Verification Regulation of Medical Diagnostical X-ray Radiation Source for Computer Tomography(CT)
Some standard content:
The People's Republic of China National Metrology Verification Regulation JJG 961--2001
Medical Diagnostic Computed Tomography Equipment
(CT)X-ray Radiation Source
Medical Dlagnostical X - ray Radistion Source for Coputer Tomography (CT)
2001-02-28
Implementation on 2001-05-01
Promulgated by the State Administration of Quality and Technical Supervision
JG 961—2001
Verification Regulation of Medical Diagnnkstical X - ray Radiaticn Suurcefar Cumputer Tomography ( CT)JJG 961 -
This verification procedure was approved by the State Administration of Quality and Technical Supervision on February 28, 20>1, and has been implemented since May 1, 2001.
Responsible unit: National Technical Committee for Ionizing Radiation Metrology Drafting unit: Beijing Institute of Metrology, Capital Medical University Medical Instrument Quality Control Technology Research Center This procedure is entrusted to the National Technical Committee for Ionizing Radiation Metrology for voice interpretation The main drafters of this procedure:
Guo Hongtao
Ying Pengchen
JIG 961—2001
(Beijing Institute of Computer Science)
(Capital Medical University Medical Instrument Quality Control Technology Research Center)2
References
Terms and measurement units
Basic measurement units
Meter performance requirements
Accuracy of tube voltage
Accuracy of wide current
Output radiation quality
Dose index (CIDI) )
Uniformity
Noise level
Low contrast resolution
Spatial resolution·
Also requires technical fog.
7 Metering instrument and its control
Verification conditions
Control items and verification methods
: Verification result processing
7.4 Verification cycle
Appendix A
CT metrological performance model
L)G 961 —2801
.. (1)
JJG961—2001
Appendix B Verification record of X-ray radiation source for medical diagnostic computer tomography (CT) Appendix C Verification certificate (received) format
Appendix Some dose benefits and dose index (TT) in the phantom of X-ray auxiliary radiation source for medical diagnostic computer tomography (CT)2
JJG 961 -2(01
Verification procedure for X-ray radiation sources for medical diagnostic computed tomography (CT) equipment Scope
This procedure applies to the determination of X-ray radiation sources for newly manufactured, in-use and after-destruction performance of used medical diagnostic computed tomography (CT) equipment 2 References
This procedure refers to the following documents:
GB/T1KK5-1997 Routine test for evaluation of medical imaging departments Part 2-6: X-ray computer imaging equipment stability certification
1℃122326 X-ray computer imaging equipment stability test (1994 edition) 8 Part 53 X-ray diagnostic image quality certification - X-ray CT equipment stability test (May 1989 edition)
PA6868 Part 53 X-ray diagnostic image quality certification - X-ray CT equipment stability test (December 5, 1989)
AAPM REPOLT' NO, 39 Specificatiun and Aarceptance Testing of Corputed Snanners (T Device Performance Design Benchmark (Building a European Recommendation)), GR/T Performance Evaluation Committee GR/T175891998 X-ray Computerized Tomography Equipment Quality Assurance Testing Specification When using this procedure, the above document, which is the current valid version, should be used: 3 Terms and Measurement Units
3.1 Techniques
3.1.1 CT value
is used to express the average X-ray attenuation coefficient related to a single area of CT equipment. The measured attenuation value can be converted into the required CT value using formula (1): CT = × 1 000
Where: —
is a linear attenuation coefficient.
