CN108074636B - Surface incident dose calculation method, device and storage medium - Google Patents
Surface incident dose calculation method, device and storage medium Download PDFInfo
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- CN108074636B CN108074636B CN201711436101.3A CN201711436101A CN108074636B CN 108074636 B CN108074636 B CN 108074636B CN 201711436101 A CN201711436101 A CN 201711436101A CN 108074636 B CN108074636 B CN 108074636B
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Abstract
The invention discloses a surface incident dose calculation method, which comprises the following steps: setting a kilovolt value and a milliampere second value of a high-voltage generator, changing the kilovolt value, and obtaining incident doses at different positions away from the focus of the bulb tube; obtaining N first fitting curves of the focal positions of the distance bulbs and the incident doses according to the incident doses at different positions of the N distance bulbs; wherein N is a positive integer; assuming that the milliampere-second value of the high-voltage generator is fixed, determining a fitting coefficient at any kilovolt value, and obtaining a second fitting curve between the focal position of the distance bulb and the incident dose; according to the relationship between the milliampere-second value of the high-voltage generator and the incident dose, obtaining a third fitting curve of any kilovolt value, any milliampere-second value, distance tube focus position and the incident dose; when the image examination is carried out, the position of the patient from the focus of the bulb tube is input into the third fitting curve, and the incident dose of the X-ray is obtained. This approach prevents the risk of incident dose overirradiation.
Description
Technical Field
The invention relates to a method, equipment and a storage medium for calculating surface incident dose, and belongs to the technical field of medical metering.
Background
The X-ray image equipment is mainly used by hospitals at present for providing medical image examination for patients, and the main principle is that different tissue structures generate different X-ray attenuation after X-rays pass through human bodies, and a flat panel detector forms a gray distribution image corresponding to the tissue structures of the human bodies according to the distribution of the X-rays generated after the X-rays pass through the human bodies, so that doctors complete the observation and diagnosis of the tissue structures of the human bodies through the image.
In clinical applications of X-ray imaging devices, surface-incident dose control of patients is a concern for all parties in recent years, since excessive X-ray radiation increases the risk of radiation damage to the human body. The countries of the European Union set up the regulation standard to require the establishment of a patient radiation dose file system, record the X-ray radiation dose of a patient receiving X-ray examination each time into a patient file, and the medical institution can perform X-ray examination about several times in the year according to the personal cumulative dose record value or evaluate whether the patient has received excessive X-ray examination. This provision has been written in a new edition of european union regulatory standards. All X-ray imaging devices exported to europe must have the capability to capture and record the incident dose on the patient's surface. Therefore, when a doctor performs an X-ray image examination on a patient, a function that the doctor must have for measuring or calculating the incident dose to the patient is required.
Existing X-ray imaging devices, such as an angiography machine, a direct digital flat panel X-ray imaging system, or a digital gastrointestinal imaging machine, mainly measure the dose value of X-rays through a dose sensor installed in front of an X-ray tube. The measured dose value is converted into a voltage signal, the voltage signal is transmitted to a processing circuit board for AD conversion, and the AD conversion value is transmitted to the computer of the image workstation. While the X-ray image is being acquired, the dose values measured at this time are also stored in an image format file and a case file. Therefore, when the doctor looks at the image, the doctor can see the surface incident dose received by the patient when the image is shot, and the value can be recorded in a case file, so that the doctor can conveniently count data by a medical institution.
However, measuring the incident dose on the surface of the patient using the sensor requires installing the sensor in the path of the X-ray and designing the AD conversion circuit, which significantly increases the complexity and cost of the product design.
Disclosure of Invention
In view of the deficiencies of the prior art, the primary technical problem to be solved by the present invention is to provide a method for calculating surface incident dose.
Another object of the present invention is to provide a surface-incident dose calculation apparatus.
A further object of the present invention is to provide a storage medium.
In order to achieve the purpose, the invention adopts the following technical scheme:
according to a first aspect of embodiments of the present invention, there is provided a surface-incident dose calculation method including the steps of:
setting a kilovolt value and a milliampere second value of a high-voltage generator, changing the kilovolt value, and obtaining incident doses at different positions away from the focus of the bulb tube;
obtaining N first fitting curves of the focal positions of the distance bulbs and the incident doses according to the incident doses at different positions of the N distance bulbs; wherein N is a positive integer;
assuming that the milliampere-second value of the high-voltage generator is fixed, determining a fitting coefficient at any kilovolt value, and obtaining a second fitting curve between the focal position of the distance bulb and the incident dose;
according to the relationship between the milliampere-second value of the high-voltage generator and the incident dose, obtaining a third fitting curve of any kilovolt value, any milliampere-second value, distance tube focus position and the incident dose;
when the image examination is carried out, the position of the patient from the focus of the bulb tube is input into the third fitting curve, and the incident dose of the X-ray is obtained.
