IEC 60336-2005 pdf – Medical electrical equipment – X-ray tube assemblies for medical diagnosis – Characteristics of focal spots.
1 Scope This International Standard applies to FOCAL SPOT s in medical diagnostic X- RAY TUBE assemblies for medical use, operating at X- RAY TUBE VOLTAGE s up to and including 200 kV. This International Standard describes the test methods for evaluating FOCAL SPOT character- istics and the means for indicating compliance. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. IEC 60417-DB:2002: Graphical symbols for use on equipment 1) IEC 60613, Electrical, thermal and loading characteristics of rotating anode X-ray tubes for medical diagnosis IEC 60788:2004, Medical electrical equipment – Glossary of defined terms 3 Terms and definitions For the purposes of this document, the terms and definitions given in IEC 60788 together with the following apply. 3.1 STAR PATTERN RESOLUTION LIMIT characteristic of the FOCAL SPOT of an X- RAY TUBE ; highest spatial frequency that can be resolved under specific measuring conditions 4 Determinations for the evaluation of the FOCAL SPOT characteristics 4.1 Statement of the FOCAL SPOT characteristics The FOCAL SPOT characteristics shall be stated for two normal directions of evaluation referred to as the length direction and width direction. An illustration for this clause can be found in Figure A.1. 4.2 Longitudinal axis of the X – RAY TUBE ASSEMBLY Generally, the longitudinal axis can be identified unambiguously. If the X- RAY TUBE ASSEMBLY does not have an identifiable longitudinal axis or if it is specified otherwise by the MANUFACTURER , the longitudinal axis shall be specified together with the FOCAL SPOT characteristics.
4.3 R EFERENCE AXIS of the X – RAY TUBE ASSEMBLY If not specified otherwise, the REFERENCE AXIS is normal to the longitudinal axis and intersects both the centre of the ACTUAL FOCAL SPOT and the longitudinal axis of the X- RAY TUBE ASSEMBLY . 4.4 Direction of evaluation for the FOCAL SPOT length The direction of evaluation for the FOCAL SPOT length is normal to the REFERENCE AXIS in the plane given by the REFERENCE AXIS and the longitudinal axis of the X – RAY TUBE ASSEMBLY . 4.5 Direction of evaluation for the FOCAL SPOT width The direction of evaluation for the FOCAL SPOT width is normal to the longitudinal axis of the X – RAY TUBE ASSEMBLY and normal to the REFERENCE AXIS . 5 FOCAL SPOT camera set-up 5.1 Overview This clause deals with the design requirements of a camera for the production of FOCAL SPOT SLIT RADIOGRAM s to be used for the determination of FOCAL SPOT dimensions in accordance with Clause 8, and the determination of the modulation transfer function in accordance with Clause 9. This clause deals also with the design requirements of a camera for the production of FOCAL SPOT PINHOLE RADIOGRAM s. 5.2 Test equipment 5.2.1 S LIT CAMERA The diaphragm of the SLIT CAMERA shall be made from materials with high ATTENUATION properties and shall have dimensions as given in Figure 1. Suitable materials are for example: – tungsten; – tantalum; – alloy of gold and 10 % platinum; – alloy of tungsten and 10 % rhenium; – alloy of platinum and 10 % iridium;
5.4 Total uncertainty of the camera set-up The uncertainty in the FOCAL SPOT measurement contributed by the set-up of the FOCAL SPOT camera shall not exceed ±5 %. 6 Production of RADIOGRAMS 6.1 Overview This clause deals with production of FOCAL SPOT SLIT RADIOGRAMS and FOCAL SPOT PINHOLE RADIOGRAMS . A method of indicating compliance with this standard of FOCAL SPOT SLIT RADIOGRAMS and FOCAL SPOT PINHOLE RADIOGRAMS is included. 6.2 Operating conditions 6.2.1 F OCAL SPOT SLIT RADIOGRAMS and FOCAL SPOT PINHOLE RADIOGRAMS F OCAL SPOT SLIT RADIOGRAMS and FOCAL SPOT PINHOLE RADIOGRAMS shall be produced using a FOCAL SPOT camera according to Clause 5. Requirements for determining FOCAL SPOT dimensions from FOCAL SPOT SLIT RADIOGRAMS are described in Clause 8; requirements for determining the MODULATION TRANSFER FUNCTION are described in Clause 9. F OCAL SPOT PINHOLE RADIOGRAM s are used only for showing the orientation, the symmetry and the distribution of radiant intensity over the FOCAL SPOT .