Preclinical biological assessment of proton and carbon ion beams at Hyogo Ion Beam Medical Center.
OBJECTIVE
To assess the biologic effects of proton and carbon ion beams before clinical use.


METHODS
Cultured cells from human salivary gland cancer (HSG cells) were irradiated at 5 points along a 190 MeV per nucleon proton and a 320 MeV per nucleon carbon ion beam, with Bragg peaks modulated to 6 cm widths. A linac 4 MV X-ray was used as a reference. Relative biologic effectiveness (RBE) values at each point were calculated from survival curves. Cells were also irradiated in a cell-stack phantom to identify that localized cell deaths were observed at predefined depth. Total body irradiation of C3H/He mice was performed, and the number of regenerating crypts per jejunal section was compared to calculate intestinal RBE values. For carbon ion and referential 4 MV X-ray beams, mouse right legs were irradiated by four-fractional treatment and followed up for skin reaction scoring.


RESULTS
RBE values calculated from cell survival curves at the dose that would reduce cell survival to 10% (D10) ranged from 1.01 to 1.05 for protons and from 1.23 to 2.56 for carbon ions. The cell-stack phantom irradiation revealed localized cell deaths at predefined depth. The intestinal RBE values ranged from 1.01 to 1.08 for protons and from 1.15 to 1.88 for carbon ions. The skin RBE value was 2.16 at C320/6 cm spread-out Bragg peak (SOBP) center.


CONCLUSIONS
The radiobiologic measurements of proton and carbon ion beams at Hyogo Ion Beam Medical Center are consistent with previous reports using proton beams in clinical settings and carbon ion beams with similar linear energy transfer (LET) values.
Kagawa
Kazufumi
K
Department of Radiology, Hyogo Ion Beam Medical Center, Hyogo, Japan. k.kagawa@hibmc.shingu.hyogo.jp
Murakami
Masao
M
Hishikawa
Yoshio
Y
Abe
Mitsuyuki
M
Akagi
Takashi
T
Yanou
Toshihiro
T
Kagiya
Go
G
Furusawa
Yoshiya
Y
Ando
Koichi
K
Nojima
Kumie
K
Aoki
Mizuho
M
Kanai
Tatsuaki
T
D000818:Animals; D002173:Cancer Care Facilities / Q000458:organization & administration; D002244:Carbon / Q000627:therapeutic use*; D002470:Cell Survival; D005260:Female; D006801:Humans; D007564:Japan; D007583:Jejunum / Q000166:cytology / Q000528:radiation effects; D051379:Mice; D008809:Mice, Inbred C3H; D061766:Proton Therapy; D011879:Radiotherapy Dosage; D012062:Relative Biological Effectiveness; D012106:Research; D012468:Salivary Gland Neoplasms / Q000532:radiotherapy*; D012867:Skin / Q000528:radiation effects; D017356:Synchrotrons; D014407:Tumor Cells, Cultured / Q000528:radiation effects; D014916:Whole-Body Irradiation
D002244:Carbon