Boron Neutron Capture Therapy Research Research Articles

Retrospective analysis of treatment-positioning accuracy and dose error in boron neutron capture therapy using a sitting-position treatment system for head and neck cancer

The neutron beam in boron neutron capture therapy (BNCT) exhibits poor directionality and significantly decreasing neutron flux with increasing distance. Therefore, the treatment site must be close to the irradiation aperture. Some patients with head and neck cancer may benefit from a sitting-position setup. The study aim was to evaluate the treatment-positioning accuracy and dose error in sitting patients receiving BNCT. Thirty-two patients with head and neck cancer who underwent sitting-position BNCT at Southern Tohoku BNCT Research Center were included in the study. Horizontal (ΔX) and vertical (ΔY) errors were defined as the displacement between the treatment planning system (TPS) digital reconstructed radiograph and the pre-treatment X-ray image. Using in-house software, image matching was performed. The beam-axial directional (ΔZ) error was compared with the parameters entered into the TPS and the actual pre-treatment measured values. The translational-position error was reflected in the TPS’s patient coordinate system with respect to the reference plan. Re-dose calculations were performed to evaluate the effect of positional error on tumor and normal-tissue doses. The [ΔX, ΔY, ΔZ] DRR-CR mean ± 1SD were − 0.40 ± 2.0, 0.30 ± 2.3, and − 1.4 ± 1.5 mm, respectively. The Dmean and D98% tumor-dose errors were 1.22 % ± 1.44 % and 0.99 % ± 1.63 %, respectively. The D2% pharyngeal and oral mucosal-dose errors were 0.98 % ± 1.91 % and 1.21 % ± 1.78 %, respectively. The tumor- and normal-tissue dose errors were typically < 5 %. High-precision treatment was feasible in sitting-positioned BNCT.

Perceptions of Canadian Radiation Oncologists, Medical Physicists, and Radiation Trainees about the Feasibility and Need of Boron Neutron Capture Therapy (BNCT) in Canada: A National Survey.

Boron Neutron Capture Therapy (BNCT) is an emerging radiotherapy. There are ongoing efforts to develop a Canadian accelerator-based BNCT center. However, it remains unclear how Canadian radiation oncologists (RO), medical physicists (MP), and their trainees perceive BNCT and its impact on radiation oncology as a discipline. A survey was created to explore the knowledge of BNCT, its clinical role, and the support for Canadian research. It was distributed through the Canadian Association of Radiation Oncology (CARO) and the Canadian Organization of Medical Physicists (COMP). We received 118 valid responses from all 10 provinces, from 70 RO (59.3%) and 48 MP (40.7%), including 9 residents. Most knew of BNCT and its indications (60.2%). Although many were unaware of the reasons behind early failures (44.1%), common reasons were a lack of clinical trials and an inaccessibility of neutron sources (42.4%) as well as reactor unsuitability (34.7%). Additionally, 90.6% showed definite (66.9%) or possible (23.7%) support for Canadian BNCT research, while 89% indicated a definite (56.8%) or possible (32.2%) willingness for BNCT referrals. Most ROs and MPs supported Canadian BNCT research and would refer patients. However, limited awareness and a lack of experiences remain a challenge. Educational sessions are needed to realize this innovative cancer treatment in Canada.

Conceptual design of a target station using a 30-MeV cyclotron accelerator for the basic study of boron neutron capture therapy at KURNS

A new target station that generates a thermal neutron field based on a 30-MeV proton accelerator was designed for the basic study of boron neutron capture therapy (BNCT). The calculated thermal neutron fluxes at the sample regions under free air conditions reached 2.84 × 109 [n/cm2/s]. The fast neutron and gamma ray dose rates per thermal neutron flux in several regions were on the order of 10−13 [Gy⋅cm2]. The beam characteristics were found to be closer to those of the heavy-water neutron irradiation facility of Kyoto University Research Reactor, which is an established facility in BNCT research. In addition, the shielding size for the new target station was realistically estimated for long-term beam operation.

