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PubMed2006

Dose-response and large relative biological effectiveness of fast neutrons with regard to mouse fetal cerebral neuron apoptosis.

To evaluate the relative biological effectiveness (RBE) of low doses of neutrons on fetal nervous development, [C57BL/6J x C3H/He] hybrid (B6C3F1) mice were exposed to cyclotron-derived fast neutrons with peak energy of 10 MeV (0.02-1.0 Gy) or 137Cs-generated gamma-rays (0.1-2.0 Gy) on embryonic day 13.5. We then evaluated the incidence of neuronal apoptosis in the cerebral cortex 24 hours after irradiation. Neuronal apoptosis increased in a dose-dependent manner in both neutron- and gamma-ray-irradiated groups: even at the lowest dose, a minimal increase in the apoptotic index was noted in response to both types of radiation. The dose-response curves were best fitted to linear quadratic models, and the evaluated RBE was 9.8, which was considered to be large for a prenatal effect and acute tissue injury induced by a low dose of neutrons.

Animals↗
PubMedDate not supplied

[Quantitative characteristics of radiation injury of the spermatogenic epithelium and the rate of its recovery after exposure to fast neutrons and gamma-radiation].

The paper submits the results of studies on the kinetics of spermatogenous epithelium cell number after exposure to fast neutrons (60-300 cGy) and gamma-radiation (200-600 cGy). It was shown that a relative decrease in the quantity of spermatocytes is determined by an exponential dose-response curve with D0 of 35 and 120 cGy for neutrons and gamma-radiation respectively. For spermatides and spermatozoa a single D0 value of 20 and 55 cGy was obtained for neutrons and gamma-radiation respectively. As the radiation dose increases the recovery process in the epithelium is substantially decelerated. The equation T1/2 = T1/2(0)e0.0009D well describes the dependence of the half-recovery period T1/2 upon the equivalent dose.

Animals↗
PubMed1980

Fast neutron teletherapy for advanced carcinomas of the oral cavity and soft palate.

A retrospective study was performed to determine the efficacy of using fast neutron radiation for treating advanced squamous cell carcinomas of the oral cavity and soft palate. The majority of patients were judged to have less than a 10% 5-year survival with conventional medical treatment. Fifteen patients with oral cavity tumors were treated for cure with neutrons alone and six were treated with a combination of neutrons and photons as part of a mixed beam fractionation scheme. In the neutron-only group, the complete regression rate was 33% in the mixed beam group, the rate was 50%. Five patients who had squamous cell carcinomas of the soft palate were treated for cure, one with neutrons alone and four with a mixed beam regimen. The complete regression rate was 100%. The two-year NED results are comparable with literature results for more selected groups of patients with oral cavity and soft palate tumors treated by conventional photon therapy. The acute treatment morbidity was perhaps somewhat greater in the subgroup of patients treated with neutrons alone, and this subgroup later developed a more pronounced subcutaneous fibrosis. Morbidity associated with the mixed beam treatment regimen was comparable to that associated with conventional radiotherapy.

Carcinoma, Squamous Cell↗
PubMed1990

Effects of split fast neutron doses on the liver cells of albino Swiss mice.

The effect of neutron doses from a D-T compact neutron generator on the liver cells of adult male and female albino Swiss mice was investigated. Fast neutrons (14.5 MeV) were delivered to the whole body in a single dose or in two, four, six or eight equal doses separated by 3-day intervals. The lowest dose, 100 rem, was given for an exposure time of 6 hours and was then steadily raised to 912 rem for an exposure time of 48 hours. During exposure the neutron flux was controlled by the activation foil technique. Animals were killed for testing after each irradiation. Histological examination of the hepatocytes in the light microscope showed marked degenerative changes only after the longer irradiation periods (24, 36 and 48 h). Electron microscopy showed cytological (cytoplasmic and nuclear) changes in the hepatocytes after only 12 hours' irradiation. Densitometric scans of electron micrographs of control and 12 h-irradiated livers indicated that the control hepatocyte interphase nucleus contains approximately 72% heterochromatin, while the irradiated nucleus contains only 64% heterochromatin.