The calculated CT value is 0 and the CT value of air is 1000HU. This value is close to the value shown in the book IIU cooking 3. [.2 Ratio
Contrast is expressed as the white fraction of the result obtained by dividing the T value of the measured object by the background (the difference in T value divided by 1KK)! .I.3 Dose index (CII) The product of the dose index divided by the number of slices perpendicular to the slice plane. Where: CTDI - CT dose index; Nominal slice thickness: JJG 61 — 2001. W - slice thickness; 3.1.4 Mean T value The average value of the CT values of all pixels in a certain region of interest. 3.1.5 Noise product The degree to which the T value of a region in the image of the average material deviates from the mean value. The size of the noise is expressed by the standard deviation of the T value of the homogeneous material in the region of interest. 3.1.6 Region of Interest (RO)
The measured area in the image, that is, the area of particular interest within a certain period of time. 3.2 Units of measurement
3.2.1 Absorbed dose
Symbol: The unit name is gray and the unit symbol is Gy. IGy = /kg
1Gy = 10'mGy = 10'μGy
4 Overview
The X-ray radiation source of the medical diagnostic computed tomography device shall consist of an X-ray tube, a generator, a detector, a control device, a computer imaging system and a bed. 5 Metrological performance requirements
5.1 Accuracy of the tube voltage
In the range of 81~145kV, the error of each level shall not exceed ±5%. 5.2 The accuracy of tube current
is within the range of 50~2000m4, and the error of each gear does not exceed ±10%=5.3 The output radiation quality
is expressed in half-value layers, and its measured value is not less than 1. Table 1 Minimum half-value voltage of different X-ray tubes E/k
ground layer/mA
5.4 Basic index (CTDL
5.4.! For head dose phantom, the useful beam radiation absorption of each point in the center and the side image shall not exceed 50mGy; for body dose phantom, the useful beam radiation absorption of each point in the center and the side image shall not exceed 20mGy and 80mGy respectively. 5.4.2 The relative deviation of the useful beam radiation absorption index of each point in the center and the side edge of the head dose phantom and the body dose phantom from the first test result shall not exceed 20.
5.5 Uniformity
J3G 951 -- 2001
When the dose index meets 5.4., the deviation between the average T value of the central area of interest in the phantom water and the average CT value of each edge point should not exceed 4 hours.
5.6 Noise level
When the dose index meets 5.4.1, the noise level should be less than 35%. 5.7 The test results of GT value
CT value should meet the requirements of Table 2. Table 2 T values of different materials at -70keV measured
Surface area ()
Nominal value/HU
Volume value/HU
Polyethylene
Polyyethy-
60 ~- 75
Polysty-
20 ~ - 30
3~+3 +85 ~ +100
Polyester
Pal ycarbo-
+ 92 -+ 120
Note: The molecular weight of polyurethane foam is CuHiu: the molecular weight of organic sphere (ax:rylir) is [sHa5.8 layer thickness
Organic glass
Ariylic
+ 102 + 1.30
Nominal is the original standard: within the range of 310mm, the absolute value of the difference between the measured value and the nominal value is not greater than 50% of the nominal value. 5.9 Low contrast resolution
When the dose index meets S.4.1 and the contrast does not exceed 1, the newly installed or repaired CT machine should be able to meet the standards of the manufacturer or the technical indicators specified in the manual and promotional materials; the CT machine in use should be able to distinguish at least 5 groups of holes with a diameter of 3.5mm. 5.10 Spatial resolution
When the dose index meets 5.4.1, the newly installed or repaired CT machine should be able to meet the standards of the manufacturer or the technical indicators specified in the manual and promotional materials. The machine in use, under head working conditions, should be able to distinguish a group of holes (at least 5 or more) with a diameter of 1.25 or 4 line pairs per centimeter (Lp/cm). Under waist working conditions, it should be able to distinguish a group of holes (at least 5 or more) with a diameter of 1.5mm or 3 line pairs per water (Im). General technical requirements
6.1 The X-ray radiation source of the medical diagnostic computed tomography device must be clearly marked with the manufacturer, model, number and date of manufacture.
6.2 The electrical, mechanical and protective performance of the X-ray radiation source of the medical diagnostic computed tomography device shall comply with the requirements specified in the corresponding national standards. 7 Control of measuring instruments
7.1 Verification conditions
7.1.1 Verification film [equipment
JJG 91
The half-value accuracy factor of the integrated dose meter with 11 consecutive times in the transmission support is not more than 5%, and the confidence interval is 59.7%:
7.1.1.2 The error coefficient of the instrument measuring the voltage of the tube is better than +2% + repeatability coefficient less than 1% within the service life of 80-14V, and the annual stability is less than 10 years.
