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At least 289 records · Page 16Linked to original sources
PubMed1976

Early assessment of normal tissue tolerance of fast neutron beam radiation therapy.

Between September 10, 1973 and May 20, 1975, 94 selected patients were treated with fast neutron beams generated by bombarding an "intermediate" beryllium target with 21 MeV deuterons. The clinical material included: 58 patients with head and neck cancers; 27 patients with cerebral glioblastoma multiforme; and 9 patients with a variety of other neoplasms. Of the 67 patients treated only with neutron beams, 31 received two increments per week and 36 received three increments per week. The calculated doses in most patients were 1800 rad n gamma (neutrons + gamma components) delivered in 6 weeks. Seventeen patients were treated with two increments of neutron beams and three increments of 60Co photons weekly to calculated total doses of 780-1050 rad n gamma + 3360-3780 rad 60Co gamma delivered over 50-54 days. Ten patients were treated with neutron bean "boosts" of 300-900 rad n gamma in three to seven increments over 8-23 days following conventional radiation therapy. Treatment has been well tolerated, with only 9 of 94 patients not completing the anticipated course. In three of these, treatment was dixcontinued because of intercurrent problems. Except for those patients with glioblastoma multiforme, treatment complications have not been dose-related. In four patients, complications probably were related to persistent cancer. Neutron beam irradiaiton may have been a factor in the neurologic deterioration of five patients with glioblastoma multiforme who did not complete treatment.

Aged↗
PubMed1988

[The TDF model of the teletherapy of malignant tumors using fast neutrons].

The paper describes a method of mathematical expressions of a TDF model in application to gamma-beam therapy of malignant tumors with fast neutrons. The maximum TDF value and an irradiated field area showed correlation; a bias for the enlargement of a single focal dose and neutron energy was introduced.

Fast Neutrons↗
PubMed2001

Determination of radionuclides induced by fast neutrons from the JCO criticality accident in Tokai-mura, Japan for estimating neutron doses.

A criticality accident occurred at a uranium conversion facility in Tokai-mura, Japan on September 30, 1999, and fission neutrons were continuously emitted for about 20 hours. Materials of stainless steel or iron, and chemical reagents were collected at places between 2 m and 270 m from the criticality accident site on October 25 and 26, 1999, November 27, 1999 and February 11, 2000. Neutron-induced radionuclides. such as 54Mn and 58Co, in the materials exposed to fast neutrons from the accident were measured to estimate the neutron fluences and energy distributions. Highly sensitive y-ray spectrometry with a well-type Ge detector was performed after radiochemical separation of Mn and Co from the materials. An instrumental neutron activation analysis was mainly applied for determinations of the target elements and chemical yields. The concentrations of 54Mn and 58Co in a mesh screen of stainless steel collected at a location 2.0 m from the accident site were determined. The total number of fission events was evaluated to be 2.5 x 10(18) by Monte-Carlo calculations of neutron transfer by considering the observed values of 54Mn and 58Co. The results presented here are fundamental to estimate the neutron doses at various distances.

Fast Neutrons↗
PubMed1982

[Computer-assisted irradiation planning for tumor therapy with fast neutrons at the Neutron Therapy Unit CIRCE in Essen].

A series of programs for the irradiation planning in tumor therapy with fast neutrons is presented. With these programs it is possible to calculate the dose distribution of single and multiple field as well as of uni- and biaxial rotating irradiations. The programs consider the patient's contour and calculate the total dose, the gamma dose and the gamma/total dose ratio. The output of the calculated dose distributions is made on a colour graph terminal. A hardcopy output by line printer is also possible.

Computers↗
PubMed1981

[Effect of 60Co gamma rays and fast neutrons on intravascular platelet aggregation and vessel wall prostacyclin activity].

The influence of gamma-rays 60Co and fast neutrons on intravascular platelet aggregation and prostacyclin activity of the vascular wall has been studied. It has been shown that 1-6 hours after irradiation of CBA mice, a great number of bone marrow platelets clump to form fibrin fibrils that often close completely the vascular lumen. Experiments with irradiated rats and guinea-pigs have demonstrated the reduction of prostacyclin-like activity in the abdominal aorta wall.

Animals↗
PubMed1979

Studies on the biological effect of fast neutrons. II. Variation of total nucleic acid content and ultrastructure in barley leaves vs. dose.

The effect of fast neutrons on the ultrastructure and nucleic acid content of leaves of barley seedlings was studied. Irradiation led to chloroplast degeneration. The walls of the cells containing degenerated plastides were abnormally thickened. Irradiation reduced the water content of the leaves. Variations in the RNA and DNA content of the leaves, expressed on a dry weight basis, could not be written as a simple function of the dose. Their content have a minimum at the semi-lethal dose.

Chloroplasts↗
PubMed1989

Fast neutron teletherapy in advanced epidermoid head and neck cancer. A review.

