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PubMed2004

Evaluation of 4-borono-2-18F-fluoro-L-phenylalanine-fructose as a probe for boron neutron capture therapy in a glioma-bearing rat model.

UNLABELLED: L-p-Boronophenylalanine (BPA) has been applied as a potential boron carrier for the treatment of malignant glioma in clinical boron neutron capture therapy (BNCT) since 1994. To provide the pharmacokinetics of BPA for clinical use of BNCT in Taiwan, 4-borono-2-(18)F-fluoro-L-phenylalanine-fructose ((18)F-FBPA-Fr) was synthesized and the biologic characteristics of this radiotracer in glioma-bearing rats were investigated. METHODS: Radiolabeled (18)F-F(2) was produced via the (20)Ne(d,alpha)(18)F reaction, and (18)F-acetyl hypofluorite ((18)F-AcOF) was generated by passing (18)F-F(2) through a column filled with tightly packed KOAc/HOAc powder. The effluent containing (18)F-AcOF was bubbled into BPA in trifluoroacetic acid, then purified by high-performance liquid chromatography, and further composited with fructose to afford (18)F-FBPA-Fr. Male Fischer 344 rats bearing F98 glioma in the left brain were used for biologic studies. The biodistribution of BPA-Fr and (18)F-FBPA-Fr was determined, and the microautoradiography and PET imaging of (18)F-FBPA-Fr were performed, on the 13th day after tumor inoculation. RESULTS: The radiochemical purity of (18)F-FBPA-Fr was >97% and the radiochemical yield of (18)F-FBPA-Fr was 20%-25%. In glioma-bearing rats, the accumulation ratios of B-10 for glioma-to-normal brain were 2.05, 1.86, 1.24, and 1.10 at 0.5, 1, 2, and 4 h, respectively, after administration of 43 mg BPA-Fr via the tail vein. The accumulation ratios of (18)F-FBPA-Fr for glioma-to-normal brain were 3.45, 3.13, 2.61, and 2.02, whereas the tumor-to-heart blood ratios were 1.72, 2.61, 2.00, and 1.93, respectively, for the same time points. The uptake characteristics of BPA-Fr and (18)F-FBPA-Fr in F98 glioma were similar with a maximum at 1 h after the drugs' administration. The results obtained from the biodistribution studies indicated that 0.5-1 h after BPA-Fr injection would be the optimal time for BNCT. Biodistribution, PET images, and brain microautoradiography of (18)F-FBPA-Fr all confirmed this finding. CONCLUSION: (18)F-FBPA-Fr showed specific tumor uptake in F98 glioma-bearing rats and could be used as a probe for BPA-Fr in BNCT. This study provides useful information for the future clinical application of BNCT in brain tumor therapy.

Animals↗
PubMed1996

Ion microscopy imaging of 10B from p-boronophenylalanine in a brain tumor model for boron neutron capture therapy.

Boron neutron capture therapy (BNCT), a binary treatment modality that can potentially irradiate tumor tissue within cellular dimensions, is critically dependent on the preferential delivery of 10B to individual neoplastic cells. In this study, ion microscopy was used to quantitatively evaluate the selectivity of p-boronophenylalanine-fructose (BPA-F) in the rat 9L gliosarcoma brain tumor model. With a spatial resolution of approximately 0.5 microm, ion microscopy images show that BPA-F delivers 3.5 times more boron to the main tumor mass [99 +/- 36 microg/g tissue (mean +/- SD)] than to the contiguous normal brain (27 +/- 12 microg/g tissue). A similar, but lower, accumulation was observed away from the main tumor mass in small clusters of neoplastic cells (47 +/- 15 microg/g tissue) invading the surrounding brain (16 +/- 8 microg/g tissue). These findings establish for the first time the selectivity of BPA-F to the neoplastic cells invading the normal brain and provide a much-needed baseline measurement of the distribution of a clinically approved BNCT drug. Given the propensity for malignant brain tumors to infiltrate the surrounding normal brain, these observations have particular significance for clinical trials of BNCT for human glioblastoma multiforme using the drug BPA-F.

Animals↗
PubMed1998

Uptake of a boronated epidermal growth factor-dextran conjugate in CHO xenografts with and without human EGF-receptor expression.

