GBZ 126-2002 Health protection standard for medical electron accelerators
Some standard content:
Ics13.100
National occupational health standard of the People's Republic of China GBZ126-2002
Radiological protection standard for using of medical electron acceleratorPromulgated on April 8, 2002
Ministry of Health of the People's Republic of China
Implementation on June 1, 2002
Normative reference documents
Technical requirements for accelerators
Protection requirements for treatment rooms
Safety operation requirements
Protection monitoring requirements
(Informative Appendix)
Appendix A
Test methods
Appendix B
Acceptance rules (Informative Appendix)
This standard is formulated in accordance with the Law of the People's Republic of China on the Prevention and Treatment of Occupational Diseases. In case of any inconsistency between the original standard GB16369-1996 and this standard, this standard shall prevail. Chapters 3 to 6 of this standard are mandatory contents, and the rest are recommended contents. Appendix A and Appendix B of this standard are informative appendices. This standard is proposed and managed by the Ministry of Health.
The drafting units of this standard are: Shanghai Institute of Radiological Medicine, Shanghai Health and Epidemic Prevention Station, Shanghai Cancer Hospital, Shanghai Medical Nuclear Instrument Factory.
The main drafters of this standard are: Qian Zhilin, Cong Shuyue, Mou Canxing, Sun Zhenxiong, Zhong Bainiu. This standard is interpreted by the Ministry of Health.
GBZ126-2002
1 Scope
Health Protection Standard for Medical Electron Accelerators
This standard specifies the protection requirements for medical electron accelerators (hereinafter referred to as accelerators) when they are used for human treatment. This standard applies to the production and use of accelerators with an energy below 50MeV. 2 Normative References
The clauses in the following documents become the clauses of this standard through reference in this standard. For any dated referenced document, all subsequent amendments (excluding errata) or revisions are not applicable to this standard. However, parties reaching an agreement based on this standard are encouraged to study whether the latest versions of these documents can be used. For any undated referenced document, the latest version applies to this standard.
GBZ128 Occupational external radiation personal monitoring specification GB9706.5 Special safety requirements for medical electron accelerators with energy of 1~50MeV GB15213 Performance and test methods of medical electron accelerators 3 Accelerator technical requirements
3.1 Accelerator radiation safety, electrical and mechanical safety technical requirements Accelerator radiation safety, electrical and mechanical safety technical requirements and test methods must comply with the relevant provisions of GB9706.5. 3.2 Requirements to prevent overdose exposure
3.2.1 The control console must display the pre-selected values of radiation parameters such as radiation type, nominal energy, irradiation time, absorbed dose, absorbed dose rate, treatment method, model filter type and specifications. 3.2.2 The start of irradiation must be interlocked with the pre-selected values of irradiation parameters displayed on the control console. Before the control console selects various irradiation parameters, irradiation shall not be started.
3.2.3 Two independent dose monitoring systems must be equipped. Each dose monitoring system must be able to terminate irradiation independently. The failure of one dose monitoring system shall not affect the function of the other system. 3.2:4 The dose readings displayed by the two dose monitoring systems must remain unchanged after the irradiation is interrupted or terminated. After the irradiation is interrupted or terminated, the display must be reset to zero before the next irradiation can be started. If the irradiation is interrupted or terminated due to component or power failure, the reading display at the time of failure must be stored in a system and retained in a readable manner for at least 20 minutes. 3.2.5 When the two-channel dose monitoring system is a dual combination, when the absorbed dose reaches the preselected value, both systems must terminate the irradiation.
3.2.6 When the two-channel dose monitoring system is a primary/secondary combination, when the absorbed dose reaches the preselected value, the primary dose monitoring system must terminate the irradiation, and the secondary monitoring system must terminate the irradiation when it exceeds the preselected absorbed dose by no more than 15% or does not exceed the absorbed dose equivalent to 0.4Gy at the normal treatment distance. 3,2:7 The control console must be equipped with an irradiation control timer with a time display and be independent of any other control irradiation termination system. When the irradiation is interrupted or terminated, the timer reading must be retained, and the timer must be reset to zero before the next irradiation can be started.
3.2,8 If the equipment is in a state that can produce an absorbed dose rate higher than twice the specified maximum value at the normal treatment distance, an interlock device must be provided to terminate the irradiation when the absorbed dose rate exceeds the specified maximum value by no more than twice. In any case, this interlock device shall not be cut off. 3.2.9 Dose distribution monitoring devices must be provided for non-straight beam accelerators. When the relative deviation of the absorbed dose distribution exceeds 4
10%, irradiation shall be terminated.
