IEC 60522-1-2020 pdf download.Medical electrical equipment – Diagnostic X-rays – Part 1: Determination of quality equivalent filtration and permanent filtration.
4 Determination of QUALITY EQUIVALENT FILTRATION
4.1 Alignment of X- RAY TUBE ASSEMBLIES and of the FILTERS
If, apart from the X- RAY TUBE ASSEMBLY under test, a reference X- RAY TUBE ASSEMBLY is used,then their REFERENCE AXES shall be aligned.
NOTE The alignment of the REFERENCE AXES is important, as the HALF – VALUE LAYER depends strongly on the effective TARGET ANGLE . Simulations show, that at the typical mammographic HIGH VOLTAGE of 30 kV, the typical error in PERMANENT FILTRATION is of the order of 1 ,5 % per one-degree misalignment. At the typical radiographic HIGH
VOLTAGE of 75 kV, it is of the order of 4 %.
Unless otherwise stated, the FILTERS are positioned perpendicular to the REFERENCE AXIS .
4.2 Generation of the X- RAY BEAM for the determination
The PERCENTAGE RIPPLE shall not be larger than 1 0 %.
It is recommended to limit the PERCENTAGE RIPPLE to 4 %, in order to maintain accuracy,– if the HIGH VOLTAGE is smaller than 50 kV, or
– if the HIGH VOLTAGE is larger than 50 kV and if the atomic number of the FILTERS is larger than 30, or
– if the HIGH VOLTAGE is larger than 50 kV and the atomic number of the FILTERS is not larger than 30, while the sum of the QUALITY EQUIVALENT FILTRATION of all materials with atomic number not larger than 26 is smaller than 0,5 mm Al.
The HIGH VOLTAGE shall be kept constant during all the steps in the determination.
NOTE Stability of the HIGH VOLTAGE during the determination is important, as the HALF – VALUE LAYER depends strongly on the HIGH VOLTAGE .
H IGH VOLTAGE -shift of the order of 1 % in one of the steps of the determination can lead to an error in the determined value of the QUALITY EQUIVALENT FILTRATION of the order of 1 0 %.
Unless other standards prescribe the HIGH VOLTAGE , the following values of the HIGH VOLTAGE are recommended:
– for mammographic applications, 28 kV,
– for dental applications, 60 kV,
– for any other application, 75 kV,
– unless the application does not include 75 kV or is centred outside 75 kV; then it is recommended to apply a HIGH VOLTAGE in the range of the application.
4.3 Requirements for RADIATION DETECTOR
An AIR KERMA RATE RADIATION DETECTOR shall be used which complies with the requirements of IEC 61 674:201 2 for the beam qualities seen by the detector during the QUALITY EQUIVALENT FILTRATION -determination.
NOTE This requirement ensures that the detector used has a sufficiently flat AIR KERMA RATE response.
4.4 Composition of reference material
Values of HALF – VALUE LAYER and QUALITY EQUIVALENT FILTRATION determined in accordance with this document apply to the reference material aluminium with 99,9 % purity or higher and density 2,70 g/cm 3 .
4.5 Determination of PERMANENT FILTRATION
4.5.1 Guideline
NOTE For guidance and overview, Table 1 serves to support selecting the appropriate method for determining the QUALITY EQUIVALENT FILTRATION . It does not replace the text of the paragraphs 4.5.2 to 4.5.4, which are to be referenced to take the final decision on the method to be applied.IEC 60522-1 pdf download.