On the repair of sub-lethal damage in V79 Chinease hamster cells resulting from irradiation with fast neutrons or fast neutrons combined with X-rays.
Explore the source record for details and available documents.
Animals↗
SEARCH · Search PubMed
Results for “Fast Neutrons”
Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Treatment of malignant melanoma by fast neutrons.
Fast neutron therapy has been used to treat 87 tumours of primary, recurrent or metastatic melanoma in 48 patients. Complete regression has been obtained in 71 percent of tumours and 91 per cent of all tumours were controlled for the remainder of the patients, lives. Median survival was 14.5 months; 30 of the 34 deaths were due to metastases. Complications arose in 22 per cent of sites and were either fibrosis, which was related to large treated areas, previous surgery or a higher than standard dose, or necrosis which was related to sites with poor circulation, such as in the lower limb. It is suggested that for the treatment of advanced local disease fast neutron therapy is more effective than X-ray treatment and has a local control rate similar to that of surgery.
Fast Neutrons↗
Treatment of advanced tumours of head and neck with fast neutrons.
Fast neutrons interact with matter in a different way from x and gamma rays. They have been used at Hammersmith Hospital for the past four years in the treatment of advanced tumours in several sites of the body, and the results of this treatment in the first 100 cases of tumours of the head and neck are described here. Altogether 62 patients who had been referred for fast neutron therapy because it was thought that no other treatment would be effective experienced complete regression of the tumours, and only two recurred. Tumours of the buccal cavity and salivary glands responded particularly well and the relief of pain and ulceration was striking. Side effects were not serious and did not differ from those seen with supervoltage radiation, apart from the reaction of the skin. Follow-up was short, however, owing to deaths from metastases, and out of 76 patients treated more than one year previously only 30 survived. Cases which have not metastasized must therefore be treated so that the effects on tumours and adjacent normal tissues can be observed for several years after treatment. The results obtained so far indicate that it is now justifiable to use neutrons in such cases.
Adenocarcinoma↗
Boron neutron capture enhancement of fast neutron radiotherapy utilizing a moderated fast neutron beam.
An investigation of the therapeutic potential of boron neutron capture (BNC) enhancement of fast neutron therapy utilizing the Harper University Hospital superconducting cyclotron-produced d(48.5)+Be fast neutron therapy beam is presented. A technique for modification of the fast neutron beam to increase the BNC enhancement is presented along with an evaluation of the effects of beam moderation on the biological effectiveness of the absorbed dose. Characteristics of the photon, neutron, and boron neutron capture components of the absorbed dose are presented. Results demonstrate the possibility of therapeutic gains greater than 50% over conventional fast neutron therapy at depths required to treat brain lesions. This enhancement is estimated assuming currently achievable boron concentrations, and is more than adequate to provide a therapeutic window for the effective treatment of Glioblastoma Multiforme without prohibitive toxicity to the normal brain.
Body Burden↗
Study on the biological effect of fast neutrons 1. Effect of fast neutrons on germinability of barley seeds and on the chlorophyll content of the seedlings according to the dose used.
Barley seeds were irradiated in the active zone of the reactor at 500 watt, at favourable flux of fast neutrons in the dose interval of 823--2144 rad. Seeds after irradiation were "cooled" for 48 hours, then germinated, and the length of shoots of the seven days old seedings was measured. The value of the half lethal dose is 1130 rad, estimated from the growth curve. There is a well-defined relation of chlorophyll content (calculated for fresh weight unit) to the dose used. It was concluded from the phenotype of the leaves that the decrease of chlorophyll content was due first of all to the presence of chlorophyll-less cells and cell lines and not to the decrease of chlorophyll content of the individual cells. Irradiation yielded genetically defected cells.
Chlorophyll↗
The effects of x-rays, 2-Mev electrons, thermal neutrons, and fast neutrons on dormant seeds of barley.
Explore the source record for details and available documents.
Edible Grain↗
Filter, collimator and moderating material to achieve boron neutron capture enhanced fast neutron therapy.
The combination of fast neutron therapy and boron neutron capture therapy is currently being studied as a possible treatment for some radio-resistant brain tumours. In an attempt to design a boron-enhanced fast neutron therapy beam for the Fermilab Fast Neutron Therapy Facility, the use of moderating material surrounding the patient's head has been investigated. Graphite, polyethylene, water and heavy water were studied as moderating materials, using MCNP. The use of tungsten, iron, lead and bismuth as materials for a small filter and collimator near the patient's head was investigated. Calculations showed that a filter and collimator made of tungsten with a graphite moderator was capable of producing a dose enhancement of 17.3 +/- 0.6% for a 100 microg g(-1) loading of 10B for a 5.6 cm diameter beam while delivering 1.5 Gy in 7 min.
