BS 7725-2 2-1994 Evaluation and routine testing in medical imaging departments - Constancy tests - Method for radiographic cassettes and film changers and film-screen contact and r.pdf

1、BRITISH STANDARD BS 7725-2.2: 1994 IEC1223-2-2: 1993 Evaluation and routine testing in medical imaging departments Part 2: Constancy tests Section 2.2 Method for radiographic cassettes and film changers and film-screen contact and relative sensitivity of the screen-cassette assemblyBS7725-2.2:1994 T

2、his British Standard, having been prepared under the directionof the Health Care Standards Policy Committee, waspublished under the authorityof the Standards Boardand comes into effect on 15February 1994 BSI 10-1999 The following BSI references relate to the work on this standard: Committee referenc

3、e HCC/73 Draft for comment 88/56156 DC ISBN 0 580 22798 7 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Health Care Standards Policy Committee (HCC/-) to Technical Committee HCC/73, upon which the following bodies were represented: Bri

4、tish Institute of Radiology College of Radiographers Department of Health Institute of Physical Sciences in Medicine (IPSM) Royal College of Radiologists Society of X-ray Technology Amendments issued since publication Amd. No. Date CommentsBS7725-2.2:1994 BSI 10-1999 i Contents Page Committees respo

5、nsible Inside front cover National foreword ii Introduction 1 1 Scope and object 1 2 References to other publications 1 3 Terminology 1 4 General condition of radiographic cassettes, intensifying screens and intensifying screens in film changers 2 5 Testing the constancy of adequate contact in film-

6、screen combinations 2 6 Testing the relative sensitivity of intensifying screen(s) and associated radiographic cassettes 3 7 Test report 5 Annex A Terminology Index of terms 6 Annex B Example of a form for the standardized test report 8 Annex C Guidance on action to be taken 10 Annex D Rationale 11

7、List of references Inside back coverBS7725-2.2:1994 ii BSI 10-1999 National foreword This Section of BS 7725 has been prepared under the direction of the Health Care Standards Policy Committee. It is identical with IEC Publication 1223-2-2:1993 Evaluation and routine testing in medical imaging depar

8、tments Part 2-2: Constancy tests Radiographic cassettes and film changers Film-screen contact and relative sensitivity of the screen-cassette assembly, prepared by the Technical Committee 62 Electrical equipment in medical practice and published by the International Electrotechnical Commission (IEC)

9、. A British Standard does not purport to include all the necessary 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. Cross-references International Standard

10、 Corresponding British Standard IEC 788:1984 BS 6641:1985 Glossary of medical radiology terms (Identical) BS 7725 Evaluation and routine testing in medical imaging departments IEC 1223-1:1993 Part 1:1994 General (Identical) IEC 1223-2-1:1993 Section 2.1:1994 Film processors (Identical) IEC 1223-2-3:

11、1994 Section 2.3:1994 Method for darkroom safelight conditions (Identical) Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages1 to 12, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendmen

12、ts incorporated. This will be indicated in the amendment table on the inside front cover.BS7725-2.2:1994 BSI 10-1999 1 Introduction Some provisions or statements in the body of this technical report require additional information. Such information is presented in Annex D, Rationale. An asterisk in t

13、he left margin of a clause or subclause indicates the presence of such additional information. 1 Scope and object 1.1 Scope This technical report applies to RADIOGRAPHIC CASSETTES and to FILM CHANGERS used to record an X-RAY PATTERN on RADIOGRAPHIC FILM by DIRECT RADIOGRAPHY. This technical report a

14、pplies to RADIOGRAPHIC CASSETTES and FILM CHANGERS that are equipped with INTENSIFYING SCREEN(S). This technical report does not apply to specialized RADIOGRAPHIC CASSETTES such as mammographic cassettes, multi-section cassettes and cassettes used in DENTAL PANORAMIC TOMOGRAPHY. Its application to R

15、ADIOGRAPHIC CASSETTES with an integrated ANTI-SCATTER GRID may not give satisfactory results. This technical report is a part of a series of Particular Publications (standards and technical reports) which will describe test methods for the constancy of properties of various subsystems of diagnostic

16、X-RAY EQUIPMENT, as described in IEC1223-1. 1.2 Object This technical report describes simple methods to check: the constancy of adequate, homogeneous contact between the INTENSIFYING SCREEN(S) and the RADIOGRAPHIC FILM in the RADIOGRAPHIC CASSETTE or the FILM CHANGER; the relative sensitivity of th

17、e INTENSIFYING SCREEN(S) and associated RADIOGRAPHIC CASSETTE. 2 References to other publications The following IEC publications are quoted in this technical report: IEC 788:1984, Medical radiology Terminology. IEC 1223-1:1993, Evaluation and routine testing in medical imaging departments Part 1: Ge

18、neral aspects. IEC 1223-2-1:1993, Evaluation and routine testing in medical imaging departments Part 2-1: Constancy tests Film processors. IEC 1223-2-3:1993, Evaluation and routine testing in medical imaging departments Part 2-3: Constancy tests Darkroom safelight conditions. IEC 1223-2-12, Evaluati

