CN101551344A - Highly stable dosage measurement circuit for medical linear accelerator and method - Google Patents
Highly stable dosage measurement circuit for medical linear accelerator and method Download PDFInfo
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- CN101551344A CN101551344A CNA2009100592323A CN200910059232A CN101551344A CN 101551344 A CN101551344 A CN 101551344A CN A2009100592323 A CNA2009100592323 A CN A2009100592323A CN 200910059232 A CN200910059232 A CN 200910059232A CN 101551344 A CN101551344 A CN 101551344A
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Abstract
The invention discloses a highly stable dosage measurement circuit for medical linear accelerator and method, involving in a medical linear accelerator, the invention is used for solving the problem of instability of the existing circuit for measuring dosage of linear accelerator, comprising an integrating meter to receive an input signal and output after enlarging integrals, an end of the integrating meter is connected with a capacitor; a comparator to receive an output signal of the integrating meter and output a reverse signal after comparing with a set reference signal; a counter to receive a reverse signal of the comparator and count a number as soon as a reverse signal is received; a digital analog converter to receive a signal of the counter, the digital analog converter outputs a voltage signal to an end of a capacitor as soon as the counter counts a number, the voltage signal makes the electric potential of the other end of the capacitor be zero.
Description
Technical field
The present invention relates to medical linear accelerator, especially a kind of dosage measurement circuit of linear accelerator and method.
Background technology
At the ray output of clinac, through the X ray and the electron beam of one-level collimation and expansion or scattering or scanning, before carrying out the secondary collimation, at first to pass through monitor ionization chamber, monitoring system is made up of two ionization chambers and corresponding metering circuit.
The measurement of clinac output dose is the important indicator of check accelerator output stability.
The penetrability ionization chamber that the linear accelerator output dose is measured under the situation of nominal accelerator voltage and dose rate electric current generally at pA (10
-12), the dosage measurement circuit of existing accelerator is generally selected for use as the integrating circuit among Fig. 1, amplifier is generally selected the cmos amplifier of high input resistance for use, feedback capacity is selected the polystyrene electric capacity of high impedance high stability for use, makes the voltage V=-It/C of output signal, and I is the electric current that ionization chamber produces in the formula, t is a Measuring Time, C is the feedback capacity value, and suitable capacitance is set, and the magnitude of voltage that makes output is between 0-5V.
Because amplifier generally all has the zero point drift about 10mV, add the instability of all elements in the metering circuit, it is unstable to cause whole metering circuit to exist, particularly when measuring low dose of rate, instability will directly influence the instability of accelerator complete machine dosage output greater than 1%.
And general national standard stipulates that all the degree of stability of linear accelerator should be less than 1%, and the raising of accelerator degree of stability is to be related to the important indicator whether performance of accelerator can satisfy use.
Summary of the invention
The objective of the invention is to solve the instability problem that existing linear accelerator dosage measurement circuit exists, a kind of improved dosage measurement circuit is provided, make the stability of its output signal only relevant with the value of feedback capacity, and the feedback capacity by selecting high stability for use or carry out positive and negative temperature compensation and make the value of feedback capacity reach the high stable performance, to improve the degree of stability of dosage measurement.
Another object of the present invention provides a kind of antihunt means of linear accelerator dosage measurement, to improve the degree of stability of dosage measurement.
The dosage measurement circuit of clinac high stable comprises
Integrator, receiving inputted signal and integration amplify back output, and the one end is connected with electric capacity;
Comparer receives the output signal of integrator and compares reverse signal of back output with the reference signal of setting;
Counter, the reverse signal of reception comparer, and reverse signal meter one number of every reception;
Digital to analog converter, the signal of count pick up device, then digital to analog converter is to an end output voltage signal of electric capacity for every meter one number of counter, and it is zero that this voltage signal makes an other terminal potential of described electric capacity.
Described integrator comprises
Amplifier, an input end is connected with first resistance with receiving inputted signal, and is connected with the output terminal of digital to analog converter by described electric capacity, and another input end connects current potential ground end, and its output terminal is connected with an input end of comparer;
First resistance, the one termination is received input signal, and the other end is connected with an input end of amplifier;
Second resistance, one end connect current potential ground end, and the other end is connected with the above-mentioned input end of amplifier;
Feedback resistance, the one end connects the above-mentioned input end of amplifier, and the other end connects the output terminal of amplifier;
Another input end of described comparer connects reference signal.
The output signal of described amplifier reaches reference signal value, and the output signal counter-rotating of comparer once.
Described counter is a single-chip microcomputer, and the output terminal of comparer is connected with an I/O interface of described single-chip microcomputer.
