Fast Neutron Radiotherapy in Relation to the Radiation Sensitivity of Human Organ Systems. Relative Radiation Sensitivities of Human Organ Systems, Part III. Elsevier; 1992. pp. 153-93. [DOI: 10.1016/b978-0-12-035415-3.50009-3]

Calculation of 9Be and 12C thick targets neutron yields from particle accelerator-induced nuclear reactions using PHITS code

The double-differential cross-sections, and neutron yields of the 9Be(4He,n)12C and 12C(d,n)13N reactions at various energies, have been calculated. The cross-sections for the consider nuclear reactions were obtained using PHITS code based on Monte Carlo method. The calculated data were validated against the available experimental data with varying agreement up to 30MeV. We have suggested the most suitable reaction, at certain energies, for better neutron yield and hence radiotherapy applications.

A portable fast neutron irradiation system for tumor therapy

A portable neutron tube was introduced as a small-sized (weight≤14.4 kg, power consumption ≤50W and cost≤ $100,000) neutron accelerator and applied for irradiation therapy on cancer. The effect of growth-inhibiting in vitro by neutrons irradiation on HeLa cells (human cervical cancer cells) was evaluated by colony formation assays, and cell apoptosis was evaluated by Flow Cytometry. A polyethylene protection device as the neutron moderator was designed and connected to the neutron tube to shield normal tissue and organs of the test animals from scatter radiation. Hematology and blood biochemistry were investigated to evaluate the protective effect of polyethylene. U14 (mice cervical cancer cell) tumor-bearing mice were further investigated to determine the tumor suppression effect of neutron irradiation. We found that cells showed a dose-dependent relationship after fast neutrons irradiation at different dose (1.11 Gy, 2.23 Gy, 3.34 Gy and 4.45Gy). Furthermore, in vivo experiments showed that the anti-tumor effect on U14 tumor-bearing mice greatly depended on the neutron irradiation dose. A high dose of fast neutron irradiation (26.73 Gy) could have tumor growth rate only 12.31% compared to 56.07% with control group. All the blood cell counts and blood biochemistry parameters were in the standard value ranges. Immunohistochemistry examinations clearly indicated the apoptosis cells in tumor tissues by the TUNEL assay. This work provides useful evidences on cancer irradiation therapy using fast neutron in pre-clinical study. And the neutron therapy system device has great potential to be a more convenient tool in clinical application with significantly lower power consumption, irradiation toxicity and cost.

Dosimetric characteristics of the University of Washington Clinical Neutron Therapy System

The University of Washington (UW) Clinical Neutron Therapy System (CNTS), which generates high linear energy transfer fast neutrons through interactions of 50.5 MeV protons incident on a Be target, has depth-dose characteristics similar to 6 MV x-rays. In contrast to the fixed beam angles and primitive blocking used in early clinical trials of neutron therapy, the CNTS has a gantry with a full 360° of rotation, internal wedges, and a multi-leaf collimator (MLC). Since October of 1984, over 3178 patients have received conformal neutron therapy treatments using the UW CNTS. In this work, the physical and dosimetric characteristics of the CNTS are documented through comparisons of measurements and Monte Carlo simulations. A high resolution computed tomography scan of the model 17 ionization chamber (IC-17) has also been used to improve the accuracy of simulations of the absolute calibration geometry. The response of the IC-17 approximates well the kinetic energy released per unit mass (KERMA) in water for neutrons and photons for energies from a few tens of keV up to about 20 MeV. Above 20 MeV, the simulated model 17 ion chamber response is 20%-30% higher than the neutron KERMA in water. For CNTS neutrons, simulated on- and off-axis output factors in water match measured values within ~2%  ±  2% for rectangular and irregularly shaped field with equivalent square areas ranging in a side dimension from 2.8 cm to 30.7 cm. Wedge factors vary by less than 1.9% of the measured dose in water for clinically relevant field sizes. Simulated tissue maximum ratios in water match measured values within 3.3% at depths up to 20 cm. Although the absorbed dose for water and adipose tissue are within 2% at a depth of 1.7 cm, the absorbed dose in muscle and bone can be as much as 12 to 40% lower than the absorbed dose in water. The reported studies are significant from a historical perspective and as additional validation of a new tool for patient quality assurance and as an aid in ongoing efforts to clinically implement advanced treatment techniques, such as intensity modulated neutron therapy, at the UW.

Neutron radiotherapy for adenoid cystic carcinoma of the lacrimal gland

PURPOSE

Lacrimal gland adenoid cystic carcinomas are rare, aggressive orbital tumors that share histopathologic similarities with salivary gland malignancies. Neutron radiotherapy may be useful for treatment due to its high biological effectiveness for salivary malignancies.

METHODS

The authors retrospectively reviewed the outcomes for 11 lacrimal gland adenoid cystic carcinoma patients treated with neutrons from 1988 to 2011. Most had undergone surgery prior to radiation therapy. However, gross residual disease was present in 8 patients. The most common American Joint Committee on Cancer stage was T4cN0M0. Four patients with skull base involvement received a radiosurgery boost and 1 received a proton therapy boost.