3.2.10 Facilities for checking all safety interlocks must be equipped to check the safety interlocks (including interlocks that prevent the dose rate from being greater than ten times the pre-selected value) during the irradiation interval to ensure the ability of various systems to terminate the correct irradiation and prevent overdose. 3.2.11 Emergency stop switches must be installed in the control console and treatment room respectively. 3.2.12 The software and hardware control programs of accelerators using computer control systems must be encrypted and shall not be accessed or modified without permission; once a computer used to monitor interlocks or as part of the measurement circuit or control circuit fails, irradiation must be terminated.
3.3 Limits on stray radiation in the useful beam
3.3.1 The X-ray share during electron beam therapy shall not exceed the requirements of Table 1. Table 1
Electron beam energy E, MeV
Ratio of absorbed dose at 10 cm outside the actual range on the electron beam center axis to the maximum absorbed dose, %<1515~35
3.3.2 During X-ray therapy, under the maximum irradiation field, the absorbed dose on the center axis surface shall not exceed the requirements of Table 2. Table 2
Maximum X-ray energy E, MeV
Ratio of absorbed dose on the surface to the maximum absorbed dose, %3.4 Limitation of radiation leakage outside the useful beam
3.4.1 At the normal treatment distance, within the cross section of the fixed beam limiter, the ratio of the absorbed dose of radiation leakage through the adjustable beam limiter to the maximum absorbed dose on the center axis of the useful beam shall meet the following limits. 3.4.1.1 During X-ray therapy, it shall not exceed 2% within the irradiation field of 10 cm×10 cm3.4.1.2 During electron beam therapy, it shall not exceed 2% on average within the range from 4 cm outside the 50% isodose curve to the edge of the maximum useful beam.
3.4.1.3 During electron beam therapy, the maximum radiation dose in the range from 2 cm outside the 50% isodose curve to the edge of the maximum useful beam shall not exceed 10%.
3.4.2 Limits for radiation leakage outside the maximum useful beam (excluding neutrons). 3.4.2.1 At the normal treatment distance, the radiation leakage on the circular plane with a radius of 2 m perpendicular to the central axis of the useful beam and with the axis as the center shall not exceed 0.2% (maximum) and (average) of the absorbed dose of the central axis of the useful beam. 3.4.2.2 The radiation leakage at 1 m from the electron track shall not exceed 0.5% of the absorbed dose of the central axis of the useful beam at the normal treatment distance.
3.4.3 Neutron leakage radiation outside the maximum useful beam. 3.4.3.1. For accelerators with a nominal X-ray energy greater than 10 MeV, the neutron leakage radiation outside the maximum useful beam shall not exceed 0.05% (maximum) and 0.02% (average) of the absorbed dose in the central axis of the useful beam within the area specified in 3.4.2.1. 3.4.3.2 The neutron leakage radiation at 1m from the electron track shall not exceed 0.05% of the absorbed dose in the central axis of the useful beam at the normal treatment distance.
3.5 For indicators such as stability, isocenter, uniformity of the irradiation field, and boundary deviation between the light field and the irradiation field and their test methods, please refer to GB15213.
3.6 Limit of induced radioactivity
For accelerators with a nominal X-ray energy greater than 10 MeV, the absorbed dose rate caused by induced radioactivity at 5cm and 1m from the surface of the equipment shall not exceed 0.2mGy·h and 0.02mGy·h respectively. 4 Treatment room protection requirements
4.1 The site selection and architectural design of the treatment room must comply with the relevant radiation health protection regulations and standards to ensure the safety of the surrounding environment.
4.2 The protective walls (including ceilings) directly projected by the useful beam shall be designed according to the primary radiation shielding requirements, and the remaining walls shall be designed according to the secondary radiation shielding requirements.
4.3 Wires, conduits, etc. passing through the protective wall shall not affect its shielding protection effect. 4.4 For accelerators with a nominal X-ray energy exceeding 10MeV, the shielding design shall take neutron radiation protection into consideration. 4.5 Monitoring and intercom equipment must be installed between the treatment room and the control room. 4.6 The treatment room should have sufficient usable area. 4.7 A protective door and a maze must be installed at the entrance of the treatment room, and the protective door must be interlocked with the accelerator. 4.8 Irradiation indicator lights and radiation hazard signs must be installed in a conspicuous place outside the treatment room. 4.9 The ventilation frequency of the treatment room should reach 3 to 4 times per hour. 5 Safety operation requirements
The accelerator user unit must be equipped with dose measurement equipment such as working dosimeters and water tanks, and should be equipped with radiotherapy quality assurance equipment such as scanners and simulation positioning machines. 5.2 The user unit must have qualified radiotherapy doctors, physical personnel and operating technicians; operating technicians must undergo occupational health training on radiation health protection and accelerator professional knowledge, and can only take up their posts after passing the assessment. 5,3 Operators must abide by various operating procedures, carefully check safety interlocks, and it is prohibited to remove safety interlocks at will. It is strictly forbidden to start the machine when the safety interlocks that may cause casualties are removed. 5.4 During the irradiation period, there must be two operators on duty, who must carefully keep records of their shifts and strictly implement the handover system. 5.5 Operators are strictly prohibited from leaving their posts without authorization. They must closely monitor the console instruments and the patient's condition and deal with abnormalities in a timely manner.
