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PubMed1979

Application of the thermoluminescent dosimetry to a pion beam.

The thermoluminescent dosimetry is currently applied to radiation therapy in order to measure dose distributions on phantoms or to control the dose in vivo for special procedures or critical organs. The application of this method to the SIN's (Switzerland) pion beam has been studied. Measurements have been made on the following thermoluminescent materials: 7LiF, 6LiF, Li(nat)F, Li2B4O7, CaF2 : Mn, and CaF2 : Dy. Except for the last one a reduction (10%) of the sensitivity of the phosphors has been observed in the peak relative to the plateau region. An increase of the 6LiF sensitivity relative to that of 7LiF has been pointed out due to the neutron background through the (n, alpha) reaction on 6Li. Glow curves of the LiF phosphors have been measured. A reduction (5%) of the intensities of peak 3 and 4 relative to peak 5 has been observed for irradiation in the peak region. This effect however can't be used in order to localize the dosimeter in the beam because the intensity of the thermoluminescence peaks shows a larger variability in a batch of dosimeters.

Elementary Particles↗
PubMed1979

Visualization of pi- and pi+ stopping density distributions in one and two dimensions.

A technique suitable for mapping pi+/- stopping density distributions in patients or phantoms is described. As a position sensitive detector a multiwire proportional chamber with a slit or a hole collimator in front was applied. Results using a water and a Rando phantom are presented for various momenta and momentum band widths of the pi+/- beam. To our knowledge the two-dimensional visualization of a pi- stopping density distribution was realized for the first time.

Elementary Particles↗
PubMed1979

Energy deposition spectra of negative pions and their application to radiation therapy.

Treatment planning for pion radiation therapy must take into account changes in radiation quality within the patient. At the biomedical channel piE3 of SIN (Swiss Institute for Nuclear Research) microdosimetric measurements have been performed to investigate radiation quality within pion irradiated phantoms. Results are presented in terms of microdosimetric spectra and derived quantities. As expected marked differences are observed between dose peak and plateau for "narrow" pion beams. The influence of simulated site diameter on measured spectra has been found to be more pronounced in the plateau region than in the peak. Investigation of the influence of peak width on radiation quality revealed a dilution of the high-LET dose fraction for broader peaks.

Elementary Particles↗
PubMed1979

Radiobiological data for clinical dosimetry in pion tumour therapy.

Ehrlich ascites tumour cells were irradiated with negative pions at different positions in the plateau and the peak of the depth absorbed dose curve. Dose-survival curves for immediate testing of the viability of the cells are given and are compared with other types of radiations in use for therapy. From the data obtained after repair of potentially lethal damage effective survival curves for fractionated irradiation are evaluated.

Animals↗
PubMed1979

Effect of negative pions, relative to 140 kV -- 29 MeV photons and 20 MeV electrons, on proliferation of Ehrlich ascites carcinoma cells.

The effect of negative pions (peak and plateau), photons (140 kV and 29 MeV), and 20 MeV electrons on the proliferative capacity of Ehrlich ascites carcinoma cells was investigated. Proliferative survival curves plotted for the modalities employed are presented. Under the experimental conditions used, the peak pions were more effective than plateau pions by a factor of about 1.4. For 50% survival, 140 kV X-rays had the same effect as peak pions but the latter was more effective (factor 1.2) at 10% survival level. When 140 kV X-rays were taken as the standard, following are the RBE values calculated as 50% survival level: plateau pions --0.73; peak pions --about 1.0; 29 MeV photons --0.73 and 20 MeV electrons --0.6. The results obtained are compared with those reported on other tumor systems and biological test objects.

Animals↗
PubMed1979

Cell survival over the depth profile after irradiation with a negative pion beam.

The colony-forming ability of Chinese hamster fibroblast cells in vitro has been investigated throughout the depth dose profile of a negative pion beam. In the peak and 2 cm beyond, the RBE for macroclones (more than 50 cells per clone) was 1.3 and in the plateau region 0.8--1.0. All of the microclones (2-49 cells per clone) were observed as well. The RBE values are the same for peak and somewhat higher for plateau and post peak than found in cell survival studies referring to macroclones.

Animals↗
PubMed1979

Biological effects of negative pions in monolayers and spheroids of Chinese hamster cells.

