Method and System for Measuring Energy Response of Ionization Chamber Based on Single-Energy X-rays

Abstract

This invention discloses a method and system for measuring the energy response of an ionization chamber based on single-energy X-rays. The method involves aligning a single-energy X-ray device with a standard detector and setting it up, counting the single-energy peaks within a preset time period; obtaining the output of the single-energy X-ray device by combining the detection efficiency; keeping the settings unchanged, aligning the single-energy X-ray device with the ionization chamber under test, recording the initial charge value of the ionization chamber under test and the charge value after the single-energy X-ray device has been turned on for a preset time; calculating the accumulated charge; dividing the accumulated charge of the ionization chamber under test by the output of the single-energy X-ray device to obtain the current energy response; adjusting the output value, and repeating the aforementioned steps to obtain the energy response curve within a preset energy range. This method can quickly and accurately test the energy range and energy response of an ionization chamber, avoiding the shortcomings of standard sources due to limitations imposed by the radiation source itself and the environment, and the biases caused by Monte Carlo simulations due to the inability to obtain accurate detector parameters.

Description

Technical Field

[0001] This invention relates to the field of radiation imaging technology, and in particular to a method and system for measuring the energy response of an ionization chamber based on monoenergetic X-rays. Background Technology

[0002] X-rays are high-frequency, extremely short-wavelength, and high-energy electromagnetic waves, widely used in medical diagnosis, industrial non-destructive testing, and scientific research. Compared to continuous-spectrum X-rays of bremsstrahlung radiation, single-energy X-rays have unique advantages. Single-energy X-ray digital subtraction angiography, applied in medical diagnosis and industrial non-destructive testing, can produce clearer, more accurate, and higher-resolution images than continuous-spectrum X-rays. Single-energy X-ray radiation devices, as standard radiation sources, can be used to study the energy linearity, energy resolution, detection efficiency, and energy response matrix of various nuclear radiation detectors. Among these, energy response, as a crucial technical indicator for detectors, determines their measurement accuracy in practical applications. Energy response refers to the ratio between the measured value of radiation measured by the detector and the true value of radiation at a given energy photon radiation field. The true value of radiation can be calculated using the conversion coefficient from photon flux to the ambient dose equivalent.

[0003] Currently, there are two commonly used methods for measuring the energy response of ionization chambers. One is the standard source method, which uses radiation source standards such as 137Cs and 60Co to measure and record the current output of the detector when irradiated with different energies. The current value is then divided by the standard radiation dose value at the measurement point to obtain the response factor for different energies. The standard source method is relatively accurate and reliable. However, this method requires that the geometry, density, composition, measurement state, calculation method of the gamma peak area, and self-absorption effect of the standard source be basically consistent with the object being measured. In practical applications, the preparation and storage of calibration standard sources are difficult due to limitations such as the short half-life of the nuclide and the high requirement for uniformity of the standard source composition. Furthermore, they are easily affected by environmental factors and change with the environment. The other measurement method is the Monte Carlo simulation method, which can generate a radiation field simulating the radiation source and simulate the interaction process between radiation and the detector. By adjusting parameters such as radiation energy and detector characteristics, the detector's response at different energies can be obtained. While this method avoids the complex preparation and management of standard sources, has a wider applicability, a larger energy range, and stronger quantitative analysis capabilities, the parameters of the detector model are easily constrained by the manufacturer, making it impossible to obtain accurate and comprehensive detector parameters. This leads to significant differences between simulated and experimental values, necessitating corrections to parameters such as crystal size, aluminum layer, and crystal spacing. Furthermore, the physical processes simulated by Monte Carlo simulations only involve the interaction of photons and secondary electrons with matter, and the Monte Carlo program's handling of electron transport differs somewhat from reality. Therefore, simulation results will also differ from actual measurement results. Summary of the Invention

[0004] The technical problem to be solved by the present invention is that the existing detection technology is greatly affected by the environment and lacks accuracy.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0006] A method for measuring the energy response of an ionization chamber based on monoenergetic X-rays, comprising:

[0007] Align the single-energy X-ray device with the standard detector, set up the single-energy X-ray device, and detect the count I0 of the single-energy peaks within a preset time; divide I0 by the detection efficiency of the standard detector to obtain the output I1 of the single-energy X-ray device.