During the irradiation period, no other personnel shall be allowed in the treatment room except the patients receiving treatment. 5.6
5.7 All kinds of accidents must be prevented. In case of an accident, irradiation must be stopped immediately, the patient must be removed from the radiation field in a timely manner, and the site must be protected to facilitate the correct estimation of the patient's radiation dose and make a reasonable evaluation. 6 Protection Monitoring
6.1 Before the accelerator is installed and put into operation, or when the operating parameters and shielding conditions change, the provincial radiation health protection supervision and monitoring department must conduct comprehensive protection monitoring and radiation safety evaluation of the relevant areas. 6.2 Under normal operation, the radiation level in the workplace and surrounding areas shall be monitored once a year: the safety interlock system shall be checked once a month.
6.3 The operator's personal dose monitoring shall be carried out in accordance with GZB128. 6.4: The calibration of the accelerator dose monitoring system shall be monitored once a week, and the percentage depth dose and uniformity shall be monitored once every six months. 6.5 All monitoring data must be recorded in detail, kept well, and filed for record. 6
Appendix A
(Informative Appendix)
Test method
A1 The total uncertainty of useful beam measurement shall be less than 5%, and the total uncertainty of protection monitoring shall be less than 30%. A2 Test of stray radiation within useful beam
A2.1 Basic test conditions
A2.1.1 The side length of the incident surface of the test phantom (such as a water tank) shall be at least 5 cm longer than the side length of the irradiation field, and its depth shall be at least 5 cm larger than the measurement requirement.
A2.1.2 The underwater correction depths for measuring X-rays and electron beams of various energies are as follows: Table A1
Radiation type
X-ray
Electron beam
Nominal energy, MeV
A2.2 Correction depth for X-ray share test during electron beam therapy, cm
The incident surface of the phantom is placed at the normal treatment distance, perpendicular to the central axis of the useful beam, and the irradiation field size is limited by the beam limiting device. The detector is placed 10 cm outside the actual range on the central axis of the electron beam inside the phantom, and the ratio of the absorbed dose to the maximum absorbed dose is measured.
A2.3 X-ray surface absorbed dose test
During X-ray treatment, the phantom surface is located at the normal treatment distance. Use 30cmX30cm or the actual maximum irradiation field (if the maximum irradiation field is less than 30cm×30cm) to measure the ratio of the absorbed dose extrapolated to the surface (minimum 0.5mm) on the beam axis to the maximum absorbed dose. All instruments should allow extrapolation to the surface absorbed dose. During the test, all beam limiters that can be removed without tools (except the field equalizer) must be removed from under the beam. A3 Useful beam leakage radiation test
A3.1 Leakage radiation test through beam limiter A3.1.1 During X-ray treatment, the beam limiter should be closed to the minimum position, and the remaining gaps should be weakened by at least two 1/10 layers of absorbing materials. The center of the detector with a maximum cross-section of no more than 1cm2 is located at the normal treatment distance and the maximum absorbed dose depth in the phantom for testing. When using overlapping beam limiters, the leakage radiation of each group of beam limiters must be tested separately. A3.12 During electron beam therapy, at the maximum nominal energy, use the light-limiting tubes of the minimum and maximum irradiation fields (the maximum irradiation field should be at least 12 cm smaller than the existing maximum geometric field) to perform film and detector measurements in turn. First, analyze the film measurements to find the maximum leakage radiation point in the area between 2 cm outside the 50% isodose line and the edge of the maximum irradiation field shielded by the beam-limiting device. Use the corresponding light-limiting tube to perform detector measurements at the maximum leakage radiation point to verify whether the maximum leakage radiation meets the 10% limit. Perform detector measurements along the X-axis and Y-axis of the irradiation field from 4 cm outside the 50% isodose line to the edge of the maximum irradiation field shielded by the beam limiter. Take the average value from these four sets of measurements to verify whether the average leakage radiation meets the 2% limit. A3.2 Maximum useful beam leakage radiation test: The adjustable beam limiter is fully closed, and the maximum useful beam cross-section is attenuated with three 1/10 layers of absorbing material. Find the high leakage radiation points from the film measurement for detector measurement. Use 8MeV nominal energy X-rays or maximum nominal energy electron beams. Measure and calculate the average leakage radiation at 16 points as shown in Figure A1 at each nominal energy. 7
