title: The influence of the channel size on the reduction of side effects in microchannel proton therapy.
abstract: The potential of proton microchannel radiotherapy to reduce radiation effects in the healthy tissue but to keep tumor control the same as in conventional proton therapy is further elucidated. The microchannels spread on their way to the tumor tissue resulting in different fractions of the healthy tissue covered with doses larger than the tumor dose, while the tumor gets homogeneously irradiated. The aim of this study was to evaluate the effect of increasing channel width on potential side effects in the normal tissue. A rectangular 180 × 180 µm(2) and two Gaussian-type dose distributions of σ = 260 µm and σ = 520 µm with an interchannel distance of 1.8 mm have been applied by 20-MeV protons to a 3D human skin model in order to simulate the widened channels and to compare the irradiation effects at different endpoints to those of a homogeneous proton irradiation. The number of protons applied was kept constant at all irradiation modes resulting in the same average dose of 2 Gy. All kinds of proton microchannel irradiation lead to higher cell viability and produce significantly less genetic damage than homogeneous proton irradiation, but the reduction is lower for the wider channel sizes. Our findings point toward the application of microchannel irradiation for clinical proton or heavy ion therapy to further reduce damage of normal tissues while maintaining tumor control via a homogeneous dose distribution inside the tumor.
authors.affiliation: Institut für Angewandte Physik und Messtechnik (LRT2), Universität der Bundeswehr München, 85579, Neubiberg, Germany, stefanie.girst@unibw.de.
authors.forename: Stefanie
authors.initials: S
authors.lastname: Girst
authors.forename: Christoph
authors.initials: C
authors.lastname: Greubel
authors.forename: Judith
authors.initials: J
authors.lastname: Reindl
authors.forename: Christian
authors.initials: C
authors.lastname: Siebenwirth
authors.forename: Olga
authors.initials: O
authors.lastname: Zlobinskaya
authors.forename: Günther
authors.initials: G
authors.lastname: Dollinger
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Schmid
mesh_terms: D002470:Cell Survival / Q000528:radiation effects; D019583:Dose Fractionation, Radiation; D006801:Humans; D015603:Keratinocytes / Q000528:radiation effects; D015162:Micronucleus Tests; D009369:Neoplasms / Q000532:radiotherapy*; D061766:Proton Therapy / Q000009:adverse effects* / Q000295:instrumentation / Q000379:methods*; D011832:Radiation Injuries / Q000517:prevention & control; D012867:Skin / Q000293:injuries / Q000528:radiation effects; D046509:Tissue Culture Techniques