The therapeutic value of pion irradiation was critically challenged by examining, in a cell culture system, various parameters of biological significance such as relative biological efficiency (RBE), oxygen enhancement ratio (OER), DNA-break formation, changes in cell cycle kinetics and regrowth. In all parameters, pions were superior to conventional low-LET radiation.

Animals↗
PubMed1979

Chromatid breaks induced in Chinese hamster cells by low doses (12--100 rad) of pi--mesons.

Monolayer cultures of the fibroblast-like Chinese hamster cell-line 19/1 were irradiated in the G2-phase of the cell cycle by pi--mesons (6 rad/min peak-pion dose rate). Frequencies of induced single- and isochromatid breaks, acentric fragments and interchanges were compared with data obtained from 140 kV X-rays. The RBE-values were for the pion dose peak between 0.8--1.2 and for the pion dose plateau 0.5--0.9. Whereas for single chromatid breaks there was no significant difference between X-rays and peak pions for identical physical doses, the isochromatid breaks alone showed a significantly higher frequency for 100 rad peak pions.

Animals↗
PubMed1979

RBE and OER values of negative pion beams from growth inhibition of Vicia faba roots.

Two pion beams of different momentum width have been used to expose meristems of Vicia Faba roots under aerobic and hypoxic conditions. The measurements of the resulting 10 days growth inhibition after exposures at various locations on the pion beam axes have been made and RBE and OER values evaluated for 50% effects compared to 60Co gamma-rays. The results have been related to the fractional doses from star products defined by telescope measurements of stopped pions along the same beams. It has been found that the RBE value increases with the fractional "star dose" up to a maximum after which the RBE decreases. The OER values, however, were found to decrease with increasing "star dose" fraction rather rapidly after which it was found to be independent of the "star dose" contribution.

Dose-Response Relationship, Radiation↗
PubMed1979

Preclinical radiobiology with pions: RBE--values for mouse skin damage as a function of single doses of pions.

The macroscopic reaction of the mouse skin was used to derive RBE values for negative pi-Mesons. Hind limbs of mice were irradiated with pions or X-rays. The pions were produced by the 590 MeV accelerator of the Schweizerisches Institut für Nuklearforschung (SIN). Early reaction was assessed over a period of 6--30 days after irradiation with single doses (20--45 Gy). The radiation damage was scored using an arbitrary scale of effect. The time pattern of development of the skin reaction and the subsequent healing after exposure both to pions and X-rays were similar, indicating that depletion and repopulation of the basal cells of the skin were comparable, both after pions and X-rays. RBE values as a function of pion doses at the peak (dose maximum), plateau and at the postpeak (12 mm downstream of the dose maximum) were computed with nonparametric statistical methods. The RBE at the peak and at the plateau relative to X-rays of the same dose rate was 1.15--1.25 and 0.85, respectively. The RBE of peak pions manifested a marked dependence on dose, when plateau pions were chosen as reference radiation. In this experiment there was no significant difference in RBE between peak and postpeak. The importance of some experimental condition (dose rate, irradiation volume) is discussed.

Animals↗
PubMed1979

Long-term effects of negative pions in female mice exposed to whole-body irradiation.

Long-term effects, especially the incidence of tumors, of whole-body exposure of female NMRI mice with either negative pions (peak or plateau region) or X rays have been studied in comparison to controls. Animals were irradiated at the age of 10 days after birth. The mice were then regularly examined for deaths and signs of severe disease, moribund animals being killed. A detailed histopathological work-up has been performed. The data show that the survival as defined by death or the time of autopsy is significantly lower in irradiated mice in comparison to controls, that there is no difference in reduction of survival between groups treated either with X rays or pions at peak region, but that a difference can be seen when comparing X rays with pions at plateau region. The incidence of ovarian tumors at any particular age is higher in mice treated with X rays or pions than in control groups, but significantly lower in animals exposed to plateau pions than in those treated with peak pions or X rays.

Animals↗
PubMed1979

Low-dose effects of X-rays and negative pions on the pronuclear zygote stage of mouse embryos.