Radiation source
Beam limiting device
Circle with radius R
Radius R+3/4·(2-R)m
Circle with radius 2m
Normal treatment distance
Radius R+1/4·(2-R)m）
Maximum square field size
@ is the measurement point
Figure A1 Average leakage radiation Distribution of 16 measurement points A3.3 For all X-rays of nominal energy, use film to find the maximum leakage radiation point, and use detectors to measure at these points to determine whether they meet the requirements of Article 3.4.2.2. A3.4 For neutron leakage radiation test, the X-ray takes the maximum nominal energy, and at the normal treatment distance, take the maximum square edge 20cm and 100cm from the central axis along each main axis of the irradiation field as shown in Figure A2 for measurement. Neutron pulse characteristics, neutron energy spectrum, leaked X-rays and indoor neutron radiation should be considered in the measurement. A4 Absorption dose rate test of induced radioactivity is performed on equipment with X-ray nominal energy greater than 10MeV. It is continuously operated for 4 hours at a cycle of 4Gy radiation every 10 minutes. The measurement is made within 5 minutes after the irradiation is terminated 10 seconds later. The X-ray and electron beam with the maximum nominal energy are used for measurement. The irradiation field or light-limiting tube is 10cm×10cm.
J Machine Vacuum Pump
E Flow Meter
Oil-free Vacuum Valve
Liquid Radium Source Container
(Diffusion Bottle)
1 Scintillation Bottle
Oil-free Vacuum Valve
Oil-free Vacuum Valve-
Desiccant
Oil-free Vacuum Valve
Figure 2 Schematic Diagram of Glass Scale System
Mercury Pressure Gauge
Figure A2 Distribution of Neutron Leakage Radiation Measurement Points
Appendix B
(Informative Appendix)
Acceptance Rules
B1 Whether the protection performance of the accelerator meets the requirements of this standard shall be inspected and qualified by the technical inspection department of the production unit before the relevant departments can accept it.
B2 The accelerator shall be tested and inspected according to the items specified in this standard before leaving the factory. B3 inspection and acceptance may be conducted in conjunction with the local radiation health and protection department, and the inspection results shall be submitted to the local radiation health and protection department for filing.6
5.7 All kinds of accidents must be prevented. In case of an accident, irradiation must be stopped immediately, the patient must be removed from the radiation field in time, and the site must be protected to facilitate the correct estimation of the patient's radiation dose and make a reasonable evaluation. 6 Protection Monitoring
6.1 Before the accelerator is installed and put into operation, or when the operating parameters and shielding conditions change, the provincial radiation health protection supervision and monitoring department must conduct comprehensive protection monitoring and radiation safety evaluation of the relevant areas. 6.2 Under normal operation, the radiation level in the workplace and surrounding areas is monitored once a year: the safety interlock system is checked once a month.
6.3 The operator's personal dose monitoring is carried out in accordance with GZB128. 6.4: The accelerator dose monitoring system calibration is monitored once a week, and the percentage depth dose and uniformity are monitored every six months. 6.5 All monitoring data must be recorded in detail, kept well, and filed for record. 6
Appendix A
(Informative Appendix)
Test Method
A1 The total uncertainty of useful beam measurement should be less than 5%, and the total uncertainty of protection monitoring should be less than 30%. A2 Test of stray radiation in useful beam
A2.1 Basic test conditions
A2.1.1 The side length of the incident surface of the test phantom (such as a water tank) should be at least 5 cm longer than the side length of the irradiation field, and its depth should be at least 5 cm greater than the measurement requirement.
A2.1.2 The underwater correction depths for measuring X-rays and electron beams of various energies are as follows: Table A1
Radiation type
X-ray
Electron beam
Nominal energy, MeV
A2.2 Correction depth for X-ray share test during electron beam therapy, cm
The incident surface of the phantom is placed at the normal treatment distance, perpendicular to the central axis of the useful beam, and the irradiation field size is limited by the beam limiting device. The detector is placed 10 cm outside the actual range on the central axis of the electron beam inside the phantom, and the ratio of the absorbed dose to the maximum absorbed dose is measured.
