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Relativebiological effectiveness RBE is an important quantity in planning particlebeam cancer therapy. In general, the RBE describes the biological effectivenessof a given primary beam with respect to a reference photon irradiation. RBEvaries not only for different primary beams but also with depth in the targetfor a given beam modality. It is not a quantity that easily lends itself tomeasurements or computation as it depends on many biological and physicalquantities. Numerous experiments in vitro using various celllines and irradiation modalities have shown that a general relationship betweenRBE and the physical quantity Linear Energy Transfer LET exists. Severalgroups have proposed including LET in the radiation therapy treatment planninginstead of the more complicated and elusive RBE. It has been shown that LET is animportant quantity to consider in treating radio-resistant tumors. The conceptof LET painting has been proposed with the goal of improving tumor controlprobability TCP for hypoxic tumors by focusing high LET radiation on thehypoxic region of the tumor while restricting the surrounding normal tissue tolow LET radiation. In order to properly incorporate LET in clinical treatment,it is important to be able to experimentally measure and verify LETdistribution. We propose a novel method for measuring LET using a dual chambermethodology exploiting the difference in the observed recombination between airfilled ionization chambers IC and liquid filled ionization chambers LIC.The resulting difference in the measured signals will be used to directly extractthe relative LET of an actual treatment beam in real time. This paper describesour initial studies of this method, presents preliminary results, and discussesfurther improvements toward a practical real-time LET measuring device.

KEYWORDS

Linear Energy Transfer, Relative Biological Effectiveness, Liquid Ionization Chambers

Cite this paper

Tegami, S. , Bello, S. , Luan, S. , Mairani, A. , Parodi, K. and Holzscheiter, M. 2017 LET Monitoring Using Liquid Ionization Chambers. International Journal of Medical Physics, Clinical Engineering and Radiation Oncology, 6, 197-207. doi: 10.4236-ijmpcero.2017.62018.





Autor: Sara Tegami1, Stephen D. Bello2, Shuang Luan3, Andrea Mairani4,5, Katia Parodi4,6, Michael H. Holzscheiter1,2*

Fuente: http://www.scirp.org/



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