CN104349083A

CN104349083A - Flat panel detector image streaking recursion correction method

Info

Publication number: CN104349083A
Application number: CN201310315491.4A
Authority: CN
Inventors: 李劲生; 阮健; 史颖琴
Original assignee: Nanjing Perlove Radial Video Equipment Co Ltd
Current assignee: Nanjing Perlove Radial Video Equipment Co Ltd
Priority date: 2013-07-25
Filing date: 2013-07-25
Publication date: 2015-02-11

Abstract

The invention relates to a flat panel detector image streaking recursion correction method and belongs to the medical apparatus technology field. The method is characterized by comprises steps that (1), an image streaking measurement method, one image is acquired under the specified exposure condition, exposure stops instantly, N images are continuously acquired, the N images comprise sequence images containing streaking information; (2), an image streaking calculation method, on the basis of the originally-acquired images, the image streaking degree is calculated by utilizing the images containing the image streaking information; (3), analysis on influence of frame frequency and dosage saturation on image streaking, the influence of the frame frequency and the dosage saturation on image streaking is analyzed, and a base is provided for bringing out the image streaking correction method; and (4), the image streaking correction method, a mathematics statistics method is utilized, a mathematics model in accordance with image streaking is established, and a calculation formula of the image streaking correction method is derived by utilizing a recursion method. The method is advantaged in that influence of image streaking on imaging quality is reduced.

Description

A kind of recurrence bearing calibration of flat panel detector image hangover

Technical field

The invention belongs to technical field of medical instruments, relate to the image processing correction method of a kind of flat panel detector image hangover.

Background technology

Flat panel detector is a kind of ray digitalized image equipment of high complexity, can be used for the radial imaging of alternative conventional film, also can be used as the image-forming block of cone-beam CT system, due to the restriction of architectural feature and manufacturing process, multiple flaw is there is in flat panel detector initial output image, directly affect its image quality, therefore usually need the image exported flat panel detector to carry out necessary correction.

At present, the bearing calibration of detector output image has a variety of, includes dark field correction, gain calibration, bad point correction, streaking correction etc.; The output valve of flat panel detector when darkfield image refers to and do not have radiation exposure, darkfield image is to be added in projected image at unlatching radiographic source, and can not change along with the Strength Changes of ray; The output characteristic parameter of a large amount of pixel of flat panel detector has dispersiveness, thus produces the inconsistent problem of gain coefficient; Bad pixel is the pixel to transmitted intensity abnormal reaction, due to the pixel enormous amount of flat panel detector, and complex manufacturing technology, thus bad pixel is generally inevitable; The conventional corrective method comparative maturity of above-mentioned three aspects, and be detected device manufacturer and extensively adopt.

Streaking (Image Lag) shows as flat panel detector and accepts X-ray and irradiate after imaging, close X source, imaging can retain a period of time on the detector, this is because inside flat panel detector in electron motion process, some " hole " the insides (traps) of material can be fallen into, struggle and could out to cause, although this time is very short, but be enough to cause very large impact to image quality, because image is equivalent to do convolution (interfering with each other between the frame of front and back) in time domain, not hard to imagine, oblong object or object are not put at pivot, image quality has the greatest impact by streaking, have the ring artifact of a circle circle.

Summary of the invention

The present invention seeks to: the bearing calibration based on streaking is external very ripe, but use also considerably less at home, the present invention discloses the recurrence bearing calibration of a kind of flat panel detector image hangover, significantly reduces the impact of streaking on image quality.

The present invention solves its technical problem and the technical scheme that adopts is: the method comprises the following steps:

First, flat panel detector is placed on the position of the certain distance of distance radiographic source, and what object dead beat between the two lets alone, it is to be exposed that imaging size of magnitude of voltage and the detector determined etc. is set, now, according to general dark field correction method, obtain the average dark field image D under equal conditions; Then, under above-mentioned conditions of exposure, gather 1 image, then stop exposure immediately, continuous acquisition N opens image, and it is exactly the sequence image containing hangover information that this N opens image.

The trailing amount that the N calculated opens sequence image is labeled as , its computing formula is as follows:

（1）

Wherein, with to represent in the image that the n-th width and conditions of exposure gather average signal value in area-of-interest respectively.

Frame frequency and dosage saturation are to the impact analysis of streaking: according to (1) formula, calculate the streaking situation under different frame frequency and various dose saturation condition, and analyze frame frequency and dosage saturation to the influence degree of streaking, proposition streaking bearing calibration is provided the foundation.

According to above-mentioned analysis, utilize mathematical statistical model method, the present invention establishes the Mathematical Modeling of a streaking, and expression formula is as follows:

（2）

Wherein, , , represent coefficient, not exclusively depend on frame frequency, with represent two attenuation constants, this amount depends on the change of frame frequency, and n represents the frame number of collection, represent the frame frequency arranged.

According to above-mentioned formula, we can use a recursive expression to calculate the image of the n-th width after smear correction , expression formula is as follows:

（3）

Wherein, represent the sequence number of the image containing hangover information collected, represent the image containing hangover information collected, can obtain in conjunction with above-mentioned two formulas,

（4）

Accompanying drawing explanation

Accompanying drawing is the flow chart of the inventive method.

Embodiment

With reference to accompanying drawing, for an X-ray flat panel detector digital imagery, flat board is pixium CBCT 2630, applies the correction that this forwarding method carries out flat panel detector image hangover, performs step as follows:

By machine reset to exposure standby condition, and what object dead beat lets alone, and arranges the imaging size of magnitude of voltage and the detector determined, waits to be exposed, now, according to general dark field correction method, obtains the average dark field image D under equal conditions; Then, under frame frequency is 35fps condition, first gather the image of 1 die body in kind, then stop exposure immediately, continuous acquisition 20 images, these 20 images are exactly the sequence image containing die body in kind hangover information.

First the average signal value of area-of-interest 10000 pixel of each streak image of seletion calculation, the trailing amount of 20 sequence images then calculated is labeled as , its computing formula is as follows:

Wherein, with represent the average signal value of 10000 pixels in area-of-interest in the image that the n-th width and conditions of exposure gather respectively.

Have selected the impact analysis of three kinds of frame frequencies and ten dosage intensity value hypograph hangovers, draw after analysis: 1) influence degree of the n-th width streak image mainly relies on the size with frame frequency; 2) degree of trailing fail display than very fast between former width streak image, and between sequence streak image rearward, decline is slow; 3) dependence of hangover degree to dosage saturation of image is smaller.

Known numeric value frame frequency, frame number, trailing amount are substituted into following formula:

Wherein, , , represent coefficient, with represent two attenuation constants.

Correction image smear redundant information is carried out according to updating formula below.

The recurrence bearing calibration of a kind of flat panel detector image hangover of the present invention can effectively reduce streaking, is a kind of reasonable, reliable, easy processing method.

Claims

1. a recurrence bearing calibration for flat panel detector image hangover, is characterized in that comprising the following steps:

1) method of measurement of streaking: gather 1 image under regulation conditions of exposure, then stop exposure immediately, continuous acquisition N opens image, and it is exactly the sequence image containing hangover information that this N opens image;

2) computational methods of streaking: based on acquired original image, make use of the degree that the image comprising streaking information carrys out computed image hangover;

3) frame frequency and dosage saturation are to the impact analysis of streaking: analyze frame frequency and dosage saturation to the influence degree of streaking, provide the foundation to proposition streaking bearing calibration;

4)the bearing calibration of streaking: utilize mathematical statistics method, establishes the Mathematical Modeling that meets streaking, uses recursion method to be deduced the computing formula of streaking bearing calibration simultaneously.