Preferably, the kilovolt value and the milliampere-second value of the high-voltage generator are set, the kilovolt value is changed, and the incident doses at different positions away from the focal point of the bulb tube are obtained, and the method comprises the following substeps:
s111, acquiring a kilovolt maximum value and a kilovolt minimum value of kilovolt values of the high-voltage generator, selecting N kilovolt values between the kilovolt maximum value and the kilovolt minimum value, and setting the values as kVj, wherein j is 1 and 2 … … N;
s112, setting the milliampere-second value of the high-voltage generator as a reference value R1;
s113, determining N distance equally dividing points according to the distance from the patient supporting surface to the focus of the bulb, wherein the positions from the focus of the bulb are respectively FIDi, i is 1,2 … … N, and N is a positive integer;
s114, setting a kilovoltage value kVj of the high-voltage generator, and acquiring incident doses of FIDi at different positions away from the focus of the bulb tube one by one;
and S115, repeating the step S114, enabling j to take the values of 1 and 2 … … N respectively, and obtaining the incident doses at different positions away from the focus of the bulb tube under each kilovolt value.
Preferably, the method for obtaining N first fitted curves of the focal point position of the distance bulb and the incident dose according to the incident doses at different positions of the N focal points of the distance bulb comprises the following substeps:
s121, establishing a coordinate system by taking the position from the focal point of the bulb as an abscissa and the incident dose value of each point as an ordinate;
s122, when the kilovoltage value of the high-voltage generator is kVj, distributing the points representing the positions of the focal points of the distance bulbs and the incident dose in a coordinate system one by one;
s123, performing curve fitting according to points in the coordinate system to obtain a first fitting curve between the focal position of the distance bulb and the incident dose;
and S124, repeating the steps S122 to S123 to enable j to take the values 1 and 2 … … N respectively, and performing curve fitting to obtain N first fitting curves of the focal position of the distance bulb and the incident dose.
Preferably, the method for determining the fitting coefficient at any kilovolt value assuming that the milliampere-second value of the high-voltage generator is fixed comprises the following substeps:
establishing a coordinate system by taking the kilovolt value as a horizontal coordinate and the fitting coefficient as a vertical coordinate;
distributing points representing the kilovolt values and the fitting coefficients in a coordinate system one by one;
and performing curve fitting according to points in the coordinate system to obtain a functional relation between the fitting coefficient and the kilovolt value, and obtaining the fitting coefficient through the kilovolt value.
Preferably, before calculating the incident dose of the X-ray, the method for calculating the incident dose on the surface further includes the following sub-steps:
and correcting the third fitting curve according to the relation error between the mAN _ SNh second value of the high-voltage generator and the incident dose in application to obtain a final fitting curve.
Preferably, the third fitting curve is corrected according to the relation error between the mAmp second value of the high-voltage generator and the incident dose in the application to obtain a final fitting curve, and the method comprises the following substeps:
at a fixed FID point, the kilovolt value of the high-voltage generator is set to be kV1, and the milliampere second value is set to be R2; measuring the incident dose RB at this location using a dosimeter;
at the fixed FID point, the kilovolt value of the high-voltage generator is set to be kV1, and the milliampere second value is set to be R1; measuring the incident dose RA at this location using a dosimeter;
calculating the incident dose RBS value when the mAmp second value is set to R2 at the FID point position; (R2/R1) × RA at RBS;
and obtaining a parameter dose multiplying factor according to the incident dose measured by the dosimeter and the incident dose obtained by calculation, and substituting the parameter dose multiplying factor into a third fitting curve to obtain a final fitting curve.
Preferably, the final fitting curve of the focus position of the distance bulb and the incident dose at any kilovolt value and any milliampere-second value is represented by the following formula:
y＝(R/R1)×M×f(kV)×x-u；
wherein y is the incident dose, R is the milliampere-second value under the current conditions, R1 is the reference value of the milliampere-second value, and f (kv) is the fitting coefficient; x is the position of the current position from the focal point of the bulb; u is the coefficient of the function and M is the parametric dose-multiplier system.
According to a second aspect of embodiments of the present invention, there is provided a surface-incident dose calculation device, comprising a processor and a memory; the memory having stored thereon a computer program operable on the processor, the computer program when executed by the processor implementing the steps of:
setting a kilovolt value and a milliampere second value of a high-voltage generator, changing the kilovolt value, and obtaining incident doses at different positions away from the focus of the bulb tube;
obtaining N first fitting curves of the focal positions of the distance bulbs and the incident doses according to the incident doses at different positions of the N distance bulbs; wherein N is a positive integer;
assuming that the milliampere-second value of the high-voltage generator is fixed, determining a fitting coefficient at any kilovolt value, and obtaining a second fitting curve between the focal position of the distance bulb and the incident dose;
according to the relationship between the milliampere-second value of the high-voltage generator and the incident dose, obtaining a third fitting curve of any kilovolt value, any milliampere-second value, distance tube focus position and the incident dose;
when the image examination is carried out, the position of the patient from the focus of the bulb tube is input into the third fitting curve, and the incident dose of the X-ray is obtained.
Wherein preferably, when said computer program is executed by said processor, the following steps are also implemented;
and correcting the third fitting curve according to the relation error between the mAN _ SNh second value of the high-voltage generator and the incident dose in application to obtain a final fitting curve.
