Room: Exhibit Hall | Forum 7
Purpose: To determine the effect of temperature on radiochromic film dosimetry during radiation exposure period rather than its effect during post-exposure storage and scanning. Rink et al. (Med Phys. 2008 Oct; 35(10):4545-55.) observed profound net optical density temperature dependence from 23 â„ƒ to 38 â„ƒ using a spectrophotometer as a real-time densitometer for irradiated EBT film.
Methods: GafChromicâ„¢ EBT3 films from the same lot were cut into 8Ã—10 cmÂ². A solid water frame was used to hold film sheets within a water tank with controlled water temperature. The film pieces were irradiated by a 5Ã—5 cmÂ² open field at 10 cm water depth with 6 different dose levels. Water temperatures ranging from 21 â„ƒ to 41 â„ƒ with the interval of 5 â„ƒ were determined by a thermo-diode. The irradiated films were stored at the same room temperature and humidity for 24 hours before being scanned on an Epson 10000XL scanner. The film pieces irradiated at the same dose levels under different temperatures were centered on the scanning window in a single scan to eliminate scan-to-scan variability. The uncompressed TIFF 48-bit RGB (16-bit per channel) images were analyzed in Image J v 1.51. For each exposed film piece, pixel values of a 2 Ã—1.5 cmÂ² region of interest at center were averaged.
Results: The responses of EBT3 films irradiated at the same dose levels under different temperatures are within 0.61% difference compared to the ones irradiated at room temperature for each color channel.
Conclusion: Unlike spectrophotometer results with a narrow wavelength band, using a waiting time window before readout and a flatbed scanner, such as the Epson 10000XL, as a densitometer measuring transmitted light integrated over a broad band of wavelength, a range of temperatures during irradiation are possible with minimal effect on readout for film dosimetry.
Radiochromic Film, Thermometry, Dosimetry