CN103405241B - Detector afterglow correction method for ray imaging - Google Patents
Detector afterglow correction method for ray imaging Download PDFInfo
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- CN103405241B CN103405241B CN201310307166.3A CN201310307166A CN103405241B CN 103405241 B CN103405241 B CN 103405241B CN 201310307166 A CN201310307166 A CN 201310307166A CN 103405241 B CN103405241 B CN 103405241B
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Abstract
The invention provides a detector afterglow correction method for ray imaging. At first, ray source voltage and currents, a detector operating mode and a collecting speed which are needed for scanning are selected according to a detection object, an afterglow attenuation model of a detector under current scanning parameters of a ray imaging system is obtained, then formal scanning is carried out, a group of projected images of the diction object are obtained, and finally fast afterglow correction computation is conducted according to the obtained afterglow attenuation model. According to the method, time constants of various attenuation components of detector materials do not need to be known, the afterglow attenuation model of the detector under the current scanning parameters of the ray imaging system can be obtained just before the formal scanning through simple afterglow modeling scanning, the method is quite convenient to implement in an actual ray imaging system, and the model can be reused to some extent. In addition, the calculated amount of afterglow correction based on a gray scale-afterglow corresponding list is greatly reduced, and obvious influences on efficiency of normal detection cannot be caused.
Description
Technical field
The invention belongs to radial imaging and detection technique field, relate to a kind of twilight sunset modeling and bearing calibration of detector radial imaging.
Background technology
In recent years, ray digital imaging (Digital Radiography, and computer tomography (ComputedTomography DR), CT) accelerated development is obtained in the field such as medical diagnosis and industrial nondestructive testing, become the detection means that some key components and parts is indispensable, wherein DR imaging is the basis of CT imaging.
Image-forming block in DR and CT imaging system is detector, is generally divided into linear array detector and planar array detector two kinds, and wherein planar array detector generally comprises flat panel detector and image intensifier two class.No matter be which kind of detector, as long as its ultimate principle converts ray to visible ray, then visible ray be converted to the signal of telecommunication, then all can there is twilight sunset phenomenon in varying degrees.The visualize of twilight sunset is exactly when then roentgenization detector certain hour stops irradiating, and the output valve of detector can't make zero at once, but presents a kind of process reduced gradually.The existence of twilight sunset can reduce the image quality of DR and CT, and main manifestations is for causing image artifacts and losing imaging precision.
Dissimilar detector often has different manufacturing process and imaging pattern, and the performance of its twilight sunset also exists significant difference usually.Medically, to based on the radiotherapy of flat panel detector and CT at a high speed the measuring method of (in real time) imaging system medium afterglow and characteristic show study more, the speed of flat panel detector output image is faster generally, and the impact of twilight sunset on image quality is larger.In the description and correction of twilight sunset, the method that multi index option modeling and recurrence correct effectively can reduce the artifact that twilight sunset causes, but amount of calculation is larger, detection efficiency can be affected in practice, in addition because the method needs the time constant obtaining the various attenuance component of material for detector in advance, this needs the experiment of a large amount of priori to measure, and domestic consumer is difficult to obtain material for detector constituent accurately and proportioning thereof, causes and is difficult to carry out in general imaging.In addition, output mode and the data recording fashion of adjustment detector also can reach certain twilight sunset inhibition, but consume when can increase extra machine, and the versatility of specific implementation method is also poor.
Summary of the invention
In order to overcome the deficiencies in the prior art, the invention provides a kind of detector afterglow correction method of radial imaging, to realize correction when detector in medical science and industrial DR, CT imaging system exists twilight sunset phenomenon, improving image quality.
The technical solution adopted for the present invention to solve the technical problems comprises the following steps:
(1) according to detected object, the radiographic source voltage needed for selected scanning and electric current, detector mode of operation and picking rate;
(2) obtain the decay of afterglow model of detector under radiation imaging system Current Scan parameter, comprise the following steps:
A () carries out twilight sunset modeling scan: the total time of detector continuous acquisition image is (T
1+ T
2) second, wherein radiographic source opens duration T
1second, close duration T
2second, T
2the image G after one group of radiographic source closedown is obtained in second; If radiographic source is pulsed, T
1for pulse irradiation duration, if radiographic source is continous way, T
1for the duration that detector can be made to stablize output, T
2last width image intensity value in G must be made to reach background values;
B () establishes G
1for the 1st width image in G, search G
1gray scale maximum pixel, with the twilight sunset value that the gray average of its neighborhood territory pixel is this moment, and the same position pixel grey scale average calculating remaining image in G is the twilight sunset value in its correspondence moment, forms decay of afterglow and measure array [picture numbers, twilight sunset value];
C () adopts
matching decay of afterglow measures array, and obtain decay of afterglow model h (t), wherein N is the number of exponential function, and the number of exponential function is determined by fitting effect, and which exponential function n represents, a
n, b
nfor fitting parameter, t is the picture numbers that decay of afterglow measures in array;
(3) formally scan, obtain one group of projected image S of detected object;
(4) carry out quick afterglow correction calculating according to gained decay of afterglow model, comprise the following steps:
A () sets the minimum available gray-scale of detector as D
min, the highest available gray-scale is D
max, D
i∈ [D
min, D
max], calculate each D
ito the twilight sunset value H of next width projected image
i, set up and store gray scale-twilight sunset correspondence table: first solving equation h (t)=D
i, obtaining gray scale is D
imoment t (D
i), then according to H
i=h (t (D
i)+1) calculate twilight sunset value;
B () afterglow correction calculates: for the pixel P of the projected image that need correct current in S, if its gray value is D
p, according to the gray value D of its last width projected image respective pixel
p' search in gray scale-twilight sunset correspondence table and obtain corresponding twilight sunset value H
p, then the gray value of P after afterglow correction
for the first width projected image in S, using himself as its last width projected image.