[0008] Keeping the single-energy X-ray device settings unchanged, aim the single-energy X-ray device at the ionization chamber device under test, and record the charge value Q0 of the ionization chamber device in the initial stage and the charge value Q1 after the single-energy X-ray device has been turned on for a preset time.

[0009] Calculate the cumulative charge Qs = Q1 - Q0 in the ionization chamber under test within a preset time.

[0010] Divide the accumulated charge Qs of the ionization chamber device under test by the output I1 of the single-energy X-ray device to obtain the current energy response;

[0011] Adjust the output value of the single-energy X-ray device and repeat all the aforementioned steps to obtain the energy response curve within the preset energy range.

[0012] On the other hand, the present invention also proposes an ionization chamber energy response measurement system based on monoenergetic X-rays, for performing the ionization chamber energy response measurement method based on monoenergetic X-rays as described above, comprising:

[0013] An electrometer for detecting charge values, a standard detector for detecting input single-energy peak counting, a single-energy X-ray device for emitting single-energy X-rays, an ionization chamber device to be tested, and an installation platform for installing positioning equipment.

[0014] The technical solution of this invention utilizes the advantages of single-energy X-ray devices, such as large flux, multiple energy points, good stability, and low manufacturing cost. It can quickly and accurately test the energy range and energy response of the ionization chamber, avoiding the disadvantages of standard sources due to limitations of the radiation source itself and the environment, as well as the deviations caused by Monte Carlo simulations due to the inability to obtain accurate detector parameters. Attached Figure Description

[0015] Figure 1 This is a flowchart of an embodiment of the ionization chamber energy response measurement method based on monoenergetic X-rays of the present invention;

[0016] Figure 2This is a flowchart of another embodiment of the ionization chamber energy response measurement method based on monoenergetic X-rays of the present invention. Detailed Implementation

[0017] To explain in detail the technical content, objectives, and effects of the present invention, the following description is provided in conjunction with the embodiments and accompanying drawings.

[0018] Please refer to Figure 1 A method for measuring the energy response of an ionization chamber based on monoenergetic X-rays, comprising:

[0019] S10: Align the single-energy X-ray device with the standard detector, set up the single-energy X-ray device, and detect the count value I0 of the single-energy peak within a preset time; divide I0 by the detection efficiency of the standard detector to obtain the output value I1 of the single-energy X-ray device.

[0020] In this embodiment, the crystal used in the single-energy X-ray device is LiF220 crystal, and the standard detector is a standard high-purity germanium detector. Of course, the crystal and standard detector can be selected from other sources, and are not limited to the description in this embodiment.

[0021] S20: Keep the single-energy X-ray device settings unchanged, point the single-energy X-ray device at the ionization chamber device under test, and record the charge value Q0 of the ionization chamber device under test in the initial stage and the charge value Q1 after the single-energy X-ray device is turned on for a preset time.

[0022] S30: Calculate the cumulative charge Q in the ionization chamber under test within a preset time. s =Q1-Q0;

[0023] S40: Divide the accumulated charge Qs of the ionization chamber device under test by the output I1 of the single-energy X-ray device to obtain the current energy response;

[0024] S50: Adjust the output value of the single-energy X-ray device according to the required energy range, and repeat the above steps S10 to S40 to obtain the energy response curve within the preset energy range.

[0025] Understandably, this scheme uses a single-energy X-ray device and a standard high-purity germanium detector for measurement, which can obtain an accurate and stable count I0 for the energy point range. The count I1 obtained can be the true value of the radiation at that energy point and can be used to calculate the energy response.

[0026] To make the measurement more accurate and eliminate the influence of changes in air pressure and temperature, the energy response measurement method in this embodiment also includes the following steps:

[0027] The temperature and pressure of the current experimental environment are detected, and a temperature and pressure correction factor is calculated to correct the data to the standard temperature and pressure environment. The temperature and pressure correction factor is used to correct the error caused by temperature and pressure on the accumulated charge.

[0028] Furthermore, the formula for calculating the temperature and pressure correction factor NT is as follows:

[0029]

[0030] Where P0 is the standard atmospheric pressure and T0 is the standard temperature;

[0031] The temperature and pressure correction factor NT is multiplied by the accumulated charge Qs to correct the effect of temperature T and pressure P on the accumulated charge Q. s The resulting error.

