Background: Phototherapy units should regularly use hand-held ultraviolet (UV) meters to assess the output of treatment lamps, and these meters should be accurately calibrated. Several medical physics departments in the UK can calibrate UV meters traceable to national standards, but there is concern that there may be disagreement among departments. In particular, there may be difficulty in calibration for narrow-band UVB phototherapy lamps (TL-01).
Objectives: To ascertain the level of agreement in UV meter calibration at expert centres in the UK, and to survey methodology at these centres, consider sources of errors and to make recommendations on calibration methods.
Methods: The same UV meter with two detectors (for UVA and UVB) was calibrated by seven medical physics departments. A questionnaire on methods was also distributed and measured spectral outputs from each centre were examined.
Results: The calibration factors for the meter varied by ± 18% for the UVA detector and by ± 60% for the UVB detector (2 standard deviations). Six centres performed calibration using a spectroradiometer and one centre used a reference meter method. The spectra of lamps used for calibration were similar. For the spectroradiometric methods there were some differences in methodology and instrumentation that may account for the differences in calibration factors.
Conclusions: UV meter calibration in the UK shows unacceptable variability, particularly for TL-01 lamps. An accuracy of around of ± 10% would be clinically acceptable and should be technically achievable.
Lloyd JJ. Variation in calibration of hand-held ultraviolet (UV) meters for psoralen plus UVA and narrow-band UVB phototherapy. Br J Dermatol. 2004 Jun;150(6):1162-6.
Dr. Jim Lloyd, RVI Unit, Newcastle upon Tyne. Tel: +44 (0)191-233-6161.
Regional Medical Physics Department, Newcastle General Hospital, Newcastle upon Tyne, NE4 6BE, UK.
Tel: +44 (0)191-233-6161 Fax: +44 (0)191-226-0970 E-mail: webmaster@rmpd.org.uk Web: http://www.rmpd.org.uk
By using this site you agree to our Terms and Conditions of Use. Please read our legal page.
Regional Medical Physics Department, a Clinical Directorate of the Newcastle upon Tyne Hospitals NHS Foundation Trust.
Copyright ©1999-2008 All Rights Reserved. Revised 28 April, 2008.