Decay of afterglow model under certain sweep parameter is once foundation, as long as the hardware performance of radiation imaging system and environmental condition do not change, then can by the afterglow correction of this model prolonged application in the detected object of employing same scan parameter, now above-mentioned steps (2) and step (4) (a) can be omitted.
The invention has the beneficial effects as follows: method provided by the invention is without the need to the time constant of the various attenuance component of detector for known material, before formal scanning, the decay of afterglow model of detector under radiation imaging system Current Scan parameter only can be obtained by easy twilight sunset modeling scan, be convenient to very much implement in actual radiation imaging system, and this model have certain can reusing.In addition, the afterglow correction based on gray scale-twilight sunset correspondence table greatly reduces amount of calculation, can not produce obviously impact to the normal efficiency detected.
Accompanying drawing explanation
Fig. 1 is the detector afterglow correction method flow diagram of radial imaging of the present invention.
Detailed description of the invention
Below in conjunction with drawings and Examples, the present invention is further described, the present invention includes but be not limited only to following embodiment.
The inventive method is applied to X-ray cone-beam CT imaging system, radiographic source is the Y.TU450-D02 of YXLON, and flat panel detector is the PaxScan2520 of Varian.
Application the inventive method is carried out the afterglow correction of radial imaging detector and is performed following steps:
(1) to an aluminum matter part, the radiographic source voltage needed for selected scanning is 220KV, and electric current is 0.25mA, and detector mode of operation is full resolution low noise, and picking rate is 3 width/second;
(2) obtain the decay of afterglow model of detector under radiation imaging system Current Scan parameter, comprise the following steps:
A () carries out twilight sunset modeling scan: the total time of detector continuous acquisition image is (T
1+ T
2) second, wherein radiographic source opens duration T
1=10 seconds, close duration T
2=15 seconds, T
2image G after the one group of radiographic source closedown obtained in second; Radiographic source used is continous way, T
1the stable output of detector within=10 seconds, can be made, T
2last width image intensity value in G within=15 seconds, can be made to reach background values;
B () establishes G
1for the 1st width image in G, search G
1gray scale maximum pixel, with the twilight sunset value that the gray average of its 3 × 3 neighborhood territory pixel is this moment, and the same position pixel grey scale average calculating remaining image in G is the twilight sunset value in its correspondence moment, forms decay of afterglow and measure array [picture numbers, twilight sunset value];
C () adopts 3 exponential functions, namely
matching decay of afterglow measures array, obtains decay of afterglow model h (t)=1341e
-2.146t+ 39.73e
-0.1194t+ 19.23e
-0.01511t.
(3) carry out formal cone-beam CT scan, obtain one group of aluminum matter part totally 360 width projected image S;
(4) carry out quick afterglow correction calculating according to gained decay of afterglow model, comprise the following steps:
A the minimum available gray-scale of () detector used is D
min=50, the highest available gray-scale is D
max=2800, D
i∈ [D
min, D
max], calculate each D
ito the twilight sunset value H of next width projected image
i, set up and store gray scale-twilight sunset correspondence table: first solving equation h (t)=D
i, obtain t (D
i), then according to H
i=h (t (D
i)+1) calculate twilight sunset value;
B () afterglow correction calculates: for the pixel P of the projected image that need correct current in S, if its gray value is D
p, according to the gray value D of its last width projected image respective pixel
p' search in gray scale-twilight sunset correspondence table and obtain corresponding twilight sunset value H
p, then the gray value of P after afterglow correction
for the first width projected image in S, using himself as its last width projected image.
According to the inventive method, after all projected images that alignment type scans carry out afterglow correction, adopt FDK algorithm to carry out cone-beam CT reconstruction, obtain the sectioning image of aluminum matter part.Aluminum matter part sectioning image contour sharpness after afterglow correction improves more than 10% before correcting, and shows that the afterglow correction method that the present invention proposes significantly can promote Cone-Beam CT sectioning image quality.
