[FUNCTIONAL STATUS OF THE THYROID GLAND FOLLOWING IRRADIATION WITH FAST NEUTRONS].
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Fast Neutrons↗
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Response of LiF to fast neutrons.
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Fast Neutrons↗
[Approximation of the dose distributions of fast neutrons].
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Fast Neutrons↗
Micronucleus induction by 60Co gamma-rays and fast neutrons in ataxia telangiectasia lymphocytes.
Ataxia telangiectasia (AT) is an autosomal recessive disease characterized by a progressive neuronal degeneration, immunodeficiency, cancer proneness and an extreme sensitivity to ionizing radiation. In this work, micronucleus dose-response curves for lymphocytes of normal and AT individuals, exposed in G(zero) to low LET gamma-rays and high LET fast neutrons, are compared. After gamma-irradiation, the micronucleus yields for AT lymphocytes are strongly increased compared with controls. The micronucleus dose-response curve for AT cells shows a linear dependence instead of a linear-quadratic one which is found for normal cells. After neutron irradiation, the increase in micronucleus yield above controls is less pronounced than with gamma-rays and the micronucleus dose-response curves are linear, as expected. The high increase in micronucleus yield compared with controls after gamma-irradiation further suggests the application of the micronucleus assay as a diagnostic tool for ataxia telangiectasia.
Ataxia Telangiectasia↗
Fast neutron radiography scanner for the detection of contraband in air cargo containers.
There is a growing need to rapidly scan bulk air cargo for contraband such as illicit drugs and explosives. The Commonwealth Science and Industrial Research Organisation (CSIRO) have been working with Australian Customs Service to develop a scanner capable of directly scanning airfreight containers in 1--2 minutes without unpacking. The scanner combines fast neutron and gamma-ray radiography to provide high-resolution images that include information on material composition. A full-scale prototype scanner has been successfully tested in the laboratory and a commercial-scale scanner is due to be installed at Brisbane airport in 2005.
Aircraft↗
The response of a mouse sarcoma to single and divided doses of x-rays and fast neutrons.
The response of an experimental sarcoma to single doses and two fractions of x-rays and fast neutrons has been investigated to test the hypothesis that slowly shrinking sarcomata will reoxygenate poorly and therefore will benefit more from fractionated neutron treatment than from fractionated x-ray treatment, in contrast with rapidly shrinking carcinomata. Neutrons were approximately three times more effective than x-rays, both for single doses and for two fractions given in 48 hours, when regrowth was used as a measure of response. This observation is closely similar to results previously obtained on a rat fibrosarcoma and contrasts with previous results from a mouse mammary carcinoma, and is in agreement with the hypothesis.
Animals↗
[Characteristics of the RBE of a therapeutic beam of fast neutrons from a U-120 cyclotron].
RBE of a therapeutic neutron beam obtained at the U-120 Cyclotron by a 9 Be(d, n)10B reaction (13.6 MeV deuterons) was determined. X-radiation of 180 kW was used as a standard. As estimated by the test of 30-day death of rats subjected to whole-body irradiation, RBE of fast neutrons varied from 3.44 to 2.03 within the dose range from 0.4 to 2.7 Gy. As estimated by the growth inhibition (during 60 days) of Guerin's carcinoma inoculated in rat femur RBE varied from 4.68 to 2.76 within the dose range from 2.3 to 12.0 Gy.
Animals↗
Induction and disappearance of G2 chromatid breaks in lymphocytes after low doses of low-LET gamma-rays and high-LET fast neutrons.