Determination of Neutron Flux in Brain Cancer Boron Neutron Capture Therapy Using Monte Carlo Simulation

Boron Neutron Capture Therapy (BNCT) is a relatively safer technology for killing cancer cells, one of which is the Glioblastoma multiforme. One of the main components of the BNCT equipment is the collimator which functions as an exit point for epithermal neutron particles that hit cancer cells. In addition to the experimental method, BNCT research can be carried out by modeling, including using the MCNPX software based on the Monte Carlo Method. This research aimed to determine the flux distribution of fast and epithermal neutrons and the dose rate of fast neutrons and gamma that hit the target cancer cells in the phantom head of ORNL MIRD. Modeling using the MCNPX software has three main parts: cell cards, surface cards, and data cards. A tally is used on the data card to calculate the neutron flux. Based on the calculation of the modeling results, the flux of epithermal neutron is 2.87 x 109 n/cm2.s. The dose ratio of the epithermal to the fast neutron flux is 2.29 x 10-14 Gy.cm2/n. Then, the balance of the dose rate of the epithermal to the gamma is 1.64 x 10-14 Gy.cm2/n, and the ratio of epithermal to thermal neutron flux is 0.004. In this study, the epithermal neutron flux hitting the target cancer cells in cell target was moderated at 4 cm so that at a depth of 8 cm, the energy was converted into thermal neutrons. Based on the analysis of the results, it can be concluded that the neutron flux that will interact with cancer tissue is thermal neutrons, not epithermal neutron flux.

Status and outlook: Research and development on the neutron source for BNCT

<p indent=0mm>Boron neutron capture therapy (BNCT) is regarded as a revolutionary means for high-accuracy cancer therapy with cell level selectivity. It has unique therapeutic effects for some malignance, such as glioblastoma multiforme, melanoma, recurrent head and neck malignance. It can also be used for cancer treatment of deep organ, such as liver and lung. Even though its principle was proposed about <sc>80 years</sc> ago, it has never been utilized in routine clinic therapy in hospital until 2020. BNCT, as a binary therapeutic method, greatly depends on both high-quality neutron beam and highly target-selective boron drug. Tumor killing in cell-level accuracy can be achieved only when the two elements work together and collaborate closely. To realize such therapeutic effect, BNCT sets high requirement on both neutron source and boron drug. The research on boron drug is related with multi-disciplines, such as chemistry, biology, medicine, radiology, pharmacy and physics. This article focuses on the neutron source for BNCT. Commonly, there are two types of BNCT neutron sources: reactor-based neutron source and accelerator-based neutron source. Up to now, almost all clinic trails of BNCT therapy were performed with the former. Due to limited resources of reactor neutron source, only less than 2000 cases BNCT treatments have been carried out in the world since BNCT method was invented. Thanks for the intense beam proton accelerator development, accelerator based neutron source can provide better beam quality, and especially importantly it can be installed in a hospital environment, which is essential for wide-range application of BNCT. In accelerator-based BNCT field, China has a sound base owing to more than <sc>20 years</sc> research and development in high intensity neutron source for spallation neutron source and accelerator-driven subcritical system. It is meaningful work to transfer the related technology to accelerator-based BNCT (AB-BNCT). In this paper we will firstly introduce the demand on neutron beam specification recommended by IAEA. Then the difficulties in BNCT slow development in passing decades are reviewed. New era of BNCT is coming and one can expect a prosperous future, owing to accelerator-based BNCT. The core technology of AB-BNCT is explored and recent research achievements on BNCT research and development in China are reported. Various types of accelerators now can be used for BNCT facility, including electro-static high voltage, cyclotron and RF linac. Their pro and con are reviewed. Majorly two kinds of neutron generation targets are utilized for BNCT, and the characteristics comparison of these two are analyzed. On the newly constructed BNCT research platform in China, new boron drug research and development work are conducted in many institutes, universities and pharmacy companies. And in recent, a new AB-BNCT facility is under construction for clinic trails in a hospital. So we can have an optimistic viewpoint for BNCT future in China.