Boron Neutron Capture Therapy↗
Boron neutron capture enhanced fast neutron radiotherapy for malignant gliomas and other tumors.
Both fast neutron radiotherapy and boron neutron capture therapy have been investigated as new radiation treatment techniques for patients with malignant gliomas. While each of these techniques individually has shown the potential for pathological eradication of malignant glioma, to date neither has evolved into an accepted, improved method of treatment. We have recently begun a research program investigating the feasibility of combining the benefits of both types of therapy. As a fast neutron beam penetrates tissue some of the particles are degraded to thermal energies. These can be captured by 10B or other suitable isotopes resulting in a highly-localized release of additional energy during a course of fast neutron radiotherapy. In this article we will review the rationale for such an approach, and review the underlying physics as well as in vitro, in vivo, and early human studies testing its feasibility. If appropriate carrier agents can be found that preferentially-localize in tumor cells, this approach ena be applied to many different tumor systems.
Animals↗
Sterilization of boll weevils with combinations of chemosterilants and x-rays, gamma rays, thermal neutrons, or fast neutrons.
Explore the source record for details and available documents.
Chemosterilants↗
Present status, trends and needs in fast neutron therapy.
Fast neutrons were introduced in cancer therapy, in the 1970s, on the basis of radiobiological arguments. After 30 years, these arguments are still valid and have not been refuted by more recent experimental data. Although neutron therapy has been applied routinely for about 25 years, there is still no general agreement concerning its value and its place among the other radiation therapy techniques. In order to be able to draw objective conclusions from the available clinical results and mainly to compare the results from the different centres in a relevant way, a consensus has to be reached on several issues: 1) a protocol for dose measurement in a homogeneous phantom in reference conditions; 2) dose computation at the level of the target volume(s) and the normal tissues at risk; 3) method of dose specification for reporting; and 4) specification of radiation quality in neutron therapy and the related RBE problems. The International Commission on Radiation Units and Measurements (ICRU) has published recommendations on Clinical Neutron Dosimetry (ICRU Report 45, 1989) which are now universally applied. As far as dose specification for reporting is concerned, ICRU recommendations for photons (ICRU Report 50, 1993) can be extended and adapted for fast neutrons. However, special care is required to take into account the tissue compositions. In fast neutron therapy, specification of radiation quality raises a particular problem because the neutron RBE, relative to gamma rays, is higher than unity (it ranges from about 2 to 5) and furthermore significantly varies with neutron beam energy. In addition, the RBE also varies with dose and biological system. In these conditions, besides the classical concept of RBE introduced jointly by the ICRP and the ICRU in 1963, the concepts of "reference RBE" and "clinical RBE" are proposed here for application in fast neutron therapy. Microdosimetry provides an adequate method to describe radiation quality, at the point of interest in the irradiated medium and in the actual irradiation conditions. From the analysis of microdosimetric spectra, a RBE value of a particular neutron beam, for a given biological system, can be predicted provided that the biological weighing function for that biological system has been obtained. In any case, correlation of the microdosimetric description of a given beam and the experimental RBE values for that beam improves the confidence in both sets of data.
Cancer Care Facilities↗
Triple chamber technique for thermal neutron dose measurements in fast neutron beams.
Collimated fast neutron beams used in radiotherapy are always contaminated with photons and thermal neutrons. From foil activation measurements the relative dose contribution of thermal neutrons to the absorbed neutron dose in different depths in a tissue equivalent phantom was determined. The sensitivities of a TE-Chamber, a GM-counter with a 6Li-shield and an unshielded GM-counter to fast neutrons, thermal neutrons and photons are presented. The triple chamber technique using these three devices is compared to foil activation technique with respect to the determination of relative thermal neutron depth dose curves. Finally the triple chamber technique is applied for the determination of depth dose curves of fast neutrons, thermal neutrons and photons in a solid TE-phantom.
Fast Neutrons↗
Modification of the University of Washington Neutron Radiotherapy Facility for optimization of neutron capture enhanced fast-neutron therapy.