An epidermal growth factor (EGF)-dextran-boron conjugate for targeting against EGF receptor-rich tumours was investigated regarding uptake and distribution in vivo. EGF served as the tumour-seeking part and dextran was the carrier for the potentially toxic boron. Nude mice carrying subcutaneous tumours on the flanks were injected with conjugate either i.v. or intratumorally. The xenografts were from Chinese hamster ovary cells transfected with the gene for the human EGF-receptor (CHO-EGFR), and these cells expressed the EGFR. Non-transfected cells without EGF-receptors (CHO) were used as controls. No accumulations in tumours could be observed following the i.v. injections but there were, in both tumour types, high accumulations in the liver. Following intratumoral injections the accumulations were higher in the CHO-EGFR tumours than in the CHO tumours. The tumour over blood and liver ratios were also higher for the CHO-EGFR tumours than for the CHO tumours. Thyroid accumulations after the intratumoral injections indicate different degradation patterns of the conjugate in CHO-EGFR animals than in CHO animals. In conclusion, after intratumoral injections the conjugate showed receptor-dependent binding to EGFR-rich tumours, and the tumour-to-blood and tumour-to-liver ratios were promising.

Animals↗
PubMed2000

Degradation pathways of a peptide boronic acid derivative, 2-Pyz-(CO)-Phe-Leu-B(OH)(2).

The peptide boronic acid derivative 2-Pyz-(CO)-Phe-Leu-B(OH)(2) is a potent inhibitor of 20S proteasome and a proposed anticancer agent. During preformulation studies, the compound presented erratic stability behavior. Efforts were made to isolate and identify the degradation products, thereby helping to identify possible mechanisms for the degradation. The reaction of 2-Pyz-(CO)-Phe-Leu-B(OH)(2) with hydrogen peroxide not only provided a convenient way to isolate the initial degradation products seen from hydrolysis in aqueous buffers but also showed that the major, initial degradation pathway was probably oxidative in nature. The isolated degradation products were characterized by nuclear magnetic resonance spectroscopy, mass spectrometry, and optical rotation dispersion. In the presence of hydrogen peroxide, the boronic acid group was cleaved from 2-Pyz-(CO)-Phe-Leu-B(OH)(2) to give an alcohol with an apparent retention of the original stereochemistry. Subsequent isomerization and further hydrolysis were then seen. Surprisingly, added ascorbate and EDTA accelerated rather than inhibited degradation. Degradation of 2-Pyz-(CO)-Phe-Leu-B(OH)(2) under acidic and basic conditions seemed to be mediated by an initial oxidative degradation pathway similar to that seen with the peroxide.

Ascorbic Acid↗
PubMed2000

Analysis of N-acetylated hexosamine monosaccharides by ferrocenyl boronation and tandem electrospray ionization mass spectrometry.

A tandem electrospray mass spectrometric (MS(n)) technique for the analysis of N-acetylated hexose carbohydrates using ferrocene boronate (F(c)Bor) derivatization was developed. The biologically important N-acetyl hexosamines can be readily distinguished utilizing this technique. The analysis is made possible by utilizing the inherent electrochemical properties of the electrospray device to produce oxidized, pre-formed single-electron ferrocenyl ions in a non-aqueous solvent system. The electrospray device was modified using a custom built cell consisting of concentric stainless steel tubes, which produced an enhanced signal for the molecular ion of each analyte species. The MS(2) spectra derived from isomeric populations of ferrocenyl boronic esters of these carbohydrates when generated under the same conditions possessed features unique to each sugar allowing easy differentiation between a number of N-acetyl hexosamine isomers.

Acetylation↗
PubMed2002

Novel carboranes with a DNA binding unit for the treatment of cancer by boron neutron capture therapy.

The synthesis and biological evaluation of two ortho-carborane derivatives which contain a 5,6,7-trimethoxyindole (TMI) unit for use in boron neutron capture therapy is described. The TMI moiety is known to be the DNA-binding part of the highly potent anticancer agent duocarmycin A. The ortho-carborane derivatives were prepared from amino alkynes which were bound to a protected TMI carboxylic acid. Addition of decaborane(14) to the alkyne triple bond with subsequent removal of the tert-butoxycarbonyl (Boc) and benzyl protecting groups gave the desired product. Boron uptake from the ortho-carborane derivatives into B-16 melanoma cells was higher and faster than that observed with L-p-boronophenylalanine (BPA), which is in use in the clinic.

Animals↗
PubMed1977

Gas chromatography chemical ionization mass spectrometry of prostaglandin Falpha cyclic boronate derivatives.

