned above, there is trade-off relationship between the edge fog degree of CT image or noise intensity.Therefore, if regulate reconstruction parameter to make noise intensity reduce, then edge fog degree can increase, otherwise regulating parameter makes edge sharper keen (blur level reduction) if think, then noise intensity can increase.Therefore finally need manufacturer that reconstruction parameter (algorithm that specifically which kind of parameter is used by manufacturer is determined) is set in the CT image re-construction system dispatched from the factory, make it possible to balance noise intensity and edge fog degree, obtain the good image of final resultant effect.Therefore, edge fog degree and/or noise intensity can be adopted as evaluation index.
Below illustrate and adopt edge fog degree EG as computing method during evaluation index.Figure 11 A is the key diagram based on reference substance device edge calculation blur level.As shown in Figure 11 A, by evaluation index computing unit 902 in evaluation index calculation procedure 1002, according to the image value of the data reconstruction in the reference substance region in CT image
with the actual value I of the known CT data of reference substance device 305
r, edge calculation blur level EG.Figure 11 B is at the schematic diagram based on the border width utilized during reference substance device edge calculation blur level.As shown in Figure 11 B, such as, when the actual edge of known reference thing device 305 is sharp keen, edge fog degree can be represented by edge gradient, and by the image value of following formula according to the data reconstruction in the reference substance region in CT image
sum and the border width corresponding with each marginal point of included marginal point are obtained:
(formula 5)
Wherein ex represents marginal point, N
exrepresent the sum of marginal point, EW represents border width (pixel distance) as shown in Figure 11 B, namely reference substance edge high level to low value zone of transition between distance.Edge fog degree statistics be rebuild the ill-defined index of reference substance in image, edge is fuzzyyer, and EW will be larger, and EG is less, and if edge is sharper keen, then EG will be larger.
In addition, adopt noise intensity identical with the first embodiment as computing method during evaluation index, do not repeat at this.
Below, the concrete example determining reconstruction parameter in the second embodiment of the present invention based on noise intensity or edge fog degree is described in detail.Figure 12 is the key diagram determining reconstruction parameter based on noise intensity or edge fog degree.
As shown in figure 12, corresponding reconstruction parameter (being generally the parameter of filter function) is weighed with the optimum of edge fog degree and/or noise intensity in order to obtain, first in process 1201, carry out organizing more parameter (parameter 1, parameter 2 ..., parameter K) test, by CT image reconstruction obtain many group CT images (image 1, image 2 ..., image K), and calculate the edge fog degree corresponding with each CT image and/or noise intensity ([EG, SD] 1, [EG, SD] 2 ..., [EG, SD] K).
In process 1202, these images are supplied to multiple doctor and select, each doctor selects them and thinks the image of optimum edge fog degree and noise intensity balance.
In process 1203, the optimal edge blur level average according to the result statistical weight selected and/or noise intensity EG
bestand/or (SD
noise)
best.Such as can calculate respectively according to following formula, wherein EG
ifor the edge fog degree of image i, (SD
noise)
ifor the noise intensity of image i, st
ifor image i is by the number of times selected.
(formula 6)
(formula 7)
In process 124, according in process 1201 many groups parameter (parameter 1, parameter 2 ..., parameter K) and edge fog degree and/or noise intensity ([EG, SD] 1, [EG, SD] 2 ..., [EG, SD] K), the relation function F2 of the relation function F1 of the parameter that carries out curve fitting out respectively and edge fog degree and/or parameter and noise intensity.
Finally, according to optimal edge blur level and/or noise intensity, determine optimum reconstruction parameter by relation function F1 and/or F2.A unique optimum reconstruction parameter is obtained when only adopting edge fog degree or noise intensity.At the same time adopt edge fog degree and noise intensity time obtain two optimum reconstruction parameter P1 and P2, can select wherein any one as optimum reconstruction parameter.
