This standard applies to medical photoelectric X-ray image intensifiers. This standard describes a method for determining the contrast and glare coefficient of photoelectric X-ray image enhancement. YY/T 0457.6-2003 Characteristics of photoelectric X-ray image intensifiers for medical electrical equipment Part 6: Determination of contrast and glare coefficient YY/T0457.6-2003 Standard download decompression password: www.bzxz.net

YY/T0457.6-—2003/IEC61262-6:1994YY/T0457 "Characteristics of optoelectronic X-ray image intensifiers for medical electrical equipment" is divided into seven parts: Part 1: Determination of human radiation field; Part 2: Determination of conversion coefficient; Part 3: Determination of brightness distribution and brightness non-uniformity; Part 4: Determination of image distortion, Part 5: Determination of detection quantum efficiency, Part 6: Determination of contrast and glare coefficient; Part 7: Determination of modulation transfer function. This part is the sixth part of YY/T0457. The consistency of this part is equivalent to IEC61262-6:1994 "Medical electrical equipment - Characteristics of optoelectronic X-ray image intensifiers - Part 6: Determination of contrast and glare coefficient" (English version). The main differences are as follows: some formatting formats have been modified according to Chinese habits, and some expressions applicable to international standards have been changed to expressions applicable to Chinese standards; the preface of international standards has been deleted;
-IEC788 has been changed to IEC60788;
5.2b) in the original text should be 5.2a); 5.2e) should be 5.2d). Appendices A and B of this part are both informative appendices. This part was proposed by the State Food and Drug Administration. This part is under the jurisdiction of the National Technical Committee for Standardization of Medical X-ray Equipment and Appliances. Drafting unit of this part: Liaoning Medical Device Product Quality Supervision and Inspection Institute. The main drafters of this part: Li Baoliang and Mu Li. YY/T0457.6—2003/IEC61262-6：1994引
Contrast ratio (CR) and glare index (VGI), defined as the inverse of CR, are measures of the response of an imaging system at low spatial frequencies and complement the ultimate spatial resolution. Ultimate spatial resolution is a measure of the high spatial frequency response of a system. In principle, although CR and VGI can be evaluated by the modulation transfer function, it is simpler to measure them directly. The contrast, represented by the difference in X-ray flux between an object and its surroundings, can be reduced by the imaging device. Usually this contrast loss is caused by the scattering of image-carrying quanta from the ideal path. The flicker in the image caused by the image-scattering quanta is called "glare". The processes that affect glare include the scattering of X-ray radiation at the input of the electro-optical X-ray image intensifier and the scattering of light at its output. For an electro-optical X-ray image intensifier, CR is the ratio of the brightness at the center of the output image when there is no test device in the X-ray beam to the brightness at the center of the output image when there is a CR test device in the X-ray beam. When CR is not limited, its range is from 1 to infinity, and VGI is limited between 0 and 1.
1 Scope
Medical electrical equipment
YY/T0457.6—2003/IEC61262-6:1994 Characteristics of electro-optical X-ray image intensifiersbzxz.net
Part 6: Determination of contrast and glare index This part of YY/T0457 applies to electro-optical X-ray image intensifiers as components of medical diagnostic X-ray equipment. This part describes a method for determining the contrast (CR) and glare index (VGI) of electro-optical X-ray image intensifiers. 2 Normative references
The clauses in the following documents become clauses of this part through reference in this part of YY/T0457. For all dated referenced documents, all subsequent amendments (excluding errata) or revisions are not applicable to this part, however, parties to agreements based on this part are encouraged to study whether the latest versions of these documents can be used. For undated references, the latest edition of the document applies to this part.
IEC6078:1984 Medical radiology - Terminology 3 Terminology
3.1 Definitions
For the purpose of this part, the terms and definitions defined in IEC60788 and the following apply to this part. When there is ambiguity between the definitions, the present definitions shall prevail.
English abbreviation for photoelectric X-ray image intensifier. 3.1.2
Entrance plane
The plane perpendicular to the axis of symmetry of the XRII and tangent to the most protruding part of the XRII in the direction of the radiation source (including the protective shell of the XRII).
Entrance field
For the XRII, the area in the entrance plane that can be used for the transmission of X-ray patterns under specific conditions. 3.1.4
entrance field size
Entrance field size
For an XRII, the diameter of the area in the entrance plane that can be used for transmission of the X-ray image at a specified source to surface distance (SED). For an XRII with more than one magnification mode, the corresponding output image diameter for each magnification mode shall correspond to the output image diameter of the XRII at the maximum entrance field size. 3.1.5
source to entrance plance distancethe distance between the focus of the X-ray tube and the entrance plane of the XRII. Abbreviation SED
YY/T 0457.6—2003/IEC 61262-6:19943.1.6
centre of the output imagecentre of the smallest circle circumscribing the output image. 3.1.7
centre of the entrance fieldpoint on the entrance plane imaged at the centre of the output image. 3.1.8
Central axis
central axis
The straight line passing through the center of the human radiation field and perpendicular to the human radiation plane. 3.1.9
Central magnificationcentral magnificationA characteristic of XRII, the ratio of the length of the output image of a small object placed symmetrically to the central axis on the human radiation plane to its actual length. 3.1.10
Nominal image sizenominal image sizeThe product of the linear size of a small object on the human radiation plane and the central magnification. 3. 1. 11
contrast ratic
Under specific conditions, the ratio of the central brightness of the output image of the unobstructed X-ray beam at the center of the human radiation field to the central brightness of the output image of the obstructed X-ray beam.