A modified neutron production target assembly has been developed to provide improved performance of the proton-cyclotron-based neutron radiotherapy facility at the University of Washington for applications involving neutron capture enhanced fast-neutron therapy. The new target produces a neutron beam that yields essentially the same fast-neutron physical depth-dose distribution as is produced by the current UW clinical system, but that also has an increased fraction of BNCT enhancement relative to the total therapeutic dose. The modified target is composed of a 5-millimeter layer of beryllium, followed by a 2.5-millimeter layer of tungsten, with a water-cooled copper backing. Measurements of the free-field neutron spectrum of the beam produced by the new target were performed using activation foils with a direct spectral unfolding technique. Water phantom measurements were performed using a tissue-equivalent ion chamber to characterize the fast-neutron depth-dose curve and sodium activation in soda-lime glass beads to characterize the thermal-neutron flux (and thus the expected neutron capture dose enhancement) as a function of depth. The results of the various measurements were quite consistent with expectations based on the design calculations for the modified target. The spectrum of the neutron beam produced by the new target features an enhanced low-energy flux component relative to the spectrum of the beam produced by the standard UW target. However, it has essentially the same high-energy neutron flux, with a reduced flux component in the mid-range of the energy spectrum. As a result, the measured physical depth-dose curve in a large water phantom has the same shape compared to the case of the standard UW clinical beam, but approximately twice the level of BNCT enhancement per unit background neutron dose at depths of clinical interest. In-vivo clinical testing of BNCT-enhanced fast-neutron therapy for canine lung tumors using the new beam was recently initiated.
Animals↗
Combined use of FLUKA and MCNP-4A for the Monte Carlo simulation of the dosimetry of 10B neutron capture enhancement of fast neutron irradiations.
Boron neutron capture enhancement (BNCE) of the fast neutron irradiations use thermal neutrons produced in depth of the tissues to generate neutron capture reactions on 10B within tumor cells. The dose enhancement is correlated to the 10B concentration and to thermal neutron flux measured in the depth of the tissues, and in this paper we demonstrate the feasibility of Monte Carlo simulation to study the dosimetry of BNCE. The charged particle FLUKA code has been used to calculate the primary neutron yield from the beryllium target, while MCNP-4A has been used for the transport of these neutrons in the geometry of the Biomedical Cyclotron of Nice. The fast neutron spectrum and dose deposition, the thermal flux and thermal neutron spectrum in depth of a Plexiglas phantom has been calculated. The thermal neutron flux has been compared with experimental results determined with calibrated thermoluminescent dosimeters (TLD-600 and TLD-700, respectively, doped with 6Li or 7Li). The theoretical results were in good agreement with the experimental results: the thermal neutron flux was calculated at 10.3 X 10(6) n/cm2 s1 and measured at 9.42 X 10(6) n/cm2 s1 at 4 cm depth of the phantom and with a 10 cm X 10 cm irradiation field. For fast neutron dose deposition the calculated and experimental curves have the same slope but different shape: only the experimental curve shows a maximum at 2.27 cm depth corresponding to the build-up. The difference is due to the Monte Carlo simulation which does not follow the secondary particles. Finally, a dose enhancement of, respectively, 4.6% and 10.4% are found for 10 cm X 10 cm or 20 cm X 20 cm fields, provided that 100 micrograms/g of 10B is loaded in the tissues. It is anticipated that this calculation method may be used to improve BNCE of fast neutron irradiations through collimation modifications.
Biophysical Phenomena↗
Boron neutron capture enhancement (BNCE) of fast neutron irradiation for glioblastoma: increase of thermal neutron flux with heavy material collimation, a theoretical evaluation.
Despite the fact that fast neutron irradiation of glioblastoma has shown on autopsies an ability to sterilize tumors, no therapeutic windows have been found for these particles due to their toxicity toward normal brain. Therefore, the Boron Neutron Capture Enhancement (BNCE) of fast neutron beam has been suggested. This paper addresses the problem of fast neutron beam collimation, which induces a dramatic decrease of the thermal neutron flux in the depth of the tissues when smaller irradiation fields are used. Thermoluminescent dosimeter TLD-600 and TLD-700 were used to determine the thermal neutron flux within a Plexiglas phantom irradiated under the Nice Biomedical Cyclotron p(60)+Be(32) fast neutron beam. A BNCE of 4.6% in physical dose was determined for a 10 x 10 cm2 field, and of 10.4% for a 20 x 20 cm2 one. A Dose Modification Factor of 1.19 was calculated for CAL 58 glioblastoma cells irradiated thanks to the larger field. In order to increase the thermal flux in depth while shaping the beam, heavy material collimation was studied with Monte Carlo simulations using coupled FLUKA and MCNP-4A codes. The use of 20 cm width lead blocks allowed a 2 fold thermal neutron flux increase in the depth of the phantom, while shielding the fast neutron beam with a fast neutron dose transmission of 23%. Using the DMF of 1.19, a BNCE of 40% was calculated in the beam axis. This enhancement might be sufficient to open, at least theoretically, a therapeutic window.
Beryllium↗
Relative biological effectiveness and tolerance dose of fission neutrons in canine skin for a potential combination of neutron capture therapy and fast-neutron therapy.
