This Article Full Text (PDF) Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Nettleton, J S Articles by Gill, J R Search for Related Content PubMed PubMed Citation Articles by Nettleton, J S Articles by Gill, J R

Calibration frequency of DAP meters

We read with interest the recent paper by Crawley et al [1] regarding calibration frequency of dose–area product (DAP) meters. Of 41 DAP meters tested over a 5-year period, the authors found that 77% of calibrations for those fitted to overcouch tubes were within 10% of the expected value; however, for undercouch tubes only 50% of calibrations were within 10%. The authors conclude that the differences are due to adjustment of DAP meters by service engineers during routine maintenance. They suggest that because of the discrepancies, calibration should be undertaken more frequently then the annual interval recommended by the Institute of Physics and Engineering in Medicine (IPEM) Report 77 [2].

Regulation 32 of the Ionising Radiations Regulations 1999 (IRR99) [3] requires that employers in control of equipment used for medical exposures (NHS Trusts, etc.) ensure that such equipment is designed or constructed and is so installed and maintained so as to be capable of restricting so far as is reasonably practicable the exposure to ionising radiation of persons undergoing medical exposure (patients) while still achieving the intended clinical purpose. The same regulation requires employers to implement a suitable quality assurance programme for such equipment; guidance as to what constitutes a suitable programme is given in L121 Work with ionising radiation [4]. As indicated by Crawley et al, care should be taken in determining the appropriate frequency of testing. However, equally important is the need for sufficient communication between service engineers and employers (such as NHS Trusts) regarding work undertaken during maintenance or repair. It is especially important that changes that might directly or indirectly affect subsequent patient exposures are highlighted. DAP meter readings are used in the assessment of patient radiation doses, which will indirectly affect future exposures. Therefore, changes to calibration settings should be communicated by service engineers during hand-back of equipment. NHS Trusts (etc.) should ensure that clear hand-over procedures are in place for equipment that has undergone maintenance and these procedures will include notification of any changes as discussed above.

In some cases, problems have been encountered regarding transfer of information between service engineering providers and NHS Trusts (etc.), with commercial confidentiality being cited as the main reason for restricting information provided. However, the quality assurance programme required by Regulation 32 of IRR99 must be sufficient to facilitate continued restriction of patient exposures to a level that is as low as reasonably practicable. This will only be achieved if there is adequate information exchange between service engineers and users. Crawley et al recommend that managers of radiology equipment come to an agreement with manufacturers that DAP meters are not adjusted by service engineers unless specifically requested by authorised employees of NHS Trusts (etc.). This recommendation should be extended to include appropriate information transfer between user and service engineers to enable compliance with Regulation 32 of IRR99. NHS Trusts (etc.) should consider this issue when placing tenders for service contracts.

Incidentally, we would wish to mention Crawley et al's assertion that IPEM Report 77 [2] is the HSE's "inspection standard" for testing radiological equipment. The HSE has commended this guidance to employers [5], but also refers to other guidance in this context [6]. It is overstating the HSE's position to refer to the IPEM report as an inspection standard. To the extent that the HSE has any such standard, it is represented by paragraphs 538–540 of the Approved code of practice [4].

Yours etc.,

J S Nettleton ¹ and J R Gill ²

¹North West Divisional Specialist Group, Field Operations Directorate, Health and Safety Executive, Grove House, Skerton Road, Manchester M16 0RB, UK and ²Physical Agents Unit, Technology Division, Health & Safety Executive, Magdalen House, Trinity Road, Bootle L20 3QZ, UK

Received for publication June 14, 2001. Accepted for publication June 21, 2001.

References

1. Crawley MT, Mutch S, Nyekiova M, Reddy C, Weatherburn H. Calibration frequency of dose–area product meters. Br J Radiol 2001;74:259–61.[Abstract/Free Full Text]
2. IPEM/CoR/NRPB. Recommended standards for routine testing of diagnostic X-ray imaging systems, IPEM Report 77. York: IPEM, 1997.
3. Ionising Radiations Regulations 1999 (Statutory Instrument 1999 No. 3232). London: HMSO, 1999.
4. Work with ionising radiation: Ionising Radiations Regulations 1999 Approved code of practice and guidance, L121. London: HMSO.
5. Fitness of equipment used for medical exposure to ionising radiation, PM77. HSE Books, 1998.
6. European Commission 1997 Radiation protection 91: Criteria of acceptability of radiological (including radiotherapy) and nuclear medicine installations. Luxembourg: Office for Official Publications of the European Communities, 1997.

This Article Full Text (PDF) Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Nettleton, J S Articles by Gill, J R Search for Related Content PubMed PubMed Citation Articles by Nettleton, J S Articles by Gill, J R