According to a third aspect of embodiments of the present invention, there is provided a computer-readable storage medium storing one or more programs, which are executable by one or more processors, to implement the steps in the surface incident dose calculation method described above.
According to the surface incident dose calculation method provided by the invention, a third fitting curve of the focal position of the distance bulb and the incident dose at any kilovolt value and any milliampere-second value is obtained; when the image examination is carried out, the position of the patient from the focus of the bulb tube is input into the third fitting curve, and the incident dose of the X-ray is obtained. Under the condition of not using a dose sensor, the surface incident dose received by the patient can be calculated according to the kV setting value, the mAs setting value and the focus position of the distance between the surface of the patient and the bulb tube, the cost can be saved, the surface of the patient can be prompted to receive the dose through calculation at any time, and the excessive radiation risk can be prevented.
Drawings
FIG. 1 is a flow chart of a method for calculating surface incident dose according to the present invention;
FIG. 2(a) is a schematic structural diagram of a first fitting curve at 31kV and 20mAs in the embodiment provided by the present invention;
fig. 2(b) is a schematic structural diagram of a first fitting curve when the mAs value is 20, 50, and 100 respectively at 35kV in the embodiment of the present invention;
FIG. 2(c) is a schematic structural diagram of a first fitting curve at a setting of 20mAs and 38kV in the embodiment provided by the present invention;
fig. 3 is a schematic structural diagram of a surface-incident dose calculation apparatus provided in an embodiment of the present invention.
Detailed Description
The technical contents of the invention are described in detail below with reference to the accompanying drawings and specific embodiments.
As shown in fig. 1, the method for calculating surface incident dose provided by the present invention includes the following steps: firstly, setting a kV value and an mAs value of a high-voltage generator, changing the kV value, and obtaining N incident doses at different positions away from a focal point of a bulb tube; secondly, obtaining N first fitting curves of the focal positions of the distance bulbs and the incident doses according to the incident doses at different positions of the N distance bulbs; then, assuming that the mAs value of the high-voltage generator is fixed, determining a fitting coefficient at any kV value, and obtaining a second fitting curve between the focal position of the distance bulb and the incident dose. Finally, according to the relation between the mAs value of the high-voltage generator and the incident dose, obtaining a third fitting curve of the position of the focal point of the distance bulb and the incident dose at any kV value and any mAs value; when the image examination is carried out, the position of the patient from the focus of the bulb (namely, the position from the focus of the bulb) is input into the third fitting curve, and the incident dose of the X-ray is obtained. This process is explained in detail below.
It should be noted that kV and mAs of the high voltage generator are two indexes characterizing the performance of the high voltage generator, wherein kV is also called kV and is the voltage applied across the bulb of the high voltage generator. The mAs value is also called as the ma second value, and the total amount of X-rays is usually described in the X-ray generator by the ma second value.
And S11, setting the kV value and the mAs value of the high-voltage generator, changing the kV value, and obtaining incident doses at different positions away from the focus of the bulb tube.
The steps specifically include the following substeps:
and S111, acquiring the kV maximum value and the kV minimum value of the kV value of the high-voltage generator, selecting N kV values between the kV maximum value and the kV minimum value, and setting j to be 1 and 2 … … N, wherein N is a positive integer.
The kV value of the medical high-voltage generator has an adjusting range, and the adjusting range of the kV value of the currently used high-voltage generator is determined firstly, namely the maximum value and the minimum value of the kV are determined. In the embodiment of the method provided by the invention, the adjustable kV minimum value is defined as kV 1. The value of kV1 was recorded.
And selecting N kV value points. Selecting a plurality of kV points according to the maximum value and the minimum value of the kV value, wherein the selecting rule is that the plurality of kV points are selected according to a certain interval. In the embodiment of the method provided by the invention, the definition is kV2 and kV3 … … kVN. The well-chosen kV values are recorded.
And S112, setting the mAs value of the high-voltage generator as a reference value R1.
There is also a regulatory range for the mAs value of the medical high voltage generator, and a clinically common mAs value was selected to define the value as R1. The selected mAs value R1 is recorded.
And S113, determining N distance equally dividing points according to the distance from the patient supporting surface to the focus of the bulb, wherein the N distance equally dividing points are positions away from the focus of the bulb and are respectively set to FIDi, i is 1,2 … … N, and N is a positive integer.
According to the distance from the actual patient supporting surface to the focal point of the bulb, N equal distance division points are determined, and the distances from the focal point are defined as FID1, FID2 and FID3 … … FIND, and the unit is mm.
S114, setting the kV value kVj of the high-voltage generator, and acquiring the incident doses of FIDi at different positions away from the focus of the bulb tube one by one.
Setting the kV value of a high-voltage generator, respectively placing a dosimeter at each FIDi position point under the setting of kV1 and R1mAs, measuring incident dose values of FID1, FID2, FID3 and FIDN points one by one, and recording the measured incident dose values of each position point into a table.
And S115, repeating the step S114, enabling j to take the values of 1 and 2 … … N respectively, and obtaining the incident doses at different positions away from the focus of the bulb tube under each kV value.