A2.3 X-ray surface absorbed dose test
During X-ray treatment, the phantom surface is located at the normal treatment distance. Use 30cmX30cm or the actual maximum irradiation field (if the maximum irradiation field is less than 30cm×30cm) to measure the ratio of the absorbed dose extrapolated to the surface (minimum 0.5mm) on the beam axis to the maximum absorbed dose. All instruments should allow extrapolation to the surface absorbed dose. During the test, all beam limiters that can be removed without tools (except the field equalizer) must be removed from under the beam. A3 Useful beam leakage radiation test
A3.1 Leakage radiation test through beam limiter A3.1.1 During X-ray treatment, the beam limiter should be closed to the minimum position, and the remaining gaps should be weakened by at least two 1/10 layers of absorbing materials. The center of the detector with a maximum cross-section of no more than 1cm2 is located at the normal treatment distance and the maximum absorbed dose depth in the phantom for testing. When using overlapping beam limiters, the leakage radiation of each group of beam limiters must be tested separately. A3.12 During electron beam therapy, at the maximum nominal energy, use the light-limiting tubes of the minimum and maximum irradiation fields (the maximum irradiation field should be at least 12 cm smaller than the existing maximum geometric field) to perform film and detector measurements in turn. First, analyze the film measurements to find the maximum leakage radiation point in the area between 2 cm outside the 50% isodose line and the edge of the maximum irradiation field shielded by the beam-limiting device. Use the corresponding light-limiting tube to perform detector measurements at the maximum leakage radiation point to verify whether the maximum leakage radiation meets the 10% limit. Perform detector measurements along the X-axis and Y-axis of the irradiation field from 4 cm outside the 50% isodose line to the edge of the maximum irradiation field shielded by the beam limiter. Take the average value from these four sets of measurements to verify whether the average leakage radiation meets the 2% limit. A3.2 Maximum useful beam leakage radiation test: The adjustable beam limiter is fully closed, and the maximum useful beam cross-section is attenuated with three 1/10 layers of absorbing material. Find the high leakage radiation points from the film measurement for detector measurement. Use 8MeV nominal energy X-rays or maximum nominal energy electron beams. Measure and calculate the average leakage radiation at 16 points as shown in Figure A1 at each nominal energy. 7
Radiation source
Beam limiting device
Circle with radius R
Radius R+3/4·(2-R)m
Circle with radius 2m
Normal treatment distance
Radius R+1/4·(2-R)m）
Maximum square field size
@ is the measurement point
Figure A1 Average leakage radiation Distribution of 16 measurement points A3.3 For all X-rays of nominal energy, use film to find the maximum leakage radiation point, and use detectors to measure at these points to determine whether they meet the requirements of Article 3.4.2.2. A3.4 For neutron leakage radiation test, the X-ray takes the maximum nominal energy, and at the normal treatment distance, take the maximum square edge 20cm and 100cm from the central axis along each main axis of the irradiation field as shown in Figure A2 for measurement. Neutron pulse characteristics, neutron energy spectrum, leaked X-rays and indoor neutron radiation should be considered in the measurement. A4 Absorption dose rate test of induced radioactivity is performed on equipment with X-ray nominal energy greater than 10MeV. It is continuously operated for 4 hours at a cycle of 4Gy radiation every 10 minutes. The measurement is made within 5 minutes after the irradiation is terminated 10 seconds later. The X-ray and electron beam with the maximum nominal energy are used for measurement. The irradiation field or light-limiting tube is 10cm×10cm.
J Machine Vacuum Pump
E Flow Meter
Oil-free Vacuum Valve
Liquid Radium Source Container
(Diffusion Bottle)
1 Scintillation Bottle
Oil-free Vacuum Valve
Oil-free Vacuum Valve-
Desiccant
Oil-free Vacuum Valve
Figure 2 Schematic Diagram of Glass Scale System
Mercury Pressure Gauge
Figure A2 Distribution of Neutron Leakage Radiation Measurement Points
Appendix B
(Informative Appendix)
Acceptance Rules
B1 Whether the protection performance of the accelerator meets the requirements of this standard shall be inspected and qualified by the technical inspection department of the production unit before the relevant departments can accept it.
