Stopping power of water for carbon ions with energies in the Bragg peak region

The stopping power of liquid water was measured for carbon ions with energies in the Bragg peak region using the inverted Doppler shift attenuation method. Among the semiempirical data, the results of this work agree best with the data recommended in the Errata and Addendum of ICRU Report No. 73, which is based on an I value of 78 eV for water. The agreement was worse when the present results were compared to the newer recommendation of the ICRU published in ICRU Report No. 90. The srim code seems to slightly overestimate the stopping power of water for carbon ions above 3 MeV. A semiexperimental stopping power of water for α particles was derived from the present results using the theoretical ratio between the stopping powers of water for carbon ions and α particles computed by means of the casp code. These values agree well with the experimental data for α particles within the uncertainties.

PROPOSAL FOR A EUROPEAN METROLOGY NETWORK ON BIOLOGICAL IONISING RADIATION EFFECTS

Progress in the field of ionising radiation (IR) metrology achieved in the BioQuaRT project raised the question to what extent radiobiological investigations would benefit from metrological support of the applied methodologies. A panel of experts from the medical field, fundamental research and radiation protection attended a workshop at Physikalisch-Technische Bundesanstalt to consult on metrology needs related to biological radiation effects. The panel identified a number of metrological needs including the further development of experimental and computational techniques for micro- and nanodosimetry, together with the determination of related fundamental material properties and the establishment of rigorous uncertainty budgets. In addition to this, a call to develop a metrology support for assisting quality assurance of radiobiology experiments was expressed. Conclusions from the workshop were presented at several international conferences for further discussion with the scientific community and stakeholder groups that led to an initiative within the metrology community to establish a European Metrology Network on biological effects of IR.

Polyamine patterns in plasma of patients with systemic lupus erythematosus and fever

Systemic lupus erythematosus (SLE) is a systemic autoimmune disease with various clinical manifestations and serologic markers. In this study, we analyzed nine polyamine (PA) profiles of plasma from patients with SLE and healthy controls (HCs), and the relationship between the PA profiles and disease activity. PA alterations in plasma of 44 patients with SLE and fever were investigated using gas chromatography mass spectrometry (GC-MS) in selected ion monitoring mode using N-ethoxycarbonyl/ N-pentafluoropropionyl derivatives, and compared with those of 43 HCs. Patients with SLE and HCs showed differences in five of nine PA profiles. Among five changed PA levels, four PAs, namely N¹-acetylcadaverine, spermidine, N¹-acetylspermidine, and spermine, were dramatically decreased. However, the level of cadaverine was increased in patients with SLE. In the partial correlation with PA profiles and disease activity markers of SLE, several disease activity markers and nutritional markers were correlated with cadaverine, spermidine, and N ⁸-acetylspermidine. Thus, our results provide a comprehensive understanding of the relationship between PA metabolomics and disease activity markers in patients with SLE.

Proton-impact ionisation cross sections for nanodosimetric track structure simulations

Monte Carlo simulations of the particle track structure require accurate ion- and electron-impact cross-section data of the medium. These data are scarce and often inconsistent when measured by different groups. In this work, literature data on ionisation cross sections (CSs) of nitrogen and propane for protons with energies 0.1-10 MeV are reviewed and implemented in the code PTra. Methane data were used to obtain proton-impact CSs of propane due to their absence in the literature. PTra is benchmarked by comparing simulated particle-track parameters to experimental results, measured with an ion-counting nanodosemeter.

Reactive oxygen species in rats with chronic post-ischemia pain

BACKGROUND

An emerging theme in the study of the pathophysiology of persistent pain is the role of reactive oxygen species (ROS). In the present study, we examined the hypothesis that the exogenous supply of antioxidant drugs during peri-reperfusion would attenuate pain induced by ischemia/reperfusion (IR) injury. We investigated the analgesic effects of three antioxidants administered during peri-reperfusion using an animal model of complex regional pain syndrome-type I consisting of chronic post-ischemia pain (CPIP) of the hind paw.