Claims (1)
1. a detector afterglow correction method for radial imaging, is characterized in that comprising the steps:
(1) according to detected object, the radiographic source voltage needed for selected scanning and electric current, detector mode of operation and picking rate;
(2) obtain the decay of afterglow model of detector under radiation imaging system Current Scan parameter, comprise the following steps:
A () carries out twilight sunset modeling scan: the total time of detector continuous acquisition image is (T
1+ T
2) second, wherein radiographic source opens duration T
1second, close duration T
2second, T
2the image G after one group of radiographic source closedown is obtained in second; If radiographic source is pulsed, T
1for pulse irradiation duration, if radiographic source is continous way, T
1for the duration that detector can be made to stablize output, T
2last width image intensity value in G must be made to reach background values;
B () establishes G
1for the 1st width image in G, search G
1gray scale maximum pixel, with the twilight sunset value that the gray average of its neighborhood territory pixel is this moment, and the same position pixel grey scale average calculating remaining image in G is the twilight sunset value in its correspondence moment, forms decay of afterglow and measure array [picture numbers, twilight sunset value];
C () adopts
matching decay of afterglow measures array, and obtain decay of afterglow model h (t), wherein N is the number of exponential function, and the number of exponential function is determined by fitting effect, and which exponential function n represents, a
n, b
nfor fitting parameter, t is the picture numbers that decay of afterglow measures in array;
(3) formally scan, obtain one group of projected image S of detected object;
(4) carry out quick afterglow correction calculating according to gained decay of afterglow model, comprise the following steps:
A () sets the minimum available gray-scale of detector as D
min, the highest available gray-scale is D
max, D
i∈ [D
min, D
max], calculate each D
ito the twilight sunset value H of next width projected image
i, set up and store gray scale-twilight sunset correspondence table: first solving equation h (t)=D
i, obtaining gray scale is D
imoment t (D
i), then according to H
i=h (t (D
i)+1) calculate twilight sunset value;
B () afterglow correction calculates: for the pixel P of the projected image that need correct current in S, if its gray value is D
p, according to the gray value D of its last width projected image respective pixel
p' search in gray scale-twilight sunset correspondence table and obtain corresponding twilight sunset value H
p, then the gray value of P after afterglow correction
for the first width projected image in S, using himself as its last width projected image.
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| CN105078494B (en) * | 2014-04-30 | 2019-03-05 | 苏州瑞派宁科技有限公司 | The production method of object mould to be imaged and the imaging method of individuation |
| CN104939859A (en) * | 2015-06-23 | 2015-09-30 | 李彬 | Method for correcting CT image |
| CN108254395B (en) * | 2017-12-28 | 2023-10-13 | 清华大学 | Scanned image correction device, method and mobile scanning equipment |
| CN109239764B (en) * | 2018-07-18 | 2022-08-23 | 重庆邮电大学 | High-yield modular production and assembly method for large flat CT detector |
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| CN1224520A (en) * | 1996-06-27 | 1999-07-28 | 模拟技术有限公司 | Mutli-processor afterglow artifact correction filter for use with computed tomography scanners |
| US6404853B1 (en) * | 2001-11-02 | 2002-06-11 | Ge Medical Systems Global Technology Company, Llc | Method for identifying and correcting pixels with excess pixel lag in a solid state x-ray detector |
| JP2003130957A (en) * | 2001-10-23 | 2003-05-08 | Shimadzu Corp | Lag correction method for x-ray flat panel detector, apparatus therefor and x-ray inspection device |
| CN1550792A (en) * | 2003-05-09 | 2004-12-01 | Method for correcting error of radioactive ray detector caused by delayed signal reproduction | |
| JP2005091815A (en) * | 2003-09-18 | 2005-04-07 | Konica Minolta Medical & Graphic Inc | Radiation image reader |
| JP2005319152A (en) * | 2004-05-11 | 2005-11-17 | Hitachi Medical Corp | X-ray ct apparatus |
| CN1913829A (en) * | 2004-04-23 | 2007-02-14 | 株式会社日立医药 | X-ray CT scanner |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2003061945A (en) * | 2001-08-30 | 2003-03-04 | Hitachi Medical Corp | X-ray ct apparatus |
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Patent Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1224520A (en) * | 1996-06-27 | 1999-07-28 | 模拟技术有限公司 | Mutli-processor afterglow artifact correction filter for use with computed tomography scanners |
| JP2003130957A (en) * | 2001-10-23 | 2003-05-08 | Shimadzu Corp | Lag correction method for x-ray flat panel detector, apparatus therefor and x-ray inspection device |
| US6404853B1 (en) * | 2001-11-02 | 2002-06-11 | Ge Medical Systems Global Technology Company, Llc | Method for identifying and correcting pixels with excess pixel lag in a solid state x-ray detector |
| CN1550792A (en) * | 2003-05-09 | 2004-12-01 | Method for correcting error of radioactive ray detector caused by delayed signal reproduction | |
| JP2005091815A (en) * | 2003-09-18 | 2005-04-07 | Konica Minolta Medical & Graphic Inc | Radiation image reader |
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| JP2005319152A (en) * | 2004-05-11 | 2005-11-17 | Hitachi Medical Corp | X-ray ct apparatus |
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