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Calypso’s array attenuation

Published online by Cambridge University Press:  05 March 2015

Célia Silva ,
Dalila Mateus ,
Sandra Vieira ,
Milton Rodrigues ,
Margarida Eiras  and
Carlo Greco
Célia Silva*
Affiliation:
Centro Clínico Fundação Champalimaud, Lisboa, Portugal Escola Superior de Tecnologias da Saúde de Lisboa, Portugal
Dalila Mateus
Affiliation:
Centro Clínico Fundação Champalimaud, Lisboa, Portugal
Sandra Vieira
Affiliation:
Centro Clínico Fundação Champalimaud, Lisboa, Portugal
Milton Rodrigues
Affiliation:
Centro Clínico Fundação Champalimaud, Lisboa, Portugal
Margarida Eiras
Affiliation:
Escola Superior de Tecnologias da Saúde de Lisboa, Portugal
Carlo Greco
Affiliation:
Centro Clínico Fundação Champalimaud, Lisboa, Portugal
*
Correspondence to: Célia Silva, R. Outeiro Cacho, 6, Loureira, 2495-161 Sta Cat Serra, Portugal. Tel: 00351919628745. E-mail: celia.psilva@gmail.com
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Abstract

Introduction

The Calypso 4D Localization System gives the possibility to track the tumour during treatment, with no additional ionising radiation delivered. To monitor the patient continuously an array is positioned above the patient during the treatment. We intend to study, for various gantry angles, the attenuation effect of the array for 6- and 10 MV and flattening filter free (FFF) 6- and FFF 10 MV photon beams.

Materials and methods

Measurements were performed using an ion chamber placed in a slab phantom positioned at the linac isocenter for 6 MV, 10 MV, FFF 6 MV and FFF 10 MV photon beams. Measurements were performed with and without array above the phantom for 0°, 10°, 20°, 40° and 50° beam angle for a True Beam STx linac, for 5×5 and 10×10 and 15×15 cm2 field size beams to evaluate the attenuation of the array. A VMAT treatment plan was measured using an ArcCheck with and without the array in the beam path.

Results and discussion

Attenuation measured values were up to 3%. Attenuation values were between 1 and 2% with the exception of the 30°–50° gantry angles which were up to 3.3%. The ratio values calculated in the ArcCheck for relative dose and absolute dose 10 were both 1·00.

Conclusion

Attenuation of the treatment beam by the Calypso array is within acceptable limits.

Keywords

ArcCheckarrayattenuationCalypso
Type
Original Articles
Information
Journal of Radiotherapy in Practice , Volume 14 , Issue 2 , June 2015 , pp. 202 - 207
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Copyright
© Cambridge University Press 2015 

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