Problems and prospects of clinical trials of boron neutron capture therapy

<p indent="0mm">Boron neutron capture therapy (BNCT) is an intracellular radiotherapy that exploits the neutron capture and fission reaction of the boron isotope, ¹⁰B. As a binary targeted tumor therapy based on intracellular radiotherapy, BNCT brings new hope to cancer patients. In 2012, the team from the Third Xiangya Hospital of Central South University, together with Prof. Yongmao Zhou’s team, started the clinical trial of BNCT in China based on the in-hospital neutron irradiator-1 (IHNI-1), and completed the first trial of BNCT in September 2014. The following is the summarization of the clinical trial: The first patient, a <sc>53 years</sc> old man with black plaque found on the left anterior palmar <sc>7 years</sc> ago, was diagnosed as malignant melanoma after pathological examination. The patient completed boron phenylalanine (BPA) drug uptake test and neutron irradiation in September 2014. After irradiation, no tumor tissue was indicated by PET-CT and pathological examination. The team continued to complete drug uptake tests and/or neutron irradiation for a total of 20 cases, including 2 cases of early malignant melanoma, who survived in the <sc>5 years</sc> of follow-up. The rest 17 patients were in advanced cancer stage, among which 8 patients had local tumor shrinkage and 9 patients were not suitable for irradiation because ¹⁰B in tumor tissue did not reach the required concentration for treatment. The trial validated the safety of IHNI-1 and boron-containing agent, and the anti-tumor effects of BNCT. However, the board application of BNCT is limited by the lack of targeted boron delivery agent. Currently available boron-containing agents cannot concentrate in tumor lesions of some patients at an early stage, resulting in the impracticable status of BNCT for these patients. Even though some difference was observed in the concentration of ¹⁰B between tumor and normal tissues in some cancer patients at an advanced stage, the difference is not large enough for in the safe application of total body irradiation by IHNI-1. On the other hand, patients at advanced stage can only enjoy little survival benefits when local radiotherapy was accomplished. We highly recommend metastatic and recurrent tumors, and advanced tumors insensitive to current chemotherapy and radiotherapy as the major indications of BNCT. The pivotal task of BNCT research is to develop targeted boron delivery agent which can achieve sufficiently high boron concentration in tumor tissue against normal tissue (<italic>T</italic>/<italic>N</italic>). Based on the clinical trial and clinical experience mentioned above, we propose that a boron drug achieving a <italic>T</italic>/<italic>N</italic> ratio higher than 10, combined with large area or whole-body neutron irradiation, might be a sign of the maturity of BNCT technology. The current available boron drugs are mainly composed of small molecules of amino acid derivatives such as BPA, which are concentrated in tumor tissues through the high metabolic mechanism of tumor tissues. The shortcomings of these drugs include off-target effects and low concentration in the tumor tissue. Deoxy glucose isotope is a tracer widely used in tumor screening; nanotechnologies such as nanosphere technology also shows good application in tumor drug concentration, and drugs assembled by antibodies and small molecule targeting ligands are becoming increasingly mature. These might be the potential directions for future boron drug development. In addition, the study and parameter design of neutron irradiation can be adjusted according to the development of boron drugs. However, neutron sources should consider irradiation area and depth to meet the requirements of large area or whole-body neutron irradiation, as the major application scenario of BNCT is to treat metastatic and recurrent tumors, and advanced tumors. Ultimately, well-designed clinical studies can be used to validate the efficiency of the newly developed boron drugs and neutron irradiation related techniques, and to give feedback for the improvement of these drugs and techniques.

ET-5 Biological effects of simultaneous use of multiple drugs in neutron capture therapy using rat brain tumor model

The world’s first clinical trial of boron neutron capture therapy (BNCT), which treats malignant brain tumors with a single dose of neutron irradiation using multiple boron drugs simultaneously, was performed at our institution, and its excellent results have stimulated BNCT research around the world. BNCT is a particle irradiation therapy that biologically targets cancer cells, and is expected to be a “new option for cancer treatment” because it can deliver a dose of radiation at the cellular level. In the case of BNCT using a combination of multiple drugs, a method to appropriately consider the biological effects of the combination in the dose calculation has not been established. At present, BNCT based on an accelerator-based irradiation system and a boron drug (BPA) based on essential amino acids has been approved by the regulatory approval for head and neck cancer and has shown good results in brain tumors. As basic research, we have continued to develop new boron drugs, which will be essential in the future, and have explored the interpretation of the biological effects of multiple boron drugs in combination and the optimal conditions required for drug development. The survival curve of BNCT in a rat brain tumor model showed that the effect of the new drug alone was comparable to that of BPA, and the effect of the combination was improved, but the effect of the combination did not match the prediction of the combined biological effect derived from each drug. However, it has been found that the effect of the combination does not match the prediction based on the combination of biological effects derived from each drug. In other words, even if the equivalent X-ray equivalent dose (Gy-Eq) is calculated, the combined effect of some drugs exceeds the prediction, while the combined effect of other drugs is poor.