Animals↗
PubMed1975

A novel fast neutron dosemeter based on fission chambers. Part I: Principles of operation and theoretical response in neutron therapy radiation fields.

A novel method is proposed of accurately measuring fast neutron doses of interest in radiotherapy. The technique, which utilizes calculated neutron fluence-to-kerma conversion factors, is based upon the combination of measurements with calibrated neptunium-237 and uranium-238 pulse fission chambers to obtain a response which matches the variation of kerma with neutron energy. The theoretical performance of a practical instrument has been assessed for a variety of neutron spectra to evaluate the spectrum dependence of the dosemeter. The overall systematic uncertainty using this absolute method of determining the neutron dose under charged particle equilibrium conditions is comparable to that encountered with ionization chamber techniques.

Hot Temperature↗
PubMed1992

The role of fast neutron radiation therapy in the management of advanced salivary gland malignant neoplasms.

Fifty-three patients with locally advanced salivary gland malignant neoplasm were treated with fast neutron radiation therapy. All patients received treatment for gross inoperable, residual unresectable, or recurrent disease--clinical situations in which results using photon irradiation were suboptimal. With a median follow-up of 42 months and a minimum follow-up of 1 year, locoregional tumor control in the treatment field was achieved in 92% (48 of 52) of patients. An additional eight patients had regional failures outside the treatment field, resulting in an overall locoregional tumor control rate of 77% (40 of 52). The 5-year actuarial locoregional control rates were 65% overall and 75% in patients with node-positive disease. Grouping patients according to prior treatment status, actuarial 5-year locoregional control rates were 92% for patients treated definitively (without a prior surgical procedure), 63% for those treated postoperatively for gross residual disease, and 51% for those treated for recurrent disease after a surgical procedure. The P values associated with these differences were 0.12 and 0.01, respectively. There were no instances of radiation-induced facial nerve damage. This study suggests that neutron irradiation alone should be the therapy of choice in the treatment of advanced-stage salivary gland tumors and that surgery should be limited to those patients in whom disease-free margins can be obtained. The potential morbidity of a debulking surgical procedure before neutron irradiation is not warranted by an improvement in loco-regional control over that achievable with neutron therapy alone.

Adult↗
PubMedDate not supplied

CT manifestation in the pararectal area following fast neutron radiotherapy.

Sixty-four pelvic CT studies of 38 patients with pelvic malignancies were obtained at various times (21 to 678 days) following fast neutron radiotherapy. Multiple scans (2 to 3) were available in 19 cases. Fractionated neutron radiotherapy was delivered over four to seven weeks to a total dose of 54 Gy to 60 Gy photon equivalent. Radiation-induced changes on CT were symmetrical thickening of the perirectal fascia (87%), widening of the presacral space (82%), and thickening of the walls of the bladder and rectum (21% and 11%, respectively). Serial CT studies showed that these changes became stable after 12 weeks from radiotherapy in 13 of 14 patients (93%). CT manifestations of radiation-induced changes in the pararectal area were rather regular and would be easy to differentiate from local recurrence or secondary disease.

Aged↗
PubMed1977

The effects of fast neutrons and X rays on the subependymal layer of the rat brain.

Some effects of irradiation of rat brain with single doses of X rays or fast neutrons have been measured. This was done by estimating the total number of cells in the subependymal layer at various times after irradiation. The gross response to X rays and neutrons was somewhat different, and the results suggest that the two histologically distinguishable cell types in the subependymal layer have different values of RBE.

Animals↗
PubMed1986

Fast neutron r.b.e. for lethality and genotoxicity in a wild-type and a repair-deficient strain of yeast.