Described electric capacity is two the positive and negative opposite polystyrene electric capacity of temperature compensation coefficient formations in parallel.
The enlargement factor of described integrator is 400 times.
The link of described amplifier and electric capacity is connected with switch, and the other end of this switch is connected with current potential ground end.
The antihunt means of clinac dosage measurement comprise
The output signal of dosage measurement and the reference signal of setting are compared the back counting;
Every meter one number is then exported the voltage signal opposite with the voltage of feedback capacity, thereby makes the stability of output signal only relevant with the stability of feedback capacity;
Feedback capacity adopts two the positive and negative opposite polystyrene electric capacity of temperature compensation coefficient formations in parallel.
The output signal of described dosage measurement reaches the reference signal value of setting, then counts a number.
Described counting is, two input ends by comparer receive the output signal of dosage measurement and the reference signal value of setting respectively, output signal reaches the reference signal value of setting, and then reverse signal of the output terminal of comparer output receives this reverse signal meter one number by single-chip microcomputer again;
The opposite voltage signal of voltage described and feedback capacity obtains by the following method
Every meter one number of single-chip microcomputer is to digital signal of digital to analog converter output, and digital to analog converter is converted to the voltage signal opposite with the voltage of feedback capacity with this digital signal, is zero thereby make the current potential of feedback capacity and amplifier link.
The present invention adopts said structure and/or method, an input end of amplifier receives the electric current of ionization chamber as input signal, and after amplifying, exports the amplifier integration as measuring-signal, this measuring-signal is after the reference signal of comparer and setting compares, form counting with reverse signal, and by digital to analog converter to the feedback capacity one end output that is connected an input end of the amplifier voltage signal opposite with its other end voltage, thereby the link current potential that makes feedback capacity and amplifier is zero, it is the magnitude of voltage that the magnitude of voltage of digital to analog converter output equals the feedback capacity two ends all the time, then the error of the output voltage of amplifier is only relevant with the value of feedback capacity, and is irrelevant with the caused drift of the instability of amplifier self zero drift and other element.On the basis of the above, strengthen the stability of dosage measurement circuit, select promptly that the positive and negative opposite polystyrene electric capacity of two temperature compensation coefficients of high stable is in parallel to be constituted for use, then degree of stability can be brought up to be better than 0.1% by the stability that increases feedback capacity.
As seen, adopt said structure of the present invention and/or method, compared with prior art, the dosage measurement degree of stability of linear accelerator has improved about 10 times.
Description of drawings
The present invention will illustrate by example and with reference to the mode of accompanying drawing, wherein:
Fig. 1 is the dosage measurement circuit of prior art cathetus accelerator.
Fig. 2 is the dosage measurement circuit of cathetus accelerator of the present invention.
Embodiment
The present invention is further illustrated below in conjunction with the drawings and specific embodiments.
As shown in Figure 2, the dosage measurement circuit of clinac comprises amplifier IC1, comparer IC2, single-chip microcomputer IC3, digital to analog converter IC4, wherein amplifier IC1 input end is by first resistance R, 1 receiving inputted signal little electric current of ionization chamber (promptly from), this input end also is connected, is connected with the output terminal of amplifier IC1, is connected with the output terminal of digital to analog converter IC4 by feedback capacity Cf by feedback resistance Rf with current potential ground end by second resistance R 2, this input end also is connected with switch J, and the other end of this switch J is connected with current potential ground end.
The another one input end of amplifier IC1 is connected with current potential ground end and keeps zero potential.
The input end that the output terminal of amplifier IC1 connects comparer IC2 connects, and another input end of comparer IC2 receives the reference signal Vref that sets, and the output terminal of comparer IC2 connects the I/O interface of single-chip microcomputer IC3.
The input end of the output terminal linking number weighted-voltage D/A converter IC4 of single-chip microcomputer IC3.
Feedback capacity Cf is two the positive and negative opposite polystyrene electric capacity of temperature compensation coefficient formations in parallel.
In one embodiment, adjust the ratio of the feedback resistance Rf and second resistance R 2, the enlargement factor that makes amplifier IC1 is 400 times.Little electric current that ionization chamber comes is introduced through first resistance R 1, charge to feedback capacity Cf, (wherein I is little electric current of ionization chamber when the value of the voltage V=-It/C on the feedback capacity Cf reaches 2.5mV, t is a Measuring Time, C is the capacitance of feedback capacity Cf), the output voltage of amplifier IC1 is 1V, and the reference signal value of setting is 1V, then once counter-rotating (promptly exporting a reverse signal) takes place in the output of comparer IC2, this reverse signal is admitted to the I/O interface of single-chip microcomputer IC3, single-chip microcomputer IC3 receives this reverse signal, then count a number, and by exporting digital signal with the link of digital to analog converter IC4 to digital to analog converter IC4, digital to analog converter IC4 receives this digital signal, then exporting reverse 2.5mV voltage signal and give feedback capacity Cf, is zero thereby make the link current potential of feedback capacity Cf and amplifier IC1.