Radiation measurement of boron neutron capture therapy research facility at T riga Mark-II research reactor Malaysia

Proper shielding ionizing radiations is a mandatory requirement in all nuclear facilities owing to the harmful effects of radiation on workers and general public. The present work is aimed to measure neutron fluxes and gamma fluxes around the Boron Neutron Capture Therapy (BNCT) research facility at the PUSPATI TRIGA Reactor. This measurement is needed in the subsequent safety assessment so as to ensure the research facility is safely operated

UV-C radiation effect on nuclear tracks of different ions in polycarbonate

The neutron autoradiography technique was developed in our laboratory using polycarbonate nuclear track detectors, to qualitatively and quantitatively analyze boron distribution and concentration in biological samples from experimental models coming from Boron Neutron Capture Therapy research. Spatial resolution was later improved by generating an imprint of the biological sample (e.g. cellular culture, tissue sections) on the detector surface, which can be microscopically observed together with nuclear tracks originated by 10B capture products. This methodology was developed for polycarbonate detectors and involves UV-C light irradiation of the sample-detector assembly. The chemical etching process of the detector, usually performed to enlarge the nuclear tracks, also “reveals” the imprint of the sample.In this work we report a fading effect in nuclear tracks due to UV-C exposure. Significant differences in track density produced by alpha ions and Li recoils coming from the neutron capture reaction, 10B(n,α)7Li, were found between exposed and unexposed to UV-C light (254 nm wavelength) polycarbonate foils. A decreasing relation between track density and exposure time to UV-C radiation could also be observed for these ions. To analyze the effect produced by UV-C radiation on nuclear tracks of different ions, polycarbonate detectors irradiated with 7Li, 12C, 16O, 32S, 127I, 197Au beams and air degraded alpha particles from a241Am source were also studied. A wavelength dependent photodegradation mechanism affecting the polycarbonate detector would be altering the nuclear tracks development in different ways, according to ion damage characteristics.

A design on the collimator for boron neutron capture therapy (BNCT) research facility at the thermal column of TRIGA MARK II

The development of the Boron Neutron Capture Therapy (BNCT) facility in Malaysia can be performed at the thermal column of the Malaysia research reactor. TRIGA MARK II is one of the facilities that can provide neutron source for BNCT facility. The specification of neutron flux and the gamma dose rate must consider for the development of the BNCT facility as a safety precaution for this research. Based on previous research, the thermal column identified as a suitable place for BNCT facility. To design the neutron collimator for BNCT purpose, the characterization of material towards thermal neutron flux explored using TLD and Microspec-6 and the collimator design was simulate using Monte Carlo N-Particle (MCNP) software based on the characterize materials in order to produce high thermal neutron flux. The combination of lead, HDPE, 30% borated polyethylene and aluminium as collimator design D1 simulate the highest thermal neutron 1.5770 x 109 neutron.cm−2s−1 and suitable for BNCT research purpose at the thermal column.

A review of the development of In-Hospital Neutron Irradiator-1 and boron neutron capture therapy clinical research on malignant melanoma

Boron neutron capture therapy (BNCT) is a binary targeting radiation therapeutic modality. Neutron source is one of the basic conditions of BNCT research. Specially designed neutron source, which could be set in hospital, is needed urgently for doctors and researchers. China research group has developed In-Hospital Neutron Irradiator-1 (IHNI-1), which is a specially designed reactor-based neutron source for BNCT with thermal power 30 kW and suitable for hospital siting. IHNI-1 has highly efficient neutron beams for both shallow and deep tumor irradiation and has the features of inherent safety, low power, small size, long-time stable, easy and quick operation, environment-friendly and low investment for construction and maintain. This paper gives a review of the development of IHNI-1, including the structure introduction and main test operation result, characterization neutron beams and finally reviews on the first BNCT clinical research at IHNI-1.

BNCT project at Tehran Research Reactor: Current and prospective plans

Boron Neutron Capture Therapy (BNCT) for brain tumor treatment is under development at the Tehran Research Reactor (TRR). This paper presents all current research activities that were performed during recent years as well as the prospective of BNCT research at TRR. The theoretical and experimental investigations show that TRR has a very good potential to consider it as a pilot facility for BNCT research in the Middle East and could be facilitated for clinical applications. In this way, there are some steps and also some challenges which are described in the paper.