The electron impact mass spectra of prostaglandins F 1alpha, F 2alpha and F 3alpha methyl ester cyclic 9,11-methane-, n-butane-, cyclohexane- and benzeneboronate 15-trimethylsilyl ethers show base peaks corresponding to [M-(C-16-C-20)]+, i.e. [M-71]+ for prostaglandins F 1alpha and F 2alpha but [M-69]+ for prostaglandin F 3alpha yielding identical ions in the latter two cases. Derivatives of prostaglandin F 2alpha and F 3alpha are difficult to separate by gas chromatography, so that the use of this ion type for single ion monitoring of either prostaglandin (as has been reported) is ambiguous. The chemical ionization mass spectra of these cyclic boronates, however, show distinctive base peaks for prostaglandins F 1alpha, F 2alpha and F 3alpha at m/e 317,315 and 313 respectively, corresponding to [M-RBO2H2-TMSO]+. Fragmentation patterns have been investigated by the use of [3,3,4,4-2H4]prostaglandin F 2alpha and by the formation of [2H9]trimethylsilyl ethers and a [2H3]methyl ester. Cleavage of the C-15-C-16 bond is of minor importance under chemical ionization conditions. The possible value of the [M-RBO2H2-TMSO]+ ions for single ion monitoring is explored: specificity is aided by the formation of the same ions from a series of boronates of characteristic retention indices.

Boron Compounds↗
PubMed2004

Boron-diindomethene (BDI) dyes and their tetrahydrobicyclo precursors--en route to a new class of highly emissive fluorophores for the red spectral range.

The X-ray crystallographic, optical spectroscopic, and electrochemical properties of a newly synthesized class of boron-diindomethene (BDI) dyes and their tetrahydrobicyclo precursors (bc-BDP) are presented. The BDI chromophore was designed to show intensive absorption and strong fluorescence in an applicationary advantageous spectral range. Its modular architecture permits fusion of a second subunit, for example, a receptor moiety to the dye's core to yield directly linked yet perpendicularly prearranged composite systems. The synthesis was developed to allow facile tuning of the chromophore platform and to thus adjust its redox properties. X-ray analysis revealed a pronounced planarity of the chromophore in the case of the BDIs, which led to a remarkable close packing in the crystal of the simplest derivative. On the other hand, deviation from planarity was found for the diester-substituted bc-BDP benzocrown that exhibits a "butterfly"-like conformation in the crystal. Both families of dyes show charge- or electron-transfer-type fluorescence-quenching characteristics in polar solvents when equipped with a strong donor in the meso-position of the core. These processes can be utilized for signaling purposes if an appropriate receptor is introduced. Further modification of the chromophore can invoke such a guest-responsive intramolecular quenching process, also for receptor groups of low electron density, for example, benzocrowns. In addition to the design of various prototype molecules, a promising fluoroionophore for Na+ was obtained that absorbs and emits in the 650 nm region and shows a strong fluorescence enhancement upon analyte binding. Furthermore, investigation of the remarkable solvatokinetic fluorescence properties of the "butterfly"-like bc-BDP derivatives suggested that a second intrinsic nonradiative deactivation channel can play a role in the photophysics of boron-dipyrromethene dyes.

Acetonitriles↗
PubMed1995

In vitro cytotoxicity testing of neodymium-iron-boron magnets.

Neodymium-iron-boron magnets are being increasingly used in orthodontic and orthopedic appliances. The purpose of this study was to investigate the in vitro cytotoxicity of these new "super" magnets. A modified agar overlay technique was performed using both L929 mouse fibroblasts and adult human oral mucosal fibroblasts. The neodyium-iron-boron magnets were tested in the following forms: uncoated magnetized, uncoated demagnetized, parylene coated demagnetized, and parylene coated magnetized. Results revealed that uncoated magnetized, uncoated demagnetized, and parylene coated magnetized were cytotoxic to both L929 mouse fibroblasts and human oral mucosal fibroblasts. However the parylene coated demagnetized neodymium magnets were only cytotoxic to the human mucosal fibroblasts. This study supports the hypothesis that these are cytotoxic effects of possibly corrosion products and of magnetism. The specific toxic effects of parylene were not examined in this present study. Statistical analysis (Mann-Whitney U-test, p = 0.014) suggested that, in this experiment, the human oral mucosal fibroblasts were more sensitive to the effects of these rare earth magnets. With the evidence of a biological effect, the use of implanted magnets must at present be limited until the safety can be assured.