CT image evaluation apparatus involved second embodiment of the invention and CT image evaluation method, by utilizing many group reconstruction parameters to generate multiple CT image, and for the optimal value of the above-mentioned objective appraisal index of the plurality of CT image statistics.And then, set up the corresponding relation between evaluation index and reconstruction parameter, determine the reconstruction parameter of the optimum being used for CT image reconstruction.Thereby, it is possible to arrange the reconstruction parameter being used for CT image reconstruction objectively.And, can realize depending on the inter-process of artificial reconstruction parameter selection course by equipment in the past, therefore such as by various means such as interpolation, greatly can also improve the accuracy of reconstruction parameter, and save the workload paid when in the past a large amount of CT image being selected by doctor to improve the accuracy of reconstruction parameter.
In addition, when being selected as optimum CT image more than 1 CT image, can comprehensively these CT images evaluation index and count the optimal value of evaluation index, and determine optimum reconstruction parameter.Greatly can improve objectivity and the accuracy of reconstruction parameter, and save the workload paid when in the past a large amount of CT image being selected by doctor to improve the accuracy of reconstruction parameter.
And in CT image, there is the relation of balance mutually in edge fog degree and noise intensity.Some as evaluation index by with in edge fog degree and noise intensity, and determine optimum reconstruction parameter according to the optimal value of this evaluation index, the edge fog degree in the CT image generated based on this reconstruction parameter and noise intensity can be weighed, obtain the CT image that final resultant effect is good.
Above with reference to the accompanying drawings of several embodiment of the present invention.Wherein, embodiment described above is only object lesson of the present invention, for understanding the present invention, and is not used in restriction scope of the present invention.Those skilled in the art can carry out the reasonable omission of various distortion, combination and key element to embodiment based on technological thought of the present invention, the mode obtained thus is also included within scope of the present invention.
Such as, in the above-described embodiment, specifically have employed the edge gradient as edge fog degree and the absolute noise intensity as noise intensity and relative noise intensity as evaluation index.But evaluation index of the present invention is not limited thereto, as long as based on the quality of reference substance device evaluate CT image, various change can be carried out according to actual conditions.Such as, when edge calculation blur level, also can carry out Fuzzy Processing by the fringe region of Gaussian smoothing to the reference substance region in CT image, then the change of computed image is tried to achieve.
Such as, in this second embodiment, when having obtained two optimum reconstruction parameters by adopting edge fog degree and noise intensity respectively, selection any one parameter is wherein set to.But be not limited thereto, also can further based on these two optimum reconstruction parameters, by averaging or the suitably computing such as intermediate value, obtain final optimum reconstruction parameter.
Such as, describe the situation possessing CT picture appraisal unit 503 in the first embodiment, describe the situation possessing reconstruction parameter determining means 903 in this second embodiment, but obviously also can combine two embodiments, possess CT picture appraisal unit 503 and reconstruction parameter determining means 903, to realize the function of the first embodiment and the second embodiment simultaneously simultaneously.
Such as, in the first embodiment, adopt noise intensity as evaluation index, utilize decreasing function to carry out computed image quality grade.But the present invention is not limited thereto, as long as image quality level can be determined with evaluation index is objective accordingly, other indexs such as edge fog degree also can be adopted as evaluation index, or utilize other corresponding relation computed image quality grades.
Claims (10)
1. a CT image evaluation apparatus, being scanned scanning area by X ray and the CT image generated for evaluating, it is characterized in that possessing:
CT image input units, input the data separate CT image reconstruction according to described scanning gained and the CT image at least comprising reference substance region generated, described reference substance region is the regulation region being provided with reference substance device in described scanning area;
Evaluation index computing unit, according to the data reconstruction in the described reference substance region in described CT image and the known CT data of described reference substance device, calculates the evaluation index for evaluating described CT image; And
CT picture appraisal unit, according to described evaluation index, evaluates described CT image.
2. CT image evaluation apparatus as claimed in claim 1, is characterized in that,
Described evaluation index computing unit calculating noise intensity is used as described evaluation index,
Described noise intensity is:
The absolute noise intensity of the data reconstruction in described reference substance region, calculates according to the difference between the data reconstruction in the described reference substance region in described CT image and the known CT data of described reference substance device; Or
The relative noise intensity of the data reconstruction in described reference substance region, when the known CT data of described reference substance device are consistent in whole reference substance region, calculate according to the difference between the data reconstruction in the described reference substance region in described CT image and the mean value of the data reconstruction in described reference substance region.
