PMID- 22496068 OWN - NLM STAT- MEDLINE DCOM- 20121119 LR - 20240210 IS - 1748-880X (Electronic) IS - 0007-1285 (Print) IS - 0007-1285 (Linking) VI - 85 IP - 1018 DP - 2012 Oct TI - Revisiting the ultra-high dose rate effect: implications for charged particle radiotherapy using protons and light ions. PG - e933-9 LID - 10.1259/bjr/17827549 [doi] AB - OBJECTIVE: To reinvestigate ultra-high dose rate radiation (UHDRR) radiobiology and consider potential implications for hadrontherapy. METHODS: A literature search of cellular UHDRR exposures was performed. Standard oxygen diffusion equations were used to estimate the time taken to replace UHDRR-related oxygen depletion. Dose rates from conventional and novel methods of hadrontherapy accelerators were considered, including spot scanning beam delivery, which intensifies dose rate. RESULTS: The literature findings were that, for X-ray and electron dose rates of around 10(9) Gy s(-1), 5-10 Gy depletes cellular oxygen, significantly changing the radiosensitivity of cells already in low oxygen tension (around 3 mmHg or 0.4 kPa). The time taken to reverse the oxygen depletion of such cells is estimated to be over 20-30 s at distances of over 100 mum from a tumour blood vessel. In this time window, tumours have a higher hypoxic fraction (capable of reducing tumour control), so the next application of radiation within the same fraction should be at a time that exceeds these estimates in the case of scanned beams or with ultra-fast laser-generated particles. CONCLUSION: This study has potential implications for particle therapy, including laser-generated particles, where dose rate is greatly increased. Conventional accelerators probably do not achieve the critical UHDRR conditions. However, specific UHDRR oxygen depletion experiments using proton and ion beams are indicated. FAU - Wilson, P AU - Wilson P AD - Gray Institute of Radiation Oncology and Biology, Oxford, UK. FAU - Jones, B AU - Jones B FAU - Yokoi, T AU - Yokoi T FAU - Hill, M AU - Hill M FAU - Vojnovic, B AU - Vojnovic B LA - eng GR - 15677/CRUK_/Cancer Research UK/United Kingdom GR - MRC_/Medical Research Council/United Kingdom PT - Journal Article PT - Research Support, Non-U.S. Gov't PT - Review DEP - 20120411 PL - England TA - Br J Radiol JT - The British journal of radiology JID - 0373125 RN - 0 (Ions) RN - S88TT14065 (Oxygen) SB - IM MH - Cell Hypoxia/radiation effects MH - Cell Survival/radiation effects MH - Humans MH - Ions/*therapeutic use MH - Neoplasms/*radiotherapy MH - Oxygen/radiation effects MH - Particle Accelerators MH - *Proton Therapy MH - Radiation Tolerance MH - Radiotherapy Dosage MH - Radiotherapy, High-Energy/*methods MH - Tumor Cells, Cultured PMC - PMC3474025 EDAT- 2012/04/13 06:00 MHDA- 2012/12/10 06:00 PMCR- 2013/10/01 CRDT- 2012/04/13 06:00 PHST- 2012/04/13 06:00 [entrez] PHST- 2012/04/13 06:00 [pubmed] PHST- 2012/12/10 06:00 [medline] PHST- 2013/10/01 00:00 [pmc-release] AID - 17827549 [pii] AID - D11613 [pii] AID - 10.1259/bjr/17827549 [doi] PST - ppublish SO - Br J Radiol. 2012 Oct;85(1018):e933-9. doi: 10.1259/bjr/17827549. Epub 2012 Apr 11.