Animals↗
PubMed1979

Boron betaine analogs: antitumor activity and effects on Ehrlich ascites tumor cell metabolism.

Several newly synthesized boron betaine analogs had antitumor activity in Ehrlich ascites, Walker 256 ascites carcinosarcoma, and Lewis lung screens and marginal activity in the B-16 melanotic melanoma screen. In vivo testing demonstrated that trimethylamine-cyanoborane inhibied Ehrlich ascites cell DNA and protein syntheses as well as gene modulation by chromatin protein phosphorylation and methylation. Trimethylamine-cyanoborane increased cyclic-AMP levels. In vitro testing showed that nuclear DNA polymerase, thymidylate synthetase, S-adenosylmethyltransferase, nonhistone chromatin methylation, deoxyribonuclease, ribonuclease, and cathepsin were inhibited by the boron analogs. These compounds did not demonstrate high antitumor activity at the doses employed, but blockage of methyl transfer from S-adenosylmethionine was established as a feasible method for controlling cell proliferation.

Animals↗
PubMed2006

Boronate-containing copolymers: polyelectrolyte properties and sugar-specific interaction with agarose gel.

Copolymers of N-acryloyl-m-aminophenylboronic acid (NAAPBA) with acryamide (AA), N,N-dimethylacrylamide (DMAA), and N-isopropylacrylamide (NIPAM) were found to adsorb on cross-linked agarose gel (Sepharose CL-6B) in the pH range from 7.5-9.2, due to specific boronate-sugar interactions. The molar percentages of phenylboronic acid (PBA) groups in the boronate-containing copolymers (BCCs), as estimated by 1H NMR spectroscopy, were 13, 10, and 16%, respectively, whereas the apparent ionization constants, the pKa values, of the copolymers were similar and equal to 9.0 +/- 0.2 at 20 degrees C. The copolymers adsorption capacities were in the range of 15-30 mg x ml(-1) gel (14-36 micromol pendant PBA ml(-1) gel) at pH 9.2 and decreased with decreasing pH value. The interaction of monomeric NAAPBA with Sepharose CL-6B was characterized by an equilibrium association constant of 53 +/- 17 M(-1), the chromatographic capacity factor k' = 1.8, and a total content of binding sites of 27 +/- 10 micromol x ml(-1) gel at pH 9.2. The weak reversible binding of monomeric NAAPBA and almost irreversible binding of NAAPBA copolymers to the gel at pH 9.2 suggested a multivalent character of the copolymer adsorption. At pH 7.5, the maximal adsorption capacity was displayed by the AA-NAAPBA copolymer (15 mg x ml(-1) gel). All the BCCs could be completely desorbed from the gel by 0.1 M fructose in aqueous buffered media with pH values from 7.5-9.2. The strong adsorption of AA-NAAPBA on agarose gel probably relates to the conformation of the copolymer in aqueous solution and provides opportunities for biomedical applications of the copolymer under physiological conditions. Multivalent, weak-affinity adsorption of BCCs to the agarose gel seems to be a tentative model for the copolymers' binding to oligo- and polysaccharides of cell membranes and mucosal surfaces.

Adsorption↗
PubMed2003

Inhibition of the enzymatic activity of prostate-specific antigen by boric acid and 3-nitrophenyl boronic acid.

BACKGROUND: Prostate specific antigen (PSA) is a well-established marker of prostate cancer, but it can also degrade extracellular matrix proteins such as fibronectin and could be involved in tumor progression and metastasis. In this study, we have addressed the use of boric acid and 3-nitrophenyl boronic acid (NPBA) as PSA inhibitors in vitro. METHODS: The inhibition of PSA by boric acid was studied by using specific fluorogenic substrates. Fibronectin, a biologically relevant substrate for PSA, was used as a substrate in a zymographic assay, and the degradation of fibronectin by PSA in the presence of boric acid and NPBA was followed by Western Blot. RESULTS: Low concentrations of boric acid partially inhibited the proteolytic activity of PSA toward a synthetic fluorogenic substrate. Also, by Western blot, we have found significant inhibition in the proteolysis of fibronectin by PSA in the presence of boric acid as well as NPBA. Results indicate that the boronated compounds used in this study can be used for the modulation of PSA activity. CONCLUSION: PSA activity is inhibited in vitro by boric acid and NPBA. If degradation of fibronectin by PSA were, in fact, an important step in the progression of prostate cancer, then borate-induced inhibition of PSA activity should help reduce the development and proliferation of prostate carcinomas.

