Is the increased relative biological effectiveness of high LET particles due to spatial or temporal effects? Characterization and OER in V79-4 cells.

The efficiency of producing biological damage varies with radiation quality. Conventional explanations rely on spatial differences in the radiation track structure; generally however there are also very large temporal differences in delivery of the radiation at the cellular level. High-LET radiation normally deposits substantial amounts of energy by individual heavily ionizing tracks on a timescale of the order of picoseconds. By contrast each low-LET radiation track deposits a small amount of energy. Many of these tracks, distributed over the whole cell, are required to deliver an equivalent dose to a high-LET track and they are usually delivered over much longer timescales (typically seconds) during which chemical, biochemical and biological processes are occurring. In this paper the design, characterization and initial application of a high-brightness, laser-plasma ultrasoft x-ray source is described. This has been used to investigate the importance of the temporal differences by irradiating mammalian cells with an energy deposition with spatial properties of low-LET radiation and temporal properties similar to high-LET radiation. The present system delivers a typical dose, to the incident surface of the cells, of 0.12 Gy per pulse delivered in <10 ps. The capabilities of the x-ray source were tested by determining the survival of V79-4 hamster cells irradiated with picosecond pulses of ultrasoft x-rays under aerobic and anaerobic conditions, which were found to be consistent with previously published non pulsed data with x-rays of similar energy. These results support the expectation that the disappearance of an oxygen effect for high-LET radiation particles is due to their spatial properties rather than the very short timescale of each particle traversal. For other effects, particularly non-targeted phenomena such as induced genomic instability, expectations may be less clear cut.

[1]  D. Goodhead,et al.  Chromosome aberrations induced in human lymphocytes by ultrasoft Al (K) and C (K) X-rays. , 1980, International journal of radiation biology and related studies in physics, chemistry, and medicine.

[2]  G. Neary.  IRRADIATION OF SIMPLE BIOLOGICAL SPECIMENS BY CHARGED PARTICLES. , 1970 .

[3]  K. Mahesh,et al.  Criterion for determining saturation current in parallel plate ionization chambers , 1978 .

[4]  D. Goodhead,et al.  Track structure analysis illustrating the prominent role of low-energy electrons in radiobiological effects of low-LET radiations. , 1991, Physics in medicine and biology.

[5]  G. Adams,et al.  A posteffect of oxygen in irradiated bacteria: a submillisecond fast mixing study. , 1973, Radiation research.

[6]  D. Goodhead,et al.  Thickness measurements on V79-4 cells: a comparison between laser scanning confocal microscopy and electron microscopy. , 1990, International journal of radiation biology.

[7]  F O'Neill,et al.  Plasma X-Ray Sources For Lithography Generated By A 0.5 J KrF Laser , 1988, Optics & Photonics.

[8]  P. O'Neill,et al.  Induction and rejoining of DNA double-strand breaks in V79-4 mammalian cells following gamma- and alpha-irradiation. , 1993, International journal of radiation biology.

[9]  K. Townsend,et al.  Nuclear area measurement on viable cells, using confocal microscopy. , 1992, International journal of radiation biology.

[10]  G. Barendsen.  IMPAIRMENT OF THE PROLIFERATIVE CAPACITY OF HUMAN CELLS IN CULTURE BY ALPHA-PARTICLES WITH DIFFERING LINEAR-ENERGY TRANSFER. , 1964, International journal of radiation biology and related studies in physics, chemistry, and medicine.

[11]  D. Goodhead,et al.  Current Status of Ultrasoft X Rays and Track Structure Analysis as Tools for Testing and Developing Biophysical Models of Radiation Action , 1990 .

[12]  D. Goodhead,et al.  Inactivation and mutation of cultured mammalian cells by aluminium characteristic ultrasoft X-rays. I. Properties of aluminium X-rays and preliminary experiments with Chinese hamster cells. , 1977, International journal of radiation biology and related studies in physics, chemistry, and medicine.

[13]  D. Goodhead,et al.  Production and dosimetry of copper L ultrasoft x-rays for biological and biochemical investigations. , 1998, Physics in medicine and biology.

[14]  Pretlow Tg nd,et al.  Problems connected with the separation of different kinds of cells. , 1975 .

[15]  F. O'Neill,et al.  A Repetitive Laser-Plasma X-Ray Source For Radiobiology Research , 1989, Other Conferences.

[16]  D. Goodhead.  Spatial and temporal distribution of energy. , 1988, Health physics.

[17]  B. L. Henke,et al.  X-Ray Interactions: Photoabsorption, Scattering, Transmission, and Reflection at E = 50-30,000 eV, Z = 1-92 , 1993 .

[18]  Ian N. Ross,et al.  Picosecond excimer laser-plasma x-ray source for microscopy, biochemistry, and lithography , 1994, Optics & Photonics.

[19]  D. Goodhead,et al.  Comments on the Recently Reported Low Biological Effectiveness of Ultrasoft X Rays , 2001, Radiation research.

[20]  J. B. Dance,et al.  X-Rays From Laser Plasmas: Generation and Applications , 1998 .

[21]  M. Hill,et al.  Dependence of the Yield of DNA Double-Strand Breaks in Chinese Hamster V79-4 Cells on the Photon Energy of Ultrasoft X Rays , 2001, Radiation research.

[22]  D. Goodhead,et al.  Effects of Radiations of Different Qualities on Cells: Molecular Mechanisms of Damage and Repair , 1993 .

[23]  D. Goodhead,et al.  Biological effectiveness of isolated short electron tracks: V79-4 cell inactivation following low dose-rate irradiation with Al K ultrasoft X-rays , 2002, International journal of radiation biology.

[24]  K M Prise,et al.  Measurement of DNA damage and cell killing in Chinese hamster V79 cells irradiated with aluminum characteristic ultrasoft X rays. , 1989, Radiation research.

[25]  A. Kellerer,et al.  A Generalized Formulation of Dual Radiation Action1 , 1978 .

[26]  S. Botchway,et al.  Induction and rejoining of DNA double-strand breaks in Chinese hamster V79-4 cells irradiated with characteristic aluminum K and copper L ultrasoft X rays. , 1997, Radiation research.

[27]  D. Goodhead,et al.  Radiobiology of ultrasoft X rays. I. Cultured hamster cells (V79). , 1987, Radiation research.