BS ISO 9236-3-1999 Photography - Sensitometry of screen film systems for medical radiography - Determination of sensitometric curve shape speed and average gradient for mammography.pdf

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1、BRITISH STANDARD BS ISO 9236-3:1999 Photography Sensitometry of screen/film systems for medical radiography Part 3: Determination of sensitometric curve shape, speed and average gradient for mammography ICS 11.040.50; 37.040.25BSISO9236-3:1999 This BritishStandard, having been prepared under the dir

2、ectionof the Consumer Products and Services Sector Committee, was published underthe authority of the Standards Committee and comesinto effect on 15April1999 BSI02-2000 ISBN 0 580 32016 2 National foreword This BritishStandard reproduces verbatim ISO9236-3:1999 and implements it as the UK national s

3、tandard. The UK participation in its preparation was entrusted to Technical Committee CPW/42, Photography, which has the responsibility to: aid enquirers to understand the text; present to the responsible international/European committee any enquiries on the interpretation, or proposals for change,

4、and keep the UK interests informed; monitor related international and European developments and promulgate them in the UK. A list of organizations represented on this committee can be obtained on request to its secretary. Cross-references The BritishStandards which implement international or Europea

5、n publications referred to in this document may be found in the BSI Standards Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Find” facility of the BSI Standards Electronic Catalogue. A British Standard does not purport to include all the necessa

6、ry provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pagesi andii, theISO tit

7、le page, pagesii toiv, pages1 to14, an inside back cover and abackcover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. Amendments issued since publication Amd. No. Date CommentsBS

8、ISO9236-3:1999 BSI 02-2000 i Contents Page National foreword Inside front cover Foreword iii Text of ISO9236-3 1ii blankBSISO9236-3:1999 ii BSI 02-2000 Contents Page Foreword iii Introduction 1 1 Scope 1 2 Normative references 1 3 Definitions 1 4 General requirements 2 4.1 Storage and handling condi

9、tions 2 4.2 Safelights 2 4.3 X-ray equipment 2 4.4 Processing 2 4.5 Densitometry 3 5 Determination of sensitometric curve shape 3 5.1 Beam qualities 3 5.2 Geometry for curve shape determination 3 5.3 Exposure 4 5.4 Evaluation 4 6 Determination of average gradient 4 7 Determination of speed 5 7.1 Def

10、inition 5 7.2 Exposure condition 5 7.2.1 Phantom 8 7.2.2 Establishment of tube voltage 8 7.3 Geometry 8 7.4 Exposure 8 7.5 Evaluation 11 8 Speed and average gradient determination without sensitometric curve 11 9 Accuracy 12 10 Presentation 12 Annex A (informative) Example of an automated intensity-

11、scale X-ray sensitometer 13 Annex B (informative) Bibliography Inside back cover Figure 1 Geometric set-up of the inverse-square-law sensitometer for irradiation of a screen/film/filmholder combination 5 Figure 2 Geometric set-up for calibration of the inverse-square-law sensitometer 6 Figure 3 Exam

12、ple of a sensitometric curve of a screen/film system for mammography 7 Figure 4 Geometric set-up for measurement of half-value layer 9 Figure 5 Geometric set-up for determination of speed 10 Figure A.1 Intensity-scale X-ray sensitometer 14 Table 1 Beam qualities for the determination of the sensitom

13、etric curve shape 3 Table 2 Exposure condition 6 Descriptors: Photography, medical radiography, photographic film, radiographic film, tests, determination, sensitivity (photography).BSISO9236-3:1999 BSI 02-2000 iii Foreword ISO (the International Organization for Standardization) is a worldwide fede

14、ration of national standards bodies (ISO member bodies). The work 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 commi

15、ttee. International organizations, governmental and non-governmental, 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. Draft International Standards adopted by the te

16、chnical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least75% of the member bodies casting a vote. International Standard ISO9236-3 was prepared by Technical Committee ISO/TC42, Photography. ISO9236 consists of the follow

17、ing parts, under the general title Photography Sensitometry of screen/film systems for medical radiography: Part1: Determination of sensitometric curve shape, speed and average gradient; Part2: Determination of the modulation transfer function (MTF); Part3: Determination of sensitometric curve shape

18、, speed and average gradient for mammography. Annex A and Annex B of this part of ISO9236 are for information only.iv blankBSISO9236-3:1999 BSI 02-2000 1 Introduction This part of ISO9236 provides methods for determining the sensitometric curve shape, the average gradient and the speed of radiograph

19、ic screen/film/filmholder/processing systems used in mammography. The sensitometric curve, which is also needed for the determination of other properties (as, for example, the modulation transfer function) is measured under low-scatter conditions via intensity scale X-ray sensitometry, using a sensi

20、tometer which is mainly based on the photometric inverse square law. For the determination of the sensitometric curve shape, the irradiation of the screen/film/filmholder combination need be measured only in relative units. While the average gradient is determined from the sensitometric curve shape,

21、 speed has to be measured in a separate way, since the exposure conditions should simulate as closely as possible those which are used in practice. Therefore, scattered radiation is included, accompanied by a slight change of beam quality compared to the beam quality used for intensity scale sensito

22、metry. The clinical exposure is simulated by using both an appropriate phantom and tube voltage. The screen/film/filmholder combination is exposed behind the phantom. The exposure shall be measured in absolute units (gray, Gy) in order to determine the speed. Speed is generally dependent on X-ray en

23、ergy, the amount of scattered radiation and the exposure time. Therefore, some variation in speed values may be expected under practical conditions. However, as the range of tube voltages applied in screen/film mammography is small, this part of ISO9236 describes only one beam quality for speed meas

24、urement. The measurement conditions described in this part of ISO9236 provide values for speed and average gradient which are representative of those found under practical conditions. 1 Scope This part of ISO9236 specifies methods for determination of the sensitometric curve shape, average gradient