METHODS

Application of a tight-fitting tourniquet for a period of 3 h produced CPIP in male Sprague-Dawley rats. Low-dose allopurinol (4 mg/kg), high-dose allopurinol (40 mg/kg), superoxide dismutase (SOD, 4000 U/kg), N-nitro-L-arginine methyl ester (L-NAME, 10 mg/kg), or SOD (4000 U/kg)+L-NAME (10 mg/kg) was administered intraperitoneally just after tourniquet application and at 1 and 2 days after reperfusion for 3 days. The effects of antioxidants in rats were investigated using mechanical and cold stimuli. Each group consisted of seven rats.

RESULTS

Allopurinol caused significant alleviation in mechanical and cold allodynia for a period of 4 weeks in rats with CPIP. Both SOD and L-NAME, which were used to investigate the roles of superoxide (O2(-)) and nitric oxide (NO) in pain, also attenuated neuropathic-like pain symptoms in rats for 4 weeks.

CONCLUSIONS

Our findings suggest that O2(-) and NO mediate IR injury-induced chronic pain, and that ROS scavengers administered during the peri-reperfusion period have long-term analgesic effects.

W values of protons in liquid water

The W values of protons in liquid water were calculated for energies from 0.1 keV to 10 MeV using the continuous slowing down approximation as well as three models for the calculation of the differential ionisation cross-sections of water for protons published in recent years. The W values determined by means of the three models differ only marginally from each other and lie between 25 and 26 eV at proton energies >5 MeV. This high-energy W value is approximately 3 eV lower than that in water vapour.

Ionization ranges of protons in water vapour in the energy range 1-100 keV

Projected ranges of protons in water vapour were experimentally determined for proton energies from 1 to 100 keV by counting the total number of ionizations produced by protons during their slow down. Using these experimental ranges and semiemprical detour factors, the stopping powers of water vapour for protons were derived and compared with semiempirical data.

W values of protons in alkane-based TE gases and dimethylether in the energy range 1-100 keV: measurements and additivity models

W values of tissue-equivalent gases based on propane and butane were measured for protons in the energy range 1-100 keV and compared with those of dimethylether and water vapour. The experimental values of the tissue-equivalent gas mixtures were compared with data calculated from the W values of the mixture components using five existing additivity models and two new models derived within the scope of the present work. Apart from one model--the simplest one--all models show a good agreement with the experimental data.

Ionization-cluster distributions of alpha-particles in nanometric volumes of propane: measurement and calculation

The probability of the formation of ionization clusters by primary alpha-particles at 5.4 MeV in nanometric volumes of propane was studied experimentally and by Monte Carlo simulation, as a function of the distance between the center line of the particle beam and the center of the target volume. The volumes were of cylindrical shape, 3.7 mm in diameter and height. As the investigations were performed at gas pressures of 300 Pa and 350 Pa, the dimensions of the target volume were equivalent to 20.6 nm or 24.0 nm in a material of density 1.0 g/cm(3). The dependence of ionization-cluster formation on distance was studied up to values equivalent to about 70 nm. To validate the measurements, a Monte Carlo model was developed which allows the experimental arrangement and the interactions of alpha-particles and secondary electrons in the counter gas to be properly simulated. This model is supplemented by a mathematical formulation of cluster size formation in nanometric targets. The main results of our study are (i) that the mean ionization-cluster size in the delta-electron cloud of an alpha-particle track segment, decreases as a function of the distance between the center line of the alpha-particle beam and the center of the sensitive target volume to the power of 2.6, and (ii) that the mean cluster size in critical volumes and the relative variance of mean cluster size due to delta-electrons are invariant at distances greater than about 20 nm. We could imagine that the ionization-cluster formation in nanometric volumes might in future provide the physical basis for a redefinition of radiation quality.