Step S114 is repeated to measure the incident dose at each FIDi location point at kV2 and R1 mAs. And according to the selected kV value points, when measuring kV2, recording the incident dose values of the FID1, the FID2, the FID3 and the FIDN at each point in a table.
And repeating the step to carry out kV3 until the incident dose value of each FIDi point when the R1mAs of each kV point selected by kVN is set, repeating the testing step to test the incident dose value of each FID point when each kV point is at the R1mAs, and recording the measured incident dose value into a table.
And S12, obtaining N first fitting curves of the focal position of the distance bulb and the incident dose according to the N incident doses at different positions of the distance bulb.
The steps specifically include the following substeps:
s121, establishing a coordinate system by taking the position from the focal point of the bulb as an abscissa and the incident dose value of each point as an ordinate;
the data obtained above is the incident dose value of each FID point under each kV point R1mAs, the distance of the FIDi point is used as the abscissa, the incident dose value of each point is used as the ordinate, and a coordinate system is established.
And S122, when the kV value of the high-voltage generator is kVj, distributing the points representing the positions of the focal points of the distance bulbs and the incident dose in a coordinate system one by one.
When the kV value of the high voltage generator is kV1, N corresponding values of the positions from the focal point of the bulb and the incident dose may be obtained in step S1, and the points representing the positions from the focal point of the bulb and the incident dose are distributed in the coordinate system one by one according to the coordinate system.
And S123, performing curve fitting according to the points in the coordinate system to obtain a first fitting curve between the focal position of the bulb and the incident dose.
The data obtained above are the incident dose values at each FID point at each kV point R1mAs, and the generation function y can be fitted to each kV value-u. The method for obtaining the first fitted curve may be any existing curve fitting method for finding the correlation between the focal position of the distance bulb and the incident dose through the existing points. And will not be described in detail herein.
And S124, repeating the steps S122 to S123 to enable j to take the values 1 and 2 … … N respectively, and performing curve fitting to obtain N first fitting curves of the focal position of the distance bulb and the incident dose.
And repeating the steps S122 to S123 to enable j to take the values 1 and 2 … … N respectively, performing curve fitting to obtain N first fitting curves of the focal positions of the distance bulbs and the incident dose, and obtaining N A values and u values.
And S13, fixing the mAs value of the high-voltage generator, determining the fitting coefficient at any kV value, and obtaining a second fitting curve between the focal position of the distance bulb and the incident dose.
As mentioned above, N first fitted curves of focal position of the distance tube and incident dose will result in N a-values and u-values.
The N A values are defined as A1, A2 … … AN. A1 corresponds to kV1, A2 corresponds to kV2, and AN corresponds to kVN. The fit results in a formula where x can represent any FID value and u is the coefficient resulting from the fit.
Regarding the fitting coefficient u, experiments show that the values of the function coefficient u fitted at each kV1 … … kVN gear are substantially the same, and in the embodiment of the method provided by the present invention, only data points with the distance of FIDi points as the abscissa and the incident dose value of each point as the ordinate under the setting of partial kV values and mAs values and a first fitting curve to be synthesized are provided. As shown in table 1, under the settings of 31kV and 20mAs, the distance between FIDi points is taken as the abscissa, the incident dose value of each point is taken as the data point of the ordinate, and a first fitting curve is fit-synthesized; the corresponding fitted curve is shown in fig. 2 (a).
Comparison relation table of FIDi point and incident dose value under the settings of 131 kV and 20mAs of table
As shown in table 2, when the mAs value is 20, 50, and 100 respectively under the setting of 35kV, the distance of FIDi point is taken as abscissa, the incident dose value of each point is taken as data point of ordinate, and the first fitting curve to be synthesized; the corresponding fitted curve is shown in fig. 2 (b). The line formed by penetrating the diamonds represents a first fitting curve which is fit-synthesized by taking the distance of FIDi points as an abscissa and the incident dose value of each point as an ordinate under the settings of 35kV and 20 mAs; the line formed by penetrating the squares represents a first fitting curve which is fit-synthesized by taking the distance of FIDi points as a horizontal coordinate and the incident dose value of each point as a vertical coordinate under the setting of 35kV and 50 mAs; the line formed by the triangle represents a first fitting curve which is fit and synthesized by taking the distance of FIDi points as the abscissa and the incident dose value of each point as the ordinate under the settings of 35kV and 100 mAs.
Comparison relation table of FIDi point and incident dose value under 235 kV setting and different mAs values
As shown in table 3, under the settings of 38kV and 20mAs, the distance between FIDi points is taken as the abscissa, the incident dose value of each point is taken as the data point of the ordinate, and the first fitting curve is fit-synthesized; the corresponding fitted curve is shown in fig. 2 (c).
Comparison relation table of FIDi point and incident dose value under table 338 kV and 20mAs settings
According to the curve analysis, the values of u are substantially the same. In the embodiment of the method provided by the invention, the average value of the values of N and u is taken for formula calculation.
Therefore, the formula can be used to calculate the incident dose value from the FID value position of the bulb focus when the R1mAs settings under the kV gears selected from kV1, kV2, kV3 and kVN are set. However, the high voltage generator is not actually only in these kV positions, so it is necessary to determine a fitting coefficient a to determine the incident dose value at each FID point at an arbitrary kV value and an mAs value of R1.
