AbstractID: 9058 Title: Dependence of Radiochromic Film Response Kinetics on Dose
Fraction
Radiochromic film (RCF) has been shown to be a precise and accurate secondary planar
dosimeter for acute exposure radiation fields. However, because the speed and extent of
post-exposure OD growth increases with decreasing dose, to the possibility of dose-rate
dependent RCF response, which would compromise accuracy of brachytherapy
measurements, can not be ruled out. To address this issue, we have compared the
response of RCF Model 55-2 to total doses of 1-20 Gy delivered in 1, 2, 4 and 5 daily
fractions. Our measured results do indeed show that film response 1 hour after exposure
increases with increasing number of fractions relative to the same dose given in a single
fraction, ranging from 14% to 40% for total doses of 20 Gy and 1 Gy, respectively, given
in five fractions.
This dose fractionation effect dissipates rapidly with increasing
exposure-to-densitometry time interval, falling to about 2% within 96 h. Our previously
described cumulative dose superposition model, based upon curve fits to the singlefraction OD versus time and dose response curves, reproduces the major trends of the
measured data.
This work was supported by grant R01 CA 46640 awarded by NIH.