From said process as can be seen, little electric current of ionization chamber reaches the condition of setting reference signal value as long as satisfy the voltage that makes on the feedback capacity Cf, then can make single-chip microcomputer IC3 count a number, and the output voltage values that makes digital to analog converter IC4 keeps equaling the magnitude of voltage at feedback capacity Cf two ends, make two input ends of amplifier IC1 keep same zero potential, its zero point drift is compensated, and can not be exaggerated device IC1 and amplify back output, and then the error of its output voltage is only relevant with the capacitance of feedback capacity Cf.
And feedback capacity Cf is two the positive and negative opposite polystyrene electric capacity of temperature compensation coefficient formations in parallel, can eliminate the influence of temperature to its capacitance.The signal that single-chip microcomputer IC4 outputs to digital to analog converter then is measurement result, and degree of stability can be better than 0.1%, compared with prior art, improves about 10 times of degree of stability.
Before each the measurement, can Closing Switch J, make feedback capacity Cf discharge, to eliminate of the influence of all the other electricity to measuring.
In each measuring process, there are not little electric current of ionization chamber or its value deficiency so that the voltage of feedback capacity Cf reaches the reference signal value of setting, then two input ends of amplifier keep zero potential always, its zero point drift can not be exaggerated the device amplification and export, next little electric current up to ionization chamber reaches requirement, the upset counting.
Disclosed all features in this instructions, or the step in disclosed all methods or the process except mutually exclusive feature and/or step, all can make up by any way.
Disclosed arbitrary feature in this instructions (comprising any accessory claim, summary and accompanying drawing) is unless special narration all can be replaced by other equivalences or the alternative features with similar purpose.That is, unless special narration, each feature is an example in a series of equivalences or the similar characteristics.
The present invention is not limited to aforesaid embodiment.The present invention expands to any new feature or any new combination that discloses in this manual, and the arbitrary new method that discloses or step or any new combination of process.
Claims (10)
1, the dosage measurement circuit of clinac high stable is characterized in that, comprises
Integrator, receiving inputted signal and integration amplify back output, and the one end is connected with electric capacity;
Comparer receives the output signal of integrator and compares reverse signal of back output with the reference signal of setting;
Counter, the reverse signal of reception comparer, and reverse signal meter one number of every reception;
Digital to analog converter, the signal of count pick up device, then digital to analog converter is to an end output voltage signal of electric capacity for every meter one number of counter, and it is zero that this voltage signal makes an other terminal potential of described electric capacity.
2, the dosage measurement circuit of clinac high stable according to claim 1 is characterized in that described integrator comprises
Amplifier, an input end is connected with first resistance with receiving inputted signal, and is connected with the output terminal of digital to analog converter by described electric capacity, and another input end connects current potential ground end, and its output terminal is connected with an input end of comparer;
First resistance, the one termination is received input signal, and the other end is connected with an input end of amplifier;
Second resistance, one end connect current potential ground end, and the other end is connected with the above-mentioned input end of amplifier;
Feedback resistance, the one end connects the above-mentioned input end of amplifier, and the other end connects the output terminal of amplifier;
Another input end of described comparer connects reference signal.
3, as the dosage measurement circuit of clinac high stable as described in the claim 2, it is characterized in that the output signal of described amplifier reaches reference signal value, the output signal counter-rotating of comparer once.
4, as the dosage measurement circuit of clinac high stable as described in the claim 3, it is characterized in that described counter is a single-chip microcomputer, the output terminal of comparer is connected with an I/O interface of described single-chip microcomputer.
As the dosage measurement circuit of clinac high stable as described in one of claim 1～4, it is characterized in that 5, to be that two positive and negative opposite polystyrene electric capacity of temperature compensation coefficient is in parallel constitute described electric capacity.
6, the dosage measurement circuit of clinac high stable according to claim 1 is characterized in that the enlargement factor of described integrator is 400 times.
7, as the dosage measurement circuit of clinac high stable as described in the claim 2, it is characterized in that the link of described amplifier and electric capacity is connected with switch, the other end of this switch is connected with current potential ground end.
