YY/T 0457.5-2003 Characteristics of photoelectric X-ray image intensifiers for medical electrical equipment Part 5: Determination of detection quantum efficiency
Some standard content:
YY/T 0457.52003/IEC 61262-5:1994YY/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 5th part of YY/T0457. The consistency of this part is equivalent to IEC61262-5:1994 "Medical electrical equipment - Characteristics of photoelectric X-ray image intensifiers - Part 5: Determination of detection quantum efficiency" (English version). The main differences are as follows: some formatting formats have been modified according to Chinese habits; - 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.
Appendix A, Appendix B, Appendix C and Appendix D of this part are all informative appendices. This part was proposed by the State Food and Drug Administration. This part is under the jurisdiction of the National Standardization Technical Committee for Medical X-ray Equipment and Appliances. The 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. I
YY/T 0457.5—2003/IEC 61262-5: 1994 Introduction
Detective quantum efficiency (DQE) is a measure of the imaging quality of a system based on the comparison of the signal-to-noise ratio (SNR) at the output of the system with the signal-to-noise ratio at the input. For linear imaging systems, the SNR and DQE can be conveniently analyzed based on sinusoidally varying signals. This standard gives detailed provisions for the measurement of DQE for photoelectric X-ray image intensifiers with spatial and temporal frequencies close to zero frequency, using the scintillation spectrum analysis (SSA) method. The input auxiliary radiation source is a radionuclide 4-can, which is superior to an X-ray source because radionuclides have the characteristics of no drift and periodic fluctuation in output and can produce gamma rays in a range of radiation energies of interest. The signal at the fluorescence output of the photoelectric X-ray image intensifier is integrated over an area larger than the output source image. In addition, the SSA method essentially requires the integration of all photon energies contributing to a single ray photon at the output of the photoelectric X-ray image intensifier. These characteristics result in measurements near zero spatial frequency and zero temporal frequency. This standard specifies the DQE measurement method only near the center of the input field. Similarly, the SSA method is not recommended for photoelectric X-ray image intensifiers with fluorescent radiation that decays significantly slower than P-20 phosphor. Generally, due to the absorption of a single ray photon, the optical pulse intensity generated by a single ray photon should be less than 10% of the peak intensity 1 ms after the start of the pulse. This assumes that the interval between the start of the pulse and the peak intensity is much shorter than 1 ms. Because the SSA method requires the integration of each individual ray photon, phosphors with very slow decay should require very low ray photon count rates that are comparable to the background count rate.
Other DQE measurement methods, such as pulse-burst analysis, rms noise analysis and methods for estimating quantum absorption from the physical properties of photoelectric X-ray image intensifiers (see Appendix D References), are acceptable as long as they meet the measurement accuracy requirements specified in this part of the measurement method. 1 Scope
Medical electrical equipment
YY/T 0457.5—2003/IEC 61262-5:1994 Photoelectric X-ray image intensifier characteristics
Part 5: Determination of detective quantum efficiency
This part of YY/T 0457 applies to photoelectric X-ray image intensifiers that are components of medical diagnostic X-ray equipment. This part describes a method for determining the detective quantum efficiency (DQE) by analyzing the pulse amplitude spectrum of single-ray photon scintillation. The method in this part is only applicable to photoelectric X-ray image intensifiers with an output radiation decay rate approximately equal to or better than P20 phosphors. 2 Normative references
The clauses in the following documents become clauses of this part through reference in this part of YY/T0457. For any dated referenced document, all subsequent amendments (excluding errata) or revisions are not applicable to this part. However, parties to an agreement based on this part 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 part.
IEC60788:1984 Medical radiology - Terminology 3 Terminology
3.1 Definitions
For the purpose of this part, the terms and definitions determined in IEC60788 and the following apply to this part. When there is ambiguity between the definitions, this definition shall take precedence.
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 XRII, the area in the entrance plane that can be used for X-ray pattern transmission under specific conditions. 3.1.4
Not used.
Source to entrance plane distance (SED) The distance between the focus of the X-ray tube and the entrance plane of the XRII. 1
YY/T 0457.5-—2003/IEC 61262-5:19943.1.6
Centre of the output imagecentre of the smallest circle circumscribing the output image. 3.1.7
centre of the entrance fieldcentre of the entrance field
the point on the incident plane that is imaged at the centre of the output image. 3.1.8
central axiscentral axis
the straight line passing through the centre of the incident field and perpendicular to the incident plane. 3.1.9
not used.
effective apertureeffective aperture
the area of the XRII input screen that is illuminated by the radiation source through the entrance aperture. Note: Due to geometric magnification and the size of the radiation source, the diameter of this area is always larger than the diameter of the entrance aperture itself. 3.1.11bzxZ.net
detective quantum efficiencydetective quantum efficiencythe ratio of the square of the signal-to-noise ratio of the output signal of the radiation detector to the square of the signal-to-noise ratio of the input signal of the radiation detector. AbbreviationDQE
quantum absorption efficiencyquantum absorption efficiencythe number of photons at the input of the radiation detector that produce the signal at the output of the radiation detector divided by the total number of photons. 3.1.13
Input aperture
The aperture that determines the cross-section of the radiation beam.