RESULTS

Median follow up was 6.2 years. Median overall survival was 11.1 years and median disease-free survival was 6.3 years. Five-year local control was estimated by the Kaplan-Meier method as 80%. Three patients had a local recurrence; 4 developed distant metastases. Six patients died. Seven patients had intact vision in the affected eye before neutron radiation. Two required enucleation for a painful dry eye. Of the 5 who avoided an enucleation, 3 had either severe visual impairment (20/400) or only light perception and 2 were without known vision compromise or complications at the time of their death. One patient developed asymptomatic frontal lobe radionecrosis after 2 courses of radiation therapy.

CONCLUSIONS

Neutron radiation therapy achieved excellent 5-year local control in this series of high-risk patients, with most cases having gross residual disease. Late recurrences and distant metastases remain a challenge. Meaningful ipsilateral vision preservation was not possible in most cases in the long term, although only 2 patients required an enucleation for treatment effects.

Biodistribution of GB-10 (Na(2)(10)B10H10 compound for boron neutron capture therapy (BNCT) in an experimental model of oral cancer in the hamster cheek pouch

OBJECTIVE

We previously proposed the hamster cheek pouch model of oral cancer for BNCT studies. We herein present the biodistribution of a non-toxic boron compound, GB-10 (Na(2)(10)B10H10), in this model to assess its potential for BNCT or BNCT enhanced Fast Neutron Therapy.

MATERIALS AND METHODS

We evaluated the uptake and retention of GB-10 in tumour and precancerous tissue and in potentially dose-limiting, clinically relevant normal tissues.

RESULTS

Mean tumour boron concentration delivered by GB-10 (50mgB/kg) peaked to 77.7+/-28.0 ppm at 20min post-administration and remained at therapeutically useful values of 31.9+/-21.4 ppm at 3h. The clearance rate for normal tissues was faster than for tumour tissue. The consistently low brain and spinal cord values would preclude normal tissue toxicity. The uptake of GB-10 by precancerous tissue may be of potential use in the treatment of field cancerized areas. GB-10 was deposited homogeneously in different tumour areas, an asset when treating heterogenous tumours. The data suggests that the joint administration of BPA and GB-10 may improve the therapeutic efficacy of BNCT.

CONCLUSIONS

GB-10 is a potential boron carrier for BNCT of head and neck tumours and for BNCT-FNT.

Design considerations for a computer controlled multileaf collimator for the Harper Hospital fast neutron therapy facility

The d(48.5) + Be neutron beam from the Harper Hospital superconducting cyclotron is collimated using a unique multirod collimator (MRC). A computer controlled multileaf collimator (MLC) is being designed to improve efficiency and allow for the future development of intensity modulated radiation therapy with neutrons. For the current study the use of focused or unfocused collimator leaves has been studied. Since the engineering effort associated with the leaf design and materials choice impacts significantly on cost, it was desirable to determine the clinical impact of using unfocused leaves in the MLC design. The MRC is a useful tool for studying the effects of using focused versus unfocused beams on beam penumbra. The effects of the penumbra for the different leaf designs on tumor and normal tissue DVHs in two selected sites (prostate and head and neck) was investigated. The increase in the penumbra resulting from using unfocused beams was small (approximately 1.5 mm for a 5 x 5 cm2 field and approximately 7.6 mm for a 25 x 25 cm2 field at 10 cm depth) compared to the contribution of phantom scatter to the penumbra width (5.4 and 20 mm for the small and large fields at 10 cm depth, respectively). Comparison of DVHs for tumor and critical normal tissue in a prostate and head and neck case showed that the dosimetric disadvantages of using an unfocused rather than focused beam were minimal and only significant at shallow depths. For the rare cases, where optimum penumbra conditions are required, a MLC incorporating tapered leaves and, thus, providing focused collimation in one plane is necessary.

New horizons for therapy based on the boron neutron capture reaction

Boron neutron capture therapy (BNCT) is currently undergoing clinical trials in the USA, Japan and The Netherlands with patients afflicted with deadly brain cancer (glioblastoma multiforme) or melanoma. This therapy relies on a binary process in which the capture of a slow neutron by a 10B nucleus leads to an energetic nuclear fission reaction, with the formation of 7Li3+ and 4He2+ and accompanied by about 2.4 MeV of energy. The fleeting 7Li3+ and 4He2+ travel a distance of only about the diameter of one cell, and they are deadly to any cell in which they have been produced. Research in progress is concerned with the development of advanced boron agents and neutron sources, other than nuclear reactors, for the treatment of a variety of cancer types using novel 10B delivery methods. Non-malignant diseases such as rheumatoid arthritis offer additional opportunities for BNCT. The entire BNCT area awaits commercialization.