BS ISO 9236-1-2004 Photography Sensitometry of screen film systems for medical radiography Determination of sensitometric curve shape speed and average gradient《摄影 医用放射照相用.pdf

1、BRITISH STANDARD BS ISO 9236-1:2004 Photography Sensitometry of screen/film systems for medical radiography Part 1: Determination of sensitometric curve shape, speed and average gradient ICS 37.040.25 BS ISO 9236-1:2004 This British Standard was published under the authority of the Standards Policy

2、and Strategy Committee on 12 February 2004 BSI 12 February 2004 ISBN 0 580 43378 1 National foreword This British Standard reproduces verbatim ISO 9236-1:2004 and implements it as the UK national standard. The UK participation in its preparation was entrusted to Technical Committee CPW/42, Photograp

3、hy, which has the responsibility to: A list of organizations represented on this committee can be obtained on request to its secretary. Cross-references The British Standards which implement international publications referred to in this document may be found in the BSI Catalogue under the section e

4、ntitled “International Standards Correspondence Index”, or by using the “Search” facility of the BSI Electronic Catalogue or of British Standards Online. This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. Compli

5、ance with a British Standard does not of itself confer immunity from legal obligations. aid enquirers to understand the text; present to the responsible international/European committee any enquiries on the interpretation, or proposals for change, and keep the UK interests informed; monitor related

6、international and European developments and promulgate them in the UK. Summary of pages This document comprises a front cover, an inside front cover, the ISO title page, pages ii to v, a blank page, pages 1 to 20, an inside back cover and a back cover. The BSI copyright notice displayed in this docu

7、ment indicates when the document was last issued. Amendments issued since publication Amd. No. Date Comments Reference number ISO 9236-1:2004(E)INTERNATIONAL STANDARD ISO 9236-1 Second edition 2004-02-01 Photography Sensitometry of screen/film systems for medical radiography Part 1: Determination of

8、 sensitometric curve shape, speed and average gradient Photographie Sensitomtrie des ensembles film/cran pour la radiographie mdicale Partie 1: Dtermination de la forme de la courbe sensitomtrique, de la sensibilit et du contraste moyen BSISO92361:2004ii BSISO92361:2004 iiiContents Page Foreword iv

9、Introduction v 1 Scope 1 2 Normative references . 1 3 Terms and definitions. 1 4 General requirements. 2 4.1 Storage and handling conditions 2 4.2 Safelights . 2 4.3 X-ray equipment 3 4.4 Air kerma meter. 3 4.5 Processing. 3 4.6 Densitometry . 4 5 Determination of sensitometric curve shape. 4 5.1 Ge

10、neral. 4 5.2 Beam qualities. 5 5.3 Geometry for curve shape determination. 5 5.4 Exposure 8 5.5 Evaluation 8 6 Determination of average gradient 8 7 Determination of speed 10 7.1 Definition 10 7.2 Beam qualities. 10 7.3 Geometry . 13 7.4 Exposure 13 7.5 Evaluation 13 8 Speed and average gradient det

11、ermination without sensitometric curve 16 9 Uncertainty 16 10 Test report . 17 Annex A (informative) Rationale .18 Bibliography . 20 BSISO92361:2004iv Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The wor

12、k of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governme

13、ntal, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2. The m

14、ain task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. A

15、ttention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO 9236-1 was prepared by Technical Committee ISO/TC 42, Photography. This second edition cancels and

16、 replaces the first edition (ISO 9236-1:1996), which has been technically revised to incorporate the following technical and major editorial changes: a spherical ionization chamber, or an equivalent detector, is required for dosimetry; only high frequency or 12-pulse high-voltage generators are allo

17、wed, 6-pulse high-voltage generators are excluded; the allowed uncertainty for the density measurement has been increased in order to comply with the other parts of the ISO 9236 series; the exposure times for the determination of speed and sensitometric curve shape have been reduced to match the cur