Single gamma-ray photon pulseThe number of photons excited by the XRII input screen caused by the action of a ray photon with a specific energy in the XRII input screen.
3.2 Degree of requirement
Auxiliary verbs in this standard:
_“shall” indicates that compliance with a requirement is necessary. _\Should means that compliance with a requirement is highly recommended but not mandatory._“May” means that compliance with a requirement is permitted in a special way in order to comply with this standard. The following words have the following meanings:
“Specific” when used with parameters or conditions: refers to a specific value or standardized arrangement, usually those required by IEC standards or laws; see IEC60788, rm-74-01. “Specified” when used with parameters or conditions: a value or arrangement usually indicated in the accompanying documents or selected for the purpose under consideration; see IEC60788, rm-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 purpose or use of the product. 2
4 Requirements
YY/T 0457.5—2003/IEC61262-5:1994This chapter gives the characteristics of the instruments and equipment for determining DQE and their setup requirements. A typical measurement setup is given in Appendix B. 4.1 Test setup
Not used.
4.2 X-ray image intensifier - operating 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, the measurement should be carried out in the specified maximum human field mode. 4.3 Input radiation
a) The input radiation source should be a can of radionuclide 241. It can emit radiation photons with an energy of 59.5 keV; b)
The output of the source may contain photons produced by non-241 radium decay, such as: IX rays and fluorescent X-rays from the materials used in the source and its container structure;
1) The non-59.5 keV photon flux should be less than 1% of the 59.5 keV photon flux. The required level of spectral purity can be achieved by using a 0.5 mm copper filter. This filter reduces the 59.5 keV photon flux by about half.
2) Any additional filtering should be as close to the radiation source as possible and closer to the radiation source than the XRII input surface or the reference detector (4.5.2).
Under the geometric conditions of 4.4.2, the radiation source activity should be such that a count rate of 50 to 500 light quanta c)
|quanta/second is obtained for 59.5 keV photons at the input aperture, for which an activity of about 10° Bq is required. 4.4 Test device
4.4.1 Input aperture
a) The cross-sectional area of the radiation beam projected onto the XRII or reference detector shall be limited by the same input aperture; in order to avoid output changes due to local changes in the thickness of the input screen, the input aperture shall be not less than 4 mm; b)
For reference detectors with simple crystals, the input aperture shall limit the radiation beam to an area not larger than the bottom area of the detector tube; c)
The radiation beam is not allowed to irradiate the crystal detector wall; d) The input aperture shall be cut from a lead plate at least 3 mm thick. Geometric layout of the test device
a) In order to limit the changes in the absorption of radiation by the XRII input screen and the enlargement of the effective aperture due to the increase in the incident angle, it shall be less than 2° (see Figure 1), 8 is expressed by the following formula:
- tan-1[(do +d,)/2L]
Where:
d. —radiation source diameter;
d——input aperture diameter;
L——distance from the radiation source to the input aperture. b) For both the reference detector and the XRII measurement, the same d, di and L settings should be used. 4.5 Measurement equipment
4.5.1 Photomultiplier tube (PMT)
If the scintillation crystal is the reference detector, the photomultiplier tube should be used to detect the light emitted by the XRII and the scintillation crystal. 4.5.1.1 PMT operating conditions
The high voltage source connected to the PMT should ensure that the PMT has a linear response; a)
b) In order to obtain the stability of the PMT response, the PMT should be connected to the high voltage at least 30 min before starting the measurement. 3
YY/T0457.5—2003/IEC61262-5:19944.5.1.2PMT setup
a) PMT and XRI should be shielded to prevent the influence of ambient light; b) For the measurement of scintillation pulse amplitude spectrum, the optical coupling efficiency between PMT and XRII output image should ensure that at least 50% of the photons generated by a single-ray photon pulse reach the PMT photocathode; this can be achieved by directly aligning the PMT with the output window of the XRII or using a propagation lens with a sufficiently large aperture (F/2 or larger);
When using a combination lens, the XRII output image should not be focused on the PMT input surface to prevent spectral expansion due to the non-uniformity of the PMT photocathode;
The background light generated by the output fluorescence outside the input aperture image area can be prevented from reaching the PMT by adding an appropriate outer cover. d)
If such a protective cover is used, its aperture shall not obstruct any photons emitted from the output image area and shall be at least twice the effective aperture image diameter.