The relative biological effectiveness (r.b.e.) of cyclotron-produced fast neutrons (11 MeV) in relation to 60Co gamma-rays, was studied in a wild-type and a DNA repair-deficient yeast strain for cell killing and genotoxicity. In the wild-type (D7) strain the r.b.e. varied from 2.7 to 4.1 for lethality, 2.8 to 7.1 for reverse mutation and 3.5 to 7.8 for mitotic gene conversion. At different survival levels, the repair deficient strain (D7 rad 52/rad 52) generally showed a lower r.b.e. for both cell killing and genotoxicity (25.2 to 37.2 per cent reduction for the cell death and 24.8 to 70.6 per cent for mutation and gene conversion) compared to the wild type. Except at very low dose levels, the r.b.e. values for cell killing and genotoxicity were similar within a given strain. At similar survival levels, neutrons were no more genotoxic than gamma-rays.

Cell Survival↗
PubMed1975

The effects of fast neutrons on inoperable carcinoma of the stomach.

Thirty-nine unselected patients suffering from inoperable, recurrent, or residual adenocarcinoma of the stomach were referred for palliation with fast neutrons from the Medical Research Council's cyclotron at Hammersmith Hospital. A full course of 1440 rads given in 12 treatments over 26 days was administered to the patients. Because of the relatively low energy (7-5 MeV) of the beam from this particular machine, it was not possible to deliver the full dose uniformly throughout the tumour except in extremely thin patients. Pain, dysphagia, vomiting, and bleeding were relieved in the majority of cases. The side effects were minimal and easily controlled. Palpable masses disappeared. Five patients required surgery after neutron therapy. All the incisions were made through irradioated tissue and all except one healed normally. Tumour was present outside the treated area, but the absence of any palpable mass within the treated area was a consistent finding. Radiologically, the stomachs remained abnormal and later changes included gross mucosal abnormality and shrinkage. Fourteen patients came to necropsy and in 10 no tumour was present macroscopocally. Tumour cells were seen in all except two cases but these were few, surrounded by dense fibrous tissue, and may not have been viable. The remaining stomach was abnormal with a thickened wall and destruction of mucosa. Three of the four cases in which macroscopic tumour was present received less than the standard dose because of the inadequate penetration of the beam. Excellent regression of tumors was achieved by the neutrons, but the stomachs did not recover from this satisfactorily. Gastrectomy four to six months after treatment is therefore suggested. This operation and other surgical procedures in other patients were successfully carried out. There is a need for higher energy neutrons to improve treatment and extend it to patients of thick-set build.

Adenocarcinoma↗
PubMed1982

A preliminary report on the clinical application of fast neutrons in Krakow.

The neutron therapy facility based on the cyclotron installed in the Institute of Nuclear Physics in Kraków, Poland, is described. Fast neutrons are produced by bombarding a beryllium target with 12.5 MeV deuterons. The unit has been used for treatment of cancer patients by the medical team of the Institute of Oncology in Kraków since September, 1978. Fifty-three patients were treated; most of these patients had advanced head and neck cancer. On the basis of the radiobiological experiments, a standard tumor dose of 1320 radn,gamma in 20 fractions over 4 weeks was established. From among 34 patients with advanced head and neck cancer, treated with neutrons only, and observed for at least one year, 10 patients, (29%) are living free of cancer.

Adult↗
PubMed1980

A comparative study of the effect of adriamycin on the sensitivity of mice to whole-body irradiation with 6-MVp photons or fast neutrons (67 MeV p--Be).

The effect of Adriamycin (doxorubicin hydrochloride) (10 mg/kg intraperitoneally) on the response of mouse gut to irradiation with 6-MVp photons or fast neutrons (67 MeV p--Be), was assessed with the six-day death endpoint. The drug reduced the LD50/6 by the same factor (approximately 1.25) for both types of radiation. Thus, the radiobiological effectiveness (RBE) (photons/neutrons) for gut damage is unaltered by the addition of Adriamycin. The data indicated no significant effect of drug scheduling if given within 16 hours before or after irradiation.

Animals↗
PubMed1985

[Fast neutron radiotherapy at NIRS, indication and prospects].

Eleven hundred and seventy one patients, 921 previously untreated and 250 recurrent, have been treated with 30 MeV (d-Be) fast neutron beam between 1975 and 1984 at NIRS. Some trends have been identified: non-randomized results have been at least as good as those of photons in carcinomas such as: supraglottic carcinoma in the larynx, pancoast type tumor of the lung, malignant melanoma of the skin and so on. Randomized results with mixed beam studies for carcinoma of the uterine cervix have indicated no significant advantages against those of photons. Treatment technique for the beam concentration must be improved to demonstrate the merit of neutrons in the next step.