PURPOSE: To determine by means of the G2 assay the number of chromatid breaks induced by low-LET gamma-rays and high-LET neutrons, and to compare the kinetics of chromatid break rejoining for radiations of different quality. MATERIALS AND METHODS: The G2 assay was performed on blood samples of four healthy donors who were irradiated with low-LET gamma-rays and high-LET neutrons. In a first set of experiments a dose-response curve for the formation of chromatid breaks was carried out for gamma-rays and neutrons with doses ranging between 0.1 and 0.5 Gy. In a second set of experiments, the kinetics of chromatid break formation and disappearance were investigated after a dose of 0.5 Gy using post-irradiation times ranging between 0.5 and 3.5 h. For the highest dose of 0.5 Gy, the number of isochromatid breaks was also scored. RESULTS: No significant differences in the number of chromatid breaks were observed between low-LET gamma-rays and high-LET neutrons for the four donors at any of the doses given. The dose-response curves for the formation of chromatid breaks are linear for both radiation qualities and RBEs = 1 were obtained. Scoring of isochromatid breaks at the highest dose of 0.5 Gy revealed that high-LET neutrons were, however, more effective at inducing isochromatid breaks (RBE = 6.2). The rejoining experiments further showed that the kinetics of disappearance of chromatid breaks following irradiation with low-LET gamma-rays or high-LET neutrons were not significantly different. Half-times of 0.92 h for gamma-rays and 0.84 h for neutrons were obtained. CONCLUSIONS: Applying the G2 assay, the results demonstrate that at low doses of irradiation, the induction as well as the disappearance of chromatid breaks is independent of the LET of the radiation qualities used (0.24 keV x microm(-1) 60Co gamma-rays and 20 keV x microm(-1) fast neutrons). As these radiation qualities produce the same initial number of double-strand breaks, the results support the signal model that proposes that chromatid breaks are the result of an exchange process which is triggered by a single double-strand break.
Adult↗
Fast neutron radiotherapy. The University of Washington experience.
An overview of the University of Washington neutron radiotherapy facility is presented. The utility of the multi-leaf, programmable, variable collimator is emphasized. Due to success in the treatment of salivary gland tumors, such patients comprise an ever increasing portion of the patients being treated. A cooperative randomized clinical trial for the treatment of salivary gland tumors was undertaken comparing fast neutrons against photon/electron radiation. At ten years, there was a statistically significant improvement in local/regional control for the neutron group (56% vs 25%, p = 0.009), but there was no improvement in survival (15% vs 25%, p = n.s.). Distant metastases were the primary reason for the failure of improved local/regional control to impact survival in the neutron group. The University of Washington experience is summarized with special emphasis on the treatment of adenoid cystic carcinomas. Excellent local/regional control can be achieved with neutrons even for large tumors arising in the paranasal sinuses. We conclude that the potential morbidity of a surgical debulking procedure is not warranted in most clinical situations.
Adult↗
Comparison of imaging plates with track detectors for fast-neutron dosimetry.
Imaging plate (IP) radiation detectors are widely used in industrial radiography, medical imagery and autoradiography. When an IP is exposed to ionising radiation, some of the energy is absorbed to form a latent image. The energy stored, which is proportional to the dose received, can be liberated by a selective optical stimulation and collected to reconstitute the distribution of the ionising radiation on the IP. In this work, IPs for use in fast-neutron measurements are characterised. The response of our IP dosemeters in conjunction with their reading system was found to be linear in dose between 75 microSv and 10 mSv. This performance is compared with those of dosemeters based on the plastic track detectors PN3 and CR-39.
Body Burden↗
[The combination treatment of malignant bone tumors using fast neutrons].
The study deals with results of a clinical trial evaluating treatment efficacy of a 6 MeV neutron beam produced by Y-120 cyclotron (Kiev). Procedures of preoperative radiotherapy and radical treatment are discussed. Radiotherapy was administered to 52 patients suffering chondrosarcoma (30 cases), osteogenic sarcoma (15) or chordoma (7). Combined treatment (radiation + surgery) was given to 22 patients whereas neutron beam therapy--to 30. All patients with osteogenic sarcoma received adjuvant combination chemotherapy. Three-year survival rate was compared to that observed in controls in whom combined treatment had included gamma-therapy. A significant increase in three-year survival rate was observed for osteogenic sarcoma and chordoma whereas for chondrosarcoma the improvement in survival proved insignificant. The use of fast neutrons in combined treatment of bone tumors was considered promising.
Adult↗
Measurement and calculation of the fast-neutron and photon spectra from the core boundary to the biological shielding in the WWER-1000 reactor model.
The fast-neutron and photon space-energy distributions have been measured in an axially (1.25 m active height) and azimuthally (60 degree symmetry sector) shortened model of the WWER-1000 reactor assembled in the LR-0 experimental reactor. The space-energy distributions have been calculated with the stochastic code MCNP and the deterministic three-dimensional code TORT. Selected results are presented and discussed in the paper. This work has been done in the frame of the EU 5th FW project REDOS REDOS, Reactor Dosimetry: Accurate determination and benchmarking of radiation field parameters, relevant for reactor pressure vessel monitoring. EURATOM Programme, Call 2000/C 294/04). All geometry and material composition data of the model as well as the available experimental data were carefully checked and revised.
