1、NORME CE1 INTERNATIONALE I EC INTERNATIONAL STANDARD 1262-7 Premire dition First edition 1995-09 Appareils lectromdicaux - Caractristiques des intensificateurs lectro-optiques dimage radiologique - Partie 7: Dtermination de la fonction de transfert de modulation Medical electrical equipment - Charac
2、teristics of electro-optical X-ray image intensifiers - Part 7: Determination of the modulation transfer function Numro de rfrence Reference number CEMEC 1262-7: 1995 Numros des publications Depuis le ler janvier 1997, les publications de la CE1 sont numrotes partir de 60000. Publications consolides
3、 Les versions consolides de certaines publications de la CE1 incorporant les amendements sont disponibles. Par exemple, les numros ddition 1.0, 1.1 et 1.2 indiquent respectivement la publication de base, la publication de base incorporant lamendement 1, et la publication de base incorporant les amen
4、dements 1 et 2. Validit de la prsente publication Le contenu technique des publications de la CE1 est constamment revu par la CE1 afin quil reflte ltat actuel de la technique. Des renseignements relatifs la date de reconfirmation de la publication sont disponibles dans le Catalogue de la CEI. Les re
5、nseignements relatifs des questions ltude et des travaux en cours entrepris par le comit technique qui a tabli cette publication, ainsi que la liste des publications tablies, se trouvent dans les documents ci- dessous: Cite web de la CEI* Catalogue des publications de la CE1 Publi annuellement et mi
6、s jour rgulirement (Catalogue en ligne)* Disponible la fois au site web, de la CEI* et comme priodique imprim Bulletin de la CE1 Terminologie, symboles graphiques et littraux En ce qui concerne la terminologie gnrale, le lecteur se reportera la CE1 60050: Vocabulaire Electro- technique International
7、 (V EI). Pour les symboles graphiques, les symboles littraux et les signes dusage gnral approuvs par la CEI, le lecteur consultera la CE1 60027: Symboles littraux A utiliser en lectrotechnique, la CE1 6041 7: Symboles graphiques utilisables sur le matriel. Index, relev et compilation des feuilles in
8、dividuelles, et la CE1 60617: Symboles graphiques pour schmas. Num bering As from 1 January 1997 all IEC publications are issued with a designation in the 60000 series. Consolidated publications Consolidated versions of some IEC publications including amendments are available. For example, edition n
9、umbers 1.0, 1.1 and 1.2 refer, respectively, to the base publication, the base publication incorporating amendment 1 and the base publication incorporating amendments 1 and 2. Validity of this publication The technical content of IEC publications is kept under constant review by the IEC, thus ensuri
10、ng that the content reflects current technology. Information relating to the date of the reconfirmation of the publication is available in the IEC catalogue. Information on the subjects under consideration and work in progress undertaken by the technical committee which has prepared this publication
11、, as well as the list of publications issued, is to be found at the following IEC sources: IEC web site* Catalogue of IEC publications Published yearly with regular updates (On-line catalogue)* Available both at the IEC web site and as a printed periodical IEC Bulletin Terminology, graphical and let
12、ter sym bo I s For general terminology, readers are referred to I EC 60050: International Electrotechnical Vocabulary (IEV). For graphical symbols, and letter symbols and signs approved by the IEC for general use, readers are referred to publications IEC 60027: Letter symbols to be used in electrica
13、l technology, I EC 6041 7: Graphical symbols for use on equipment. Index, survey and compilation of the single sheets and IEC 60617: Graphical symbols for diagrams. * Voir adresse 4te webs sur la page de titre. * See web site address on title page. NORME INTERNATIONALE INTERNATIONAL STANDARD CE1 IEC
14、 126217 Premire dition First edition 1995-09 Appareils lectromdicaux - Caractristiques des in tens if icateu rs lectro-optiques dimage radiologique - Partie 7: Dtermination de la fonction de transfert de modulation Medical electrical equipment - Characteristics of electro-optical X-ray image intensi
15、fiers - Part 7: Determination of the modulation transfer function 0 CE1 1995 Droits de reproduction reserves - Copyright - all rights reserved Aucune partie de cette publication ne peut tre reproduite ni utilis8e sous quelque forme que soit et par aucun pro- c8d. lectronique ou mcanique, y corrpns l
16、a photocopie et les microfilms. sans laccord Bait de lditeur. No part of this publication may be reproduced or utilized in any form or by any means, electronic or medianical. including photocopying and microfilm, without permission in wrhg from the publisher. Bureau Central de ia Commission Electrot
17、echnique Internationale 3. rue de Varemb Genve, Suisse Commission Electrotechnique Internationale CODE PRIX international Electrotechnical Commission PRICE CODE Q Mewcnywapontian 3newporexecnaf1 HOMHCWR Pourprix. voir catalogue en vigueur For price. see current catalogue -2- 1262-7 O CE111 995 SOMMA
18、IRE Pages AVANT-PROPOS INTRODUCTION . Articles 1 Domaine dapplication 2 Rfrences normatives . 3 Terminologie 3.1 Dfinitions 3.2 Degr des prescriptions et instructions relatives la lecture 4 Prescriptions 4.1 Montage dessai . 4.2 INTENSIFICATEUR DIMAGE RADIOLOGIQUE - Conditions de fonctionnement . 4.
