Low LET protons focused to submicrometer shows enhanced radiobiological effectiveness

T. E. Schmid, C. Greubel, V. Hable, O. Zlobinskaya, D. Michalski, S. Girst, C. Siebenwirth, E. Schmid, M. Molls, G. Multhoff, G. Dollinger

Research output: Contribution to journalArticlepeer-review

24 Scopus citations


This study shows that enhanced radiobiological effectiveness (RBE) values can be generated focusing low linear energy transfer (LET) radiation and thus changing the microdose distribution. 20 MeV protons (LET = 2.65keV m 1) are focused to submicrometer diameter at the ion microprobe superconducting nanoprobe for applied nuclear (Kern) physics experiments of the Munich tandem accelerator. The RBE values, as determined by measuring micronuclei (RBE MN= 1.48 ± 0.07) and dicentrics (RBE D= 1.92 ± 0.15), in human-hamster hybrid (A L) cells are significantly higher when 117 protons were focused to a submicrometer irradiation field within a 5.4×5.4m 2matrix compared to quasi homogeneous in a 1×1m 2matrix applied protons (RBE MN= 1.28 ± 0.07; RBE D= 1.41 ± 0.14) at the same average dose of 1.7 Gy. The RBE values are normalized to standard 70kV (dicentrics) or 200kV (micronuclei) x-ray irradiation. The 117 protons applied per point deposit the same amount of energy like a 12C ion with 55 MeV total energy (4.48MeV u 1). The enhancements are about half of that obtained for 12C ions (RBE MN= 2.20 ± 0.06 and RBE D= 3.21 ± 0.10) and they are attributed to intertrack interactions of the induced damages. The measured RBE values show differences from predictions of the local effect model (LEM III) that is used to calculate RBE values for irradiation plans to treat tumors with high LET particles.

Original languageEnglish
Pages (from-to)5889-5907
Number of pages19
JournalPhysics in Medicine and Biology
Issue number19
StatePublished - 7 Oct 2012


Dive into the research topics of 'Low LET protons focused to submicrometer shows enhanced radiobiological effectiveness'. Together they form a unique fingerprint.

Cite this