25、and speed of a single sample of a screen/film/filmholder/processing system in mammography. The filmholder may be any means which ensures close screen/film contact and prevents the film from being exposed to ambient light. In particular, the filmholder may be a light-tight vacuum bag, as often used i

26、n the laboratory, or a radiographic cassette as used in mammography. NOTEHereafter, screen/film/filmholder combinations will be referred to as “combinations”, and will be referred to as “systems” when the processing is included. 2 Normative references The following standards contain provisions which

27、, through reference in this text, constitute provisions of this part of ISO9236. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this part of ISO9236 are encouraged to investigate the possibility of applying the

28、 most recent editions of the standards indicated below. Members of IEC and ISO maintain registers of currently valid International Standards. ISO5-2:1991, Photography Density measurements Part2: Geometric conditions for transmission density. ISO5-3:1995, Photography Density measurements Part3: Spect

29、ral conditions. ISO554:1976, Standard atmospheres for conditioning and/or testing Specifications. 3 Definitions For the purposes of this part of ISO9236, the following definitions apply. 3.1 air kerma, K energy which is transferred by ionizing radiation (for instance X-rays) to air molecules divided

30、 by the mass of air in that volume where the energy is released. The unit is the gray (Gy) 3.2 sensitometric curve plot of the density of a processed photographic film as a function of the logarithm of the exposure 3.3 speed, S quantitative measure of the response of the screen/film system to radian

31、t energy for the specified conditions of exposure, processing, and density measurement 3.4 average gradient, slope of the straight line joining two specified points on a sensitometric curve 3.5 net density D density of an exposed and processed film minus the density of an unexposed and processed sam

32、ple of that film GBSISO9236-3:1999 2 BSI 02-2000 4 General requirements 4.1 Storage and handling conditions The films 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 2) C (see

33、ISO554) 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, exposure

34、and processing. 4.3 X-ray equipment For all tests described in this part of ISO9236 a6-pulse,12-pulse, high frequency (multipulse), or constant-potential generator shall be used. For dosimetry, a measuring detector shall be used that is calibrated to measure air kerma for the beam quality applied. T

35、he accuracy of readings shall be better than5% for collimated beams without scatter, and better than7% for radiation measurements behind the phantom when scattered radiation is included. NOTEA spherical ionization chamber is recommended for measurements where scattered radiation is involved. The cen

36、tre of the spherical chamber is to be considered the reference point; the stem of the spherical chamber should point in a direction opposite to the focal spot direction. 4.4 Processing Screen/film systems including either manual or automatic processing may be tested in accordance with this part of I

37、SO9236. Processing should be carried out in accordance with the film manufacturers recommendations. Nothing shall be construed to require the disclosure of proprietary information. No processing specifications are described in this part of ISO9236, in recognition of the wide range of chemicals and e

38、quipment 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 characteristics specified for the process are produced. Processing information shall be provided

39、by the film manufacturer or others who quote speed and average gradient values and shall specify the processing chemicals, times, temperatures, agitation, equipment and procedures used for each of the processing steps, and any additional information required to obtain the sensitometric results descr

40、ibed. The values for speed and average gradient obtained using other processing procedures may differ significantly. The processing conditions selected by a person using this part of ISO9236 are, in any case, part of the system being tested. Different speeds for a particular film may be achieved by

41、varying the processes, but the user should be aware that other changes may accompany the speed changes. In order to minimize any effects due to latent-image instability or process variability, all film samples shall be processed together, neither less than30min nor more than4h after exposure. Betwee

42、n exposure and processing, the temperature of the film shall be maintained at(23 2) C, and its moisture content shall be such that the film will be in equilibrium at a relative humidity of(50 20)%. Since films are generally processed in practice a few minutes after exposure, the speed observed in pr

43、actice may differ from that determined by this part of ISO9236 due to latent-image fading of some films. Therefore, the speed measured with a time delay of30min to4h between exposure and processing shall be corrected to the value one would obtain if the film were processed soon after exposure. For t

44、he purposes of this part of ISO9236, a time delay of5,0min is used for computing speed. NOTE 1The information about the necessary correction may easily be gained by exposing film strips in a light sensitometer and varying the time between exposure and processing. In the case of double-emulsion films

45、, care should be taken that both front and back emulsions are exposed equally by the sensitometer. NOTE 2Since the time required for the many individual exposures to obtain the sensitometric curve is comparatively long, a time delay of at least30min between exposure and processing is prescribed. Tha

46、t time delay is considered to be sufficient to minimize any differences in latent-image fading for the individual exposures. The following processing information and accuracies shall be specified: a) trade designations of all chemicals, if proprietary; otherwise, the formula;BSISO9236-3:1999 BSI 02-

47、2000 3 b) temperature of the developer to within 0,3 C; c) temperature of other solutions to within 2 C; d) immersion times in the developer solution to within3%; e) whether the developer is fresh or “seasoned” (if“seasoned”, the type and amount of film used for seasoning), the density of the proces

48、sed film and the replenishment procedure; f) agitation specifications, in terms of volume of solution recirculated or rate at which a gas is used; g) drying temperature to within 5 C; h) trade designation of processing equipment. NOTEThe term “seasoned developer” means that the developer is no longe

49、r unused or fresh, but is already used and in a “normal working condition”. 4.5 Densitometry ISO standard visual diffuse transmission density of the processed images shall be measured using a densitometer complying with the geometric conditions specified in ISO5-2 and spectral conditions specified in ISO5-3. Readings shall be made in a uniform area of the image. The densities, D, shall be measured with an accuracy of %D/D = 0,02 or %D = 0,02, whichever is the greater. 5 Determination of sensitometric curve shape In this pa