H. Tsutsui

Improvement of dose distribution in phantom by using epithermal neutron source based on the Be(p,n) reaction using a 30 MeV proton cyclotron accelerator.

In order to generate epithermal neutrons for boron neutron capture therapy (BNCT), we proposed the method of filtering and moderating fast neutrons, which are emitted from the reaction between a beryllium target and 30 MeV protons accelerated by a cyclotron, using an optimum moderator system composed of iron, lead, aluminum, calcium fluoride, and enriched (6)LiF ceramic filter. At present, the epithermal-neutron source is under construction since June 2008 at Kyoto University Research Reactor Institute. This system consists of a cyclotron to supply a proton beam of about 1 mA at 30 MeV, a beam transport system, a beam scanner system for heat reduction on the beryllium target, a target cooling system, a beam shaping assembly, and an irradiation bed for patients. In this article, an overview of the cyclotron-based neutron source (CBNS) and the properties of the treatment neutron beam optimized by using the MCNPX Monte Carlo code are presented. The distribution of the RBE (relative biological effectiveness) dose in a phantom shows that, assuming a (10)B concentration of 13 ppm for normal tissue, this beam could be employed to treat a patient with an irradiation time less than 30 min and a dose less than 12.5 Gy-eq to normal tissue. The CBNS might be an alternative to the reactor-based neutron sources for BNCT treatments.

Impact of accelerator-based boron neutron capture therapy (AB-BNCT) on the treatment of multiple liver tumors and malignant pleural mesothelioma

BACKGROUND AND PURPOSEnTo confirm the feasibility of accelerator-based BNCT (AB-BNCT) for treatment of multiple liver tumors and malignant pleural mesothelioma (MPM), we compared dose distribution and irradiation time between AB-BNCT and reactor-based BNCT (RB-BNCT).nnnMATERIAL AND METHODSnWe constructed treatment plans for AB-BNCT and RB-BNCT of four multiple liver tumors and six MPM. The neutron beam data on RB-BNCT were those from the research reactor at Kyoto University Research Reactor Institute (KURRI). The irradiation time and dose-volume histogram data were assessed for each BNCT system.nnnRESULTSnIn BNCT for multiple liver tumors, when the 5 Gy-Eq dose was delivered as the mean dose to the healthy liver tissues, the mean dose delivered to the liver tumors by AB-BNCT and RB-BNCT was 68.1 and 65.1 Gy-Eq, respectively. In BNCT for MPM, when the mean lung dose to the normal ipsilateral lung was 5 Gy-Eq, the mean dose delivered to the MPM tumor by AB-BNCT and RB-BNCT was 20.2 and 19.9 Gy-Eq, respectively. Dose distribution analysis revealed that AB-BNCT is superior to RB-BNCT for treatment of deep-seated tumors.nnnCONCLUSIONSnThe feasibility of the AB-BNCT system constructed at our institute was confirmed from a clinical viewpoint in BNCT for multiple liver tumors and MPM.

Compact hard x‐ray source based on the photon storage ring

A compact synchrotron light source, which is composed of an exactly circular electron storage ring, features not only soft x‐ray generation but also laser emission as well as hard x‐ray generation. An insertion device is not applicable for the exact circular storage ring, since it has no straight section. However an optical resonator installed around the electron orbit functions like an optical undulator. The photon storage ring (PhSR) so named is essentially a free‐electron laser. A use of the Compton back scattering enables the PhSR to generate hard x rays. Sizable amount of hard x rays is expected from calculation.

Features of the compact photon storage ring

Abstract The compact photon storage ring (PhSR) is a hybrid machine that features both linac driven FEL and storage ring driven FEL. The lasing condition is determined by the exactly circular electron storage ring, but a continuous electron injection is possible without disturbing the lasing. An effect of coherent synchrotron radiation takes an important role in the lasing. It is found that the compact PhSR is promising in lasing up to a wavelength of less than 10 μm with 10 A accumulated current.

Behavior of the TEpj1 mode in the Photon Storage Ring

Abstract Behavior of the TEpj1 mode in the Photon Storage Ring (PhSR) is studied analytically as well as by computer simulations. Simulations were carried out for an exact circular electron storage ring with 511 MeV electron energy. The growth rate of the TE mode obtained with the simulation is in good agreement with the analytical one. The observed microbunching in the simulation manifests the lasing mechanism similar to a conventional FEL. The nature of the PhSR is discussed.

Measurement of the thermal neutron distribution in a water phantom using a cyclotron based neutron source for boron neutron capture therapy

We have been developed an epithermal neutron source for boron neutron capture therapy(BNCT), consisting of a cyclotron accelerator that can provide a ∼ 1 mA, 30 MeV proton beam, a neutron production beryllium target and the moderator that can reduce the energy of fast neutrons to an effective energy range. In order to validate the simulations, we measured the depth distribution of the thermal neutron flux in water phantom located at the treatment position. The measured results were compared with the simulations using the MCNPX Monte Carlo code. The good agreement between the simulations and measurements was shown. The thermal neutron flux with the proton current of 430 μA was 7.4 × 108 (neutrons cm−2 s−1) at the depth of around 20 mm in the water phantom. This intensity corresponds to the neutron source of Kyoto University Research Reactor (KUR), at which 275 clinical trials of BNCT have been performed. We experimentally confirmed that our cyclotron based neutron source can use for clinical trials of BNCT.