19、3 RAYONNEMENT dentre 4.4 DISPOSITIF DESSAI 4.5 Appareils de mesure 5 Dtermination de la FONCTION DE TRANSFERT DE MODULATION . 5.1 Prparation 5.2 Mesure . 5.3 Correction 5.4 Dtermination de la CHUTE BASSE-FREQUENCE 5.5 Justesse gnrale de la dtermination 6 P - Explications, conseils, introductions, no
20、ncs de porte gnrale et exceptions: petits caractres romains; - Modalits dessais: caractres italiques; - TERMES UTILISS DANS CETTE NORME QUI SONT DFINIS EN 3.1 ET LANNEXE A: PETITES CAPITALES. 1262-7 O IEC:1995 -5- INTERNATIONAL ELECTROTECHNICAL COMMISSION MEDICAL ELECTRICAL EQUIPMENT - CHARACTERISTI
21、CS OF ELECTRO-OPTICAL X-RAY IMAGE INTENSIFIERS - Part 7: Determination of the modulation transfer function FOREWORD 1) The IEC (International Electrotechnical Commission) is a worldwide organization for standardization comprising all national electrotechnical committees (IEC National Committees). Th
22、e object of the IEC is to promote inter- national cooperation on all questions concerning standardization in the electrical and electronic fields. To this end and in addition to other activities, the IEC publishes International Standards. Their preparation is entrusted to technical committees; any I
23、EC National Committee interested in the subject dealt with may participate in this preparatory work. International, governmental and non-governmental organizations liaising with the IEC also participate in this preparation. The IEC collaborates closely with the International Organization for Standar
24、dization (ISO) in accordance with conditions determined by agreement between the two organizations. 2) The formal decisions or agreements of the IEC on technical matters, prepared by technical committees on which all the National Committees having interest therein are represented, express, as nearly
25、 as possible, an international consensus of opinion on the subject dealt with. 3) They have the form of recommendations for international use published in the form of standards, technical reports or guides and they are accepted by the National committees in that sense. 4) In order to promote interna
26、tional unification, the IEC National Committees undertake to apply IEC International Standards transparently to the maximum extent possible in their national and regional standards. Any divergence between the IEC standard and the corresponding national or regional standard shall be clearly indicated
27、 in the latter. International Standard IEC 1262-7 has been prepared by sub-committee 628: Diagnostic imaging equipment, of IEC technical committee 62: Electrical equipment in medical practice. The text of this standard is based on the following documents: I DIS I ReDort on voting I I I 62Bl2501DIS 6
28、2Bl269lRVD 1 Full information on the voting for the approval of this standard can be found in the report on voting indicated in the above table. Annexes A, 6, C and D are for information only. In this standard, the following print types are used: - Requirements, compliance with which can be tested,
29、and definitions: in roman type; - Explanations, advice, introductions, general statements, and exceptions: in smaller type; - Test specifications: in italic type; - SMALL CAPITALS. TERMS USED THROUGHOUT THIS STANDARD WHICH HAVE BEEN DEFINED IN 3.1 AND IN ANNEX A: -6- 1262-7 O CEI:1995 INTRODUCTION L
30、es systmes de formation dimage ont souvent t valus laide de mesures subjectives de performances telles que la limite de rsolution. Ces mthodes de caractrisation dimage ne dcrivent pas ncessairement les performances appropries lutilisation attendue du systme et sont sensibles la variabilit des observ
