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Specification for testing of quality control in helical tomotherapy unit
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Basic data
| Standard ID | WS 531-2017 (WS531-2017) |
| Description (Translated English) | Specification for testing of quality control in helical tomotherapy unit |
| Sector / Industry | Health Industry Standard |
| Classification of Chinese Standard | C57 |
| Word Count Estimation | 13,136 |
| Date of Issue | 2017-04-10 |
| Date of Implementation | 2017-10-01 |
| Regulation (derived from) | State-Health-Communication (2017) 2 |
| Issuing agency(ies) | National Health and Family Planning Commission of the People's Republic of China |
WS 531-2017: Specification for testing of quality control in helical tomotherapy unit
---This is a DRAFT version for illustration, not a final translation. Full copy of true-PDF in English version (including equations, symbols, images, flow-chart, tables, and figures etc.) will be manually/carefully translated upon your order.
Specification for testing of quality control in helical tomotherapy unit
ICS 13.100
C 57
WS
Specification for quality control and testing of spiral tomotherapy devices
2017-04-10 released
2017-10-01 implementation
Issued by the National Health and Family Planning Commission of the People's Republic of China
People's Republic of China Health Industry Standard
Table of contents
Foreword III
1 Scope...1
2 Normative references...1
3 Terms and definitions...1
4 General requirements for quality control testing...1
5 Quality control test items and technical requirements...2
6 Testing methods and evaluation requirements for quality control testing items...2
Attachment A (informative appendix) The main structure and technical parameters of the spiral tomotherapy device...5
Attachment B (informative appendix) Basic elements of quality control testing technical report for spiral tomotherapy device...7
Attachment C (Normative appendix) Test items and technical requirements for spiral tomotherapy devices...8
Attachment D (informative appendix) Reference phantom selected for output dose testing...9
References...10
Foreword
This standard was drafted in accordance with the rules given in GB/T 1.1-2009.
4.1~4.5, 5.1 and Appendix C of this standard are mandatory, and the rest are recommended.
Drafting organizations of this standard. Beijing Center for Disease Control and Prevention, Peking Union Medical College Hospital of Chinese Academy of Medical Sciences, China Center for Disease Control and Prevention
Cardiac Radiation Protection and Nuclear Safety Medicine Institute, Hunan Provincial Occupational Disease Prevention and Treatment Hospital, Chinese People's Liberation Army General Hospital.
The main drafters of this standard. Ma Yongzhong, Qiu Jie, Yang Bo, Feng Zechen, Wan Ling, Lou Yun, Zhang Fuquan, Cheng Jinsheng, Xu Shouping, Zhai Zi
slope.
Specification for quality control and testing of spiral tomotherapy devices
1 Scope
This standard specifies the quality control and testing requirements for helical tomotherapy unit (TOMO)
method.
This standard applies to the quality control testing of spiral tomotherapy devices.
2 Normative references
The following documents are indispensable for the application of this document. For dated reference documents, only the dated version applies to this document.
For undated references, the latest version (including all amendments) applies to this document.
GB 18871 Basic standard for ionizing radiation protection and radiation source safety
GBZ 126 Radiation Protection Requirements for Electron Accelerator Radiotherapy
GBZ 179 Basic requirements for radiation protection from medical exposure
3 Terms and definitions
The following terms and definitions apply to this document.
3.1
Helical tomotherapy unit
Install the linear accelerator on the slip ring frame, apply the principle of reverse CT imaging, and use an intensified fan beam to rotate in a spiral
Means of radiotherapy.
Note. See Appendix A for the structure, coordinate system and main technical parameters of the treatment device.
3.2
Gantry isocenter
Treatment plane isocenter
The center point of the gantry aperture in the fan beam irradiation path of the spiral tomography device.
3.3
Virtual isocenter
The Y-axis direction above the treatment bed is located at a point -700mm from the isocenter of the gantry, and the height is consistent with the isocenter of the gantry.
4 General requirements for quality control testing
4.1 Medical institutions that carry out spiral tomographic radiotherapy should follow the requirements of GB 18871, GBZ 126 and GBZ 179,
Quality assurance program and quality control testing plan or program that are compatible with treatment technology.
4.2 Medical institutions should be equipped with basic dosimetry equipment and quality control testing instruments and tools compatible with the operation of the spiral tomotherapy device.
Effective maintenance and maintenance of treatment devices and testing equipment.