3. CT image evaluation apparatus as claimed in claim 1 or 2, is characterized in that,
Described CT picture appraisal unit, based on the predetermined corresponding relation between described noise intensity and image quality level, determines the image quality level of described CT image according to described noise intensity, thus evaluates described CT image.
4. CT image evaluation apparatus as claimed in claim 1, is characterized in that,
Multiple CT images that described CT image input units input utilizes CT image reconstruction respectively based on many group reconstruction parameters and generates;
The data reconstruction of described evaluation index computing unit according to described multiple CT image described reference substance region separately and the known CT data of described reference substance device, calculate described multiple CT image described evaluation index separately;
Described CT image evaluation apparatus also possesses:
Reconstruction parameter determining means, for the optimal value of evaluation index described in described multiple CT image statistics, and based on the corresponding relation between described evaluation index and described reconstruction parameter, determines the optimum reconstruction parameter being used for CT image reconstruction.
5. CT image evaluation apparatus as claimed in claim 4, is characterized in that,
Described reconstruction parameter determining means is for described multiple CT image, and the number of times being selected as optimum CT image using each CT image is weighted on average as the described evaluation index of weight to CT image, thus adds up the optimal value of described evaluation index.
6. the CT image evaluation apparatus as described in claim 4 or 5, is characterized in that,
Described evaluation index computing unit edge calculation blur level and/or noise intensity are used as described evaluation index.
7. CT image evaluation apparatus as claimed in claim 6, is characterized in that,
Described edge fog degree is edge gradient, and sum and the border width corresponding with each marginal point of the marginal point included by the data reconstruction in the described reference substance region in described CT image calculate,
Described noise intensity is:
The absolute noise intensity of the data reconstruction in described reference substance region, calculates according to the difference between the data reconstruction in the described reference substance region in described CT image and the known CT data of described reference substance device; Or
The relative noise intensity of the data reconstruction in described reference substance region, when the known CT data of described reference substance device are consistent in whole reference substance region, calculate according to the difference between the data reconstruction in the described reference substance region in described CT image and the mean value of the data reconstruction in described reference substance region.
8. the CT image evaluation apparatus as described in claim 1 or 4, is characterized in that,
A certain in multiple circles of the rectangle of the annular that the reference substance device arranged in described reference substance region is integrated, one, multiple rectangles of split, split, the sweep object configuration that will scan in described scanning area equably.
9. a CT image evaluation method, being scanned scanning area by X ray and the CT image generated for evaluating, it is characterized in that, comprise:
CT image input step, input the data separate CT image reconstruction according to described scanning gained and the CT image at least comprising reference substance region generated, described reference substance region is the regulation region being provided with reference substance device in described scanning area;
Evaluation index calculation procedure, according to the data reconstruction in the described reference substance region in described CT image and the known CT data of described reference substance device, calculates the evaluation index for evaluating described CT image; And
CT picture appraisal step, according to described evaluation index, evaluates described CT image.
10. CT image evaluation method as claimed in claim 9, is characterized in that,
In described CT image input step, input and utilize CT image reconstruction respectively based on many group reconstruction parameters and multiple CT images of generating;
In described evaluation index calculation procedure, according to the data reconstruction in described multiple CT image described reference substance region separately and the known CT data of described reference substance device, calculate described multiple CT image described evaluation index separately;
Described CT image evaluation method also comprises:
Reconstruction parameter deciding step, for the optimal value of evaluation index described in described multiple CT image statistics, and based on the corresponding relation between described evaluation index and described reconstruction parameter, determines the optimum reconstruction parameter being used for CT image reconstruction.
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| JP6296942B2 (en) | 2018-03-20 |
| CN104463828B (en) | 2018-04-10 |
| JP2015058355A (en) | 2015-03-30 |
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