18、rent state of the art; the phantom of Technique IV has been changed (leaving the beam quality unchanged) in order to reduce the air kerma rate; the distances between the focal spot of the x-ray tube and the screen-film combination when determining speed and average gradient may now be in the range f

19、rom 1,5 m to 4,0 m; the use of a monitoring detector is no longer mandatory, because the precision of modern x-ray tubes and high-voltage generators is often superior to that of monitoring detectors; the total uncertainty which can be reached has been changed; an informative annex has been added in

20、order to describe the background of speed and curve shape measurements, the choice of phantoms, and the energy dependence of speed values. ISO 9236 consists of the following parts, under the general title Photography Sensitometry of screen/film systems for medical radiography: Part 1: Determination

21、of sensitometric curve shape, speed and average gradient Part 3: Determination of sensitometric curve shape, speed and average gradient for mammography The following part is under preparation: Part 2: Method for determining modulation transfer function (MTF) BSISO92361:2004 vIntroduction This part o

22、f ISO 9236 provides methods for determining the sensitometric curve shape, the average gradient and the speed of radiographic screen/film/filmholder/processing systems used in medical radiography, except in mammography and dental radiography. The sensitometric curve shape, which is also needed for t

23、he determination of other properties (as, for example, the modulation transfer function), is measured under low scatter conditions via intensity scale X-ray sensitometry, preferably using an inverse square sensitometer. For the determination of the sensitometric curve shape, as well as for a subsequ

24、ent determination of the average gradient from the measured curve, but not for speed, the irradiation of the screen/film/filmholder combination need to be measured only in relative units. Speed is measured in a separate way, under exposure conditions which simulate medical practice more closely, inc

25、luding realistic fractions of scattered radiation. Different types of medical exposures are simulated by using appropriate phantoms and X-ray tube voltages, and the screen/film/filmholder combination is exposed behind the respective phantom. The irradiation is measured in absolute units of air kerma

26、 (gray, Gy) in order to determine the speed. Four different techniques are defined, differing in beam quality and fraction of scattered radiation, simulating the imaging of extremities, skull, lumbar spine and colon, and chest. Speed may be measured for each technique of interest. Owing to its depen

27、dence on X-ray energy and scatter, screen/film system speed varies widely in medical practice. The four measurement conditions described in this part of ISO 9236 provide values that are representative of those found under practical conditions. BSISO92361:2004BSISO92361:2004 1Photography Sensitometry

28、 of screen/film systems for medical radiography Part 1: Determination of sensitometric curve shape, speed and average gradient 1 Scope This part of ISO 9236 specifies methods for the determination of the sensitometric curve shape, average gradient and speed of a single sample of a screen/film/filmho

29、lder/processing system for medical radiography. It is not applicable to special radiographic applications such as mammography, dental radiography and direct- exposing medical radiographic systems (see for example ISO 5799 3 ). The filmholder can be any means that ensures close screen/film contact an

30、d prevents the film from being exposed to ambient light. In particular, the filmholder can be a light-tight vacuum bag, as often used in the laboratory, or a radiographic cassette as used in medical radiography. 2 Normative references The following referenced documents are indispensable for the appl

31、ication of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 5-2:2001, Photography Density measurements Part 2: Geometric conditions for transmission density ISO 5-3:1995,

32、 Photography Density measurements Part 3: Spectral conditions ISO 554:1976, Standard atmospheres for conditioning and/or testing Specifications IEC 60522:1999, Determination of the permanent filtration of X-ray tube assemblies 3 Terms and definitions For the purposes of this document, the following

33、terms and definitions apply. 3.1 screen/film system radiographic imaging system consisting of screen(s), film, filmholder and film processing NOTE Hereafter, screen/film/filmholder combinations will be referred to as “combinations” and will be referred to as “systems” when the processing is included

34、. BSISO92361:20042 3.2 air kerma K sum of the initial kinetic energies of all charged particles (e.g., electrons) liberated by uncharged particles (e.g., X-ray photons) from air molecules, divided by the mass of air in that volume where the charged particles are liberated NOTE The unit is the gray (