An extensive review of clinical studies employing fast neutron teletherapy for advanced epidermoid carcinomas of the head and neck is presented. Head and neck tumors have represented an excellent study site because of their accessibility to physical examination for measurement of tumor response, and because early neutron beams have had poor depth dose characteristics, making the treatment of more deeply seated tumors technically difficult. A summary of the major trials comparing neutron and mixed-beam (combination neutron and photon) therapy with conventional therapy indicates no conclusive evidence of improvement in local control or survival rates for the experimental arms. Exceptions to this are the Hammersmith experience and the slightly higher lymph node control rates seen in two studies. An evaluation of toxicity indicates that with the new generation of cyclotrons, complication rates may approach parity with those of photon linear accelerators.

Carcinoma, Squamous Cell↗
PubMedDate not supplied

[Theoretical study of the relation of the RBE of fast neutrons to dose for normal human skin and connective tissue].

The dependence of the relative biological effectiveness (RBE) of fast neutrons upon radiation dose was given a mathematical description. The formula obtained permitted to make calculations which, as was shown by comparison, were in a good agreement with the known experimental dependences of the RBE upon dose. The proposed formula may be applied in planning neutron therapy and in determining the RBE dependence upon radiation dose for any tissue with the known radiobiological parameters.

Cell Survival↗
PubMed1977

Lyoluminescence dosimetry in photon and fast neutron beams.

The lyoluminescence (LL) technique using mannose, a monosaccharide, is described. Dose-response curves for 60Co-gamma-rays (5 rad to 120 krad), fission neutrons, 5.3 MeV and 15 MeV neutrons (100 rad to 20 krad) have been measured. The close tissue-equivalence of mannose makes this material well suited for dosimetric use in low energy X-ray fields for radiotherapy and radiobiology. It also provides a cheap, simple and reproducible dosemeter in industrial applications of radiation (sprouting inhibition of onions and potatoes; control of insect infestation). After correction for the gamma contamination of the neutron beam the LL signal per rad in ICRU muscle tissue from the neutron irradiations has been derived and the relative effectiveness of the LL signal for fast neutrons in mannose has been calculated as 0.34 +/- 0.03 (fission neutrons), 0.63 +/- 0.07 (5.3 MeV neutrons) and 0.74 +/- 0.05 (15 MeV neutrons). These results are compared with data from other systems. It is concluded that mannose can be used as a transfer system in neutron dosimetry, if its variation in sensitivity with neutron energy is taken into account.

Cobalt Radioisotopes↗
PubMed1985

Clinical results after therapy with fast neutrons (DT, 14 MeV) since 1976 in Hamburg-Eppendorf.

In Hamburg since 1976 to 1980 we have treated 328 patients with fast neutron (DT, 14 MeV) and after reconstruction of the generator further 69 patients in 1984. The therapy with DT-neutrons had the best curative effect on high differentiated tumors. With the standard dose of 16 Gy in four weeks or--treating tumors in radiosensitive organs like brain and intestine--with a photon-neutron schedule, we have seen no necroses in normal tissues. The rate of medium or slight subcutaneous fibroses is not more than 10%. The local effect on tumors in our pilot study has been better than with megavoltage therapy in invasive thyroid cancer, prostate cancer stage C, soft tissue sarcoma and also in rectum-carcinoma. The best results have been achieved with neutrons only, but a photon-neutron schedule may be more effective as megavoltage therapy only. With our DT-neutrons we find some indications for better results than with megavoltage therapy if we use sophisticated treatment planning and if we strictly observe the tolerance dose of the different tissues and organs. The therapeutic index of our monoenergetic DT-neutrons is higher than with cyclotron-produced neutrons.

Aged↗
PubMed2006

Compact multileaf collimator for conformal and intensity modulated fast neutron therapy: electromechanical design and validation.

The electromechanical properties of a 120-leaf, high-resolution, computer-controlled, fast neutron multileaf collimator (MLC) are presented. The MLC replaces an aging, manually operated multirod collimator. The MLC leaves project 5 mm in the isocentric plane perpendicular to the beam axis. A taper is included on the leaves matching beam divergence along one axis. The 5-mm leaf projection width is chosen to give high-resolution conformality across the entire field. The maximum field size provided is 30 x 30 cm2. To reduce the interleaf transmission a 0.254-mm blocking step is included. End-leaf steps totaling 0.762 mm are also provided allowing opposing leaves to close off within the primary radiation beam. The neutron MLC also includes individual 45 degrees and 60 degrees automated universal tungsten wedges. The automated high-resolution neutron collimation provides an increase in patient throughput capacity, enables a new modality, intensity modulated neutron therapy, and limits occupational radiation exposure by providing remote operation from a shielded console area.

Electronics, Medical↗
PubMed1980

Fast neutron teletherapy for advanced carcinoma of hypopharynx and supraglottic larynx.