[0032] In this embodiment, in order to eliminate the error caused by natural leakage current of the ionization chamber device under test and improve the detection accuracy, the energy response measurement method further includes the following steps:

[0033] The average leakage charge Q of the ionization chamber device under test is detected within a preset time. L ;

[0034] Calculate the cumulative charge Q in the ionization chamber under test within a preset time. s *=Q1-Q0-Q L .

[0035] Building upon this, the process of setting up a single-energy X-ray device further includes:

[0036] Install the crystal, adjust the crystal rotation platform to the angle position required for the energy, adjust the tube voltage and current according to the required energy, and record the angle, voltage and current;

[0037] The corresponding monoenergetic X-ray peak can be viewed using the connected software.

[0038] This invention also proposes a single-energy X-ray-based ionization chamber energy response measurement system for performing the above-described single-energy X-ray-based ionization chamber energy response measurement method, comprising:

[0039] An electrometer for detecting charge values, a standard detector for detecting input single-energy peak counting, a single-energy X-ray device for emitting single-energy X-rays, an ionization chamber device to be tested, and an installation platform for installing positioning equipment.

[0040] In this embodiment, the single-energy X-ray device uses a LiF220 crystal, the standard detector uses a standard high-purity germanium detector, and the electrometer uses a model 6517B electrometer. Of course, other equipment can be selected, and they are not limited to the description in this embodiment.

[0041] Based on this embodiment, in order to correct the error caused by the thermometer pressure, the energy response measurement system also includes: a thermometer for detecting the temperature of the experimental environment and a barometer for detecting the pressure of the experimental environment.

[0042] In another embodiment of the invention, refer to the appendix. Figure 2 As shown, the ionization chamber energy response measurement method includes the following steps:

[0043] Step 1: According to the ionization chamber structure provided by the manufacturer, use a banana wire to connect its positive and negative terminals and the signal ground wire, and connect the other end to the electrometer 6517B.

[0044] Step 2: Set the electrometer 6517B as a power source and switch it to charge measurement mode.

[0045] Step 3: Using a standard high-purity germanium detector, place it on the experimental platform, adjust the platform height so that the high-purity germanium probe is horizontally aligned with the light-emitting collimating tube opening, and check the control software to record the current coordinate position P1.

[0046] Step 4: Place the ionization chamber to be tested on the same experimental platform as the high-purity germanium, adjust the platform height so that the ionization chamber to be tested is horizontally aligned with the light-emitting collimating tube opening, and check the control software to record the current coordinate position P2.

[0047] Step 5: Install the LiF220 crystal on the crystal rotation platform of the single-energy X-ray device.

[0048] Step 6: Fix the induction probes of the thermometer, hygrometer, and barometer to the experimental platform for easy observation and recording of their readings during the experiment. During the process, corrections need to be made to the ionization current; the temperature is corrected to 20℃, and the air pressure to 101.325 kPa. Based on the thermometer and barometer readings: temperature T, humidity, and air pressure P, the temperature and pressure correction factor formula is used:

[0049]

[0050] The temperature and pressure correction factor N was obtained. T .

[0051] Step 7: After the ionization chamber under test stabilizes, time for 60 seconds and measure its leakage charge. A total of 3 sets of data were measured, and the average leakage charge Q was calculated. L .

[0052] Step 8: Adjust the platform position to coordinate P1. At this point, the light output port should be aligned with the high-purity germanium detector. After turning on the equipment, adjust the crystal rotation platform to the angle position required for the energy. Adjust the tube voltage and current according to the theoretical energy corresponding to this angle, and record the angle, voltage, and current. The monoenergetic X-ray peak corresponding to this angle can be seen on the software of the high-purity germanium detector. If there is still a deviation, the rotation of the crystal platform can be controlled and adjusted. Set the high-purity germanium detector to a 60-second timer and record the count I0 of the monoenergetic peak within 60 seconds.

[0053] Step 9: Adjust the platform position to coordinate P2. At this time, it should be aligned with the ionization chamber to be tested. Since the angle and tube voltage and current were fixed in step 8, the X-ray energy should be the same as that in step 8. After the platform moves to the target position and stabilizes, time it for 60 seconds and record the charge value Q0 at 0 seconds and the instantaneous charge value Q1 at 60 seconds.

[0054] Step 10, use Q1-Q0-Q L The accumulated charge Qs over 60s is obtained.

[0055] Step 11, use the temperature and pressure correction factor N obtained in step 6. T Multiplying by the accumulated charge Qs yields the corrected charge Q. T .

