CN113835115B - CT detector state detection method - Google Patents
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- 238000012360 testing method Methods 0.000 claims description 24
- 238000000528 statistical test Methods 0.000 claims description 22
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- 238000009434 installation Methods 0.000 description 7
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- 238000001276 Kolmogorov–Smirnov test Methods 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
- G01T7/00—Details of radiation-measuring instruments
- G01T7/005—Details of radiation-measuring instruments calibration techniques
Abstract
The invention relates to the technical field of medical images, in particular to a state detection method of a CT detector, which comprises the following steps: collecting dark current data of a plurality of groups of CT detectors; correcting dark current data according to the circuit structure of the CT detector; according to the corrected dark current data, carrying out statistical calculation and inspection on each module unit and each detector channel after the CT detector is installed, and distinguishing whether the state of the module unit and the state of each detector channel are normal or not; the advantages are that: compared with the prior art, the state of the detector is judged by adopting various detection indexes of a detector monitoring system, the method utilizes the characteristics of dark current data by combining a statistical method and a circuit structure of the detector, calculates and collects multiple groups of dark current data, and distinguishes whether the state of the CT detector after being installed is normal or not, and has the advantages of simple and efficient operation and calculation process and objective and reliable obtained conclusion.
Description
Technical Field
The invention relates to the technical field of medical images, in particular to a CT detector state detection method.
Background
Signals acquired by a tomographic (CT) scanner are acquired by a CT detector. Generally, before the CT scanner equipment leaves the factory, manufacturers need to debug and calibrate the CT detector, so that the CT detector meets the specified requirements. In addition, the CT detector module may have accidents such as misoperation and incorrect installation in the processes of processing, transporting, installing and the like, so that the CT detector module has the conditions of damaged performance, unqualified installation or light leakage and the like. Therefore, in the debugging process before delivery, the state of the CT detector module after installation needs to be evaluated, so that the detector module is ensured to meet preset standards such as packaging stability, no light leakage and the like in the production and installation processes, and the stability of the quality of the reconstructed image is realized.
On the other hand, with the increase of the number of times of use of the CT scanner, some misoperation may occur during long-term use, so that the performance and stability of a part of the module of the CT detector may change, and in the post-maintenance of the CT scanner, for such possible changes of the performance and stability of the module, the module may need to be disassembled, adjusted, replaced, and other operations, which also requires that the adjusted and replaced module and the whole CT detector also meet the above preset standards such as package stability, no occurrence of light leakage, and the like.
In order to solve such problems as the packaging is not up to standard, light leakage and the like, which may be caused by production, installation errors and the like in the production and installation processes, it is necessary to detect the state of the installed CT detector.
Disclosure of Invention
In order to solve the above problems, an object of the present invention is to provide a method for detecting a state of a CT detector.
In order to achieve the above object, the technical scheme of the present invention is as follows:
a method for detecting the state of a CT detector, comprising the steps of:
s100, collecting dark current data of a plurality of groups of CT detectors;
s200, correcting dark current data according to a circuit structure of the CT detector;
s300, according to the corrected dark current data, carrying out statistical calculation and inspection on each module unit and each detector channel after the CT detector is installed, and distinguishing whether the state of the module unit and the state of each detector channel are normal or not.
Further, the collection of the dark current data in step S100 specifically includes the following:
dark current data I 0 (x, y, T) is the data acquisition of an n x m detector without exposure, wherein each group of dark current data corresponds to each time T for a total of T times, x represents the x-th channel in the direction of the detector channel, n is the total number of channels in the direction of the detector channel, y represents the y-th row in the direction of the detector row, and m is the detectionTotal number of channels in row direction.
Further, in the step S200, the correction of the dark current data includes the following steps:
s210, calculating dark current mean value vector V of all dark current data in the direction of time T 0 (x，y)，
S220, enabling dark current data I at each time t 0 (x, y, t) subtracting the dark current mean vector V 0 (x, y) to obtain dark current corrected data I 1 (x，y，t)。
Further, the statistical calculation and inspection of the detector channels comprises the steps of:
s310, extracting correction data I of each detector channel at all moments 1 (x, y, t) signals from which an observed square distribution function F of dark current data of the detector labeled (x, y) channel can be obtained x，y (I) Wherein F x，y (I)＝hist(I 1 (x, y, T)), t=1,.. hist (I) in the formula represents distributing the input data I histogram;
s320, a statistical test formula of a channel with the detector labeled (x, y) is as follows: h is a x，y (k)＝TEST(F x，y ，P ideal A), wherein TEST is a statistical TEST mode, α is the significance level of the statistical TEST for each detector channel, P ideal Represents a constant variable representing a cumulative distribution function of normal dark current data noise, h x，y (k) The number of the statistical test results for the (x, y) channel labeled by the detector is 0 or 1;
if the test result h x，y (k) If the value is 0, the state of the channel marked as (x, y) of the detector is normal and accords with the standard;
if the test result h x，y (k) If 1, it indicates that the status of the (x, y) channel of the detector may be abnormal, suggesting further inspection.