B2 The accelerator shall be tested and inspected according to the items specified in this standard before leaving the factory. B3 inspection and acceptance may be conducted in conjunction with the local radiation health and protection department, and the inspection results shall be submitted to the local radiation health and protection department for filing.6
5.7 All kinds of accidents must be prevented. In case of an accident, irradiation must be stopped immediately, the patient must be removed from the radiation field in time, and the site must be protected to facilitate the correct estimation of the patient's radiation dose and make a reasonable evaluation. 6 Protection Monitoring
6.1 Before the accelerator is installed and put into operation, or when the operating parameters and shielding conditions change, the provincial radiation health protection supervision and monitoring department must conduct comprehensive protection monitoring and radiation safety evaluation of the relevant areas. 6.2 Under normal operation, the radiation level in the workplace and surrounding areas is monitored once a year: the safety interlock system is checked once a month.
6.3 The operator's personal dose monitoring is carried out in accordance with GZB128. 6.4: The accelerator dose monitoring system calibration is monitored once a week, and the percentage depth dose and uniformity are monitored every six months. 6.5 All monitoring data must be recorded in detail, kept well, and filed for record. 6
Appendix A
(Informative Appendix)
Test Method
A1 The total uncertainty of useful beam measurement should be less than 5%, and the total uncertainty of protection monitoring should be less than 30%. A2 Test of stray radiation in useful beam
A2.1 Basic test conditions
A2.1.1 The side length of the incident surface of the test phantom (such as a water tank) should be at least 5 cm longer than the side length of the irradiation field, and its depth should be at least 5 cm greater than the measurement requirement.
A2.1.2 The underwater correction depths for measuring X-rays and electron beams of various energies are as follows: Table A1
Radiation type
X-ray
Electron beam
Nominal energy, MeV
A2.2 Correction depth for X-ray share test during electron beam therapy, cm
The incident surface of the phantom is placed at the normal treatment distance, perpendicular to the central axis of the useful beam, and the irradiation field size is limited by the beam limiting device. The detector is placed 10 cm outside the actual range on the central axis of the electron beam inside the phantom, and the ratio of the absorbed dose to the maximum absorbed dose is measured.
A2.3 X-ray surface absorbed dose test
During X-ray treatment, the phantom surface is located at the normal treatment distance. Use 30cmX30cm or the actual maximum irradiation field (if the maximum irradiation field is less than 30cm×30cm) to measure the ratio of the absorbed dose extrapolated to the surface (minimum 0.5mm) on the beam axis to the maximum absorbed dose. All instruments should allow extrapolation to the surface absorbed dose. During the test, all beam limiters that can be removed without tools (except the field equalizer) must be removed from under the beam. A3 Useful beam leakage radiation test
A3.1 Leakage radiation test through beam limiter A3.1.1 During X-ray treatment, the beam limiter should be closed to the minimum position, and the remaining gaps should be weakened by at least two 1/10 layers of absorbing materials. The center of the detector with a maximum cross-section of no more than 1cm2 is located at the normal treatment distance and the maximum absorbed dose depth in the phantom for testing. When using overlapping beam limiters, the leakage radiation of each group of beam limiters must be tested separately. A3.12 During electron beam therapy, at the maximum nominal energy, use the light-limiting tubes of the minimum and maximum irradiation fields (the maximum irradiation field should be at least 12 cm smaller than the existing maximum geometric field) to perform film and detector measurements in turn. First, analyze the film measurements to find the maximum leakage radiation point in the area between 2 cm outside the 50% isodose line and the edge of the maximum irradiation field shielded by the beam-limiting device. Use the corresponding light-limiting tube to perform detector measurements at the maximum leakage radiation point to verify whether the maximum leakage radiation meets the 10% limit. Perform detector measurements along the X-axis and Y-axis of the irradiation field from 4 cm outside the 50% isodose line to the edge of the maximum irradiation field shielded by the beam limiter. Take the average value from these four sets of measurements to verify whether the average leakage radiation meets the 2% limit. A3.2 Maximum useful beam leakage radiation test: The adjustable beam limiter is fully closed, and the maximum useful beam cross-section is attenuated with three 1/10 layers of absorbing material. Find the high leakage radiation points from the film measurement for detector measurement. Use 8MeV nominal energy X-rays or maximum nominal energy electron beams. Measure and calculate the average leakage radiation at 16 points as shown in Figure A1 at each nominal energy. 7
Radiation source
Beam limiting device
Circle with radius R
Radius R+3/4·(2-R)mwww.bzxz.net
Circle with radius 2m
Normal treatment distance
Radius R+1/4·(2-R)m）
Maximum square field size
@ is the measurement point
Figure A1 Average leakage radiation Distribution of 16 measurement points A3.3 For all X-rays of nominal energy, use film to find the maximum leakage radiation point, and use detectors to measure at these points to determine whether they meet the requirements of Article 3.4.2.2. A3.4 For neutron leakage radiation test, the X-ray takes the maximum nominal energy, and at the normal treatment distance, take the maximum square edge 20cm and 100cm from the central axis along each main axis of the irradiation field as shown in Figure A2 for measurement. Neutron pulse characteristics, neutron energy spectrum, leaked X-rays and indoor neutron radiation should be considered in the measurement. A4 Absorption dose rate test of induced radioactivity is performed on equipment with X-ray nominal energy greater than 10MeV. It is continuously operated for 4 hours at a cycle of 4Gy radiation every 10 minutes. The measurement is made within 5 minutes after the irradiation is terminated 10 seconds later. The X-ray and electron beam with the maximum nominal energy are used for measurement. The irradiation field or light-limiting tube is 10cm×10cm.
