The results of a detailed characterization study of a novel UV-activated colorimetric oxygen indicator are described. The indicator uses nanoparticles of titania to photosensitize the reduction of methylene blue by triethanolamine in a polymer encapsulation medium, using UVA light. Upon UV irradiation, the indicator bleaches and remains in this colorless state in the dark, unless and until it is exposed to oxygen, whereupon its original color is restored. The indicator is reusable and irreversible. The rate of color recovery is proportional to the level of oxygen present. A layer of PET (poly(ethylene terephthalate)), of thickness b, placed on top of the indicator film slows down its response, and the 90% recovery time is proportional to b.

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A novel UV indicator is described, comprising nanocrystalline particles of titania dispersed in a film of a polymer, hydroxyl ethyl cellulose (HEC), containing: a mild reducing agent, triethanolamine (TEOA) and a redox indicator, methylene blue (MB). The UV indicator film is blue-coloured in the absence of UV light and loses colour upon exposure to UV light, attaining within a few min a steady-state degree of bleaching that can provide a measure of the irradiance of the incident light. The original blue colour of the film returns once the source of UV light is removed. The spectral characteristics of a typical UV indicator film, and its components, are discussed and the UV-absorbing action of the titania particles highlighted. From the measured %bleaching undergone by a typical UV indicator as a function of light irradiance the indicator appears fully bleached, within 7 min, by a UV irradiance of 3 mW cm(-2) or greater. The mechanism by which the UV indicator works is described. The reversible nature of the UV indicator is removed by covering a typical UV indicator with a thin, largely oxygen impermeable, polymer film, such as the regenerated cellulose found in Sellotape. The product is a UV dosimeter, the response of which is related to the intensity and duration of the incident UV light, as well as the amount of titania in the film. A typical UV dosimeter film is fully bleached by 250 mJ cm(-2) of UV light. The possible use of these novel indicators to measure UV exposure levels, irradiance and dose, is discussed.

Recent developments in Radiotherapy treatment technology (Intensity Modulated Radio-therapy (IMRT), Volumetric Arc Radiotherapy, (VMAT) and Flattening Filter Free, (FFF) in addition to new products used to build bunkers place an ever-increasing demand on traditional empirical calculations. They are usually based on look up tables featured in the above publications and employed in spreadsheets to predict the exiting dose rate on the other side of the barrier. Furthermore, upgrades of departments and changing national legislation governing environmental radiation levels reflect in a need to continuously update and validate the spreadsheets. The design of each radiotherapy bunker is unique due to the particular department which requires a reworking of the spreadsheets and calculation. Each review tends to be detailed; time consuming but must be precise (errors are costly when barrier thickness of up to 3.0m concrete is required to attenuate the

In 2012, a plan to develop Stereotactic treatments using a Cyberknife was unveiled at the Hermitage Medical Clinic, Dublin. Due to planning restrictions the new facility had to be contained in the existing hospital's blue print with the only available location being an unused CT simulation room. The room design would be different from conventional radiotherapy bunkers due to the fact the Cyberknife can fire an unfiltered beam in any direction bar the roof (restriction of 22° above the horizontal). Therefore all walls must be primary barriers with the roof designed to protect against the large leakage radiation resulting from the high MU's used during the treatments. Space consideration indicated that concrete alone could not be used to restrict the radiation beam to acceptable limits. To this end a combination of steel, lead, normal and heavy concrete were used to meet the dose constraints established by the Irish licensing authorities.