A heavy particle comparative study. Part III: OER and RBE

Abstract

The results of a comparative study of heavy particles of interest in radiotherapy are reported in four parts. In this Part III, cell-survival measurements under aerobic and hypoxic conditions were made for various heavy particle beams. For heavy charged-particle beams, the measurements were made at the beam entrance (plateau), peak centre (10 cm wide peaks), and distal peak (1 cm from dose fall-off). Chinese hamster cells (V79) were used. Metabolic depletion was used to obtain hypoxia. The results indicate that the differences in RBE between the entrance region and peak are not very large when the Bragg peaks are broadened to 10 cm. The RBE for argon ions remains the same at the entrance and peak centre, and the RBE at the distal side of the Bragg peak is significantly reduced compared to the peak centre and entrance region because of saturation effects at high LET. The OER for protons is not significantly different from that for X rays. The OER for helium ions, carbon ions, and negative pions is larger, for neon ions is similar, and for argon ions is smaller when compared with fast neutrons. The OER values for heavy ions are higher than expected and could be due to a large delta-ray penumbra associated with the energy deposited by energetic heavy ions. The oxygen effect may depend upon energy deposition over distances of the order of nanometers.

Heavy-Ion Radiobiology: Cellular Studies

“…In general, argon beams have considerably more fragmentation than neon beams of similar range, and silicon beams have intermediate levels. Both cellular Chapman et al, 1977;Curtis et al, 1982;Raju et al, 1978c) and tissue studies (Alpen and Power~Risius, 1981;Alpen et a1., 1980;Goldstein et al, 198la, 198lb;Raju and Carpenter, 1978) (1979) used heavy ions of 400 to 570 MeV/u produced at the Bevalac. In each case the OER is high (2.7-2.9) at low LET, and decreases to 1.2 or less at greater than about 250 keV/~m.…”

“…The results are compiled from eight different cell systems Ujcke-H"Ohle et al, 1979;Ngo et al, 1981;Roots et al, 1980;Chapman et al, 1977;Curtis et al ., 1981;Leith et al, 1975;Goldstein et al, 198la). (XBL 7810-3663A) Chapman et al, 1977Chapman et al, , 1978 Raju et al, 1978c;Alpen, 1980, 1981;Lucke-Huhle et al, 1980. (XBL 832-3567) .54…”

Biological Dose Estimation Model for Proton Beam Therapy

“…Ionization track structures and microdosimetric energy spectra of protons at various depths are typically analyzed to convert LET [26]- [30] of individual protons into an RBE value [13] [31] [32], of a therapeutic beam. We propose a simple method that allows one to determine the dose averaged LET value at each point along the measured Bragg peak.…”

Role of proton therapy in the treatment of cancer

“…[8,12] Standart foton radyasyonla proton arasında OER (oksijen artırma oranı) (2.5-3) açısından bir fark bulunmadığı yapılan çalışma-larla gösterilmiştir. [13,14] Klinikte kullanılmak için elde edilen proton ışının enerji sınırı 250 MeV'a kadar ulaşmaktadır. Proton lineer akseleratör, siklotron veya sinkrotron kullanılarak yüksek enerjiye hızlandırılabilir.…”