OSL films for in-vivo entrance dose measurements

Measuring entrance exposures to diagnostic or therapeutic radiology patients is valuable to infer dose distributions within their bodies in order to minimize unnecessary exposures. For this purpose, we investigated the development of dosimeters consisting of waterproof, transparent, and flexible films containing OSL microcrystals. In our method, films are produced by casting solutions, followed by solvent evaporation. Non-aggressive chemicals are used, which allows production of a film containing large quantities of crystals without altering their structure. In this proof of principle, we chose polyvinyl chloride (PVC) as a polymer matrix due to its high transparency and its waterproof nature and we produced films loaded with microcrystals of CaF2:Ce. A mixture of acetone:benzene (40:60 wt%) was selected as the best solvent for producing PVC films loaded with CaF2:Ce crystals. This solvent offers ease of handling, low toxicity, low cost, and does not affect the crystal structure nor its OSL emission. The PVC films can be loaded with any luminescent material. For proof of concept we chose to load it with CaF2:Ce micron sized particles because they emit an intense OSL signal for a low beta dose of 100 mGy, showing very good sensitivity for dosimetric applications. The results indicate that films loaded with OSL crystals may be suitable for the production of novel OSL dosimeter, which adheres closely to the body and could be used during a radiological procedure to estimate the entrance dose. As OSL materials are sensitive to light, the films would have somehow to be shielded from light for dosimetric purposes.