Mouse embryos in the pronuclear-zygote stage (day 0 of gestation) were irradiated with 13.5 rad of 140kV X-rays or negative pions. On day 13 the fetuses were examined for developmental anomalies such as intrauterine death, growth retardation and malformations. Significant decreases in the percentage of normal implantations were obtained with peak pions (high LET) and X-rays, whereas the effect of plateau pions was less obvious. Irradiation with peak pions was more effective than with X-rays by a factor of about 1.7.

Abnormalities, Radiation-Induced↗
PubMed1979

Effect of negative pi mesons on vascular permeability of brain in neonatal rats.

Neonatal rats and their radiation-induced cerebral petechial hemorrhages were used as an experimental system for evaluating the effects of negative pions on healthy tissue and especially on the microvasculature. Dose response curves for peak and plateau pions (dose range 150--250 rad and 100--400 rad, respectively) were obtained and compared with those of 200 kV X-rays of corresponding dose rates. The RBE of the peak pions was 1.1, that of the plateau pions 0.6 resulting in a peak/plateau ratio of 1.8. Implications were made as to the importance of this favorable peak/plateau relationship since the response of the capillary endothelium to pion-irradiation might be one of the limiting factors in radiotherapy.

Animals↗
PubMed1978

[Bone mineral content during chronic hemodialysis long term observation by 125-i photonabsorptiometry (author's transl)].

40 out of 98 patients on chronic haemodialysis show an obviously lowered bone mineral content of the radius (mean -20.4%), 51 patients attain values in the normal range (mean -1%) and 7 subjects slightly increased values (mean +10.9%). A bone mineral loss of 2.5% could be found after long-term observations of this parameter between 6 to 30 months (mean observation period: 15 months). In general a progressive loss of the bone mineral content may be noticed with an increased duration of haemodialysis. This tendency is more distinct after the 40th year of life because of the simultaneous age-depending physiological decrease of bone mass. Abruptly occurring mineral losses of the skeleton may be due to a high incretion of parathyroid hormone and possibly require subtotal parathyroidectomy.

Adolescent↗
PubMed1977

[The use of photon absorptiometry in renal osteodystrophy (author's transl)].

In 58 patients with end-stage renal failure before commencement of regular hemodialyses treatment (RTD) and 58 patients under RTD bone mineral content (BMC) was determined by the use of the photon absorptiometry. Further the effect of a treatment with bitamin D3 and 5,6-trans-25-OH-vitamin D3 on BMC was studied. There existed a negative correlation between the duration of chronic renal failure or of RDT as well as of the serum parathyroid hormone level to BMC. No correlation was found between BMC and serum calcium level. During a 14 months-course treatment with vitamin D3 or 5,6-trans-25-OH-vitamin D3 BMC increased. The method of photon absorptiometry presented itself as an easy and well reproducible technique for routine examinations.

Adolescent↗
PubMed1995

Effect of a chiral impulse on the weak interaction induced handedness in a prebiotic medium.

Previously we have carried out simulation of the Weak Neutral Current and symmetry breaking transition bifurcation process addressing some of the issues raised by critics of the approach. We now include the effects of a chiral impulse on the transition and show that under certain cases this could greatly alter the transition time. Examples of a chiral impulse could be a nearby Supernova and an impulse of beta-emitters. We briefly discuss the possibility of these processes in the early solar system.

Biophysical Phenomena↗
PubMed1975

Neutral currents in weak interactions and molecular asymmetry.

Weak interactions are parity violating forces, i.e. they differentiate between mirror images. Therefore it is a very attractive hypothesis to invoke weak interactions in explaining the origin of molecular asymmetry. It is, however, not clear whether weak interactions may operate between electrons and/or between electrons and protons? For these types of interactions so called neutral currents are needed. Recent experiments with muon neutrinos at CERN gave some evidence for the existence of neutral currents. Thus we may suppose that parity violating forces are active in molecules. In the first part of this paper a very elementary theory of weak interactions is outlined with special reference to the discovery of neutral currents. In the second part we show how weak interactions may differentiate between mirror image molecules. The asymmetrically distributed static charges in chiral molecules represent a helical potential field. This potential field may exert an effect on the orbital electrons and therefore coupling of spins and momenta occurs. Thus the enantiomers are parity transformed images not only as geometrical bodies, but their orbital electrons are parity transformed too as "a helical electron gas". Weak interactions will differentiate between L and D forms because their orbital electrons have a nonzero spin polarization with respect to their velocity.

Electrochemistry↗