This International Standard applies to test procedures which, for the determination of
characteristics of systems or components of medical diagnostic X-RAY EQUIPMENT, require
well-defined RADIATION CONDITIONS.
Except for mammography, this standard does not apply to conditions where discontinuities in
radiation absorption of elements are deliberately used to modify properties of the RADIATION
BEAM (for example by rare earth filters).
The most complete specification of RADIATION FIELDS is given by the spectral distribution of the
photon fluence. Since the measurement of X-RAY SPECTRA is a demanding task, this standard
expresses RADIATION QUALITIES in terms of the X-RAY TUBE VOLTAGE, the first and second HALFVALUE
LAYER. In the case of RADIATION CONDITIONS, specifications are performed additionally in
terms 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 the
mutually conflicting requirements of avoiding excessive efforts for establishing a RADIATION
QUALITY and of the complete absence of any ambiguity in the definition of a RADIATION
QUALITY. 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 XRAY
TUBE VOLTAGE having the same first HALF-VALUE LAYER can still have quite different
spectral distributions. Given the inherent ambiguity in the characterization of RADIATION
QUALITY, 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 to
jeopardise the underlying objective of this standard. This standard is to ensure that
measurements of the properties of medical diagnostic equipment should produce consistent
results 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 RADIATION
CONDITION could be established in the framework of the first edition of this standard have been
removed. The essential restriction introduced in this second edition is that the X-RAY TUBE
VOLTAGE is measured and set to its 'correct' value. The second step is to attempt to establish
the prescribed first HALF-VALUE LAYER by adding into the beam the necessary amount of
ADDITIONAL FILTRATION. If the INHERENT FILTRATION provided by the X-RAY TUBE alone is so
strong that the HALF-VALUE LAYER of the RADIATION BEAM emerging from the X-RAY TUBE
ASSEMBLY as such is larger than that to be established, the X-RAY TUBE ASSEMBLY used is not
suited for producing the desired RADIATION CONDITION. This may occur if the anode angle of
the X-RAY TUBE ASSEMBLY is too small and/or in the case of excessive anode roughening due
to tube ageing.
In the approach outlined in the two preceding paragraphs the X-RAY TUBE VOLTAGE plays a
decisive role. It is therefore essential that the ‘correct’ X-ray tube voltage is chosen
irrespective of the type of high voltage generator connected to the X-RAY TUBE. The way in
which this is realized in this standard is by measuring the X-RAY TUBE VOLTAGE in terms of the
PRACTICAL PEAK VOLTAGE. This quantity is a weighted mean of all values of the X-RAY TUBE
VOLTAGE occurring during an exposure. The weighting is done in such a way that identical
values of the PRACTICAL PEAK VOLTAGE give identical values of the low level contrast on a radiograph irrespective of the waveform supplied by the generator.
IEC 61267:2005 Referenced Document
IEC 61674:1997 Medical electrical equipment - Dosimeters with ionization chambers and/or semi-conductor detectors as used in X-ray diagnostic imaging
IEC 61676:2002 Medical electrical equipment - Dosimetric instruments used for non-invasive measurement of X-ray tube voltage in diagnostic radiology
ISO 4037-1:1996 X and gamma reference radiation for calibrating dosemeters and doserate meters and for determining their response as a function of photon energy - Part 1: Radiation characteristics production methods
IEC 61267:2005 history
2005IEC 61267:2005 Medical diagnostic X-ray equipment - Radiation conditions for use in the determination of characetristics
1994IEC 61267:1994 Medical diagnostic X-ray equipment - Radiation conditions for use in the determination of characteristics