7.1.1.3 Measurement, etc. The needle-shaped surface of the flow is within the range of 50 to 1000m1, and its accuracy is better than ±3. 7.1.1.4 The model body must be the model temporarily recorded. 7.1.1.5 The standard button sheet series or light value layer tester, the line of the lead sheet is more than 99%, and the thickness measurement error does not exceed 0.05m
7.1.1.6 The head dose mother mold uses
The head dose reading body is a straight light of 16 0mm: a round body with a height of 150m, there are 5 through holes with a diameter of 13mm in the center of the round rod (the distance between the center of the 4 side holes and the nearest edge of the body is 10m), and it is equipped with 5 diameter rods with a diameter of 12.7m, the material of which is glass. 7.1.1.7 Abdominal dose tray mounting
The main dose phantom is a round body with a height of 150mm, there are 5 through holes with a diameter of 13mm in the center and 4 symmetrical spaces (the distance between the nearest edges of the 4 side holes is 10mm), and it is equipped with 5 diameter rods with a diameter of 12.7m, the material of which is organic slope. 7.1.2 Other preparations for inspection
7,.2.1 Ruler-F, the maximum graduation value is not less than 1um,7.1.2.2
Thermometer, the minimum temperature is not more than 0.5%.
7,1.2.3 Barometer, minimum scale value not less than 100Pa: 7.1.2.4 Hot water
7.1.3 Test environment conditions
Specified external temperature is between 18 and 7.2
Test items and test methods
Test preparation
Table 3 List of test items
Test items
General voltage Accuracy of the insulator
radiation quality of the output
radiation index (TDI
uniformity
diffuse sound
low contrast resolution
spatial resolution
second calibration
subsequent over-determination
industrial specification
7.2.2 Accuracy of tube voltage
JJG 961—2001
7.2.2.1 Place the detector of the voltmeter at the center of the radiation load, with the wiring harness and the detector vertically hidden. 7.2.2.2 Select several measuring points at regular intervals, and measure each point at least 3 times. Take the average value and use the relative deviation F to express the accuracy of the instrument, as shown in the formula (): V.- V..
Formula: K——Measured half-mean value of CT tube current: kV; V is the actual value of CT tube current, kV.
7.2. Accuracy of tube current
7.2.3.1 Place the detector of the ammeter close to the high-voltage generator of the CT plate in the opposite direction of the X-ray tube: 7.2.3.2: Select several commonly used points, each with a repetition rate of at least 3 times, and the average value is the relative difference between the minimum current and the minimum current:
×100%
Where: 1—Measured average value of CT tube current, mA; -Actual value of tube current, m
7.2.4 Quality of output radiation
7.2.4.1 Place the central part of the CT ionization tube in the center of the X-ray field: The X-ray tube is placed in a non-rotating state, and the absorption sheet is placed between the X-ray tube ignition point and the ionization rate, and the distance between them is greater than 2 mm and parallel to the ionization chamber: 7.2.4.2 Measure the air kinetic energy release rate when no absorption sheet is added and the absorption sheet with no shield is passed through. 2.4.3 The air kinetic energy release rate is calculated by the graphical method or calculation method to obtain the absorption rate of the air when it drops to the initial value (the absorption rate of the absorption sheet at ordinary times), which is the radiation mass released:
7.2.5 Dose index
2.5.1 Place the upper and lower dose phantoms in the center of the irradiation book respectively, and place the long ionization air in the phantom through the hole in turn. The remaining holes can be dropped into the circle, and the head and cavity parts are used to scan the dose phantom. The material inside should have a color response:
7.2.5.2 The dose index in the body is calculated according to formula (5) D = lx+Nx*F,-F2-K,+K/d
Wx——the calibration factor of the X-ray calibration function in the standard laboratory, 2.58×10-1C-cm（kg*rliv）；F,—the conversion coefficient of the radiation indication of the measuring ear into the receiving ear in the air, 33.97×10mGy-kg/C；F.| |tt||The conversion factor for converting the absorbent in the air into the absorbent in the phantom is 0.8. The correction factor for layer thickness is given in Table 4: K
Peak density correction factor;
The layer thickness sequence scanned by the T machine, .m
Layer thickness/m
(center)
(edge)
(center)
(edge):
JFG 941 -- 2001
Table 4 Peak positive factor for different layer thicknesses
: The peak positive factor for the room with a length of 100m is only 6
7.2.5.3 Change of dose barrier index CTTI, calculated according to formula (6), the unit is mGy. CTDL=D·KuA
Where: Kmt—
7.2.6 Uniformity
The ratio of 1000 mA-second to the actual scanned ampere-second. 3
7.2.6,1 Place the main phantom filled with evaporated water in the center of the radiation field, and scan the water phantom under the condition of the T machine head. There should be no material affecting the beam around the scanned area. 7.2.6,2 Select 5 measurement areas in the scanned image, and take an area of about 100 mm at the center and 10 mm to the right of the image edge, and measure its CT value and standard deviation. The difference between the average T value of the central interest area in water and the average T value of each point on the edge is used to represent the uniformity. It is expressed by formula (7):
U-CT-CT
Where: -bzxz.net
represents uniformity, H.