AbbreviationCR
veiling glare indexThe reciprocal of CR.
Abbreviations VGI
3.2 Degree of requirements
—“shall” indicates that compliance with a requirement is necessary. “should” indicates that compliance with a requirement is strongly recommended but not mandatory. “may” indicates that compliance with a requirement is permitted in a particular way in order to comply with this standard. The following words have the following meanings:
“specific” when used with a parameter or condition: refers to a particular value or standardized arrangement, usually those required by IEC standards or by law, see IEC 60788, RM-74-01. —“specified” when used with a parameter or condition: a value or arrangement usually indicated in the accompanying documents or selected with regard to the purpose in mind; see IEC 60788, IM-74-02. “designed for” when used in a standard to describe the characteristics of equipment, devices, components or arrangements: indicates the intended and usually obvious application or use of the product. 4 Requirements
In order to determine CR and VGI, the equipment characteristics and settings for CR and VGI determination are given here. 4.1 Test settings
a) SED should be 100 cm ± 1 cm;
b) The focus of the X-ray tube should be on the central axis, c) The distance between the focus of the X-ray tube and any additional filter should not exceed 33 cm: d) The X-ray field should completely cover the human radiation field, but its area should not exceed 10% of the human radiation field area. 2
YY/T 0457.6-2003/1EC 61262-6: 1994 The limitation of the X-ray field should be achieved by a diaphragm placed immediately in front of the human radiation surface. The beam limiting device of the X-ray source assembly should be used to limit the X-ray beam to this diaphragm. The attenuation rate of the aperture to the air kerma rate should be at least 100. 4.2 X-ray Image Intensifier - Working Conditions
a) XRII should be used under normal operating conditions specified by the manufacturer; b) Anti-scatter grids or protective covers should not be used; c) In the case of multi-field XRII, measurements should be completed under the specified maximum human radiation field, and measurements of other radiation fields are optional. 4.3 Input Radiation
a) The radiation quality shall be that of an X-ray beam having a half-value layer of 2.0 mm ± 0.2 mm thick aluminium (99.9% purity) of 50 kV ± 2 kV peak. The radiation quality corresponds to having a total filtration of approximately 3 mm aluminium equivalent. b) An additional determination is permitted with an X-ray beam radiation quality presenting a half-value layer of 7.0 mm ± 0.2 mm aluminium and having a total filtration of 22.5 mm ± 0.5 mm aluminium equivalent, of which at least 20 mm is aluminium. These conditions require the use of a peak X-ray tube voltage of approximately 75 kV.
1) Any additional filtration shall be uniform and placed as close as possible to the X-ray source (see 4.1c); 2) The use of this radiation quality shall be stated in the presentation of the results. Transient fluctuations in the air kerma rate shall not contribute more than 2% to the measurement uncertainty. Since the brightness measurements are made at different time intervals, the X-ray tube output shall be monitored and the measurement results shall be corrected accordingly. 4.4 Test Devices
a) The CR test device shall be a lead disk with a thickness of at least 3 mm; b) One disk shall have a diameter of 10 mm ± 0.5 mm; the other disks shall have a diameter such that the area of ​​each disk is 10% ± 0.5% of the area determined by the incident field size used for measurement; such a test device is called a 10% area test device. d) The test device shall be placed tangential to the incident plane. 4.5 Measurement Equipment
4.5.1 Photometer
The photometer is used to measure the brightness of the XRII output image. The maximum linear size of the sampling aperture of the photometer on the output image plane shall a)
not exceed 1/3 of the diameter of the nominal image size imaged by the test device; b)
the error caused by the nonlinearity of the photometer brightness response shall not exceed 1%; c)
the error caused by the photometer dark current shall not exceed 1% of the minimum brightness measurement. 4.5.2 Monitoring of X-ray Flux Rate
A radiation detector such as a scintillator crystal with a photodiode should be used on the incident surface to measure the relevant X-ray flux rate; a)
If a radiation detector is used, it should be able to detect a deviation of ±3% of the flux rate; b)
If the radiation detector is placed in the X-ray beam, c)
1) The distance from the radiation detector to the incident surface should be not less than 50 cm, 2) The projection of the radiation detector should not be within the incident field; 3) The radiation detector should remain stationary in the X-ray field during the entire measurement process. If the measurement is carried out in an X-ray beam with an additional filter plate, the radiation detector should be placed between the additional filter plate and the incident surface d)
.