19、on and routine testing in medical imaging departments Part 2-12: Constancy tests Film illuminators. (under consideration) 3 Terminology 3.1 Use of terms This technical report contains a number of terms that are defined in IEC 788, in IEC 1223-1 and in IEC 1223-2-1 (see Annex A, Terminology Index of

20、terms). Where these terms are used with the meanings given in their definitions, they are printed in capital letters to signify that the defined meaning applies. Words forming a part of the whole of any defined term may also appear in lower-case letters. In that event, the meaning is not intended ne

21、cessarily to correspond to any formal definition, but to be derived from the customary meaning of the words in the language and from the actual context. Terms derived from those formally defined (for example, the plural form of a term defined in the singular or the adjectival form of a term defined

22、as a noun), are used where appropriate and, if printed in capital letters, have meanings linked to the definitions of the source terms concerned. The term: 3.2 Definitions 3.2.1 FILM ILLUMINATOR luminous surface in combination with additional provisions for the observation of transparent objects suc

23、h as RADIOGRAMS on RADIOGRAPHIC FILM “specific” when used with parameters or conditions: refers to a particular value or standardized arrangement, usually to those required in an IEC publication or a legal requirement. “specified” when used with parameters or conditions: refers to a value or arrange

24、ment to be chosen for the purpose under consideration and indicated usually in ACCOMPANYING DOCUMENTS.BS7725-2.2:1994 2 BSI 10-1999 4 General condition of RADIOGRAPHIC CASSETTES, INTENSIFYING SCREENS and INTENSIFYING SCREENS in FILM CHANGERS* Any relevant instructions given in the ACCOMPANYING DOCUM

25、ENTS of the RADIOGRAPHIC CASSETTES, FILM CHANGER, and the INTENSIFYING SCREEN(S) should be observed when examining the devices. The following measures should be taken: Each single INTENSIFYING SCREEN or each pair of INTENSIFYING SCREENS is given an individual identification such as a number; this id

26、entification is written with permanent ink in an unobtrusive position on one INTENSIFYING SCREEN, so that it will be recorded on the film; *NOTEAttention has to be paid to the fact that permanent ink may affect or destroy the protective layer of INTENSIFYING SCREENS. this identification is indicated

27、 on the outside of the RADIOGRAPHIC CASSETTE. Each RADIOGRAPHIC CASSETTE and FILM CHANGER should be labelled with name of manufacturer of INTENSIFYING SCREEN(S) contained; type(s) of INTENSIFYING SCREEN(S) contained; date of acquisition of the INTENSIFYING SCREEN(S). The general condition of all RAD

28、IOGRAPHIC CASSETTES and the INTENSIFYING SCREENS should be checked as follows, at least every six months: 1) The exterior and interior of each cassette is examined for correct labelling; cleanliness; signs of warping and fatigue of the material provided to ensure the contact between RADIOGRAPHIC FIL

29、M and INTENSIFYING SCREEN. 2) The hinge assembly and closure mechanism of the cassette are examined for wear and damage. 3) Each INTENSIFYING SCREEN is examined for cleanliness; worn and stained areas; and *as appropriate, any screen or pair of screens is cleaned or replaced, and the date recorded.

30、NOTEIt is generally undesirable to replace only one of a pair of INTENSIFYING SCREENS. 4) *Taking appropriate precautions to protect the eyes of the examiner, INTENSIFYING SCREENS are examined under ultra-violet light to reveal artefacts; regions where the protective coat has been worn away. 5 Testi

31、ng the constancy of adequate contact in film-screen combinations 5.1 Summary The adequacy of the contact between the RADIOGRAPHIC FILM and INTENSIFYING SCREENS is determined by viewing the uniformity in blackening of the DIRECT RADIOGRAM, and the clarity of the image of a standard TEST DEVICE placed

32、 in front of the RADIOGRAPHIC CASSETTE or FILM CHANGER to be tested. 5.2 Test equipment 5.2.1 RADIOGRAPHIC FILM The RADIOGRAPHIC FILM used for the test should be typical of that used with the INTENSIFYING SCREENS and associated RADIOGRAPHIC CASSETTES or FILM CHANGERS to be tested. For successive tes

33、ts, RADIOGRAPHIC FILM of the same type should be used. 5.2.2 Standard TEST DEVICE The TEST DEVICE required for this test is a metal wire mesh of linear dimensions not smaller than the IMAGE RECEPTION AREA of the RADIOGRAPHIC CASSETTE or FILM CHANGER to be tested. *The wire mesh should have a square

34、pattern of such a quality that its structure appears uniform when viewed on a FILM ILLUMINATOR. To facilitate the measurement of the optical density of the RADIOGRAM obtained during the test, the standard TEST DEVICE should have an opening in the centre of the wire mesh of 1 cm square or 1 cm in dia

