Perspex dosimeter

In radiation sterilization, a plastic (olien perspex) dosimeter which gradually darkens in proportion to the radiation absorbed gives an accurate measure of the radiation dose and is considered to be the best technique currently available for following the radiosterilization process. 

Resin-impregnated samples were irradiated for 40 h at a dose rate of 1 kGy/h (total dose, 40 kGy). Monomer-impregnated samples were cured in two batches, one at a dose rate of 0.6 kGy/h and the other at 1 kGy/h, also for 40 h (total doses of 24 kGy and 40 kGy, respectively). Dosimetry was carried out by using a Red Perspex dosimeter, based on the radiation coloration of commercial red-dyed Perspex type Red 4034 and a calibration curve relating the induced absorption coefficient to dose. 

Polymethylmethacrylate dosimeter. Several types of polymethylmethacrylate are known as potential dosimeters, and one system, clear (HX) Perspex, was developed for routine dose measurement (ISO/ASTM 51276). It is prepared using benzod peroxide as polymerization initiator. The irradiated clear Perspex dosimeters are measured hy spectrophotometry usually at 314 nm or 315 nm, as the most stable wavelengths for evaluation (Chadwick 1969). The response of the HX Perspex was found to be independent of irradiation temperature in the range of 0-30° C, but at higher temperatures the response was decreasing (Miller and McLaughlin 1981). Miller et al. (1975) observed the effect of dose rate on the response too at values above 10 Gy s . ... 

When irradiating the red Perspex dosimeter, the appearance of an optical band absorbing between 600 nm and 700 nm can be observed resulting in the darkening of the original red color of the 1 cm x 3 cm dosimeter (Whitakker et al. 1985). Spectrophotometric evaluation of... 

The Perspex dosimeter family is frequently used in radiation processing for process control in a wide dose range mainly in gamma radiation processing. Due to the combined effects of environmental factors, however, they - like most dosimeters used in radiation processing - should be calibrated under conditions of use (Glover et al. 1985). 

Whatever the source of radiation used, the dose delivered to the biological samples is determined by the time of exposure to radiations. Thus the dose delivered by the radiation source must be measured with precision. Dosimetry can be performed with a ferrous sulfate solution (Fricke and Morse, 1927), thermoluminescent dosimeters, bleaching of films (Hart and Fricke, 1967), Perspex dosimetry (Berry and Marshall, 1969), or calibration with standard enzymes (Beauregard et al., 1980 Beauregard and Potier, 1982 Lo et al., 1982). In many laboratories, control enzymes with known D37 are added to protein preparations as internal standards so that any variation between experiments could be corrected for. Because of the better precision of dose rate in Gammacell irradiators, this precaution is not necessary. 

Dyed polymethylmethacrylate (PMMA) dosimeter. Polymethylmethacrylate dosimeters containing different types of dyes have been developed for routine dosimetry mainly in radiation sterilization and have been used extensively for many decades (Whitakker 1970 ISO/ASTM 2002e). Various types of the PMMA dosimeters are known, but the most popular are the red Perspex, the amber Perspex, and the Gammachrome YR. 

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