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Theoretical and empirical investigations of K Cl : Eu 2 + for nearly water‐equivalent radiotherapy dosimetry
Author(s) -
Zheng Yuanshui,
Han Zhaohui,
Driewer Joseph P.,
Low Daniel A.,
Li H. Harold
Publication year - 2010
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.3271338
Subject(s) - dosimeter , dosimetry , materials science , ionization chamber , monte carlo method , dose profile , imaging phantom , sensitivity (control systems) , effective atomic number , optics , photon , ionization , nuclear medicine , physics , electronic engineering , ion , mathematics , medicine , statistics , engineering , quantum mechanics
Purpose The low effective atomic number, reusability, and other computed radiography‐related advantages make europium doped potassium chloride ( K Cl : Eu 2 + ) a promising dosimetry material. The purpose of this study is to model K Cl : Eu 2 +point dosimeters with a Monte Carlo (MC) method and, using this model, to investigate the dose responses of two‐dimensional (2D) K Cl : Eu 2 +storage phosphor films (SPFs). MethodsK Cl : Eu 2 +point dosimeters were irradiated using a 6 MV beam at four depths ( 5 – 20 cm ) for each of five square field sizes ( 5 × 5 – 25 × 25cm 2 ) . The dose measured by K Cl : Eu 2 +was compared to that measured by an ionization chamber to obtain the magnitude of energy dependent dose measurement artifact. The measurements were simulated using DOSXYZnrc with phase space files generated by BEAMnrcMP. Simulations were also performed for K Cl : Eu 2 +films with thicknesses ranging from 1 μ m to 1 mm . The work function of the prototype K Cl : Eu 2 +material was determined by comparing the sensitivity of a 150 μ m thick K Cl : Eu 2 +film to a commercial Ba F Br 0 . 85I 0 . 15 : Eu 2 +‐based SPF with a known work function. The work function was then used to estimate the sensitivity of a 1 μ m thick K Cl : Eu 2 +film. Results The simulated dose responses of prototype K Cl : Eu 2 +point dosimeters agree well with measurement data acquired by irradiating the dosimeters in the 6 MV beam with varying field size and depth. Furthermore, simulations with films demonstrate that an ultrathin K Cl : Eu 2 +film with thickness of the order of 1 μ m would have nearly water‐equivalent dose response. The simulation results can be understood using classic cavity theories. Finally, preliminary experiments and theoretical calculations show that ultrathin K Cl : Eu 2 +film could provide excellent signal in a 1 cGy dose‐to‐water irradiation. Conclusions In conclusion, the authors demonstrate that K Cl : Eu 2 +‐based dosimeters can be accurately modeled by a MC method and that 2D K Cl : Eu 2 +films of the order of 1 μ m thick would have minimal energy dependence. The data support the future research and development of a K Cl : Eu 2 +storage phosphor‐based system for quantitative, high‐resolution multidimensional radiation therapy dosimetry.