Assuming that the mAs value of the high-voltage generator is fixed, determining a fitting coefficient at any kV value, and specifically comprising the following steps:
s131, establishing a coordinate system by taking the kV value as a horizontal coordinate and the fitting coefficient as a vertical coordinate.
And establishing a coordinate system by taking kV1 … … kVN as a horizontal coordinate and the N fitting coefficients A1 … … AN as vertical coordinates obtained in the steps.
And S132, distributing the points representing the kV values and the fitting coefficients in a coordinate system one by one.
Each point composed of the kV value obtained in step S2 and the fitting coefficient a is taken into the coordinate system.
And S133, performing curve fitting according to points in the coordinate system to obtain a functional relation between a fitting coefficient A and a kV value, and obtaining the fitting coefficient A through the kV value.
Curve fitting was performed from points in the coordinate system to obtain a functional relationship between the fitting coefficient a and kV values, denoted as a ═ f (kV). At this time, the fitted formula is used, and the coefficient A at any kV value can be determined.
After this step, a second fitted curve of the focal point position of the distance tube and the incident dose can be obtained, wherein the formula is y ═ f (kv) x-u. kV is a kV value set by the high-voltage generator, and x is a position away from the focus of the bulb tube. The incident dose value of any kV at the FIDi point under the condition of R1mAs (mAs value is R1) can be calculated through the formula.
And S14, obtaining a third fitting curve of the focus position of the distance bulb and the incident dose at any kV value and any mAs value according to the relation between the mAs value and the incident dose of the high-voltage generator.
In practical use, the mAs value of the high voltage generator is also adjustable within a range, and the incident dose under the R1mAs value (the mAs value is R1) at any FID and any kV value can be calculated after the above steps, so that the whole mAs value cannot be used. Therefore, it is necessary to convert y ═ f (kv) × x-uAnd (5) performing expansion. Since the incident dose and the mAs value are in direct proportion, it is assumed according to this principle that the actual use is adjusted to any mAs value as R, and at this time, the third fitted curve of the focal point position of the distance tube and the incident dose at any kV value and any mAs value is obtained as follows: y ═ R/R1 × (kv) × x-uAnd the incident dose at any position away from the focus of the bulb tube under the conditions of any kV value and any mAs value can be calculated through the third fitting curve.
And S15, inputting the position of the patient from the focus of the bulb tube into the third fitting curve when the image examination is carried out, and obtaining the incident dose of the X-ray.
And S16, correcting the third fitting curve according to the relation error of the mAs value of the high-voltage generator and the incident dose to obtain a final fitting curve.
In practical experiments, the direct relation between the mAs value and the incident dose has certain error, and the error is caused by different mAs value accuracies of different generators. To correct for this error, an M-parameter dose multiplier factor is introduced. Correcting the third fitting curve according to the relation error between the mAs value of the medium-high voltage generator and the incident dose to obtain a final fitting curve, and specifically comprising the following steps of:
s161, setting the kV value of the high-voltage generator to be kV1 and the mAs value to be R2 at a fixed FID point position; measuring the incident dose RB at this location using a dosimeter;
at a fixed FID point position, the kV value of the high-voltage generator is set to be kV1, a mAs value is selected to be R2, the incident dose of the FID point is measured by using a dosimeter, and the incident dose value is recorded to be RB.
S162, setting the kV value of the high-voltage generator to be kV1 and setting the mAs value to be R1 at the fixed FID point position; measuring the incident dose RA at this location using a dosimeter;
the incident dose value at this FID point of the R1mAs value at kV1 measured in the previous step is set as RA.
S163, calculating the incident dose RBS value when the mAs value is set to be R2 at the FID point position; (R2/R1) × RA at RBS;
it is theorized that the incident dose RBS value of this FID point at R2mAs (mAs value R2) should be equal to (R2/R1). times.RA.
And S164, obtaining a parameter dose multiplying factor according to the incident dose measured by the dosimeter and the incident dose obtained through calculation, and substituting the parameter dose multiplying factor into a third fitting curve to obtain a final fitting curve.
The actually measured RB value is definitely not equal to the calculated value RBS, the RB/RBS is the M dose multiplying factor at the moment, the calculated error caused by the difference of the accuracy of the mAs value can be corrected by adding the value into a third fitting curve formula, and when any kV value and any mAs value are obtained, a final fitting curve between the focal position of the distance spherical tube and the incident dose is obtained:
y＝(R/R1)×M×f(kV)×x-u。
wherein y is the incident dose, y is the calculated x point away from the focal point of the bulb, the mAs value is R, the incident dose value is at the kV value, and the dose value unit is the dose unit selected when the dosimeter is used for testing. R is the mAs value under the current condition, and R1 is the reference value of the mAs value and is a fixed value. And f (kV) is a fitting coefficient, and an A coefficient formula which is determined according to measurement fitting and takes a kV value as a variable. x is the distance from the current position to the focal point of the bulb; u is a function coefficient, a fixed value determined when fitting the formula. And M is a calculation error brought by the difference of mAs by determining a dose multiplying factor according to an experiment.