Algorithms↗
The determination of calcium in faecal samples by instrumental fast neutron activation analysis.
A method is described for the determination of calcium in faecal material by a purely instrumental technique, namely fast neutron activation analysis. The major advantage of the technique over existing methods is that it requires minimal sample preparation. In addition, only a single standard is used and the method is also fairly rapid and simple. The method is well suited to the routine analysis of large numbers of samples and the results are shown to be comparable with atomic absorption spectrophotometry in accuracy. Finally, the technique can be extended to include the determination of several other elements providing a standard for each element is included.
Activation Analysis↗
A comparison of biological effects of modulated carbon-ions and fast neutrons in human osteosarcoma cells.
PURPOSE: To compare the biological effects of a 135 MeV/u carbon-ion beam and 13 MeV fast neutron beam using human osteosarcoma cells. METHODS AND MATERIALS: We have studied the clonogenic cell survival, recovery of potentially lethal damage (PLD) in plateau phase cells, and spheroid cure in multicellular spheroid after irradiation at various positions in the plateau and spread out Bragg peak (SOBP) of a 135 MeV/u carbon-ion beam and with 13 MeV neutrons. The carbon beam had a 4-cm range in water and a range filter was used to produce a 3-cm extended-peak region. The reference radiation was 137Cs gamma-rays. RESULTS: The relative biological effectiveness (RBE) values for 10% survival level of plateau phase cells for carbon-ions at the position of plateau, proximal peak, midpeak, and distal peak within the SOBP, and neutrons were 1.71, 2.48, 2.63, 3.47, and 2.29, respectively. Corresponding RBE values at 1% level were 1.64, 1.93, 2.06, 2.49, and 2.05. The extent of recovery from PLD was reduced after carbon-ions at proximal peak, midpeak, and distal peak, and neutrons, although not substantially reduced after carbon-ions at plateau. The RBE values for 50% spheroid cure level of spheroids for carbon-ions at the position of plateau, proximal peak, midproximal peak, middistal peak, and distal peak within the SOBP, and neutrons were 1.69, 1.88, 1.87, 1.94, 2.03, and 1.90, respectively. CONCLUSIONS: The biological parameters measured all indicate an approximately comparable biological effectiveness between 75-80 KeV/microns carbon-ions of the SOBP and 13 MeV neutrons in the human tumor model studied in vitro.
Carbon↗
The dosimetry of bone irradiated by fast neutrons.
The previous work on the dosimetry of bone is briefly reviewed. A dosimetric theory for the response of detectors irradiated by fast neutrons is applied to the problem of bone dosimetry. In the theory the detector or cavity shape is characterised by distributions of chord lengths along which the neutron-produced charged particles travel and deposit energy. Cavities of different convex geometries can be treated. A simplified version of the theory uses a single mean chord length to characterise the cavity. The absorbed dose to individual marrow cavities in trabecular bone is calculated over a large range of marrow cavity size for monoenergetic neutrons ranging from 0.5 to 7.0 MeV and for 252Cf neutrons. The influence of cavity shape is explored by considering spheres and cylinders of different elongation. The difference in absorbed dose is not great. Also the simplified model using a single mean chord length gives results in close agreement with the results obtained with chord length distributions. The mean marrow dose to different human bones has been calculated in three ways. First by using measured chord length distributions for the marrow cavities in the bones, second by using a sphere with the same mean chord length as the measured distribution and third by applying the measured single mean chord length. The difference between the three approaches is small and the agreement is good with results obtained by other workers who used the Monte Carlo technique. The dose to the endosteal cell layer has also been calculated by approximating the layer with an infinite slab.
Adult↗
Sr/Ca mass ratio determination in bones using fast neutron activation analysis.
The Sr/Ca mass ratio in human bones reveals information regarding the diet which is of interest in archaeology. By using fast neutron activation analysis this ratio can be measured in a non-destructive manner, which is important when bones are considered too precious to allow for destructive analysis. Simulations and measurements showed that the nuclear reactions 88Sr(n, 2n)87mSr and 44Ca(n, p)44K are highly useful for the purpose.
Archaeology↗