Input screen
Radiation source
4.5.2 Reference detector
Input aperture
Input window
Figure 1 Geometric relationship between radiation source and input aperture
Effective aperture
The reference detector is used to measure the 59.5 keV photon flux on the incident plane. The quantum absorption efficiency of the reference detector at this energy level shall be sufficiently high or determined with sufficient accuracy that the contribution to the measurement uncertainty does not exceed ±2% of the absolute value. 4.5.3 Pulse processor
a) The pulse processor is an electronic device that provides an output signal to the multi-channel analyser (MCA) whose amplitude is proportional to the amplitude of the input pulse.
When measuring the spectrum of single-ray photon pulses from XRII, the pulse processor is placed in the signal path between the PMT output and the MCA input. The pulse processor can also be used when the count rate is determined using a reference detector. b) For the measurement of the scintillation efficiency I (see 5.4) derived from the amplitude spectrum of single-ray photon pulses, the processor may contain components to suppress the distorted signal generated by the superposition of two or more pulses during the single-pulse measurement, however, superposition suppression is generally not required at the recommended count rates;
c) For the measurement of the quantum absorption rate A (see 5.4), superposition interference suppression should not be used. If superposition interference suppression is used, it should be coupled to the average value of the accumulated effective measurement time (live time). When the processor can receive a signal, accumulation is only performed during these intervals, otherwise, the count rate measurement will be incorrect. 4.5.4 Multi-channel Analyser (MCA) a) The signal output of the pulse processor shall be recorded so that the number of detected events can be determined as a function of the amplitude of the single-ray quantum pulse. The MCA is a commercially available electronic instrument that can perform this task; the channel corresponding to zero pulse amplitude should be known so that the energy spectrum can be accurately calculated. Precision pulse generators are commercially available for this purpose. b) The MCA shall have a low-level discriminator (LLD) that filters out all pulses below a selectable threshold level; d) The MCA shall provide a method of accumulating dead time during which the MCA cannot receive input pulse signals: in order to prevent the MCA from saturating due to a large number of low-energy background pulses, the LLD should be set to a closed value level so that the total dead time does not exceed 5% of the total measurement time. 5 Determination of Detection Quantum Efficiency
Appendix C gives the flash pulse amplitude spectra of typical reference detectors and XRII. 5.1 Preparation
5.1.1 Measurement of incident radiation flux
a) Set up the radiation source according to the geometry established in 4.4.2a), including its filtration (if necessary) and input aperture; b) The input aperture should be set between the radiation source and the reference detector; c) The reference detector should be set up taking into account the input aperture diameter and used to measure the radiation flux at the input aperture with the uncertainty requirements specified in 5.2.1.
5.1.2 Measurement of scintillation pulse amplitude spectrum
a) The radiation source, including its filter (if necessary) and input aperture, should be arranged in the geometrical layout established in 4.4.2a); the input aperture should be between the radiation source and the XRII: b)
c) The radiation source and the input aperture should be aligned along the central axis. The input aperture should be set as close to the input surface as possible; d)
e) Collimate the PMT to detect the output of the XRII. Connect the PMT output to the pulse processor, and the output of the pulse processor to the MCA.
5.2 Measurement
5.2.1 Incident ray flux rate
Use the radiation source to irradiate the reference detector. In the energy range that meets the requirements of the measurement accuracy of the ray flux rate in 5.2.1g), the radiation source plus the background pulse rate R
should be determined by setting an appropriate ILD reading level to filter out the signal with energy less than 10keV from the reference detector; remove the radiation source to measure the background pulse count rate R, c
should subtract the background pulse R from the total count rate R, d)
The total counting time T should make the accumulated pulse number (R, -R,) × not less than 100000; e)
Note: "represents the active time, that is, the total measurement time minus the dead time when the system does not receive and process signals. The difference between R.-R, should be calculated according to 59.The detector quantum absorption efficiency of the 5keV photon reference is corrected to produce the corrected source f
count rate R. The measurement of
R, should be accurate to within ±1%.
Scintillation pulse amplitude magic spectrum
Use the radiation source to irradiate XRII and measure the single-ray photon pulse spectrum; a)
The time zx for obtaining the spectrum should be long enough to make the net spectrum count (see 5.2.2d) at least 100,000; b)
Note: tx represents the active time, that is, the total measurement time minus the dead time when the system does not receive and process signals. Only when the radiation source is removed, the background noise spectrum within the same time tx is measured; d) For each ray photon pulse level E, the background spectrum should be subtracted from the spectrum of 5.2.2a) to obtain the net spectrum number N; e) The low energy threshold should be identified according to the energy, and the energy interval spectrum of 0keV to 25keV in this energy range is the smallest. According to this part, the number of low-energy threshold pulses shall not exceed 20% of the number of pulses corresponding to the peak energy of the pulse with completely absorbed energy of 59.5keV photons.