Evaluation of Design Neutron Filters in BNCT

7 neutrons per Second per milliampere of electron current is shown to be obtainable. The useful neutron energy range for BNCT purposes is from 1 eV to 10 keV (sometimes 40 keV is as-summed). The effectiveness of the treatment is expected to increase both the amount of boron in the cells and the neutron flux increase. In this treatment, advantage is taken of the nuclear reaction between boron and thermal neutrons, resulting in cell death from the energy deposited along the paths of resultant alpha particles and lithium ions. Abstract This paper reviews the development of neutron filters using Boron Neutron Capture Therapy (BNCT). At present BNCT research necessity of an epithermal beam is to generate the necessary thermal neutron field at the desired depth. Through the use of an epithermal beam, deeper-seated tumors can be treated more effectively (1). Epithermal neutron beams can be generated by small nuclear reactors and by accelerator based neutron sources. So far, only reactors have been actually used to produce therapeutically useful epithermal neutron beams for BNCT; accelerator- based epithermal neutron sources may constitute the basis for a more deployable technology for BNCT than reactor- based sources in the long term (2). Accelerators offer a number of potential advantages over reactor-based neutron sources for clinical applications (3). The goal of reactor epithermal neutron filter conceptual design effort was to provide a low cost, simple filter design that is easy to fabricate and install while meeting or exceeding the nuclear performance requirements of the BNCT program. Therefore, in this work the use of aluminum compound, teflon compound and fluental and heavy water was considered.

Intercalibration of physical neutron dosimetry for the RA-3 and MURR thermal neutron sources for BNCT small-animal research

New thermal neutron irradiation facilities to perform cell and small-animal irradiations for Boron Neutron Capture Therapy research have been installed at the Missouri University Research Reactor and at the RA-3 research reactor facility in Buenos Aires, Argentina. Recognizing the importance of accurate and reproducible physical beam dosimetry as an essential tool for combination and intercomparisons of preclinical and clinical results from the different facilities, we have conducted an experimental intercalibration of the neutronic performance of the RA-3 and MURR thermal neutron sources.

Not boring at all

The element boron is not renowned among biologists, short of a few specialists who know that it is an essential nutrient for plants and an element in boromycin—an antibiotic compound produced by Streptomyces . Yet, on the whole, molecular biologists and, in particular, those in drug development seem to have little use for carbon's left‐hand neighbour in the periodic table. This is about to change. Currently, boron is largely produced in Turkey and the USA, and is used in a wide range of products, including glass, detergents, fire retardants, fibres to reinforce plane fuselages and body armour, and in superhard materials. Now, both researchers and the pharmaceutical industry are showing an increasing interest in boron as an alternative to carbon in drug design. > …both researchers and the pharmaceutical industry are showing an increasing interest in boron as an alternative to carbon in drug design A series of recent scientific and commercial developments indicate that boron‐based compounds are interesting drug candidates against all disease categories and might even speed up drug development. Pharmaceutical companies have already increased their boron research, particularly GlaxoSmithKline (GSK; Brentford, UK), which announced a US$2.5 billion investment in the US company Anacor (Palo Alto, CA, USA) in November 2008. Anacor was founded in 2002 to develop boron‐based antibacterial drugs, but has since expanded into antivirals and other targets with its boron‐based platform. Co‐founders Lucy Shapiro and Stephen Benkovic began collaborating in 2001 to look for novel inhibitors of several newly identified bacterial target sites that, they thought, could lead to more effective antibiotics. “They randomly inserted boron and got good activity,” said David Perry, CEO of Anacor. This serendipitous discovery led to the formation of Anacor a year later. “We were lucky,” Perry conceded. “At that stage we had no idea what the broader potential of boron …

Study of neutron-DNA interaction at the IPEN BNCT research facility

Our group at the Laboratorio do Acelerador Linear (IFUSP- USP) is currently developing several studies related to the interaction of different kinds of radiation with DNA. Initially, our plan is to study the interactions proton-DNA, gamma-DNA and neutron-DNA. In this work we describe the most important features of the neutron-DNA study, which we plan to perform by selecting thermal, epithermal and fast neutrons. To improve the information about radiation-DNA interaction is important in order to achieve more secure and efficient cancer treatments by using radiation therapy. Nowadays, one important technique is the boron neutrons capture therapy, where neutrons are used to initiate a nuclear reaction at the tumor site. The effects of the neutrons on the health tissue, however, must be better understood. The study of neutron-DNA interaction, in this scenario, is of great importance. The research facility for Boron Neutron Capture Therapy (BNCT) in the IEA-R1 Reactor of the IPEN-CNEN/SP[1] will be used for studying the neutron-induced DNA damage. At present, we are evaluating the characteristics of the neutron flux at the biological sample, and we are carrying out simulations of the experimental procedure through Monte Carlos N Particle transport code system version 4C (MCNP-4C)[2] to find the experimental conditions necessary to minimize such contamination, and also verify the effects of those gamma's on the DNA molecule. The first step is the selection of filters configurations, which will allow us to irradiate the DNA sample with thermal, epithermal and fast neutrons. We present the results of our simulations, and describe the experimental setup show the best sets of materials necessary to obtain neutron spectra for different neutrons energies.