4.3 The quality control test of the spiral tomotherapy device includes acceptance test, status test and stability test. Acceptance inspection and status inspection
A qualified radiological health technical service agency should be entrusted; the stability test shall be conducted by the medical agency itself or by commission.
4.4 Spiral tomotherapy device after new installation, major maintenance or replacement of important components should be accepted and tested every time after operation.
State inspection shall be carried out once a year, and stability inspection shall be carried out during operation.
4.5 In the quality control test, the test result of the performance index shall be compared with the index evaluation value specified in Chapter 6.If it deviates from the evaluation value, it shall be
Identify the cause and correct it in time to ensure that all indicators are within the range of the evaluation value. Spiral tomography devices with unqualified indicators should not be used
Clinical use.
4.6 The status of each quality control test shall be recorded and archived in time. The recorded content shall include the information of the testing equipment used,
The environmental conditions, irradiation conditions and test results etc. The technical report for quality control testing shall include but not be limited to the basic requirements listed in Appendix B
Vegetarian.
5 Quality control test items and technical requirements
5.1 The technical indicators and technical requirements of the test items shall be implemented in accordance with Table C.1 in Appendix C of this standard.
5.2 The specific testing methods of testing items shall be implemented in accordance with the requirements of Chapter 6, and the equipment selected in the testing shall meet the corresponding index testing
Performance requirements.
5.3 The selected phantom parameters for static output dose and rotary output dose stability testing are shown in D.1 and D.2 in Appendix D, respectively. Acceptance inspection
Test and status detection can use this type of phantom or use other equivalent phantoms.
6 Testing methods and evaluation requirements for quality control testing items
6.1 Static output dose
6.1.1 Set the beam out conditions with a fixed angle of the treatment gantry at 0o and an irradiation field of 40cm×5cm or 10cm×5cm.
6.1.2 The dose detection phantom is set on the treatment bed, the source skin distance (SSD) is 85cm, and the center of the dose measurement point in the phantom is the virtual isocenter
alignment.
6.1.3 Insert the dosimeter measuring probe into the phantom, the dose measurement reference point is located 1.5cm below the surface of the phantom, the probe is connected with the electrometer,
Warm up and calibrate the temperature and air pressure to ensure that the instrument functions normally.
6.1.4 The treatment device emits beams at a predetermined time, records the measurement readings of the electrometer, and calculates with the parameters such as instrument verification or calibration factors
The absorbed dose from the reference point of the phantom.
6.1.5 The deviation between the measured value of the absorbed dose at the reference point in the phantom and the nominal value should be within ±2.0%.
6.2 Rotating output dose
6.2.1 Design a spiral tomographic conformal intensity-modulated radiation treatment plan on the intensity-modulated verification phantom.
6.2.2 Position the intensity modulation verification phantom on the treatment bed according to the conditions of the treatment plan, and insert the dosimeter probe into the intended measurement position in the phantom.
6.2.3 Recall the treatment plan set in 6.2.1, and control the rotation of the gantry to simulate treatment irradiation.
6.2.4 Record the measured readings of the electrometer according to the method in 6.1.4 and calculate the absorbed dose at the reference point of the phantom.
6.2.5 The deviation between the measured value of the absorbed dose at the reference point of the phantom and the treatment plan dose value should be within ±4.0%.
6.3 Radiation quality (percent depth dose, PDD)
6.3.1 Set the TOMO rack angle to be fixed at 0o, and the irradiation field to be 40cm×5cm or 10cm×5cm.
6.3.2 Set the dose distribution detection phantom or scanning water tank on the treatment bed with a source skin distance of 85cm.
6.3.3 Measure and obtain the percentage depth dose curve of 40cm×5cm or 10cm×5cm irradiation field, or the same dose as described in 6.1.2
The dose measurement values at 10cm and 20cm below the surface of the phantom are obtained on the detection phantom.
6.3.4 Normalize the dose at a depth of 1.5cm below the surface of the phantom or water tank, and the percentage depth dose of 10cm below the surface of the phantom (PDD10)
And the percentage depth dose (PDD20) 20cm below the surface of the phantom are compared with the planned PDD respectively. The deviation of the two should be within ±3.0%.
At the same time, the deviation between the measured PDD20/PDD10 in the phantom and the planned PDD20/PDD10 should also be within ±3.0%.
6.4 Transverse cross-sectional dose distribution of the radiation field
6.4.1 Use a scanning water tank or other equivalent phantom for measurement, the TOMO frame angle is fixed at 0o, and the irradiation field is 40cm×5cm or 10cm
×5cm, the source skin distance is 85cm.
