Journal Article A New Approach for Quantifying Radio-Biological Effects using the Time Course of Mouse Leg Contracture

Ueno, Megumi  ,  Nakanishi, Ikuo  ,  Ken-ichiro, Matsumoto

A digitization approach to the time course of radiation-induced mouse leg contracture was proposed for quantifying the radiation effect on an individual living mouse. The shortening of the mouse leg length can be easily measured with a caliper/ruler to offer a very simple digitalized index of the radiation effect. Left hind legs of mice were irradiated with single dose of 32 Gy of 290 MeV carbon-ion beam using 0, 50, or 117 mm binary filter (BF). The right legs were used as a control. The lengths of both hind legs of the mice were measured using a digital caliper before irradiation and every week after irradiation. The degree of leg contracture, ΔSt, at the time point t was estimated by subtraction of the left irradiated leg length from the right control leg length. Equation 1 was fitted on the daily time course of ΔSt, and two parameters, ΔSmax and Ts, were estimated.ΔSt = ΔSmax × ( 1 – exp(t / Ts) )[1]where ΔSmax is the maximum degree of leg contracture, and Ts is time of leg contracture. The effect of carbon-ion irradiation on a living mouse was quantified by ΔSmax and Ts of the leg contracture, and then compared to that of X-rays. By 32 Gy irradiation, ΔSmax was largest for the BF117 experiment, followed by X-ray ~ BF50 > BF0. Ts was shortest for the BF50 experiment, while other irradiation conditions give similar Ts. A logarithmic function was successfully repurposed for the evaluation of radio-biological response.

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