The results of a Phase I clinical trial using fast neutron teletherapy for advanced squamous cell carcinoma of the hypopharynx and supraglottic larynx are reported. Ten patients with hypopharyngeal tumors were treated for cure using neutrons alone and 6 patients with hypopharyngeal tumors were treated for cure using a combination of neutrons and photons as part of a mixed beam fraction scheme. In the neutron-only group, the initial complete remission rate was 4/10 (40%). The mean survival of this group of patients with initial complete remission was only 5.75 months (range 2--10) but all patients died without evidence of recurrent tumor at the primary site. In the mixed beam group, the initial complete remission rate was 5/6 (83%) but the local control rate dropped rapidly to 41 per cent when displayed on an actuarial plot. Six patients with advanced tumors of the supraglottic larynx were treated for cure, 5 with neutrons alone and one with a mixed beam regime. The initial complete remission rate was 3/6 (50%) but 2 of these patients rapidly recurred, which reduced the local control rate on an actuarial plot to 16 per cent. The relative adverse effects of the neutron-only treatment regime appear to be substantially greater than those of the mixed beam treatment regime.

Clinical Trials as Topic↗
PubMedDate not supplied

Design of flattening filters for the fast-neutron beam at TAMVEC by use of decrement lines.

Isodose distributions in a tissue-equivalent phantom produced by fast neutrons from 50-MeV deuterons incident on a thick beryllium target exhibit strong forward peaking, particularly for large fields. The design by use of decrement lines and the construction of polyethylene filters used to "flatten" those distributions are discussed and the results are illustrated. Also, the compromises of central-axis attenuation versus effective filter width and of off-axis peaking versus depth of "flattening" are discussed.

Fast Neutrons↗
PubMed1993

Radiolytic footprinting. Beta rays, gamma photons, and fast neutrons probe DNA-protein interactions.

Ionizing radiations induce numerous damages in DNA, especially strand breaks. The hydroxyl radical OH., produced by the radiolysis of water, is mainly responsible for this effect. The fact that strand breakage occurs at all nucleotides and that bound proteins may locally radioprotect DNA at the binding site lead us to develop a radiolytic footprinting method to study DNA-protein interactions. Three different radiations were used: beta rays, gamma photons, and fast neutrons. In order to validate this technique, three well-known interaction systems were tested: the lac repressor-lac operator of Escherichia coli, the cyclic AMP receptor protein (CRP) of E. coli and its specific site in the lac regulation region, and the core nucleosome. Radiolytic footprinting gives results similar to those obtained by more classical probes: DNase I, complexes of orthophenanthroline (OP) and copper, complexes of ethylenediaminetetraacetate ion (EDTA) and iron, and UV light. For the same system (lac repressor), irradiation with either gamma photons or fast neutrons gives identical results.

Animals↗
PubMed1977

Renewal of mouse gastric mucous cells following fast neutron irradiation. An ultrastructural and carbohydrate histochemical study.

Mouse gastric mucosa was studied ultrastructurally and histochemically after exposure to fast neutron irradiation, the number of cells per gastric gland was decreased and the glands were shorter. At day 9, several glands showed a dilated lumen lined by flattened cells. Between days 9 and 16, some of the glands disappeared. Parietal and chief cells disappeared from the remaining glands. At the same time, restoration of the mucosa started. At day 6, proliferative cells were scattered along the isthmus. As in controls, the isthmus contained a few undifferentiated cells many differentiating surface mucous cells (SMC) with developing rough endoplasmic reticulum and silver proteinate-reactive Golgi elements and small secretory granules. At day 9, numerous proliferative cells were clustered in foci. Almost all these cells contained silver proteinate-reactive Golgi elements, granules and vesicles. Most of them were SMC, others mucous neck cells (MNC) or intermediates. At day 16, proliferative foci were larger and consisted of differentiated mucous cells. Regenerated foveolae and glands consisted of large SMC and MNC and a few fibrillovesicular cells. In conclusion, proliferative activity is confined to undifferentiated cells and differentiating mucous cells, which identifies them as the progenitors of the other gastric cell types.

Animals↗
PubMedDate not supplied

Clinical results with fast neutrons (DT, 14 MeV).

In Hamburg, the therapy with DT-neutrons had the best curative effect on highly differentiated tumors. With the standard dose of 15.6 Gy in four weeks with fast neutrons only or--in treating tumors in radiosensitive organs such as brain and intestine--with a photon-neutron schedule, we have seen no necroses in normal tissues. The rate of medium or slight subcutaneous fibroses has been no more than 10%. The local effect on tumors in our pilot study has been better than with megavoltage therapy in invasive thyroid cancer, prostate cancer stage C, soft tissue sarcoma, and rectal carcinoma. The best results have been achieved with neutrons only, but a photon-neutron schedule may be more effective as megavoltage therapy only. With our DT-neutrons we find some indications for better results than with megavoltage therapy if we use sophisticated treatment planning and if we strictly observe the tolerance dose of the different tissues and organs. The therapeutic index of our DT-neutrons is higher than with cyclotron-produced neutrons.

Fast Neutrons↗
PubMed2004

Prospects for efficient detectors for fast neutron imaging.

A physical model describing in detail the process of fast neutron imaging in luminescent screens is presented. The detection quantum efficiency, luminosity and inherent spatial resolution of the screen were calculated using this model. Properties of transparent and disperse screens were compared. Two imaging systems were suggested to improve the detection efficiency and spatial resolution. A stack consisting of alternating neutron converters and image plates can help in obtaining both high spatial resolution and efficiency. A system containing a screen of special form and a diaphragm can be of use especially in the case of the fan beam.

Journal Article↗