Adult↗
PubMed1985

Mouse testis weight loss and survival of differentiated spermatogonia following irradiation with 250 kV X-rays and 5.5 MeV fast neutrons.

Twenty eight after whole body irradiation of male BALB/c mice with 0.1-4.0 Gy of 250 kV X-rays or with 0.05-1.0 Gy of 5.5 MeV fast neutrons a decrease in testis weight and number of spermatozoa were observed. After plotting the testis weight loss against the radiation dose a mono-component curve characterized by D0 equal to 6.2 Gy and 1.31 Gy for X-rays and neutrons, respectively, was obtained. Relative biological effectiveness (RBE) was 4.25. Similar relation between the number of spermatozoa and the dose had a form of a two component curves. The sensitive components of the testis were characterized by the A-type curves with D0 equal to 0.49 Gy and 0.10 Gy for X-rays and neutrons, respectively. The resistant components were characterized by the B-type curves with D0 equal to 5.07 and 0.97 Gy for X-rays and neutrons, respectively. The RBE was 4.57. The obtained RBE values allowed to modify the total neutron dose and its fractionation in the therapy of malignant tumors at the Institute of Oncology, Krakow.

Animals↗
PubMedDate not supplied

[Effect of interferon on the yield of chromosome aberrations in cultured human lymphocytes irradiated with fast neutrons].

A study was made of the influence of leucocytic interferon on the yield of chromosome aberrations in a human lymphocyte culture after irradiation of cells with fast neutrons (0.85 MeV) at the G0- and G1-stages. It was shown that in cells treated with interferon (50 UE/ml) prior to irradiation the total yield of aberrations and of some of their types was invariable as compared to the irradiated control.

Cell Cycle↗
PubMed1996

Microdosimetric specification of the radiation quality of a d(48.5)+Be fast neutron therapy beam produced by a superconducting cyclotron.

The proportional counter microdosimetric technique has been employed to quantify variations in the quality of a d(48.5)+Be fast neutron beam passing through a homogeneous water phantom. Single event spectra have been measured as a function of spatial location in the water phantom and field size. The measured spectra have been separated into component spectra corresponding to the gamma, recoil proton and alpha plus heavy recoil ion contribution to the total absorbed dose. The total absorbed dose normalized to the "monitor units" used in daily clinical use has been calculated from the measured spectra and compared to the data measured with calibrated ion chambers. The present measurements agree with the ion chamber data to within 5%. The RBE of the neutron beam is assumed to be proportional to the microdosimetric parameter y* for the dose ranges pertinent to fractionated neutron therapy. The relative variations in y*, assumed to be representative of variations in the RBE are mapped as a function of field size and spatial location in the phantom. A variation in the RBE of about 4% for points within and 8% for points outside a 10 cm x 10 cm field is observed. The variations in the RBE within the beam are caused by an increase in the gamma component with depth. An increase in the RBE of about 4% is observed with increasing field size which is attributed to a change in the neutron spectrum. Compared to the uncertainties in the prescribed dose, associated with uncertainties in the clinically used RBE, variation in the RBE between various tissues, and other dosimetric uncertainties caused by factors such as patient inhomogeneities, patient setup errors, patient motion, etc., the measured spatial RBE variations are not considered significant enough to be incorporated into the treatment planning scheme.

Biophysical Phenomena↗
PubMed1997

A rather intense source of fast neutrons for small scale activation.

A thick beryllium target has been developed for installation onto a small proton cyclotron (CTI RDS 112), providing an intense source of fast neutrons for activation purposes. Careful attention was paid to cooling and irradiation geometry, allowing cubic centimeter scale samples to approach the proton beam strike surface to within 5 mm. This proximity assures approximately equal to 10(11) neutron/s passing through the irradiated sample when 20 microgramsA of 11 MeV protons are incident on the beryllium primary target.

Beryllium↗