[0056] Step 12: Based on the detection efficiency of the standard high-purity germanium detector, divide I0 by the detection efficiency of its corresponding energy to obtain I1, which is the theoretical high-purity germanium count.

[0057] Step 13, according to the formula, the energy response value is equal to:

[0058]

[0059] Obtain the energy response at this energy point.

[0060] Repeat steps 8 to 13 to obtain the energy response curve for the desired energy range.

[0061] In summary, the technical solution of this invention utilizes the advantages of a single-energy X-ray device, such as large flux, multiple energy points, good stability, and low manufacturing cost, enabling rapid and accurate testing of the energy range and energy response of the ionization chamber under test. It effectively avoids the limitations of standard sources due to the radiation source itself and the environment, and avoids the biases caused by the inability to obtain accurate detector parameters in Monte Carlo simulations.

[0062] The above are merely embodiments of the present invention and do not limit the patent scope of the present invention. Any equivalent modifications made based on the content of the present invention's specification and drawings, or direct or indirect applications in related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method of ionization chamber energy response measurement based on monoenergetic X-rays, characterized by, Comprising: S1: aligning the monochromatic X-ray device to the standard detector, setting the monochromatic X-ray device, detecting the count of the monochromatic peak within a preset time; calculating the output of the monochromatic X-ray device from the count and the detection efficiency of the standard detector; S2: keeping the monochromatic X-ray device setting unchanged, aligning the monochromatic X-ray device to the ionization chamber device to be measured, recording the initial stage charge of the ionization chamber device to be measured and the charge after the monochromatic X-ray device is turned on for a preset time; S3: calculating the cumulative charge of the ionization chamber to be measured within a preset time; S4: dividing the cumulative charge of the ionization chamber device to be measured by the output of the monochromatic X-ray device to obtain the current energy response; S5: adjusting the output value of the monochromatic X-ray device, repeating all the above steps to obtain the energy response curve within a preset energy range; Further comprising steps: detecting the temperature and air pressure of the current experimental environment, obtaining a temperature and air pressure correction factor by temperature and air pressure calculation, correcting the data to the standard temperature and air pressure environment, and then using the temperature and air pressure correction factor to correct the error caused by temperature and air pressure to the cumulative charge; Temperature and pressure correction factors used The formula for calculating the temperature and pressure correction factors is: where, P is the standard pressure, T is the standard temperature; Temperature and pressure correction factor is multiplied by the accumulated charge to correct the error caused by temperature T and pressure P. Further comprising steps: Detecting leakage charge Q of ionization chamber device within preset time L ; Calculating the accumulated charge Q of the ionization chamber under test in a preset time s = Q1 - Q0 - Q L ; Q0 is the charge value at the initial stage, Q1 is the charge value after the single-energy X-ray device is turned on for a preset time, Q s is the accumulated charge.

2. The method of ionization chamber energy response measurement based on monoenergetic X-rays according to claim 1, characterized in that, The process of setting the monochromatic X-ray device includes: installing the crystal, adjusting the crystal rotation platform to the angle position of the required energy, adjusting the tube voltage and current according to the required energy, and recording the angle, voltage and current.

3. The method of ionization chamber energy response measurement based on monoenergetic X-rays according to claim 1, characterized in that, The crystal used by the monochromatic X-ray device is LiF220.

4. The method of ionization chamber energy response measurement based on monoenergetic X-rays according to claim 1, characterized in that, The standard detector uses a standard high-purity germanium detector.

5. A system for measuring the energy response of an ionization chamber based on monoenergetic X-rays, characterized in that, For performing the monochromatic X-ray based ionization chamber energy response measurement method as claimed in any one of claims 1 to 4, comprising: an electrometer for detecting the charge value, a standard detector for detecting the input monochromatic peak count, a monochromatic X-ray device for emitting monochromatic X-rays, an ionization chamber device to be measured, and a mounting platform for mounting and positioning the device.

6. The single-energy X-ray based ionization chamber energy response measurement system of claim 5, wherein, Further comprising: a thermometer for detecting the temperature of the experimental environment and an air pressure gauge for detecting the air pressure of the experimental environment.

7. The single-energy X-ray based ionization chamber energy response measurement system of claim 5, wherein, The monochromatic X-ray device uses LiF220 crystal, the standard detector uses a standard high-purity germanium detector, and the electrometer uses a model 6517B electrometer.

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