The incident dose value calculated by the surface incident dose calculation method provided by the invention is compared with the value tested by using a dosimeter, and the calculation error meets the use requirement.
TABLE 4 comparison table of incident dosage value and testing value using dosimeter
The comparison table of the incident dose value obtained by the calculation of the part of the table 5 and the testing value of the dosimeter is verified by actual testing and calculation, and the incident dose corresponding to the position of any distance from the focal point of the bulb tube in the path of the emergent line can be very accurately calculated by adopting the surface incident dose calculation method provided by the invention. If the method is used in the X-ray imaging equipment, the incident dose value can be obtained without using the existing dose sensor for measurement, and meanwhile, the incident dose value prompt can be provided for doctors, so that the patient can be effectively protected from receiving excessive X-ray radiation.
In summary, the method for calculating the surface incident dose provided by the invention changes the kV value by setting the kV value and mAs value of the high voltage generator, and obtains the incident doses of N different positions from the focus of the bulb tube; obtaining N first fitting curves of the focal positions of the distance bulbs and the incident doses according to the incident doses at different positions of the N distance bulbs; then, the mAs value of the high-voltage generator is fixed, the fitting coefficient of any kV value is determined, and a second fitting curve between the focal position of the distance bulb and the incident dose is obtained. Finally, according to the relation between the mAs value of the high-voltage generator and the incident dose, a third fitting curve between the focal position of the distance bulb and the incident dose at any kV value and any mAs value is obtained; when the image examination is carried out, the position of the patient from the focus of the bulb tube is input into the third fitting curve, and the incident dose of the X-ray is obtained. According to the method, the surface incident dose received by the patient can be calculated according to the set kVmAs and the distance between the incident surface of the patient and the focus of the bulb tube when the X-ray imaging device is used. The method does not depend on a dose sensor, can display the calculated incident dose value at any time when a patient is in position and dose is set, gives a prompt to a doctor, and can prevent the incident dose from over-radiating risks.
The invention also provides surface incident dose calculation equipment which is used for realizing the surface incident dose calculation method. As shown in fig. 3, the apparatus includes a processor 22 and a memory 21 storing instructions executable by the processor 22;
the processor 22 may be a general-purpose processor, such as a Central Processing Unit (CPU), a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), or one or more integrated circuits configured to implement embodiments of the present invention, among others.
The memory 21 is used for storing the program codes and transmitting the program codes to the CPU. Memory 21 may include volatile memory, such as Random Access Memory (RAM); the memory 21 may also include non-volatile memory, such as read-only memory, flash memory, a hard disk, or a solid state disk; the memory 21 may also comprise a combination of memories of the kind described above.
Specifically, the surface-incident dose calculation device provided by the embodiment of the present invention includes a processor 22 and a memory 21; the memory 21 has stored thereon a computer program operable on the processor 22, which when executed by the processor 32, performs the steps of:
setting a kilovolt value and a milliampere second value of a high-voltage generator, changing the kilovolt value, and obtaining incident doses at different positions away from the focus of the bulb tube;
obtaining N first fitting curves of the focal positions of the distance bulbs and the incident doses according to the incident doses at different positions of the N distance bulbs; wherein N is a positive integer;
assuming that the milliampere-second value of the high-voltage generator is fixed, determining a fitting coefficient at any kilovolt value, and obtaining a second fitting curve between the focal position of the distance bulb and the incident dose;
according to the relationship between the milliampere-second value of the high-voltage generator and the incident dose, obtaining a third fitting curve of any kilovolt value, any milliampere-second value, distance tube focus position and the incident dose;
when the image examination is carried out, the position of the patient from the focus of the bulb tube is input into the third fitting curve, and the incident dose of the X-ray is obtained.
Setting a kV value and an mAs value of a high-voltage generator, changing the kV value, and obtaining incident doses at different positions away from a focus of a bulb tube; the following steps are implemented when the computer program is executed by the processor 22;
s211, acquiring the kV maximum value and the kV minimum value of the kV value of the high-voltage generator, selecting N kV values between the kV maximum value and the kV minimum value, and setting j to be 1 and 2 … … N, wherein N is a positive integer.
And S212, setting the mAs value of the high-voltage generator as a reference value R1.
And S213, determining N distance equally-dividing points according to the distance from the patient supporting surface to the focus of the bulb, wherein the positions from the focus of the bulb are respectively FIDi, i is 1,2 … … N, and N is a positive integer.
S214, setting the kV value kVj of the high-voltage generator, and acquiring the incident doses of FIDi at different positions away from the focus of the bulb tube one by one.
And S215, repeating the step S214 to enable j to take the values of 1 and 2 … … N respectively, and obtaining the incident doses at different positions away from the focus of the bulb tube under each kV value.