Further, the statistical calculation and verification of the detector module unit comprises the following steps:
s330, for the Kth detector module unit, extracting N of all channels at all moments in the module unit M Correction data I for x T channels 1 (x, y, t) signals from which the observed direct distribution function F of the kth module unit dark current data can be obtained M (K) (I) wherein
S340, carrying out statistical test on all channels in the detector module, wherein a statistical test formula is as follows:
h M (k)＝TEST(F M，(k) ，P ideal ，α M ) The method comprises the steps of carrying out a first treatment on the surface of the Wherein alpha is M To statistically test the significance level for the modular units, h M (k) A value of 0 or 1 is the statistical test result of the kth detector module unit;
if the test result h M (k) If the value is 0, the state of the kth detector module is normal and accords with the standard;
if the test result h M (k) If 1, it indicates that the state of the kth detector module may be abnormal, suggesting further inspection.
Further, a cumulative distribution function P of the normal dark current data noise ideal The acquisition of (1) comprises the steps of: collecting multiple groups of normal dark current data by using a CT scanner with the same type and normal state; correcting normal multiple groups of dark current data; performing histogram statistics on multiple groups of corrected normal dark current data to obtain histogram distribution Hist ideal The method comprises the steps of carrying out a first treatment on the surface of the For histogram distribution Hist ideal Polynomial fitting is carried out to obtain a cumulative distribution function P ideal 。
The invention has the advantages that: compared with the prior art, the state of the detector is judged by adopting various detection indexes of a detector monitoring system, the method utilizes the characteristics of dark current data by combining a statistical method and a circuit structure of the detector, calculates and collects multiple groups of dark current data, and distinguishes whether the state of the CT detector after being installed is normal or not, and has the advantages of simple and efficient operation and calculation process and objective and reliable obtained conclusion.
Drawings
Fig. 1 is a schematic diagram of dark current data acquisition of a detector in an embodiment.
Detailed Description
The present invention is described in further detail below with reference to examples.
According to the state detection method of the CT detector, the characteristics of dark current data are utilized in combination with the circuit structure of the CT detector, and the collected multiple groups of dark current data are subjected to statistical calculation, so that whether the state of the CT detector after installation is normal or not is judged. The method specifically comprises the following steps:
s100, collecting dark current data of a plurality of groups of CT detectors; each group of dark current data corresponds to each time T, and total T times, in general, in order to ensure the data validity of statistical calculation analysis, the number of times T should be selected to be a larger number, such as 512;
dark current data I at each time t 0 (x, y, t) is the data acquisition of an n×m detector without exposure, as shown in fig. 1 below, where x represents the x-th channel in the detector channel direction, n is the total number of channels in the detector channel direction, y represents the y-th row in the detector row direction, and m is the total number of channels in the detector row direction;
s200, correcting dark current data according to a circuit structure of the CT detector;
s210, calculating dark current mean value vector V of all dark current data in the direction of time T 0 (x,y)，
S220, enabling dark current data I at each time t 0 (x, y, t) subtracting the dark current mean vector V 0 (x, y) to obtain dark current corrected data I 1 (x,y,t)；
S300, according to the corrected dark current data I 1 (x, y, t) performing statistical calculation and inspection on each module unit and each detector channel after the CT detector is installed,and distinguishing whether the states of the module units and the detector channels are normal or not.
According to corrected data I 1 And (x, y, t) carrying out statistical calculation and inspection to judge whether the state of the CT detection darker after installation is normal. Since the noise of the normal dark current data should conform to a certain distribution P ideal Therefore, the state of each module unit and the state of each detector channel can be judged whether to be normal or not by carrying out statistical analysis on the corrected dark current data of each module unit and the corrected dark current data of each detector channel.
From the above, it is necessary to obtain the cumulative distribution function P of the noise of the normal dark current data in advance ideal . Typically cumulative distribution function P ideal As a reference constant variable, can be acquired in advance by acquisition and calculation, P ideal The acquisition method of (1) comprises the following steps:
collecting multiple groups of normal dark current data by using a CT scanner with the same type and normal state;
using the method of step S200, calibrating the normal multiple sets of dark current data;
performing histogram statistics on the calibrated multiple groups of normal dark current data to obtain histogram distribution Hist ideal ；
For histogram distribution Hist ideal Polynomial fitting is carried out, and the fitting result is a cumulative distribution function P which needs to be acquired ideal 。
Statistical calculations and checks for the detector channels include the following steps:
s310.CT detector total n×m detection channels, extracting correction data I of each detector channel at all times 1 (x, y, t) signals from which an observed square distribution function F of dark current data of the detector labeled (x, y) channel can be obtained x，y (I) Wherein F x，y (I)＝hist(I 1 (x, y, T)), t=1,.. hist (I) in the formula represents distributing the input data I histogram;
s320, a statistical test formula of a channel with the detector labeled (x, y) is as follows: h is a x，y (k)＝TEST(F x，y ，P ideal α), wherein TEST is a statistical TEST method, and a statistical TEST method such as Kolmogorov-Smirnov TEST, chi-square TEST, etc. may be selected; alpha is the significance level for which a statistical test is performed for each detector channel; p (P) ideal Represents a constant variable representing a cumulative distribution function of normal dark current data noise, h x，y (k) The number of the statistical test results for the (x, y) channel labeled by the detector is 0 or 1;
if the test result h x，y (k) If the value is 0, the state of the channel marked as (x, y) of the detector is normal and accords with the standard;
if the test result h x，y (k) If 1, it indicates that the status of the (x, y) channel of the detector may be abnormal, suggesting further inspection.