A critical assessment of boron neutron capture therapy: an overview.

Boron neutron capture therapy (BNCT) is based on the nuclear reaction that occurs when boron-10 is irradiated with neutrons of the appropriate energy to produce high-energy alpha particles and recoiling lithium-7 nuclei. BNCT has been used clinically to treat patients with high-grade gliomas, and a much smaller number with primary and metastatic melanoma. The purpose of this special issue of the Journal of Neuro-Oncology is to provide a critical and realistic assessment of various aspects of basic and clinical BNCT research in order to better understand its present status and future potential. Topics that are covered include neutron sources, tumor-targeted boron delivery agents, brain tumor models to assess therapeutic efficacy, computational dosimetry and treatment planning, results of clinical trails in the United States, Japan and Europe, pharmacokinetic studies of sodium borocaptate and boronophenylalanine (BPA), positron emission tomography imaging of BPA for treatment planning, and finally an overview of the challenges and problems that must be faced if BNCT is to become a useful treatment modality for brain tumors. Clinical studies have demonstrated the safety of BNCT. The next challenge is an unequivocal demonstration of therapeutic efficacy in one or more of the clinical trails that either are in progress or are planned over the next few years.

Irradiation facility for boron neutron capture therapy application based on a rf-driven D–T neutron source and a new beam shaping assembly (abstract)

Selecting the best neutron source for boron neutron capture therapy (BNCT) requires optimizing neutron beam parameters. This involves solving many complex problems. Safety issues related to the use of nuclear reactor in hospital environments, as well as lower costs have led to interest in the development of accelerator-driven neutron sources. The BNCT research programs at the Nuclear Departments of Pisa and Genova Universities (DIMNP and DITEC) focus on studies of new concepts for accelerator-based DT neutron sources. Simple and compact accelerator designs using relatively low deuteron beam energy, ∼100 keV, have been developed which, in turn, can generate high neutron yields. New studies have been started for optimization of moderator materials for the 14.1 MeV DT neutrons. Our aim is to obtain an epithermal neutron beam for therapeutic application at the exit end, with minimal beam intensity losses, the specific goal is to achieve an epithermal neutron flux of at least of 1×109 n/cm2 s at the beam port, with low gamma and fast neutron dose contamination. According to the most recent neutron BNCT beam parameters some moderating and spectrum shifter materials and geometrical configurations have thus far been tested, and neutron and gamma beam data at beam port have been computed. A possible beam shaping assembly model has been designed. This research demonstrates that a DT neutron source could be successfully implemented for BNCT application, with performance surpassing the minimum requirements stated above, using DT neutron sources with yields in the range 1013–1014 n/s. The latest Monte Carlo simulation results of an accelerator based facility which relies on a rf-driven DT fusion neutron generator will be presented.

Determination of the range of alpha particles in histological samples using a proton beam

The 70 μm -thick sliced mouse samples used in boron neutron capture therapy research are normally freeze-dried and permanently mounted on a sticky tape. Such a preparation alters the tissue density and makes it impossible to correctly determine the ranges of the alpha particles from the 10B(n, α) 7Li reaction. Proton radiography utilising etched-track detectors can be successfully used for the density determination of these histological samples. The technique is based on the measurement of different energy losses in different tissues. A computer simulation was made in order to estimate the efficiency and sensitivity of this technique. Some typical values for tissue density and elemental composition were taken from the SRIM program database. The applicability of this technique was illustrated and ranges of alpha particles in a histological sample of tumor-bearing mouse were determined using proton ranges as a reference.

10B quantitative determination in ppb range by particle tracks reading for boron neutron capture therapy

Quantitative determination of ppb-order 10B was carried out in a small number of cultured tumor cells by particle tracks by the 10B(n,α)7Li reactions using solid state nuclear track detector (SSNTD) for boron neutron capture therapy research. The detection limit of 10B concentration in tumor cells is less than 1·10-3 ppm under our experimental conditions which permits the quantitative determination of 10B in a small number of boronated tumor cells (105/ml = ca. 0.1 mg). Boron quantities in tumor cells determined were well compatible with the tumor cell killing effects of boron neutron capture therapy.