5 Determination of contrast and glare coefficient
5.1 Preparation
a) The test device should be placed in a plane as close as possible to but not more than 10 mm in front of the human incident plane and parallel to the human incident plane; b) The center of the test device should be on the central axis; 1) When measuring with a 10 mm test device, the deviation of the center of the test device from the central axis should not exceed 5 mm; 3
YY/T 0457.6—2003/IEC 61262-6: 19942) When measuring with a test device with 10% of the area size, the deviation of the center of the test device from the central axis should not exceed 5 mm. c) A minimal amount of support material should be used to suspend the test device in the X-ray field. A plastic sheet of only 1 mm thick can cause a reduction in measurable contrast. d) The brightness measurement of the output image should be completed at the center of the output image. 1) When measuring with a 10 mm test device, the center of the photometer sampling hole should not deviate from the center of the output image by more than 0.1 mm; 2) When measuring with a 10% area test device, the center of the photometer sampling hole should not deviate from the center of the output image by more than 1.0 mm.
5.2 Measurement
When the XRII is irradiated, measure the brightness L1 at the center of the output image; a)
Remove the test device;
The X-ray flux should be reproduced on the incident surface within the error range of ± 3% of the value in b); c)
When the XRII is irradiated, measure the brightness L2 at the center of the output image; d)
e) For the maximum incident field size of the XRII, the measurement should use a 10 mm diameter test device and a test device with 10% area size. 5.3 Correction
In addition to the original light emitted from the image sampling area, the light scattered by the optical elements in the photometer and the components of the test setup can affect the brightness measurement. If the false components exceed 3% of the minimum brightness measured in the measurement, these false components should be corrected. Appendix B gives a method for determining the correction.
5.4 Determination
CR is the quotient of L2/L, and VGI is the quotient of Li/L2, where L and L2 are defined in 5.2a) and 5.2d) respectively. 6 Expression of contrast and glare factor
a) The presentation of results shall include the following:
- XRII identification, e.g. type, name or model; - diameter of the CR test device (expressed in mm), and ·CR as a numerical value and/or
·VGI as a fraction.
b) Unless otherwise specified, the indicated CR or VGI or both shall refer to: - radiation quality at 50 kV ± 2 kV (peak X-ray tube voltage) and a 2.0 mm ± 0.2 mm aluminum (purity 99.9%) half-value layer without additional filtration;
maximum human field size.
7 Declaration of conformity
If the determination of contrast and glare of X-ray image intensifier complies with this standard, the following shall be indicated: contrast: YY/T0457.6—2003, and glare coefficient: YY/T0457.6—2003. 4
IEC 60788
Unit names in the International System of Units
Undefined derived terms
Undefined terms
Early unit names
Abbreviations
3.1 in YY/T 0457
Accompanying document
Added filter
Air kerma rate
Anti-scatter grid attenuation ratio
Beam limiting device
central axis
central magnificationcenter of the entrance fieldcentre of the output imagecontrast ratio
diaphragm
Appendix A
(Informative)
Term index
electro-optical X-ray intensifierelectro-optical X-ray intensifierentrance field
entrance field sizeentrance plane
focal spot
have-value layer
normal use
normal focal spot valuenominal image size·output image
radiation detectorradiation quality
radiation source
distance from source to entrance planesource to entrance plane distancespecific
specified
specified
test device
total filtration
YY/T 0457.6—-2003/IEC 61262-6 : 1994rm
rm-82-01
rm-35-02
rm13-11 and rm13-13
rm-32-06
rm-13-40
rm-37-28
.3.1.8
rm-37-29
rm-32-40
rm-20-13s
rm-13-42
rm-82- 04
rm-20-14
rm-32-49
rm-51-01
rm- 13-28
rm-20-01
rm-74-01
rm-74-02
rm-71-04
rm- 13-48
YY/T0457.6--2003/IEC61262-6:1994 glare coefficient veiling glare index
X-ray beamX-ray beam
X-ray equipmentX-ray equipment
X-ray fieldX-ray filed
X-ray image intensifierX-ray pattern||tt| |X-ray source assemblyX-ray tubeX-ray tube
X-ray tube voltageX-ray tube voltage photoelectric X-ray image intensifier XRII
rm-37-05+
rm-20-20
rm-37-07+
rm-32-3
rm-32-01
rm-20-05+
rrm-22-03
rm-36-02
Appendix B|| tt||(Informative Appendix)
Determination of glare correction for photometers
The following are recommended steps for determining the correction for glare brightness measurements with photometers. To measure brightness, set the photometer according to the accompanying documents. YY/T 0457.6—2003/IEC 61262-6: 1994 Place a light-tight cover with one hole as close as possible to the plane containing the image to be analyzed. The diameter of the hole should be variable within the range of 0.7 to 1.4 of the diameter of the photometer image sampling hole. The output of the measured photometer is a function of the area of ​​the hole in the housing. The photometer signal is measured by interpolation. If the housing diameter is exactly the same as the The photometer sampling hole is matched, and SI should be obtained. Without using an opaque cover, the brightness meter signal S2 is obtained. Since the glare of the brightness meter S2 will be greater than S1. Calculate the correction factor K = S1/S2. When a CR is used at this position When the test device measures luminance, under the same conditions of image content and photometric spectrum, the photometer signal is multiplied by the factor K. The resulting magnitude can be used for calculations as in 5.4 of this section.
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