A study of the correction factor for ultraviolet phototherapy dose measurements made by the indirect method

Abstract

The DIR should be applied to any measurements made using radiometers without a person or equivalent phantom in a cabin. It is proposed that standard values are appropriate for groups of cabins with a single type of lamp and similar reflectors.

/ Method’s evaluation System for monitoring UV radiation level in phototherapy cabins in Poland

“…The manikin (such as normally used in clothes shops) simulates a rather thin patient, whereas the dressed manikin imitates the presence of a stockier patient in the cabin. The attenuation range found by the CCS in LPC corresponds to the correction factor obtained in earlier studies [ 14 ]. Table III shows that the nominal doses set by the nursing staff were about 20% higher than the ones measured by the CCS for Mode B of LPC testing.…”

“…Assessment of the cabin performance requires the irradiance measurements with and without a person in the cabinet to establish a correction factor accounting for the presence of the body, which itself absorbs UV radiation [ 5 ]. The body correction factor varies between 0.80 and 0.96, and it depends on the cabinet design and patient posture [ 13 , 14 ].…”

An update and guidance on narrowband ultraviolet B phototherapy: a British Photodermatology Group Workshop Report

“…Skin and eyes must be protected from UV exposure, for example by use of a UV‐protective suit. Other indirect methods may be used provided a correction factor is applied to account for the occupancy effect of the patient inside the cabin 107 . Automated systems can provide a reproducible technique for measurement of irradiance over a range of directions in a whole cabin and provide more detailed information on dose distributions 108 .…”

Guidelines on the measurement of ultraviolet radiation levels in ultraviolet phototherapy: report issued by the British Association of Dermatologists and British Photodermatology Group 2015

“…Especially problematic are types reliant on monitoring a small number of lamps . More recent types compensate reasonably well for differences in the amount of shielding of the fluorescent tubes by patients of differing sizes . However, it should be recognized that internal dosimeters monitor the UV that is reflected from a relatively small area of skin and do not measure the average irradiance to the whole patient.…”

“…Correction factors are applied to allow for this, with measurements made by the indirect method, described in section 14·2. For NB‐UVB, factors between 0·85 and 0·96 have been reported, and for UVA factors between 0·80 and 0·87 have been reported . The factor may be less for both smaller and elliptical cabins, as the patient intercepts a larger proportion of the UVR emitted.…”