This International Standard applies to X-RAY TUBE ASSEMBLIES and to FILTERING MATERIAL, in medical diagnostic applications up to a HIGH VOLTAGE of 150 kV. For HIGH VOLTAGES greater than 50 kV, this standard applies to X-RAY TUBE ASSEMBLIES with tungsten or tungsten-alloy TARGETS only. NOTE 1 The FILTERING MATERIAL in the x-ray beam can be removable or irremovable; it can be positioned in any orientation or can have any shape (e.g. tapering thickness) although usually plane-parallel material, perpendicular to the REFERENCE AXIS is applied. Examples of FILTERING MATERIALS are ADDED FILTERS, a PATIENT table (in case of an under-table X-RAY TUBE ASSEMBLY), materials in the BEAM LIMITING DEVICE, or a breast COMPRESSION DEVICE. NOTE 2 The methodology and statement of compliance given in this standard is for flat filters only, but the methodology can be used for any kind of non-flat filter. In that case further data needs to be included with the result to be useful, e.g. field size, geometry/position on filter, etc. This standard defines the concept of PERMANENT FILTRATION of X-RAY TUBE ASSEMBLIES, and it defines the term FILTERING MATERIAL. Methods are given to determine the PERMANENT FILTRATION of an X-RAY TUBE ASSEMBLY and for determining the QUALITY EQUIVALENT FILTRATION of FILTERING MATERIALS. It contains requirements for statements of compliance of X-RAY TUBE ASSEMBLIES in ACCOMPANYING DOCUMENTS and for markings on X-RAY TUBE ASSEMBLIES. NOTE 3 This standard does not contain requirements for any specific values of permanent filtration. For X-ray equipment used for diagnostic purposes, filtration requirements are given in e.g. IEC 60601-1-3:2008 + A1:2013 or in the applicable particular standard, e.g. IEC 60601-2-28:2017. NOTE 4 The method of determination described in this standard is suitable as a type test. It is not intended as a test to be applied by the user.