Obtaining N first fitting curves of the focal positions of the distance bulbs and the incident doses according to the incident doses at different positions of the N distance bulbs; the following steps are implemented when the computer program is executed by the processor 22;
s221, establishing a coordinate system by taking the position far away from the focus of the bulb as an abscissa and the incident dose value of each point as an ordinate;
s222, when the kV value of the high-voltage generator is kVj, distributing the points representing the positions of the focal points of the distance ball tubes and the incident dose in a coordinate system one by one;
s223, performing curve fitting according to points in the coordinate system to obtain a first fitting curve between the focal position of the distance bulb and the incident dose;
and S224, repeating the steps S222 to S223 to enable j to take the values 1 and 2 … … N respectively, and performing curve fitting to obtain N first fitting curves of the focal position of the distance bulb and the incident dose.
The mAs value of the high-voltage generator is fixed, and the fitting coefficient at any kV value is determined; the following steps are implemented when the computer program is executed by the processor 22;
establishing a coordinate system by taking the kV value as a horizontal coordinate and the fitting coefficient as a vertical coordinate;
distributing points representing the kV value and the fitting coefficient in a coordinate system one by one;
and performing curve fitting according to points in the coordinate system to obtain a functional relation between the fitting coefficient A and the kV value, and obtaining the fitting coefficient A through the kV value.
Wherein the computer program when executed by the processor 22 further realizes the following steps;
and correcting the third fitting curve according to the relation error between the mAs value of the medium-high voltage generator and the incident dose to obtain a final fitting curve.
Correcting the third fitting curve according to the relation error between the mAs value of the high-voltage generator and the incident dose in application to obtain a final fitting curve; the following steps are implemented when the computer program is executed by the processor 22;
at a fixed FID point position, the kV value of the high-voltage generator is set to be kV1, and the mAs value is set to be R2; measuring the incident dose RB at this location using a dosimeter;
at the fixed FID point position, the kV value of the high-voltage generator is set to be kV1, and the mAs value is set to be R1; measuring the incident dose RA at this location using a dosimeter;
calculating the incident dose RBS value when the mAs value is set to be R2 at the position of the FID point; (R2/R1) × RA at RBS;
and obtaining a parameter dose multiplying factor according to the incident dose measured by the dosimeter and the incident dose obtained by calculation, and substituting the parameter dose multiplying factor into a third fitting curve to obtain a final fitting curve.
The invention also provides a computer readable storage medium. The computer-readable storage medium herein stores one or more programs. Among other things, computer-readable storage media may include volatile memory, such as random access memory; the memory may also include non-volatile memory, such as read-only memory, flash memory, a hard disk, or a solid state disk; the memory may also comprise a combination of memories of the kind described above. When the one or more programs in the computer-readable storage medium are executable by the one or more processors to perform some or all of the steps of the above-described surface-incident dose calculation method.
The surface incident dose calculation method, apparatus, and storage medium provided by the present invention are described in detail above. Any obvious modifications to the invention, which would occur to those skilled in the art, without departing from the true spirit of the invention, would constitute a violation of the patent rights of the invention and would carry a corresponding legal responsibility.
Claims (9)
1. A surface incident dose calculation method characterized by comprising the steps of:
setting a kilovolt value and a milliampere second value of a high-voltage generator, changing the kilovolt value, and obtaining incident doses at different positions away from the focus of the bulb tube; the method comprises the following substeps:
s111, acquiring a kilovolt maximum value and a kilovolt minimum value of kilovolt values of the high-voltage generator, selecting N kilovolt values between the kilovolt maximum value and the kilovolt minimum value, and setting the values as kVj, wherein j is 1 and 2 … … N;
s112, setting the milliampere-second value of the high-voltage generator as a reference value R1;
s113, determining N distance equally dividing points according to the distance from the patient supporting surface to the focus of the bulb, wherein the positions from the focus of the bulb are respectively FIDi, i is 1,2 … … N, and N is a positive integer;
s114, setting a kilovoltage value kVj of the high-voltage generator, and acquiring incident doses of FIDi at different positions away from the focus of the bulb tube one by one;
s115, repeating the step S114, enabling j to take the values of 1 and 2 … … N respectively, and obtaining incident doses at different positions away from the focus of the bulb tube under each kilovolt value;
obtaining N first fitting curves of the focal positions of the distance bulbs and the incident doses according to the incident doses at different positions of the N distance bulbs; wherein N is a positive integer;
assuming that the milliampere-second value of the high-voltage generator is fixed, determining a fitting coefficient at any kilovolt value, and obtaining a second fitting curve between the focal position of the distance bulb and the incident dose;
according to the relationship between the milliampere-second value of the high-voltage generator and the incident dose, obtaining a third fitting curve of any kilovolt value, any milliampere-second value, distance tube focus position and the incident dose;
when the image examination is carried out, the position of the patient from the focus of the bulb tube is input into the third fitting curve to obtain a final fitting curve so as to obtain the incident dose of the X-ray.