Blotting, Western↗
PubMed1988

Interaction of peptide boronic acids with elastase: circular dichroism studies.

Boronic acid derivatives of good peptide substrates of the serine proteases cause slow-binding inhibition, manifested as biphasic binding (Kettner and Shenvi: J. Biol Chem. 259:15106-15114, 1984). These inhibitors are thought to act as reaction-intermediate analogs. Three peptide boronic acids--Ac-Pro-boro-Val-OH, DNS-Ala-Pro-boro-Val-OH, and Ac-Ala-Ala-Pro-boro-Val-OH--were chosen for far-ultraviolet circular dichroism (CD) studies in order to determine whether the second phase involves a conformational change of pancreatic elastase. The dipeptide is a simple competitive inhibitor (Ki = 0.27 microM) and the latter are slow-binding inhibitors (Ki = 16.4 and 0.25 nM, respectively). Spectral deconvolution and correction for the formation of antiparallel beta-sheet by the peptide inhibitor itself indicate that there is no significant change in the secondary structure of the enzyme in either the initial or final inhibitor complex. A kinetic experiment confirmed that the slow-binding step was not associated with a CD spectral change, and that therefore a protein conformational change was not responsible for the slow binding.

Animals↗
PubMed1989

Pre-clinical studies on boron neutron capture therapy.

The present report provides an overview of the multidisciplinary research effort on BNCT that currently is in progress at The Ohio State University. Areas under investigation include the preparation of boron containing monoclonal antibodies, the synthesis of boron containing derivatives of promazines and phathalocyanines, the development of a rat model for the treatment of glioblastoma by means of BNCT, the design of an accelerator-based neutron irradiation facility, and 10B concentration measurements using alpha track autoradiographic methods. Progress in each of these areas is described and the direction of future research is indicated.

Animals↗
PubMed1991

Interactive effects of boron, selenium, and dietary protein on survival, growth, and physiology in mallard ducklings.

High concentrations of boron (B) and selenium (Se) have been found in aquatic food chains associated with irrigation drainwater. Total biomass of invertebrates, a major source of protein for wild ducklings, is sometimes diminished in agricultural drainwater ponds contaminated with Se and B. Day-old mallard (Anas platyrhynchos) ducklings received an untreated diet (controls) containing 22% protein or diets containing 15 ppm (microgram/g) Se (as selenomethionine), 60 ppm Se, 1,000 ppm B (as boric acid), 15 ppm Se with 1,000 ppm B, or 60 ppm Se with 1,000 ppm B. In a concurrent experiment, the above sequence was repeated with a protein-restricted (7%) but isocaloric diet. After four weeks, blood and tissue samples were collected for biochemical and histological examination. With 22% protein and 60 ppm Se in the diet, duckling survival and growth was reduced and histopathological lesions of the liver occurred. Boron alone caused some reduction in growth. Several interactive effects occurred between B and Se, including further reduction in growth, and increases in plasma glutathione reductase activity, hematocrit, hemoglobin and plasma protein concentrations. With 7% protein, the growth of controls was less than that with 22% protein, 60 ppm Se caused 100% mortality, and growth effects of 15 ppm Se and 1,000 ppm B alone were more pronounced than with 22% protein. Selenium accumulation increased in the liver with 7% protein. Interactive effects were greater for Se and B with 7% protein than with 22% protein and included significant mortality and enhanced accumulation of Se in the liver. These findings suggest the potential for more severe toxicological effects of Se and B independently and interactively on duckling survival and development when dietary protein is diminished.

Animals↗
PubMed1993

Boron, molybdenum, and selenium in aquatic food chains from the lower San Joaquin River and its tributaries, California.

