Real time transit dosimetry for the breath-hold radiotherapy technique: An initial experience

Author： Piermattei Angelo Cilla Savino Grimaldi Luca Viola Pietro Frattarolo Lorenzo D'Onofrio Guido Craus Maurizio Fidanzio Andrea Azario Luigi Greco Francesca Digesu Cinzia Deodato Francesco Macchia Gabriella Morganti Alessio

Publisher： Informa Healthcare

ISSN： 0284-186X

Source： Acta Oncologica, Vol.47, Iss.7, 2008-01, pp. : 1414-1421

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Abstract

Introduction. The breath-hold is one of the techniques to obtain the dose escalation for lung tumors. However, the change of the patient's breath pattern can influence the stability of the inhaled air volume, IAV, used in this work as a surrogate parameter to assure the tumor position reproducibility during dose delivery.Materials. and methodIn this paper, an Elekta active breathing coordinator has been used for lung tumor irradiation. This device is not an absolute spirometer and the feasibility study here presented developed (i) the possibility to select a specific range ε of IAV values comfortable for the patient and (ii) the ability of a transit signal rate [image omitted] , obtained by a small ion-chamber positioned on the portal image device, to supply in real time the in vivo isocenter dose reproducibility. Indeed, while the selection of the IAV range depends on the patient's ability to follow instructions for breath-hold, the [image omitted] monitoring can supply to the radiation therapist a surrogate of the tumor irradiation reproducibility.Results. The detection of the [image omitted] in real time during breath-hold was used to determine the interfraction isocenter dose variations due to the reproducibility of the patient's breathing pattern. The agreement between the reconstructed and planned isocenter dose in breath-hold at the interfraction level was well within 1.5%, while in free breathing a disagreement up to 8% was observed. The standard deviation of the [image omitted] in breath-hold observed at the intrafraction level is a bit higher than the one obtained without the patient and this can be justified by the presence of a small residual tumor motion as heartbeat.Conclusion. The technique is simple and can be implemented for routine use in a busy clinic.