Enhancement of biological effectiveness of carbon-ion beams by applying a longitudinal magnetic field

Abstract Purpose: A magnetic field longitudinal to an ion beam will potentially affect the biological effectiveness of the radiation. The purpose of this study is to experimentally verify the significance of such effects. Methods and materials: Human cancer and normal cell lines were exposed to low (12 keV/μm) and high (50 keV/μm) linear energy transfer (LET) carbon-ion beams under the longitudinal magnetic fields of B// = 0, 0.1, 0.2, 0.3, or 0.6 T generated by a solenoid magnet. The effects of the magnetic fields on the biological effectiveness were evaluated by clonogenic cell survival. Doses that would result in a survival fraction of 10% (D10s) were determined for each cell line and magnetic field. Results: For cancer cells exposed to the low (high)-LET beams, D10 decreased from 5.2 (3.1) Gy at 0 T to 4.3 (2.4) Gy at 0.1 T, while no further decrease in D10 was observed for higher magnetic fields. For normal cells, decreases in D10 of comparable magnitudes were observed by applying the magnetic fields. Conclusions: Significant decreases in D10, i.e. significant enhancements of the biological effectiveness, were observed in both cancer and normal cells by applying longitudinal magnetic fields of B//  ≥ 0.1 T. These effects were enhanced with LET. Further studies are required to figure out the mechanism underlying the observed results.

[1]  S. Yonai,et al.  EXPERIMENTAL EVALUATION OF DOSIMETRIC CHARACTERIZATION OF GAFCHROMIC EBT3 AND EBT-XD FILMS FOR CLINICAL CARBON ION BEAMS , 2018, Radiation protection dosimetry.

[2]  T. Inaniwa,et al.  Adaptation of stochastic microdosimetric kinetic model for charged-particle therapy treatment planning , 2018, Physics in medicine and biology.

[3]  Nobuyuki Kanematsu,et al.  Treatment planning of intensity modulated composite particle therapy with dose and linear energy transfer optimization , 2017, Physics in medicine and biology.

[4]  Steven H. Lin,et al.  Biological responses of human solid tumor cells to X‐ray irradiation within a 1.5‐Tesla magnetic field generated by a magnetic resonance imaging–linear accelerator , 2016, Bioelectromagnetics.

[5]  S. Crozier,et al.  Proton beam deflection in MRI fields: Implications for MRI-guided proton therapy. , 2015, Medical physics.

[6]  B. Fallone,et al.  Magnetic field effects on the energy deposition spectra of MV photon radiation , 2009, Physics in medicine and biology.

[7]  C. Claussen,et al.  In Vitro Evaluation of Magnetic Resonance Imaging at 3.0 Tesla on Clonogenic Ability, Proliferation, and Cell Cycle in Human Embryonic Lung Fibroblasts , 2007, Investigative radiology.

[8]  Tatsuaki Kanai,et al.  Examination of GyE system for HIMAC carbon therapy. , 2006, International journal of radiation oncology, biology, physics.

[9]  B W Raaymakers,et al.  Integrating a MRI scanner with a 6 MV radiotherapy accelerator: dose increase at tissue–air interfaces in a lateral magnetic field due to returning electrons , 2005, Physics in medicine and biology.

[10]  S. Sato,et al.  Present status of secondary beam courses in HIMAC , 2004 .

[11]  J. Miyakoshi,et al.  Effects of exposure of CHO-K1 cells to a 10-T static magnetic field. , 2002, Radiology.

[12]  M Scholz,et al.  Track structure and the calculation of biological effects of heavy charged particles. , 1996, Advances in space research : the official journal of the Committee on Space Research.