J Machine Vacuum Pump
E Flow Meter
Oil-free Vacuum Valve
Liquid Radium Source Container
(Diffusion Bottle)
1 Scintillation Bottle
Oil-free Vacuum Valve
Oil-free Vacuum Valve-
Desiccant
Oil-free Vacuum Valve
Figure 2 Schematic Diagram of Glass Scale System
Mercury Pressure Gauge
Figure A2 Distribution of Neutron Leakage Radiation Measurement Points
Appendix B
(Informative Appendix)
Acceptance Rules
B1 Whether the protection performance of the accelerator meets the requirements of this standard shall be inspected and qualified by the technical inspection department of the production unit before the relevant departments can accept it.
B2 The accelerator shall be tested and inspected according to the items specified in this standard before leaving the factory. B3 inspection and acceptance may be conducted in conjunction with the local radiation health and protection department, and the inspection results shall be submitted to the local radiation health and protection department for filing.1 During X-ray therapy, the beam limiter should be closed to the minimum position, and the remaining gaps should be weakened by at least two 1/10 layers of absorbing materials. The center of the detector with a maximum cross-section of no more than 1 cm2 should be located at the normal treatment distance and the depth of the maximum absorbed dose in the phantom for testing. When using overlapping beam limiters, the leakage radiation of each set of beam limiters must be tested separately. A3.12 During electron beam therapy, at the maximum nominal energy, use the light limiter of the minimum and maximum irradiation fields (the maximum irradiation field should be at least 12 cm smaller than the existing maximum geometric field) to perform film and detector measurements in turn. First, analyze the film measurement to find the maximum leakage radiation point in the area between 2 cm outside the 50% isodose line and the edge of the maximum irradiation field shielded by the beam limiter. Use the corresponding light limiter to perform detector measurement at the maximum leakage radiation point to verify whether the maximum leakage radiation meets the 10% limit. Perform detector measurements along the X-axis and Y-axis of the irradiation field from 4 cm outside the 50% isodose line to the edge of the maximum irradiation field shielded by the beam limiter. Take the average value from these four sets of measurements to verify whether the average leakage radiation meets the 2% limit. A3.2 Maximum useful beam leakage radiation test: The adjustable beam limiter is fully closed, and the maximum useful beam cross-section is attenuated with three 1/10 layers of absorbing material. Find the high leakage radiation points from the film measurement for detector measurement. Use 8MeV nominal energy X-rays or maximum nominal energy electron beams. Measure and calculate the average leakage radiation at 16 points as shown in Figure A1 at each nominal energy. 7
Radiation source
Beam limiting device
Circle with radius R
Radius R+3/4·(2-R)m
Circle with radius 2m
Normal treatment distance
Radius R+1/4·(2-R)m）
Maximum square field size
@ is the measurement point
Figure A1 Average leakage radiation Distribution of 16 measurement points A3.3 For all X-rays of nominal energy, use film to find the maximum leakage radiation point, and use detectors to measure at these points to determine whether they meet the requirements of Article 3.4.2.2. A3.4 For neutron leakage radiation test, the X-ray takes the maximum nominal energy, and at the normal treatment distance, take the maximum square edge 20cm and 100cm from the central axis along each main axis of the irradiation field as shown in Figure A2 for measurement. Neutron pulse characteristics, neutron energy spectrum, leaked X-rays and indoor neutron radiation should be considered in the measurement. A4 Absorption dose rate test of induced radioactivity is performed on equipment with X-ray nominal energy greater than 10MeV. It is continuously operated for 4 hours at a cycle of 4Gy radiation every 10 minutes. The measurement is made within 5 minutes after the irradiation is terminated 10 seconds later. The X-ray and electron beam with the maximum nominal energy are used for measurement. The irradiation field or light-limiting tube is 10cm×10cm.