6.4.2 Measure the dose distribution curve of the transverse section at a depth of 1.5 cm from the surface of the phantom under the same irradiation field conditions.
6.4.3 Analyze and determine the symmetry of the dose distribution curve.
6.4.4 The symmetry deviation of the dose distribution curve in the transverse section should be within ±3.0%.
6.5 The longitudinal section dose distribution of the radiation field
6.5.1 Use a scanning water tank or other equivalent phantom to measure, the TOMO frame angle is fixed at 0o, and the source skin distance is set to 40cm at 85cm
×5cm or 10cm×5cm irradiation field.
6.5.2 Measure the longitudinal section dose distribution curve at a depth of 1.5 cm from the surface of the phantom under the corresponding irradiation field conditions.
6.5.3 Analyze and determine the half-height width of the dose distribution curve, and compare it with the planned width of the irradiation field in the Y-axis direction.
6.5.4 The deviation of the half-height width of the longitudinal section dose distribution curve from the planned radiation field width should be within ±1.0mm.
6.6 Multi-leaf collimator (MLC) lateral offset
6.6.1 Use film to measure, set the film on the center plane of the rack, the source wheelbase (SAD) is 85cm, and the rack angle is 0°, 32～
Expose once when the leaves 33 and 27-28 are opened;
6.6.2 Illuminate again when the frame angle is 180° and only 27-28 leaves are opened, the image shown in Figure 1 will be obtained after film irradiation.
Figure 1 Film image of MLC lateral offset test
6.6.3 Analyze Figure 1 to determine the center point of the middle irradiation field and the center points of the irradiation fields on both sides.
6.6.4 The distance deviation between the center point of the irradiation field on both sides and the center point of the middle irradiation field should be within ±1.5mm.
6.7 The green laser light indicates the accuracy of the virtual isocenter
6.7.1 Measurement by phantom method. use the measurement phantom in 6.2.1 or the phantom described in D.2 in Appendix D, with the center of the phantom aligned with the green laser light,
After scanning the image, perform registration to determine the offset of the green laser light in the Z-axis and X-axis directions. The offset distance should be within ±1.0mm.
6.7.2 Measurement by film method. mark the position of the green laser light on the film, and irradiate after 70cm in the bed. The width of the Y-axis irradiation field during irradiation is
1cm, measure the offset of the green laser light in the Y-axis direction, the offset distance should be within ±1.0mm.
6.8 Red laser light indicating accuracy
6.8.1 When the red laser light is in the initial position, check its coincidence with the green laser light.
6.8.2 Within ±20cm from the virtual isocenter, the coincidence deviation of the red laser light and the green laser light should be within ±1.0mm.
6.9 Movement accuracy of the treatment bed
6.9.1 Under the condition of uniform weight bearing of 70kg on the treatment bed, confirm the virtual isocenter position on the treatment bed and mark the mark point.
6.9.2 Control the movement of the treatment bed through the positioning control panel, and move the treatment bed in and out 20cm and lift 20cm.
6.9.3 While moving in and out of the treatment bed and moving up and down, observe and use a ruler to measure the distance between the marked point and the green laser light. Offset
The distance should be within ±1.0mm.
6.10 Synchronization of bed movement and frame rotation
6.10.1 Spread a piece of film on the treatment bed and mark the position of the laser light on the film.
6.10.2 Rotate the film when the irradiation field width in the Y-axis direction is 1cm, the frame rotation period is 20s/revolution, and the total rotation is 13 revolutions.
The bed speed is 0.5mm/s, and all the blades are opened when the frame is 270°～90° in the second, seventh and 12th laps.
6.10.3 The image shown in Figure 2 is formed after the film is irradiated, and the distance between the centers of adjacent irradiation fields is analyzed. The distance and the set bed movement
The deviation of the distance should be within ±1.0mm.
Lap 12 Lap 7 Lap 2
Figure 2 Film image of the synchronization test of bed movement and frame rotation
Appendix A
(Informative appendix)
The main structure and technical parameters of the spiral tomotherapy device
A.1 The main structure of the spiral tomotherapy device
The irradiation implementation system of the spiral tomography device is mainly composed of linear accelerator, secondary collimator, multi-leaf collimator, MVCT detector and main
Beam lead shielding composition. Figure A.1 shows the appearance of the treatment device and its coordinate system, and Figure A.2 and Figure A.3 show the main structure of the treatment device.