5.3 Amendment
Not used.
5.4 Determination
a) Calculate DQE
as follows
--scintillation efficiency, determined as follows:
--scintillation efficiency, determined as follows:
--scintillation efficiency, determined as follows:
--scintillation efficiency, determined as follows:
--scintillation efficiency, determined as follows:
--scintillation efficiency, determined as follows:
--scintillation efficiency, determined as follows:
DQE = Aα × I
I (M)\/(M2 × M.)
--the first component of the scintillation pulse amplitude spectrum, given by:M = ZN; ×(E)
Nj--the number of pulses with amplitude E,
The minimum value of E, in these calculations shall correspond to the low-energy value given in 5.2.2e). The quantum absorption rate Aα of XRII is determined by the following formula AQ = (Mo/tx)/Rs
wherein:
determined according to 5.4a);
tx — spectral integration time as described in 5.2.2b), and R. — determined according to 5.2.1;
Note: The derivation of the DQE formula is given in Appendix D, References [1], [2] and [3]. b) The determination should be accurate to within ±2% of the absolute value. 6 Expression of detective quantum efficiency
The expression of DQE shall include:
XRII identification, such as type, specification, model; -DQE percentage;
7 Declaration of conformity
If the determination of DQE of X-ray image intensifier complies with this part, it shall be expressed as: Detective quantum efficiency YY/T 0457.5—2003; or:
--DQE:YY/T 0457.5---2003.
IEC60788
Unit names in the International System of Units
Undefined derived terms
Undefined terms…
Early unit names
Abbreviations
3.1 in YY/T 0457.5
accompanying document
Random documents
Activity
Added filter
Anti-scatter grid central axis
Appendix A
(Informative)
Term index
centre of the entrance field axiscentre of the output imagedetective quantum efficiencyeffective aperture
electro-optical X-ray intensifierelectro-optical X-ray intensifierentrance field
entrance plane
filter
input apertul
input screen ..
normal use
output image
output screen
quantum absorption efficiencyradiation beam ·
radiation detector
radiation source.
single-gamma-rayphotonpulsesource to entrance plane distance,SEDtest derice
X-ray equipment .
X-ray image intensifierX-ray image intensifierX-ray imageX-raypattern
photoelectric X-ray image intensifierXRII
YY/T 0457.5---2003/1EC 61262-5:1994rm
rm-82-01
rrm-13-18
rm-35-02
rm-32-06
rm-32-40
rm-35-01
3. 1. 13
rm-32-47
rm-82-04
* rm-32-49
rm-32-48
.3.1.12
rm-37-05
rm-51-01
rm-20-01
center center guide
rm-71-04
rm-20-20
rm-32-39
rm-32-01
YY/T 0457.5—2003/IEC 61262-5:1994 Source beam limiter
Y-ray source.
Input aperture
Y-ray source
Appendix B
(Informative Appendix)
Typical test setup
Lens and output shading plate (optional)
Photoelectric X-ray
Image intensifier
Preamplifier
Photomultiplier tube
Scintillator crystal
Photomultiplier tube
Amplified pulse processor
Multi-channel analyzer
Phosphorus selection
Spectral minimum area
Yanqi Di Yi peak
Low energy noise
Low level discrimination
Low energy radiation
Appendix C
(Informative Appendix)
Typical scintillation pulse intensity spectrum
Reference detector
YY/T 0457.5—2003/1EC 61262-5 : 199480
Photoelectric X-ray image intensifier
Energy kev
Energy, kev
YY/T0457.5—2003/IEC61262-5:1994Appendix D
(Informative Appendix)
References
[1J Journal of Applied Physics, Vol. 44,Sep. 1973, RK Swank,\Absorption and noise in X-ray phos-phors，\pp.4199-4203.
E2J Journal of Applied Physics, Vol. 45, Aug. 1974, R. K, Swank,\ Measurement of Absorption andNoise in an X-ray Image Intensifier\pp.3673-3678.[3] Medical Physics, Vol. 10, Nov. /Dec. 1983, JARowlands and KW Taylor,\ Absorption andNoise in Cesium Iodide X-ray Image Intensifiers\pp. 786-795. -ray Image Intensifiers: Comparison of Scintillation Spectrum and rms Methods,\pp.597-601.
[5J Proceedings of SPIE,Vol. 206,27-29 Au9. 1079,H. Roehrig,B. Lum,D. Fisher,D. Ouimette,M,PCapp ,MM Frost,and S. Nudelman,\Digital method to evaluate the noise of X-ray image intensifiers\,pp. 135-145.
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