IEC 61267-2005 医用诊断X射线设备.测定特性时使用的辐射条件

标准号：IEC 61267-2005
中文标准名称：医用诊断X射线设备.测定特性时使用的辐射条件
英文标准名称：Medical diagnostic X-ray equipment - Radiation conditions for use in the determination of characetristics
标准类型：C43
发布日期：1999/12/31 12:00:00
实施日期：1999/12/31 12:00:00
中国标准分类号：C43
国际标准分类号：11.040.50
引用标准：IEC 61674-1997;IEC 61676-2002;ISO 4037-1-1996
适用范围：This International Standard applies to test procedures which, for the determination ofcharacteristics of systems or components of medical diagnostic X-RAY EQUIPMENT, requirewell-defined RADIATION CONDITIONS.Except for mammography, this standard does not apply to conditions where discontinuities inradiation absorption of elements are deliberately used to modify properties of the RADIATIONBEAM (for example by rare earth filters).The most complete specification of RADIATION FIELDS is given by the spectral distribution of thephoton fluence. Since the measurement of X-RAY SPECTRA is a demanding task, this standardexpresses RADIATION QUALITIES in terms of the X-RAY TUBE VOLTAGE, the first and second HALFVALUELAYER. In the case of RADIATION CONDITIONS, specifications are performed additionally interms of PHANTOM properties and geometry.The attempt to characterize a spectral distribution just by means of the X-RAY TUBE VOLTAGE,the first and possibly the second HALF-VALUE LAYER is thus a compromise between themutually conflicting requirements of avoiding excessive efforts for establishing a RADIATIONQUALITY and of the complete absence of any ambiguity in the definition of a RADIATIONQUALITY. Due to differences in the design and the age of X-RAY TUBES in terms of anode angle,anode roughening and INHERENT FILTRATION, two RADIATION QUALITIES produced at a given XRAYTUBE VOLTAGE having the same first HALF-VALUE LAYER can still have quite differentspectral distributions. Given the inherent ambiguity in the characterization of RADIATIONQUALITY, it is essential that further tolerances introduced by allowing certain ranges of values,e.g. for X-RAY TUBE VOLTAGE and first HALF-VALUE LAYER, must be sufficiently small not tojeopardise the underlying objective of this standard. This standard is to ensure thatmeasurements of the properties of medical diagnostic equipment should produce consistentresults if RADIATION QUALITIES or RADIATION CONDITIONS in compliance with this standard are used.To achieve this objective, certain degrees of freedom in the way in which a RADIATIONCONDITION could be established in the framework of the first edition of this standard have beenremoved. The essential restriction introduced in this second edition is that the X-RAY TUBEVOLTAGE is measured and set to its 'correct' value. The second step is to attempt to establishthe prescribed first HALF-VALUE LAYER by adding into the beam the necessary amount ofADDITIONAL FILTRATION. If the INHERENT FILTRATION provided by the X-RAY TUBE alone is sostrong that the HALF-VALUE LAYER of the RADIATION BEAM emerging from the X-RAY TUBEASSEMBLY as such is larger than that to be established, the X-RAY TUBE ASSEMBLY used is notsuited for producing the desired RADIATION CONDITION. This may occur if the anode angle ofthe X-RAY TUBE ASSEMBLY is too small and/or in the case of excessive anode roughening dueto tube ageing.In the approach outlined in the two preceding paragraphs the X-RAY TUBE VOLTAGE plays adecisive role. It is therefore essential that the ‘correct’ X-ray tube voltage is chosenirrespective of the type of high voltage generator connected to the X-RAY TUBE. The way inwhich this is realized in this standard is by measuring the X-RAY TUBE VOLTAGE in terms of thePRACTICAL PEAK VOLTAGE. This quantity is a weighted mean of all values of the X-RAY TUBEVOLTAGE occurring during an exposure. The weighting is done in such a way that identicalvalues of the PRACTICAL PEAK VOLTAGE give identical values of the low level contrast on a radiograph irrespective of the waveform supplied by the generator.