35、Gy). 3.3 sensitometric curve plot of the density of a processed photographic film as a function of the logarithm to the base 10 of the exposure 3.4 speed S quantitative measure of the response of the screen/film system to radiant energy for the specified conditions of exposure, processing and densit

36、y measurement 3.5 average gradient Gslope of the straight line joining two specified points on a sensitometric curve 3.6 net density D density of an exposed and processed film minus the density of an unexposed and processed sample of that film 3.7 coverage factor k numerical factor, used as a multip

37、lier of the combined standard uncertainty in order to obtain an expanded uncertainty NOTE The coverage factor is explained in the Guide to the expression of uncertainty in measurement 8 . Its value is typically in the range of 2 to 3. The coverage factor is chosen based on the level of confidence de

38、sired. A coverage factor (k) of 2 generally will result in a level of confidence of approximately 95 %, and a coverage factor of 3 generally will result in a level of confidence of approximately 99 %. This association of confidence level and coverage factor is based on an assumption regarding the pr

39、obability distribution of measurement results. 4 General requirements 4.1 Storage and handling conditions The film and screens shall be stored according to the manufacturers recommendations. Before and during exposures, the temperatures of the films and screens shall be maintained at 23 C 2 C (see I

40、SO 554) and the moisture content of the film shall be such that it will be in equilibrium at a relative humidity of (50 20) %. 4.2 Safelights To eliminate the possibility of safelight illumination affecting the sensitometric results, all films shall be kept in total darkness during handling, exposur

41、e and processing. BSISO92361:2004 34.3 X-ray equipment For all tests described in this part of ISO 9236, high frequency (multipulse) high voltage generators or at least 12-pulse high voltage generators shall be used. For all tests described in this part of ISO 9236, X-ray tubes equipped with fixed a

42、nodes or rotating anodes may be used. In either case, the target material shall be tungsten or a tungsten-based alloy. NOTE 1 The target is that part of the anode onto which the electron beam is directed to produce X-radiation. For technological reasons it is common practice to use alloys of tungste

43、n with up to 10 % rhenium for the target, while other parts of the anode can consist of other materials (e.g. molybdenum). The permanent filtration of the X-ray tube and its housing, as defined in IEC 60522, shall be equivalent to 2,5 mm 0,2 mm of aluminium. NOTE 2 The permanent filtration of the X-

44、ray tube and its housing is effected by permanently fixed materials intercepting the X-ray beam, which are not intended to be removed for any application. As the permanent filtration is usually stated on the X-ray tube housing and in the accompanying documents, its measurement, as described in IEC 6

45、0522, is not necessary. 4.4 Air kerma meter For the air kerma measurement, calibrated detectors shall be used. The uncertainty of air kerma measurement (level of confidence 95 %) shall be less than 3 % for collimated beams without scatter, and less than 5 % for radiation measurements behind the phan

46、tom when scattered radiation is included. A spherical ionization chamber of 30 cm 3to 100 cm 3volume should be used for measurements where scattered radiation is involved. The chamber shall be calibrated for the beam qualities given in Table 2, including scattered radiation. The centre of the spheri

47、cal chamber is to be considered the reference point; the stem of the spherical chamber should point in a direction opposite to the radiation source. NOTE During calibration of the air kerma meter and during usage, scattered radiation originating not from the phantom but from, for example, the stem o

48、f the chamber, can be minimized in order to meet the specified uncertainty requirement. 4.5 Processing Screen/film systems, including either manual or automatic processing, may be tested in accordance with this part of ISO 9236. Processing should be carried out in accordance with the film manufactur

49、ers recommendations. Nothing shall be construed to require the disclosure of proprietary information. No processing specifications are described in this part of ISO 9236 in recognition of the wide range of chemicals and equipment used. Speed and average gradient values provided by film manufacturers generally apply to the system when the film is processed in accordance with their recommendations so that the photographic ch