Boron (B), molybdenum (Mo), and selenium (Se) were measured in water, sediment, particulate organic detritus, and in various biota--filamentous algae, net plankton, macro-invertebrates, and fishes--to determine if concentrations were elevated from exposure to agricultural subsurface (tile) drainage during the spring and fall 1987, in the San Joaquin River, California. Concentrations of B and Se, but not Mo, were higher in most samples from reaches receiving tile drainage than in samples from reaches receiving no tile drainage. Maximum concentrations of Se in water (0.025 microgram/mL), sediment (3.0 micrograms/g), invertebrates (14 micrograms/g), and fishes (17 micrograms/g) measured during this study exceeded concentrations that are detrimental to sensitive warmwater fishes. Toxic threshold concentrations of B and Mo in fishes and their foods have not been identified. Boron and Mo were not biomagnified in the aquatic food chain, because concentrations of these two elements were usually higher in filamentous algae and detritus than in invertebrates and fishes. Concentrations of Se were lower in filamentous algae than in invertebrates and fishes; however, concentrations of Se in or on detritus were similar to or higher than in invertebrates and fishes. These observations suggest that high concentrations of Se accumulated in invertebrates and fishes through food-chain transfer from Se-enriched detritus rather than from filamentous algae.

Animals↗
PubMed1978

Boron-neutron capture therapy in relation to immunotherapy.

The essential feature of tumour therapy rests upon host-tumour interaction. To achieve therapeutic effects, a prerequisite to immunotherapy is the reduction of tumour cells in the host's body. Such measures should not be immunosuppressive. Cytotoxic chemotherapy is not appropriate in this regard. Supraradical surgery and non-specific radiotherapy are not desirable for preservation of nervous function, if their immunosuppression is not as severe as cytotoxic substances. Boron-neutron capture therapy is a highly specific and least immunosuppressive means of reducing tumour cells of the central nervous system. A brief introductory review of basic research is presented. The interim clinical results are: (i) Treatment of recurrent glioblastoma: Survival extension obtained by neutron capture therapy is 21.9 +/- 7.2 mos in contrast to that obtained by conventional treatments of 6.7 +/- 0.6 mos (p less than 0.001), (Total survival 26.3 +/- 6.7 mos); and (ii) only three patients including two glioblastoma cases were treated with neutron by the same surgeon who, by performing the first tumour operation, had the advantage in topographic knowledge for determining the radiation field. They survived 4, 5, and 6 years in almost fully active conditions. The new Musashi Institute of Technology Reactor Thermal Neutron Therapy Facility and the increased domestic production of boron-10 isotope have enlarged the therapeutic capacity to two dozen patients a year.

Adolescent↗
PubMedDate not supplied

Accelerator-based epithermal neutron sources for boron neutron capture therapy of brain tumors.

This paper reviews the development of low-energy light ion accelerator-based neutron sources (ABNSs) for the treatment of brain tumors through an intact scalp and skull using boron neutron capture therapy (BNCT). A major advantage of an ABNS for BNCT over reactor-based neutron sources is the potential for siting within a hospital. Consequently, light-ion accelerators that are injectors to larger machines in high-energy physics facilities are not considered. An ABNS for BNCT is composed of: (1) the accelerator hardware for producing a high current charged particle beam, (2) an appropriate neutron-producing target and target heat removal system (HRS), and (3) a moderator/reflector assembly to render the flux energy spectrum of neutrons produced in the target suitable for patient irradiation. As a consequence of the efforts of researchers throughout the world, progress has been made on the design, manufacture, and testing of these three major components. Although an ABNS facility has not yet been built that has optimally assembled these three components, the feasibility of clinically useful ABNSs has been clearly established. Both electrostatic and radio frequency linear accelerators of reasonable cost (approximately 1.5 M dollars) appear to be capable of producing charged particle beams, with combinations of accelerated particle energy (a few MeV) and beam currents (approximately 10 mA) that are suitable for a hospital-based ABNS for BNCT. The specific accelerator performance requirements depend upon the charged particle reaction by which neutrons are produced in the target and the clinical requirements for neutron field quality and intensity. The accelerator performance requirements are more demanding for beryllium than for lithium as a target. However, beryllium targets are more easily cooled. The accelerator performance requirements are also more demanding for greater neutron field quality and intensity. Target HRSs that are based on submerged-jet impingement and the use of microchannels have emerged as viable target cooling options. Neutron fields for reactor-based neutron sources provide an obvious basis of comparison for ABNS field quality. This paper compares Monte Carlo calculations of neutron field quality for an ABNS and an idealized standard reactor neutron field (ISRNF). The comparison shows that with lithium as a target, an ABNS can create a neutron field with a field quality that is significantly better (by a factor of approximately 1.2, as judged by the relative biological effectiveness (RBE)-dose that can be delivered to a tumor at a depth of 6cm) than that for the ISRNF. Also, for a beam current of 10 mA, the treatment time is calculated to be reasonable (approximately 30 min) for the boron concentrations that have been assumed.

Beryllium↗