Relative biologic effectiveness determination in mouse intestine for scanning proton beam at Paul Scherrer Institute, Switzerland. Influence of motion

Journal Article · Fri Jul 01 04:00:00 EDT 2005 · International Journal of Radiation Oncology, Biology and Physics

DOI:https://doi.org/10.1016/j.ijrobp.2005.03.048· OSTI ID:20698587

Gueulette, John ^[1]; Blattmann, Hans ^[2]; Pedroni, Eros ^[2]; Coray, A ^[2]; Coster, Blanche de ^[1]; Mahy, Pierre ^[1]; Wambersie, Andre ^[1]; Goitein, Gudrun ^[2]

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1. Universite catholique de Louvain, Brussels (Belgium)
2. Paul Scherrer Institute, Villigen (Switzerland)

Purpose To determine the relative biologic effectiveness (RBE) of the Paul Scherrer Institute (PSI) scanning proton beam in reference conditions and to evaluate the influence of intestine motion on the proton dose homogeneity. Methods and Materials: First, RBE was determined for crypt regeneration in mice after irradiation in a single fraction. Irradiation was performed at the middle of a 7-cm spread out Bragg peak (SOBP; reference position), as well as in the proximal part of the plateau and at the distal end of the SOBP. Control {gamma}-irradiation was randomized with proton irradiation and performed simultaneously. Second, motion of mouse intestine was determined by radiographs after copper wire markers had been placed on the jejunum and intestinal wall. Results: Proton RBE (reference {sup 60}Co {gamma}) was equal to 1.16 for irradiation at the middle of the SOBP and to 1.11 and 1.21 for irradiation in the initial plateau and end of the SOBP, respectively. The confidence intervals for these RBE values were much larger than those obtained in the other proton beams we have tested so far. They exceeded {+-}0.20 (compared with the usual value of {+-}0.07), which resulted from the unusually large dispersion of the individual proton data. The instantaneous positions of the mice intestines varied by {+-}2 mm in the course of irradiation. Conclusion: The results of this study have shown that the RBE of the PSI proton beam is in total accordance with the RBE obtained at the other centers. This experiment has corroborated that proton RBE at the middle of the SOBP is slightly larger than the generic value of 1.10 and that there is a slight tendency for the RBE to increase close to the end of the SOBP. Also, excessive dispersion of individual proton data may be considered to result from intestine motion, taking into account that irradiation at the PSI is delivered dynamically by scanning the target volume with a pencil proton beam ('spot scanning'). Because 2-mm movements resulted in significant variations in local dose depositions, this should be considered for moving targets. Strategies to reduce this effect for the spot scanning technique have been developed at the PSI for radiotherapy of humans.

• OSTI ID: 20698587
• Journal Information: International Journal of Radiation Oncology, Biology and Physics, Journal Name: International Journal of Radiation Oncology, Biology and Physics Journal Issue: 3 Vol. 62; ISSN IOBPD3; ISSN 0360-3016
• Country of Publication: United States
• Language: English

Related Subjects

62 RADIOLOGY AND NUCLEAR MEDICINE
BRAGG CURVE
COBALT 60
COPPER
GAMMA RADIATION
IMAGES
IRRADIATION
MICE
PROTON BEAMS
RADIATION DOSES
RADIOTHERAPY
RBE
SMALL INTESTINE
SWITZERLAND