35、meter. *The wire should be made from metal composed predominantly of elements with an atomic number of at least 26, for example copper or zinc. The diameter of the wire should be approximately0,5 mm and the separation between the centres of adjacent wires should be approximately six diameters. 5.2.3

36、 FILM PROCESSOR The FILM PROCESSOR used for the test should have been tested and found satisfactory, according to IEC1223-2-1. 5.2.4 Densitometer Optical densities are measured with a densitometer which reads consistently within 0,02. 5.2.5 FILM ILLUMINATOR The FILM ILLUMINATOR used for the test sho

37、uld have been tested and found satisfactory, according to IEC1223-2-12.BS7725-2.2:1994 BSI 10-1999 3 5.3 Criterion for satisfaction* The contact between RADIOGRAPHIC FILM and INTENSIFYING SCREEN(S) is satisfactory if the optical density of the image of the standard TEST DEVICE on the RADIOGRAM appea

38、rs uniform. 5.4 Test procedure 1) Prior to starting any constancy check, the identity is established of any device such as a RADIOGRAPHIC CASSETTE, INTENSIFYING SCREEN, FILM CHANGER, or ACCESSORY used for the test, and having properties that can influence the result of the test. 2) The conditions of

39、 the RADIOGRAPHIC CASSETTE and INTENSIFYING SCREENS as described in clause4 are checked, and any action necessary before commencing the test is taken. 3) *If shown worthwhile, any ANTI-SCATTER GRID present is removed from the equipment used for the test and from a FILM CHANGER to be tested. 4) The R

40、ADIOGRAPHIC CASSETTE or FILM CHANGER is loaded with the type of RADIOGRAPHIC FILM selected according to 5.2.1. 5) *Unless otherwise chosen for the test, the test is not continued until at least 15 min after loading the RADIOGRAPHIC CASSETTE. 6) The standard TEST DEVICE is placed flat on the outside

41、of, and in contact with, the incident face of the RADIOGRAPHIC CASSETTE, or when testing a FILM CHANGER, the TEST DEVICE is placed on the PATIENT SUPPORT or another suitable support immediately in front of the FILM CHANGER to avoid contact with the surface of the FILM CHANGER. 7) The FOCAL SPOT TO I

42、MAGE RECEPTOR DISTANCE is set to the distance used in normal clinical practice. 8) The dimensions of the X-RAY FIELD are adjusted to the IMAGE RECEPTION AREA, and the RADIOGRAPHIC CASSETTE or FILM CHANGER is aligned with the X-RAY BEAM. 9) The individual RADIOGRAPHIC CASSETTE or FILM CHANGER is iden

43、tified with lead numbers. 10) The standard TEST DEVICE is irradiated, using the smallest available FOCAL SPOT and LOADING FACTORS that will produce an optical density in the processed RADIOGRAM of about 2 above FILM BASE PLUS FOG DENSITY in the image of the opening in the wire mesh. 11) In general,

44、for testing RADIOGRAPHIC CASSETTES and FILM CHANGERS, an X-RAY TUBE VOLTAGE of not more than 70 kV is used. Rapid type FILM CHANGERS should be tested in the static and dynamic mode, by making: two RADIOGRAMS in static mode, and a series of at least six RADIOGRAMS in dynamic mode at the highest frequ

45、ency normally used in the department. Other FILM CHANGERS are tested in the static mode. Equipment identification, test conditions and other pertinent information shall be included in the test report (see clause 7). 5.5 Evaluation The RADIOGRAMS are viewed on the FILM ILLUMINATOR from a distance of

46、2 m to 3 m. If regions of the image of the TEST DEVICE on the RADIOGRAM appear dark or non-uniform, or details of the image are blurred, the film-screen contact is poor, and will impair the quality of the recorded diagnostic information. 5.6 Further action If the image of the TEST DEVICE shows the d

47、efects described in 5.5, consideration should be given to the repair or replacement of screen-cassette assemblies showing poor film-screen contact. 5.7 Frequency of testing Adequate, homogeneous contact between the RADIOGRAPHIC FILM and INTENSIFYING SCREEN(S) should be tested: initially on acquisiti

48、on; and then at least annually; or when poor film-screen contact is suspected. 6 Testing the relative sensitivity of INTENSIFYING SCREEN(S) and associated RADIOGRAPHIC CASSETTES* 6.1 Summary The relative sensitivity of screen-cassette assemblies is determined by comparing the optical density produce

49、d by simultaneously and equally irradiated identical films placed in each of a group of three test and one reference RADIOGRAPHIC CASSETTES. The process is repeated for all RADIOGRAPHIC CASSETTES to be tested, using the same reference screen-cassette assembly for all the groups. *The screen-cassette assemblies are then sorted into groups that produce similar optical densities, and therefore are of similar sensitivity.BS7725-2.2:1994 4 BSI 10-1999 6.2 Test equipment 6.2.1 RADIOGRAPHIC FILM (see 5.2.1) 6.2.