To investigate the potential efficacy of fission neutrons from a fast-neutron reactor for the treatment of radioresistant tumors, the relative biological effectiveness (RBE) and tolerance dose of fission neutrons in canine skin were determined. The forelimbs of 34 healthy mongrel dogs received a single dose of fission neutrons (5.6, 6.8, 8.2, 9.6 or 11 Gy) or 137Cs gamma rays (10, 15, 20, 25 or 30 Gy). Based on observations of radiodermatitis for each radiation, the single-fraction RBE of fission neutrons in the sixth month was calculated as approximately 3. The tolerance doses of fission neutrons and gamma rays, defined as the highest doses giving no moist desquamation on the irradiated skin in the recovery phase, were estimated as 7.6 Gy and 20 Gy, respectively. The tolerance dose of 7.6 Gy of fission neutrons included 5.0 Gy of fast neutrons possessing high anti-tumor effects and 1.4 x 10(12) n/cm2 of thermal neutrons, which could be applicable to neutron capture therapy (NCT). The combination of fast-neutron therapy and NCT using a fast-neutron reactor might be useful for the treatment of radioresistant tumors.
Animals↗
Concomitant boron-neutron capture therapy during fast-neutron irradiation of a rat glioma.
PURPOSE: Fast-neutron irradiation and boron-neutron capture therapy (BNCT) have been independently investigated as treatments for malignant disease. This study tested the feasibility of enhancing fast-neutron irradiation with concomitant BNCT. MATERIALS AND METHODS: Seventeen male Fisher rats, each weighing 180-200 g and bearing 36B10 gliomas, were irradiated with graded doses of fast-neutron radiation. Half of the animals received an L-para-boronophenylalanine (BPA) fructose complex prior to treatment. An in vitro colony-forming assay was used to measure surviving fraction. RESULTS: A significantly lower surviving fraction was noted in the tumors from the BPA group compared with those receiving neutrons alone at the three lower neutron doses (P < .005). With use of a linear quadratic curve fit of cell survival, the dose modifying factor was 1.32 at the 0.10 surviving fraction. Mean tumor boron concentration was 68.4 micrograms/g. CONCLUSIONS: BNCT enhancement of fast-neutron irradiation is feasible in an in vivo tumor system.
Animals↗
Sites of strand breakage in DNA irradiated by fast neutrons.
Therapeutic fast neutrons are densely ionizing particles, with a high relative biological effectiveness relative to 60Co gamma rays (RBE) and a low oxygen enhancement ratio (OER). The molecular basis of their properties is not yet entirely understood. In a previous work, we have shown that neutrons induce a different number of DNA frank strand breaks as compared to gamma photons, and we have revealed the presence of breaks due to the direct effects of neutrons. In the present work, we searched for eventual differences in the chemical nature of the attacked sites in DNA irradiated in oxygenated diluted solution. We compare our results with neutrons to those previously reported by other authors using gamma- or X-rays. Using sequencing gel electrophoresis of short natural DNA restriction fragments, or synthetic oligonucleotides, we have shown that, in the case of neutrons, the attack occurs with almost the same probability, at each nucleotide, as reported for gamma- and X-rays. The doubling of bands in the bottom of gels shows the presence of two types of termini, the 3'-phosphate and the 3'-phosphoglycolate. Upon neutron irradiation, the 3'-phosphate end appears with a higher yield than the 3'-phosphoglycolate, whereas equal amounts were obtained with gamma- or X-rays.
Base Sequence↗
Monte Carlo calculation of dose enhancement by neutron capture of 10B in fast neutron therapy.
Since 1978 the Essen Medical Cyclotron Facility has been used for fast neutron therapy. The treatment of deep-seated tumours by d(14) + Be neutron beam therapy (mean energy = 5.8 MeV) is still limited because of the steep decrease in depth-dose distribution. The interactions of fast neutrons in tissue leads to a thermal neutron distribution. These partially thermalized neutrons can be used to produce neutron capture reactions with 10B. Thus incorporation of 10B in tumours treated with fast neutrons will increase the relative local tumour dose due to the reaction 10B (n, alpha) 7Li. The magnitude of dose enhancement by 10B depends on the distribution of the thermal neutron fluence, 10B concentration, field size of the neutron beam, beam energy and the specific phantom geometry. The slowing down of the fast neutrons, resulting in a thermal neutron distribution in a phantom, has been computed using a Monte Carlo model. This model, which includes a deep-seated tumour, was experimentally verified by measurements of the thermal neutron fluence rate in a phantom using neutron activation of gold foil. When non-boronated water phantoms were irradiated with a total dose of 1 Gy at a depth of 6 cm, the thermal fluencies at this depth were found to be 2 x 10(10) cm-2. The absorbed dose in a tumour with 100 ppm 10B, at the same depth, was enhanced by 15%.
Boron Neutron Capture Therapy↗