TY - JOUR
T1 - Epid cine acquisition mode for in vivo dosimetry in dynamic arc radiation therapy
AU - Fidanzio, Andrea
AU - Mameli, Alessandra
AU - Placidi, Elisa
AU - Greco, Francesca
AU - Stimato, Gerardina
AU - Gaudino, Diego
AU - Ramella, Sara
AU - D'Angelillo, Rolando
AU - Cellini, Francesco
AU - Trodella, Lucio
AU - Cilla, Savino
AU - Grimaldi, Luca
AU - D'Onofrio, Guido
AU - Azario, Luigi
AU - Piermattei, Angelo
PY - 2008
Y1 - 2008
N2 - In this paper the cine acquisition mode of an electronic portal imaging device (EPID) has been calibrated and tested to determine the in vivo dose for dynamic conformal arc radiation therapy (DCAT). The EPID cine acquisition mode, that allows a frame acquisition rate of one image every 1.66 s, was studied with a monitor unit rate equal to 100 UM/min. In these conditions good signal stability, ±1% (2SD) evaluated during three months, signal reproducibility within ±0.8% (2SD) and linearity with dose and dose rate within ±1% (2SD) were obtained. The transit signal, St, (due to the transmitted beam below the phantom) measured by the EPID cine acquisition mode was used to determine, (i) a set of correlation functions, F(w,L), defined as the ratio between St and the dose at half thickness, Dm, measured in solid water phantoms of different thicknesses, w and with square fields of side L, (ii) a set of factors, f(d,L), that take into account the different X-ray scatter contribution from the phantom to the St signal as a function of the variation, d, of the air gap between the phantom and the EPID. The reconstruction of the isocenter dose, Diso, for DCAT was obtained convolving the transit signal values, obtained at different gantry angles, with the respective reconstruction factors determined by a house-made software. The method was tested with cylindrical and anthropomorphic phantoms and the results show that the reconstructed Diso values can be obtained with an accuracy within ±2.5% in cylindrical phantom and within ±3.4% for anthropomorphic phantom. In conclusion, the transit dosimetry by EPID was assessed to be adequate to perform DCAT in vivo dosimetry, that is not realizable with the other traditional techniques. Moreover, the method proposed here could be implemented to supply in vivo dose values in real time. © 2007 Elsevier B.V. All rights reserved.
AB - In this paper the cine acquisition mode of an electronic portal imaging device (EPID) has been calibrated and tested to determine the in vivo dose for dynamic conformal arc radiation therapy (DCAT). The EPID cine acquisition mode, that allows a frame acquisition rate of one image every 1.66 s, was studied with a monitor unit rate equal to 100 UM/min. In these conditions good signal stability, ±1% (2SD) evaluated during three months, signal reproducibility within ±0.8% (2SD) and linearity with dose and dose rate within ±1% (2SD) were obtained. The transit signal, St, (due to the transmitted beam below the phantom) measured by the EPID cine acquisition mode was used to determine, (i) a set of correlation functions, F(w,L), defined as the ratio between St and the dose at half thickness, Dm, measured in solid water phantoms of different thicknesses, w and with square fields of side L, (ii) a set of factors, f(d,L), that take into account the different X-ray scatter contribution from the phantom to the St signal as a function of the variation, d, of the air gap between the phantom and the EPID. The reconstruction of the isocenter dose, Diso, for DCAT was obtained convolving the transit signal values, obtained at different gantry angles, with the respective reconstruction factors determined by a house-made software. The method was tested with cylindrical and anthropomorphic phantoms and the results show that the reconstructed Diso values can be obtained with an accuracy within ±2.5% in cylindrical phantom and within ±3.4% for anthropomorphic phantom. In conclusion, the transit dosimetry by EPID was assessed to be adequate to perform DCAT in vivo dosimetry, that is not realizable with the other traditional techniques. Moreover, the method proposed here could be implemented to supply in vivo dose values in real time. © 2007 Elsevier B.V. All rights reserved.
KW - Dynamic treatments
KW - EPID
KW - In vivo dosimetry
KW - Dynamic treatments
KW - EPID
KW - In vivo dosimetry
UR - http://hdl.handle.net/10807/204828
U2 - 10.1016/j.nimb.2007.11.038
DO - 10.1016/j.nimb.2007.11.038
M3 - Article
SN - 0168-583X
VL - 266
SP - 658
EP - 666
JO - NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH. SECTION B, BEAM INTERACTIONS WITH MATERIALS AND ATOMS
JF - NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH. SECTION B, BEAM INTERACTIONS WITH MATERIALS AND ATOMS
ER -