Volume 45, Issue 7 p. 3379-3390
Research Article

Impact of cardiosynchronous brain pulsations on Monte Carlo calculated doses for synchrotron micro- and minibeam radiation therapy

Francisco Manchado de Sola

Francisco Manchado de Sola

Servicio de Radiofísica y Protección Radiológica, Hospital Juan Ramón Jiménez, Ronda Exterior Norte, s/n, E-21005 Huelva, Spain

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Manuel Vilches

Manuel Vilches

Servicio de Radiofísica y Protección Radiológica, Centro Médico de Asturias/IMOMA, Avda. Richard Grandío, s/n, E-33193 Oviedo, Spain

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Yolanda Prezado

Yolanda Prezado

Laboratoire Imagerie et Modélisation en Neurobiologie et Cancérologie, CNRS, 5 rue Georges Clemenceau, F-91406 Orsay Cedex, France

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Antonio M. Lallena

Corresponding Author

Antonio M. Lallena

Departamento de Física Atómica, Molecular y Nuclear, Universidad de Granada, E-18071 Granada, Spain

Author to whom correspondence should be addressed. Electronic mail: [email protected]Search for more papers by this author
First published: 15 May 2018
Citations: 10

Abstract

Purpose

The purpose of this study was to assess the effects of brain movements induced by heartbeat on dose distributions in synchrotron micro- and minibeam radiation therapy and to develop a model to help guide decisions and planning for future clinical trials.

Methods

The Monte Carlo code PENELOPE was used to simulate the irradiation of a human head phantom with a variety of micro- and minibeam arrays, with beams narrower than 100 μm and above 500 μm, respectively, and with radiation fields of 1 × 2 cm and 2 × 2 cm. The dose in the phantom due to these beams was calculated by superposing the dose profiles obtained for a single beam of 1 μm × 2 cm. A parameter δ, accounting for the total displacement of the brain during the irradiation and due to the cardiosynchronous pulsation, was used to quantify the impact on peak-to-valley dose ratios and the full width at half maximum.

Results

The difference between the maximum (at the phantom entrance) and the minimum (at the phantom exit) values of the peak-to-valley dose ratio reduces when the parameter δ increases. The full width at half maximum remains almost constant with depth for any δ value. Sudden changes in the two quantities are observed at the interfaces between the various tissues (brain, skull, and skin) present in the head phantom. The peak-to-valley dose ratio at the center of the head phantom reduces when δ increases, remaining above 70% of the static value only for minibeams and δ smaller than ∼200 μm.

Conclusions

Optimal setups for brain treatments with synchrotron radiation micro- and minibeam combs depend on the brain displacement due to cardiosynchronous pulsation. Peak-to-valley dose ratios larger than 90% of the maximum values obtained in the static case occur only for minibeams and relatively large dose rates.