2. The method of calculating surface incident dose of claim 1, wherein obtaining N first fitted curves of the focal point position of the distance tube and the incident dose according to the incident dose at N different positions from the focal point of the distance tube comprises the following sub-steps:
s121, establishing a coordinate system by taking the position from the focal point of the bulb as an abscissa and the incident dose value of each point as an ordinate;
s122, when the kilovoltage value of the high-voltage generator is kVj, distributing the points representing the positions of the focal points of the distance bulbs and the incident dose in a coordinate system one by one;
s123, performing curve fitting according to points in the coordinate system to obtain a first fitting curve between the focal position of the distance bulb and the incident dose;
and S124, repeating the steps S122 to S123 to enable j to take the values 1 and 2 … … N respectively, and performing curve fitting to obtain N first fitting curves of the focal position of the distance bulb and the incident dose.
3. The surface incident dose calculation method of claim 1, wherein the fitting coefficient at an arbitrary kilovolt value is determined assuming that the milliampere-second value of the high voltage generator is fixed, comprising the sub-steps of:
establishing a coordinate system by taking the kilovolt value as a horizontal coordinate and the fitting coefficient as a vertical coordinate;
distributing points representing the kilovolt values and the fitting coefficients in a coordinate system one by one;
and performing curve fitting according to points in the coordinate system to obtain a functional relation between the fitting coefficient and the kilovolt value, and obtaining the fitting coefficient through the kilovolt value.
4. The surface incident dose calculation method of claim 1, further comprising, before calculating the incident dose of the X-rays, the substeps of:
and correcting the third fitting curve according to the relation error between the mAN _ SNh second value of the high-voltage generator and the incident dose in application to obtain the final fitting curve.
5. The method of calculating surface incident dose of claim 4, wherein the third fitted curve is corrected according to the error of the relationship between the mAmp second value of the high voltage generator and the incident dose in the application to obtain the final fitted curve, comprising the following substeps:
at a fixed FID point, the kilovolt value of the high-voltage generator is set to be kV1, and the milliampere second value is set to be R2; measuring the incident dose RB at this location using a dosimeter;
at the fixed FID point, the kilovolt value of the high-voltage generator is set to be kV1, and the milliampere second value is set to be R1; measuring the incident dose RA at this location using a dosimeter;
calculating the incident dose RBS value when the mAmp second value is set to R2 at the FID point position; RBS ═ (R2/R1) × RA;
and obtaining a parameter dose multiplying factor according to the incident dose measured by the dosimeter and the incident dose obtained by calculation, and substituting the parameter dose multiplying factor into a third fitting curve to obtain a final fitting curve.
6. The surface incident dose calculation method of claim 4, wherein the final fitted curve of the focal point position of the distance tube and the incident dose at any kv value and at any msec value is represented by the following formula:
y＝(R/R1)×M×f(kV)×x-u；
wherein y is the incident dose, R is the milliampere-second value under the current conditions, R1 is the reference value of the milliampere-second value, and f (kv) is the fitting coefficient; x is the position of the current position from the focal point of the bulb; u is the coefficient of the function and M is the parametric dose-multiplier system.
7. A surface-incident dose calculation device comprising a processor and a memory; the memory having stored thereon a computer program operable on the processor, the computer program when executed by the processor implementing the steps of:
setting a kilovolt value and a milliampere second value of a high-voltage generator, changing the kilovolt value, and obtaining incident doses at different positions away from the focus of the bulb tube; the method comprises the following substeps:
s111, acquiring a kilovolt maximum value and a kilovolt minimum value of kilovolt values of the high-voltage generator, selecting N kilovolt values between the kilovolt maximum value and the kilovolt minimum value, and setting the values as kVj, wherein j is 1 and 2 … … N;
s112, setting the milliampere-second value of the high-voltage generator as a reference value R1;
s113, determining N distance equally dividing points according to the distance from the patient supporting surface to the focus of the bulb, wherein the positions from the focus of the bulb are respectively FIDi, i is 1,2 … … N, and N is a positive integer;
s114, setting a kilovoltage value kVj of the high-voltage generator, and acquiring incident doses of FIDi at different positions away from the focus of the bulb tube one by one;
s115, repeating the step S114, enabling j to take the values of 1 and 2 … … N respectively, and obtaining incident doses at different positions away from the focus of the bulb tube under each kilovolt value;
obtaining N first fitting curves of the focal positions of the distance bulbs and the incident doses according to the incident doses at different positions of the N distance bulbs; wherein N is a positive integer;
assuming that the milliampere-second value of the high-voltage generator is fixed, determining a fitting coefficient at any kilovolt value, and obtaining a second fitting curve between the focal position of the distance bulb and the incident dose;
according to the relationship between the milliampere-second value of the high-voltage generator and the incident dose, obtaining a third fitting curve of any kilovolt value, any milliampere-second value, distance tube focus position and the incident dose;
when image examination is carried out, the position of the patient from the focus of the bulb tube is input into the third fitting curve to obtain a final fitting curve, and the incident dose of X-rays is obtained.
8. Surface-incident-dose calculation apparatus according to claim 7, wherein the computer program, when executed by the processor, further implements the steps of;
and correcting the third fitting curve according to the relation error between the mAN _ SNh second value of the high-voltage generator and the incident dose in application to obtain the final fitting curve.
9. A computer-readable storage medium storing one or more programs which are executable by one or more processors to implement the steps of the surface-incident dose calculation method according to any one of claims 1 to 6.
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