7.2.7 Night Noise Level
Take the average standard deviation (SD) of the CT values of the above five measurement areas, and calculate the noise level according to formula (8): × 100%
Where: H——Night Noise Level-;
K =I 000HU.
7.2.8 TT value
.2.8.1 Place the CT value calibration plug-in in the main phantom filled with distilled water, and scan the 5 kinds of low-density substances and water in the phantom under the head and center conditions of the CT machine. 7.2.8.2 Select a measurement area of about 100mm in each substance in the scanned image, and record the T value. 7.2.8.3 Select a measurement value that is closest to the nominal value as the CT value of the substance: 7.2.9 Thickness
7.2. Multiple.1 Place the layer thickness plug-in in the phantom filled with distilled water, and place the water phantom in the center of the radiation field, and scan the water phantom under the head conditions of the CT machine with different layer thicknesses. 7.2.9.2. Set the CT machine window width to the minimum, adjust the window position to half of the sum of the CT value of the object to be measured and the CT value of the background object, measure the width of the image at three positions, and the average value is the actual layer thickness. 7.2.10 Spatial resolution
7.2.10.1 Head resolution
JJG 961—-2001
1) Put the head ring on the resolution plug-in and put it in the main phantom filled with distilled water. Scan the main phantom according to the procedures in 7.2.6.1.
2) Minimize the window width of the machine and adjust the window position to resolve the minimum aperture. 7.2.10.2 Partial resolution
1) Place the resolution plug-in in a phantom filled with distilled water, and put the plug-in on the main phantom. The main phantom is placed in the center of the radiation field. Scan the water phantom with the machine waist-down condition. The scanned area should not have any material that affects the radiation beam.
2) Adjust the window width of the CT machine to the minimum, and adjust the window position to obtain the minimum aperture of the resolution group. 7.2.11 Low contrast resolution
7.2.11.1 Place the low contrast plug-in in a phantom filled with distilled water, and scan the water phantom with the machine head-down condition at a maximum layer of 10mm. The scanned area should not have any material that affects the radiation beam. 7.2.11.2 Select a measurement area in the water and plug-in respectively in the general contrast plug-in, measure the CT value and standard deviation of the two materials [5ID), and adjust the window position and window view according to formulas (9) and (10) to obtain the minimum aperture. CTw+CTV
WW=（CT-CTw）+SSDmm
WL: image window level, IIU: WW: image window height, HU: CTw—water T value; CTm—low contrast material T value; SDm—the larger standard deviation of the two measured areas. 7.3 Result processing
7.3.1 According to the provisions of this procedure According to the regulations and requirements, a certificate shall be issued to the qualified medical diagnostic computed tomography device (CT) radiation source, and a non-qualified notice shall be issued to the unqualified one. 7.3.2 The format of the inner page of the certificate is shown in Appendix B. The non-qualified items shall be indicated in the non-qualified notice. 7.4 Verification cycle
The verification cycle of the medical diagnostic computed tomography device (CT) radiation source is generally not more than 1 year. After debugging and repair, they must be re-calibrated for the first time.
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