Statistical calculations and checks for the detector module unit comprise the following steps:
s330, for the Kth detector module unit, extracting N of all channels at all moments in the module unit M Correction data I for x T channels 1 (x, y, t) signals from which the observed direct distribution function F of the kth module unit dark current data can be obtained M (K) (I) wherein
S340, carrying out statistical test on all channels in the detector module, wherein a statistical test formula is as follows:
h M (k)＝TEST(F M，(k) ，P ideal ，α M ) The method comprises the steps of carrying out a first treatment on the surface of the Wherein alpha is M To statistically test the significance level for the modular units, h M (k) A value of 0 or 1 is the statistical test result of the kth detector module unit;
if the test result h M (k) If the value is 0, the state of the kth detector module is normal and accords with the standard;
if the test result h M (k) 1, then indicates that the state of the kth detector module may be abnormal, the module unit is in productionAbnormal conditions may occur during production and installation, suggesting further inspection.
The above embodiments are only for illustrating the concept of the present invention and not for limiting the protection of the claims of the present invention, and all the insubstantial modifications of the present invention using the concept shall fall within the protection scope of the present invention.
Claims (2)
1. A method for detecting the state of a CT detector, comprising the steps of:
s100, collecting dark current data of a plurality of groups of CT detectors; the acquisition of dark current data specifically comprises the following contents: dark current data I 0 (x, y, T) is the data acquisition of an n x m detector without exposure, wherein each group of dark current data corresponds to each time T for a total of T times, x represents the x-th channel in the direction of the detector channel, n is the total number of channels in the direction of the detector channel, y represents the y-th row in the direction of the detector row, and m is the total number of channels in the direction of the detector row;
s200, correcting dark current data according to a circuit structure of the CT detector;
s210, calculating dark current mean value vector V of all dark current data in the direction of time T 0 (x,y)，
S220, enabling dark current data I at each time t 0 (x, y, t) subtracting the dark current mean vector V 0 (x, y) to obtain dark current corrected data I 1 (x,y,t)；
S300, carrying out statistical calculation and inspection on each module unit and each detector channel after the CT detector is installed according to the corrected dark current data, and distinguishing whether the state of the module unit and the state of each detector channel are normal or not;
the statistical calculation and inspection of the detector channels comprises the following steps:
s310, extracting correction data I of each detector channel at all moments 1 (x, y, t) signals from which detector channels labeled (x, y) can be derivedObservation of the square distribution function F of dark current data of (2) x,y (I) Wherein F x,y (I)＝hist(I 1 (x, y, T)), t=1, …, T, where hist (I) represents histogram distribution of the input data I;
s320, a statistical test formula of a channel with the detector labeled (x, y) is as follows: h is a x,y (k)＝TEST(F x,y ,P ideal Alpha), where TEST is the statistical TEST mode, alpha is the level of significance of the statistical TEST for each detector channel, P ideal Represents a constant variable representing a cumulative distribution function of normal dark current data noise, h x,y (k) The number of the statistical test results for the (x, y) channel labeled by the detector is 0 or 1;
if the test result h x,y (k) If the value is 0, the state of the channel marked as (x, y) of the detector is normal and accords with the standard;
if the test result h x,y (k) If 1, the state of the channel marked (x, y) of the detector may be abnormal, and further examination is recommended;
the statistical calculation and inspection of the detector module unit comprises the following steps:
s330, for the Kth detector module unit, extracting N of all channels at all moments in the module unit M Correction data I for x T channels 1 (x, y, t) signals from which the observed direct distribution function F of the kth module unit dark current data can be obtained M,(K) (I) Wherein
S340, carrying out statistical test on all channels in the detector module, wherein a statistical test formula is as follows:
h M (k)＝TEST(F M,(k) ,P ideal ,α M ) The method comprises the steps of carrying out a first treatment on the surface of the Wherein alpha is M To statistically test the significance level for the modular units, h M (k) A value of 0 or 1 is the statistical test result of the kth detector module unit;
if the test result h M (k) Is that0, the state of the kth detector module is normal and accords with the standard;
if the test result h M (k) If 1, it indicates that the state of the kth detector module may be abnormal, suggesting further inspection.
2. The method of claim 1, wherein said cumulative distribution function P of normal dark current data noise ideal The acquisition of (1) comprises the steps of: collecting multiple groups of normal dark current data by using a CT scanner with the same type and normal state; correcting normal multiple groups of dark current data; performing histogram statistics on multiple groups of corrected normal dark current data to obtain histogram distribution Hist ideal The method comprises the steps of carrying out a first treatment on the surface of the For histogram distribution Hist ideal Polynomial fitting is carried out to obtain a cumulative distribution function P ideal 。
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