J Machine Vacuum Pump
E Flow Meter
Oil-free Vacuum Valve
Liquid Radium Source Container
(Diffusion Bottle)
1 Scintillation Bottle
Oil-free Vacuum Valve
Oil-free Vacuum Valve-
Desiccant
Oil-free Vacuum Valve
Figure 2 Schematic Diagram of Glass Scale System
Mercury Pressure Gauge
Figure A2 Distribution of Neutron Leakage Radiation Measurement Points
Appendix B
(Informative Appendix)
Acceptance Rules
B1 Whether the protection performance of the accelerator meets the requirements of this standard shall be inspected and qualified by the technical inspection department of the production unit before the relevant departments can accept it.
B2 The accelerator shall be tested and inspected according to the items specified in this standard before leaving the factory. B3 inspection and acceptance may be conducted in conjunction with the local radiation health and protection department, and the inspection results shall be submitted to the local radiation health and protection department for filing.1 During X-ray therapy, the beam limiter should be closed to the minimum position, and the remaining gaps should be weakened by at least two 1/10 layers of absorbing materials. The center of the detector with a maximum cross-section of no more than 1 cm2 should be located at the normal treatment distance and the depth of the maximum absorbed dose in the phantom for testing. When using overlapping beam limiters, the leakage radiation of each set of beam limiters must be tested separately. A3.12 During electron beam therapy, at the maximum nominal energy, use the light limiter of the minimum and maximum irradiation fields (the maximum irradiation field should be at least 12 cm smaller than the existing maximum geometric field) to perform film and detector measurements in turn. First, analyze the film measurement to find the maximum leakage radiation point in the area between 2 cm outside the 50% isodose line and the edge of the maximum irradiation field shielded by the beam limiter. Use the corresponding light limiter to perform detector measurement at the maximum leakage radiation point to verify whether the maximum leakage radiation meets the 10% limit. Perform detector measurements along the X-axis and Y-axis of the irradiation field from 4 cm outside the 50% isodose line to the edge of the maximum irradiation field shielded by the beam limiter. Take the average value from these four sets of measurements to verify whether the average leakage radiation meets the 2% limit. A3.2 Maximum useful beam leakage radiation test: The adjustable beam limiter is fully closed, and the maximum useful beam cross-section is attenuated with three 1/10 layers of absorbing material. Find the high leakage radiation points from the film measurement for detector measurement. Use 8MeV nominal energy X-rays or maximum nominal energy electron beams. Measure and calculate the average leakage radiation at 16 points as shown in Figure A1 at each nominal energy. 7
Radiation source
Beam limiting device
Circle with radius R
Radius R+3/4·(2-R)m
Circle with radius 2m
Normal treatment distance
Radius R+1/4·(2-R)m）
Maximum square field size
@ is the measurement point
Figure A1 Average leakage radiation Distribution of 16 measurement points A3.3 For all X-rays of nominal energy, use film to find the maximum leakage radiation point, and use detectors to measure at these points to determine whether they meet the requirements of Article 3.4.2.2. A3.4 For neutron leakage radiation test, the X-ray takes the maximum nominal energy, and at the normal treatment distance, take the maximum square edge 20cm and 100cm from the central axis along each main axis of the irradiation field as shown in Figure A2 for measurement. Neutron pulse characteristics, neutron energy spectrum, leaked X-rays and indoor neutron radiation should be considered in the measurement. A4 Absorption dose rate test of induced radioactivity is performed on equipment with X-ray nominal energy greater than 10MeV. It is continuously operated for 4 hours at a cycle of 4Gy radiation every 10 minutes. The measurement is made within 5 minutes after the irradiation is terminated 10 seconds later. The X-ray and electron beam with the maximum nominal energy are used for measurement. The irradiation field or light-limiting tube is 10cm×10cm.
J Machine Vacuum Pump
E Flow Meter
Oil-free Vacuum Valve
Liquid Radium Source Container
(Diffusion Bottle)
1 Scintillation Bottle
Oil-free Vacuum Valve
Oil-free Vacuum Valve-
Desiccant
Oil-free Vacuum Valve
Figure 2 Schematic Diagram of Glass Scale System
Mercury Pressure Gauge
Figure A2 Distribution of Neutron Leakage Radiation Measurement Points
Appendix B
(Informative Appendix)
Acceptance Rules
B1 Whether the protection performance of the accelerator meets the requirements of this standard shall be inspected and qualified by the technical inspection department of the production unit before the relevant departments can accept it.
B2 The accelerator shall be tested and inspected according to the items specified in this standard before leaving the factory. B3 inspection and acceptance may be conducted in conjunction with the local radiation health and protection department, and the inspection results shall be submitted to the local radiation health and protection department for filing.
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