31、ateurs humains. II est possible danalyser les systmes de formation dimage linaires et invariants aux translations, daprs leurs fonctions de TRANSFERT. Le TRANSFERT de signaux de tels systmes systme un signal sinusodal en fonction de sa frquence spatiale. La FONCTION DE peut tre spcifi par la FONCTIO
32、N DE TRANSFERT OPTIQUE (FTO) qui indique ia rponse du TRANSFERT DE MODULATION (FTM), qui est le module de ia FTO , est Suffisante pour dcrire le TRANSFERT de Signaux des INTENSIFICATEURS DIMAGE RADIOLOGIQUE. LeS SyStemeS Sont Varie pas avec la position. Noter que les INTENSIFICATEURS DIMAGE RADIOLOG
33、IQUE Sont considrs comme invariants aux translations si LA FONCTION DE DISTRIBUTION PONCTUELLE ne gnralement invariants aux translations mais seulement dans une aire limite: la rgion isoplantique. La FONCTION DE TRANSFERT DE MODULATION peut tre dtermine de diverses manires (voir par exemple l de lan
34、nexe D): - partir des rponses un signal crneau; - partir de ia transforme de Fourier de la FONCTION DE DISTRIBUTION LINAIRE; - a partir de la transforme de Hankel de la FONCTION DE DISTRIBUTION PONCTUELLE; - partir du balayage de limage dune fente avec un filtre spatial. Toute mthode est acceptable
35、si elle est applique correctement. Pour des raisons de simplicit, la prsente norme repose sur deux mthodes: la transforme de Fourier de la FONCTION DE DISTRIBUTION LINAIRE, dsigne comme la mthode LSF, et ia mthode du filtre spatial. La dtermination prCiSe de la FONCTION DE TRANSFERT DE MODULATION nC
36、eSSite un quipement spcialis et ne se prte gnralement pas une mesure sur site. La presente norme spcifie des mthodes concernant Uniquement la mesure de la FONCTION DE TRANSFERT DE MODULATION des INTENSIFICATEURS DIMAGE RADIOLOGIQUE a proximit du CENTRE DU CHAMP DENTRE. 1262-7 O IEC:1995 -7- INTRODUC
37、TION Imaging systems are often being evaluated using subjective measures of performance, such as limiting resolution. These methods do not necessarily describe the performance appropriately in imaging tasks that are relevant to the intended use of the system, and are susceptible to the variability o
38、f human observers. Linear shift-invariant imaging systems can be conveniently analysed in terms of their TRANSFER FUNCTION (OTF), which shows the response of the system to sine waves as a function of their spatial frequency. The MODULATION TRANSFER FUNCTION (MTF), the modulus of the OTF, is shift-in
39、variant when the POINT SPREAD FUNCTION does not vary with position. Note that X-RAY IMAGE INTENSIFIERS generally are shift-invariant over a limited area only: the isoplanatic region. functions. The signai TRANSFER Of such Systems Can be specified by the OPTICAL TRANSFER sufficient for describing the
40、 signai TRANSFER Of X-RAY IMAGE INTENSIFIERS. Systems are called The MODULATION TRANSFER FUNCTION can be determined in several ways (see, for example l of annex D): - from square wave responses; - from the Fourier transform of the LINE SPREAD FUNCTION; - from the Hankel transform of the POINT SPREAD
41、 FUNCTION; - from scanning a slit image with a spatial filter. Any method is acceptable if performed correctly. For the purpose of simplicity, this standard elaborates on two methods: the Fourier transform of the LINE SPREAD FUNCTION, referred to as the LSF method, and the spatial filter method. Acc
42、urate determination of the MODULATION performed at field installations. TRANSFER FUNCTION requires specialized EQUIPMENT and does not generally lend itself to be This standard only specifies methods for measurement Of the MODULATION TRANSFER FUNCTION Of X-RAY IMAGE INTENSIFIERS near the CENTRE OF THE ENTRANCE FIELD.
