IEC 62467-1 pdf download Medical electrical equipment – Dosimetric instruments as used in brachytherapy – Part 1: Instruments based on well-type ionization chambers
4 General requirements
4.1 P ERFORMANCE REQUIREMENTS
Each of the components of a WELL – TYPE CHAMBER SYSTEM shall comply with the individual requirements in the appropriate clauses or subclauses in addition to the general requirements. The instruments shall be installed and operated in accordance with the MANUFACTURER ’s instructions. In Clauses 5 and 6, the performance requirements are stated for a complete WELL – TYPE CHAMBER SYSTEM including both the WELL – TYPE IONIZATION CHAMBER and MEASURING ASSEMBLY .
For a MEASURING ASSEMBLY designed to operate with one or more WELL – TYPE IONIZATION CHAMBERS , each combination of the WELL – TYPE CHAMBER SYSTEM shall comply with the requirements in 4.4, and in Clauses 5 and 6 relevant to this combination. During the immunity tests for electromagnetic compatibility (see IEC 60731 ) BASIC SAFETY and ESSENTIAL PERFORMANCE shall be guaranteed.
E SSENTIAL PERFORMANCE is guaranteed if the limits listed in Table 2 are not exceeded during the immunity tests. E SSENTIAL PERFORMANCE is also ensured if during the immunity tests the reading of the MEASURING ASSEMBLY , or the data output, are clearly characterized as invalid, e.g. by means of a warning message or in case of a latch-up.
NOTE Examples for warning messages for invalid readings are high voltage error or overload messages.
4.2 M EASURING ASSEMBLY The MEASURING ASSEMBLY shall conform to field class instruments of IEC 60731 , unless stated otherwise.
4.3 Source types
4.3.1 General The BRACHYTHERAPY source determines the insert used in the WELL – TYPE IONIZATION CHAMBER . For each BRACHYTHERAPY source type, the MANUFACTURER of the WELL – TYPE IONIZATION CHAMBER shall specify the insert type to be used. The tests below shall be made with the insert type specified by the MANUFACTURER of the WELL – TYPE IONIZATION CHAMBER
4.3.2 Beta particle-emitting sources Measurements on beta particle-emitting sources of the same radionuclide and activity will vary greatly with insert composition (for example glass versus plastic) and wall thickness. Some inserts depend on a measure of BREMSSTRAHLUNG produced by the deceleration of the beta particles in the insert material; other inserts are designed to measure the betas directly. Reproducible measurements depend upon consistent insert selection and consistency in the manner in which the instrument is used.
4.3.3 Low-energy-photon-emitting sources The wall thickness of the insert plus the thickness of the interior wall of the WELL – TYPE IONIZATION CHAMBER may cause a significant attenuation for low-energy photons. Wide variations in wall materials and source materials may result in variations in RESPONSE .
4.4 Quantity to be measured The following quantities are used: AIR KERMA STRENGTH in units of Gy m 2 /s, ABSORBED DOSE RATE TO WATER at a specified distance from the source in units of Gy/s, REFERENCE AIR KERMA RATE in units of Gy/s.