8, the antihunt means of clinac dosage measurement is characterized in that, comprise
The output signal of dosage measurement and the reference signal of setting are compared the back counting;
Every meter one number is then exported the voltage signal opposite with the voltage of feedback capacity, thereby makes the stability of output signal only relevant with the stability of feedback capacity;
Feedback capacity adopts two the positive and negative opposite polystyrene electric capacity of temperature compensation coefficient formations in parallel.
9, as the antihunt means of clinac dosage measurement as described in the claim 8, it is characterized in that the output signal of described dosage measurement reaches the reference signal value of setting, then counts a number.
10, as the antihunt means of clinac dosage measurement as described in the claim 9, it is characterized in that, described counting is, two input ends by comparer receive the output signal of dosage measurement and the reference signal value of setting respectively, output signal reaches the reference signal value of setting, then reverse signal of the output terminal of comparer output receives this reverse signal meter one number by single-chip microcomputer again;
The opposite voltage signal of voltage described and feedback capacity obtains by the following method
Every meter one number of single-chip microcomputer is to digital signal of digital to analog converter output, and digital to analog converter is converted to the voltage signal opposite with the voltage of feedback capacity with this digital signal, is zero thereby make the current potential of feedback capacity and amplifier link.
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| CN2009100592323A CN101551344B (en) | 2009-05-08 | 2009-05-08 | Highly stable dosage measurement circuit for medical linear accelerator and method |
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| CN2009100592323A CN101551344B (en) | 2009-05-08 | 2009-05-08 | Highly stable dosage measurement circuit for medical linear accelerator and method |
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101807506A (en) * | 2010-04-20 | 2010-08-18 | 江苏海明医疗器械有限公司 | Control method and system for electron gun to emit beams in medical linear accelerator |
| CN102866415A (en) * | 2012-07-24 | 2013-01-09 | 山东新华医疗器械股份有限公司 | Dose monitoring system of medical accelerator |
| CN103091693A (en) * | 2013-01-14 | 2013-05-08 | 中国科学院合肥物质科学研究院 | Medical linear accelerator stability judging method based on two-dimension plane dose |
| WO2017016469A1 (en) * | 2015-07-29 | 2017-02-02 | 武汉中派科技有限责任公司 | Photon measurement front-end circuit |
| CN114007293A (en) * | 2021-10-20 | 2022-02-01 | 成都利尼科医学技术发展有限公司 | Magnetron filament heating current control system |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2308109A1 (en) * | 1975-04-16 | 1976-11-12 | Cgr Mev | IMPROVEMENTS TO AN IRRADIATION DOSE MEASURING DEVICE USED IN RADIOTHERAPY EQUIPMENT |
| US6249565B1 (en) * | 1998-06-18 | 2001-06-19 | Siemens Medical Systems, Inc. | Fractional monitor unit radiation delivery control using dose rate modulation |
| CN1219220C (en) * | 2003-08-06 | 2005-09-14 | 南京大学 | Measuring method and device for electronic linear accelerator ray scanning characteristics |
| CN100483119C (en) * | 2004-09-14 | 2009-04-29 | 同方威视技术股份有限公司 | Method and its circuit for monitoring accelerator single pulse dose change |
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2009
- 2009-05-08 CN CN2009100592323A patent/CN101551344B/en active Active
Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101807506A (en) * | 2010-04-20 | 2010-08-18 | 江苏海明医疗器械有限公司 | Control method and system for electron gun to emit beams in medical linear accelerator |
| CN102866415A (en) * | 2012-07-24 | 2013-01-09 | 山东新华医疗器械股份有限公司 | Dose monitoring system of medical accelerator |
| CN102866415B (en) * | 2012-07-24 | 2015-04-08 | 山东新华医疗器械股份有限公司 | Dose monitoring system of medical accelerator |
| CN103091693A (en) * | 2013-01-14 | 2013-05-08 | 中国科学院合肥物质科学研究院 | Medical linear accelerator stability judging method based on two-dimension plane dose |
| CN103091693B (en) * | 2013-01-14 | 2017-02-08 | 中国科学院合肥物质科学研究院 | Medical linear accelerator stability judging method based on two-dimension plane dose |
| WO2017016469A1 (en) * | 2015-07-29 | 2017-02-02 | 武汉中派科技有限责任公司 | Photon measurement front-end circuit |
| US10809395B2 (en) | 2015-07-29 | 2020-10-20 | Wuhan Zhong Pai Technology Co., Ltd. | Photon measurement front-end circuit with integral module and a negative feedback module |
| CN114007293A (en) * | 2021-10-20 | 2022-02-01 | 成都利尼科医学技术发展有限公司 | Magnetron filament heating current control system |
| CN114007293B (en) * | 2021-10-20 | 2024-03-29 | 成都利尼科医学技术发展有限公司 | Magnetron filament heating current control system |
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