Jerry Howard

The fragmentation of 670A MeV neon-20 as a function of depth in water. I. Experiment

We present the final analysis of an experiment to study the interaction of a beam of 670A MeV neon ions incident on a water column set to different thicknesses. The atomic number Z (and, in some cases, the isotopic mass A) of primary beam particles and of the products of nuclear interactions emerging from the water column close to the central axis of the beam was obtained for nuclei between Be (Z = 4) and Ne (Z = 10) using a time-of-flight telescope to measure the velocity and a set of silicon detectors to measure the energy loss of each particle. The fluence of particles of a given charge was obtained and normalized to the incident beam intensity. Corrections were made for accidental coincidences between multiple particles triggering the TOF telescope and for interactions in the detector. The background due to beam particles interacting in beam line elements upstream of the detector was calculated. Sources of experimental artifacts and background in particle identification experiments designed to characterize heavy ion beams for radiobiological research are summarized, and some of the difficulties inherent in this work are discussed. Complete tables of absolutely normalized fluence spectra as a function of LET are included for reference purposes.

Response of Rat Spinal Cord to Single and Fractionated Doses of Accelerated Heavy Ions

region, RBE values of 1.45 ? 0.25 (propagated 95% confidence limits) and 1.46 ? 0.33, respectively, were obtained. In the spread peak regions for carbon and neon ions, the RBE values were 1.48 ? 0.18 and 1.86 ? 0.42, respectively. These values were obtained using the dose needed to produce 50% paralysis in a group of irradiated rats as the isoeffect comparison dose (ED50 dose). Similarly, in groups of rats receiving four daily exposures, the RBE values for carbon and neon ions in the plateau ionization region were 1.31 ? 0.27 and 1.80 + 0.24, respectively. In the spread peak regions of ionization for carbon and neon ions, the RBE values were 1.95 ? 0.19 and 2.18 ? 0.23, respectively. Similar values for RBE were obtained using changes in the activity of enzymes in spinal cord tissue (cyclic nucleotide phosphohydrolase and y--glutamyl transpeptidase). Also, it was estimated that, for X irradiation, the fractional amount of dose repaired (at the EDso dose) was 0.64 ? 0.10 (95% confidence limits). For carbon and neon ions in the plateau ionization region, the values for the fractional amount of dose repaired were 0.70 ? 0.27 and 0.48 ? 0.20, and for carbon and neon ions in the spread peak region of ionization, the fractional repair values were 0.40 ? 0.10 and 0.52 ? 0.17. Spinal cord tissue therefore shows a high capacity for subeffective damage repair, and even at the highest LET investigated (neon ions in the spread peak region) there is still indication of a significant amount of repair of radiation damage.

Induction of heteroallelic reversions and lethality in Saccharomyces cerevisiae exposed to radiations of various LET ( 60 Co rays, heavy ions and - mesons) in air and nitrogen atmospheres.

Induction of heteroallelic reversion in diploid yeast is one of the most radiosensitive processes known. Reversion to arginine independence in a diploid strain BZ34 of Saccharomyces cerevisiae was used to measure the relative biological effectiveness (RBE) of π- mesons and heavy ions. Exposures were also conducted under anoxic conditions to obtain the oxygen enhancement ratio (OER) for these radiations and for60 Co γ rays. The linear energy transfer (LET) values used covered a range from 3 to 5500 MeV

Measurement of OER and RBE of a 910 MeV Helium Ion Beam, Using Cultured Cells (T-1)

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Human Cell Survival as a Function of Depth for a High-Energy Neon Ion Beam

. The OER values obtained for60 Co γ rays and π- mesons were 2.5 and 1.9, respectively. The response of this yeast system was found to be nearly the same at dose rates of 40 rads/hr and 40 rads/min of60 Co γ rays. With increasing LET, the RBE rose to a maximum value in the region 2000 MeV

Early and late effects of accelerated charged particles on normal tissues.

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Residual Skin Damage in Rats 1 Year after Exposure to X Rays or Accelerated Heavy Ions

, corresponding to that of carbon ions. The OER decreased with increasing LET, approaching unity for neon ions. The study was extended to induction of lethality with t...

INFLUENCE OF LINEAR ENERGY TRANSFER ON THE RADIORESISTANCE OF BUDDING HAPLOID YEAST CELLS.

Abstract The depth-dose distribution of a 910 MeV monoenergetic helium ion beam was modified by using a ridge filter in the beam path, making the region of maximum dose uniform over a distance of about 6 cm of water. Studies of the relative biological effectiveness (RBE) and oxygen enhancement ratio (OER) using human kidney cells (T-l) indicated that the RBE at the broad peak region was about 1.3-1.4, compared with that at the beam entrance. The OER was reduced to about 1.7–1.9.

Cell-Survival Measurements as a Function of Depth for a High-Energy Argon-Ion Beam

Cultured human kidney cells were irradiated while suspended in a gelatin cylinder using a 400-MeV/u neon ion beam produced by the Berkeley BEVALAC. The Bragg peak was transformed to a width of 4 cm with a ridge filter, and cell survival (colony-forming ability) was determined as a function of depth and dose. A cell survival curve in the broadened peak region appeared to be exponential, and RBE values in the peak and plateau regions were approximately 3.0 and 1.8, respectively, at the 10 percent survival level. Thus, the results indicate that the biological effect is enhanced even when the narrow peak is broadened. The secondary particles (ions lighter than neon and neutrons) produced by neon ions do not cause much cell killing beyond the range of neon ions and, thus, do not seem to be a limiting factor for the use of neon ion beam in radiotherapy.(auth)

Biological response across a ridge filter carbon ion Bragg peak.

Abstract The response of skin and spinal cord to accelerated charged particle irradiation has been examined. For skin, irradiation with helium or neon ions in the plateau region of ionization yields RBE values (compared to 230 kV X-rays) of about 1.0 and 1.5 respectively. Irradiation with helium or neon ions in a therapeutically modified (“spread-out”) Bragg peak region of ionization yields RBE values of about 1.3 and 2.2–2.5 respectively. After exposure to divided doses of either helium or neon ions in the spread-out Bragg peak region of ionization, the amount of dose recovered appeared to be decreased by about 30% (as compared to the amount of dose recovered after exposure to divided doses of X-rays given over an interval of 24 hr) for the helium ion irradiations, and appeared to be decreased by about 75% for the neon ion irradiations. For effects on spinal cord, the degree of myelopathy appeared to be similar after irradiation with helium ions in either the plateau or spread-out Bragg peak regions of ionization; while after exposure to neon ions in the plateau region of ionization, the RBE appeared to be about 1.3.