Nanodosimetric measurements with an avalanche confinement TEPC

This paper illustrates a tissue-equivalent proportional counter designed to have high gas gain and good energy resolution at nanometric simulated site sizes. Microdosimetric neutron and gamma spectra were measured in dimethyl ether and in propane-based tissue-equivalent gas mixture down to 35 nm. The comparison of experimental data with the results of Monte Carlo calculations shows a satisfactory agreement.

Track nanodosimetry of an alpha particle

Experimental measurements and calculations are described of ionisation distributions in propane wall-less gas cavities of about 20 nm simulated size, performed at different distances from a 244Cm alpha particle track. Ionisation events are detected one by one by collecting electrons from the sensitive volume and by separating them with a drift column. Experimental results and Monte Carlo calculations indicate that, in the delta ray cloud, conditional probability curves, average cluster size and the ratio of second moment above first moment of the cluster distribution are invariant with track distance.

W values and radial dose distributions for protons in TE-gas and air at energies up to 500 MeV

The dosimetry of charged-particle beams is frequently performed by measuring the ionization yield produced in gas-filled ionization chambers and converting it into absorbed dose using the mean energy W expended in a gas per ion pair formed, or its differential value omega for the filling gas. Because of the increasing importance of proton therapy and the lack of accurate values of W and omega at high proton energies in particular, we investigated the ionization yield formation by protons in air and methane-based tissue-equivalent gas in the energy range up to 500 MeV. For this purpose, we analysed the available experimental values of W and omega and, in a second step, investigated the ionization-yield formation by protons as a function of their initial energy using an analytical method based on the Spencer-Fano equation in the framework of the continuous-slowing-down approximation. To estimate possible ionization losses which can be expected if the ionometric method is applied in the case of an incomplete secondary-electron equilibrium, a new analytical model has been developed which can be used to calculate the radial distribution of the ionization yield produced by secondary electrons around high-energy proton tracks.

W values for helium particles in nitrogen and argon in the energy range from 10 keV to 10 MeV

An analytical model is presented that facilitates the calculation of the mean energy W expended to produce an ion pair upon complete slow-down for heavy particles in gases. This model is applied to the calculation of the W values for helium beams of energies from 10 keV to 10 MeV in argon and nitrogen gas. Good agreement of the theoretical W values with the experimental ones is found in the case of nitrogen. The theoretical results for argon are about 15% higher than the experimental values throughout the entire energy range. However, they show a similar energy dependence. The theoretical and the experimental W values for nitrogen exhibit an extraordinary energy dependence at energies around 300 keV, at which the cross-section for charge exchange cycles reaches the maximal value. Such a phenomenon was also observed in the case of the W values for protons, which show a clear minimum at the energy of the maximal cross-section for charge exchange cycles.

Age-dependent alterations in the response of isolated rat aortas to thiobarbiturates

Responses to thiamylal and thiopental were compared in helical strips of rat thoracic aortas of different ages (5-6, 10-12 and 20-22 weeks old), precontracted partially with phenylephrine or prostaglandin F(2alpha) (PGF(2alpha)). Thiamylal and thiopental, in concentrations of 3 x 10(-5) to 10(-4) M, produced a dose-dependent relaxation in aortas at 5-6 weeks of age, no significant change of tension in those at 10-12 weeks of age, and a marked constriction in those at 20-22 weeks of age. These thiobarbiturates, in a high concentration of 10(-3) M, produced a profound relaxation in aortas at any age studied. It is concluded that the responses to thiobarbiturates of thoracic aorta precontracted with phenylephrine or PGF(2alpha) alter with age.

Halothane-induced relaxation of vascular smooth muscle: a possible contribution of increased cyclic GMP formation

Halothane (0.75 to 2.25%) dose-dependently relaxed the vascular smooth muscle of endothelium-denuded rat aortae previously contracted with KCl, and the relaxing effect was not significantly affected by indomethacin nor dexamethasone, but partly inhibited by methylene blue. The cyclic GMP levels were increased by treatment with halothane (2.25%). It was suggested that halothane-induced relaxation of vascular smooth muscle is partly mediated by cyclic GMP formation.