Figure A.1 The shape and coordinate system of the spiral tomotherapy device
A.2 The main technical parameters of a typical spiral tomotherapy device
The main technical parameters of a typical spiral tomotherapy device are as follows.
a) Treatment X-ray. 6MV X-ray, fan-shaped narrow beam;
b) Source-to-axis distance (SAD). 85cm;
c) Irradiation field. at the isocenter of the gantry, the irradiation field is 40cm long (the patient is horizontal or the treatment bed is horizontal, the X axis direction), 1cm
Narrow and long radiation field (rectangular radiation field) up to 5cm wide (patient longitudinal or treatment bed longitudinal axis direction, Y axis direction), the largest radiation field
It is 40cm×5cm; the typical field width used in clinical treatment is 1cm, 2.5cm and 5cm;
d) The output dose rate at the center of the rack. 8-9Gy/min;
e) Treatment methods. spiral tomography with continuous rotation of the gantry and continuous movement of the treatment bed, and X-ray computerized spiral tomography equipment
The scanning method of setting (spiral CT) is the same. During therapeutic irradiation, after the primary beam passes through the primary collimator, the width can be adjusted
The secondary collimator forms a long and narrow fan beam, which passes through a multi-leaf collimator composed of 64 blades, each blade
The equivalent width at the isocenter is 6.25mm, and the intensity of the treatment beam is modulated by adjusting the opening and closing time of each blade;
f) MVCT image guidance equipment. 3.5MV X-ray;
g) Device shielding. the secondary collimator with width adjustment function is composed of 23cm thick metal tungsten, which is used in the acceleration tube, target and collimator
A lead block is set around to block the leakage radiation; on the opposite side of the main beam and below the MVCT detector, the other side of the aperture is set
There is a main beam lead shield, which is composed of a 13cm thick lead block. The main beam lead shield rotates randomly and is located in the main beam at any time.
Directly in front of the wiring harness.
Appendix B
(Informative appendix)
The basic elements of the quality control test technical report of the spiral tomotherapy device
The basic elements of the quality control test technical report of the spiral tomotherapy device include the following items.
a) The name of the treatment device;
b) Equipment usage;
c) Equipment model;
d) Equipment serial number;
e) Production unit;
f) Use place;
g) The name and detailed address of the testing unit and testing department;
h) Test category and test date;
i) The main technical standards and related technical documents based on the testing;
j) Information signed by inspectors, test report preparers, checkers, reviewers and report issuers;
k) The main test indicators, evaluation values, test results and judgment conclusions;
l) The conclusion of the comprehensive evaluation of the eligibility of the indicators tested by the treatment device;
m) Measures and suggestions for handling unqualified items of test indicators;
n) The key indicators of radiation source items and other relevant information that should be provided in the test.
Appendix C
(Normative appendix)
Testing items and technical requirements of spiral tomotherapy device
The testing items and technical requirements of the spiral tomotherapy device shall meet the requirements of Table C.1.
Appendix D
(Informative appendix)
Reference phantom selected for output dose detection
D.1 Reference phantom selected for static output dose stability test
The specifications and quantities of the reference phantoms selected for the static output dose stability test of the spiral tomotherapy device are as follows.
a) Phantom specification. tissue equivalent phantom, rectangular 15cm×55cm;
b) Thickness of the phantom. The total thickness of the square phantom is 24cm, including multiple phantoms of 0.5cm, 1cm, 2cm, and 5cm thick.
Choose from them when measuring time.
D.2 Reference phantom selected for the rotation output dose stability test
The shape and main specifications of the reference phantom used for the detection of the stability of the rotating output dose of the spiral tomotherapy device are as follows.
a) Shape of the phantom. Figure D.1 shows the equivalent uniform phantom of cylindrical tissue selected for the rotation output dose detection of the spiral tomotherapy device
shape.
Figure D.1 Cylindrical structure equivalent uniform phantom
b) The main specifications of the phantom, including.
1) Dimensions of the phantom. 30cm in diameter and 18cm in length, composed of two semi-cylindrical tissue equivalent uniform solid water phantoms;
2) Organize equivalent solid water plunger and ionization chamber socket. the upper row in Figure D.1 is the front view of the phantom, and the socket indicated by arrow 1 contains
There is a removable equivalent solid water plunger, arrow 2 is the ionization chamber socket; the upper row right picture depicts the film insertion phantom
In the case of the internal coronal plane, set the ionization chamber in the upper hole of the film plane to detect the dosimetry index;
The bottom row of D.1 is the back view of the phantom. There are 20 jacks on the phantom, and all the holes can be inserted with tissue equivalent plungers.
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