Biomedical subjects

Naruhiro Matsufuji

Publications and source records attributed to Naruhiro Matsufuji.

6 recordsLinked to original sources

PubMed2006

Biological dose calculation with Monte Carlo physics simulation for heavy-ion radiotherapy.

Treatment planning of heavy-ion radiotherapy involves predictive calculation of not only the physical dose but also the biological dose in a patient body. The biological dose is defined as the product of the physical dose and the relative biological effectiveness (RBE). In carbon-ion radiotherapy at National Institute of Radiological Sciences, the RBE value has been defined as the ratio of the 10% survival dose of 200 kVp x-rays to that of the radiation of interest for in vitro human salivary gland tumour cells. In this note, the physical and biological dose distributions of a typical therapeutic carbon-ion beam are calculated using the GEANT4 Monte Carlo simulation toolkit in comparison with those with the biological dose estimate system based on the one-dimensional beam model currently used in treatment planning. The results differed between the GEANT4 simulation and the one-dimensional beam model, indicating the physical limitations in the beam model. This study demonstrates that the Monte Carlo physics simulation technique can be applied to improve the accuracy of the biological dose distribution in treatment planning of heavy-ion radiotherapy.

Carbon↗

PubMed2006

Examination of GyE system for HIMAC carbon therapy.

PURPOSE: A retrospective analysis was made to examine appropriateness in the estimation of the biologic effectiveness of carbon-ion radiotherapy using resultant data from clinical trials at the heavy-ion medical accelerator complex (HIMAC) at the National Institute of Radiological Sciences in Chiba, Japan. METHODS AND MATERIALS: At HIMAC, relative biologic effectiveness (RBE) values of therapeutic carbon beams were determined based on experimental results of cell responses, on values expected with the linear-quadratic model, and based on experiences with neutron therapy. We use fixed RBE values independent of dose levels, although this apparently contradicts radiobiologic observations. Our RBE system depends only on LET of the heavy-ion radiation fields. With this RBE system, over 2,000 patients have been treated by carbon beams. With data from these patients, the local control rate of non-small-cell lung cancer was analyzed to verify the clinical RBE of the carbon beam. The local control rate was compared with rates published by groups from Gunma University and Massachusetts General Hospital. Using a simplified tumor control probability (TCP) model, clinical RBE values were obtained for different levels of TCP. RESULTS: For the 50% level of the clinical TCP, the RBE values nearly coincide with those for in vitro human salivary gland cell survival at 10%. For the higher levels of clinical TCP, the RBE values approach closer to those adapted in clinical trials at HIMAC.

Algorithms↗

PubMed2005

Spatial fragment distribution from a therapeutic pencil-like carbon beam in water.

The latest heavy ion therapy tends to require information about the spatial distribution of the quality of radiation in a patient's body in order to make the best use of any potential advantage of swift heavy ions for the therapeutic treatment of a tumour. The deflection of incident particles is described well by Molière's multiple-scattering theory of primary particles; however, the deflection of projectile fragments is not yet thoroughly understood. This paper reports on our investigation of the spatial distribution of fragments produced from a therapeutic carbon beam through nuclear reactions in thick water. A DeltaE-E counter telescope system, composed of a plastic scintillator, a gas-flow proportional counter and a BGO scintillator, was rotated around a water target in order to measure the spatial distribution of the radiation quality. The results revealed that the observed deflection of fragment particles exceeded the multiple scattering effect estimated by Molière's theory. However, the difference can be sufficiently accounted for by considering one term involved in the multiple-scattering formula; this term corresponds to a lateral 'kick' at the point of production of the fragment. This kick is successfully explained as a transfer of the intra-nucleus Fermi momentum of a projectile to the fragment; the extent of the kick obeys the expectation derived from the Goldhaber model.

Carbon↗

PubMed2003

Influence of fragment reaction of relativistic heavy charged particles on heavy-ion radiotherapy.

The production of projectile fragments is one of the most important, but not yet perfectly understood, problems to be considered when planning for the utilization of high-energy heavy charged particles for radiotherapy. This paper reports our investigation of the fragments' fluence and linear energy transfer (LET) spectra produced from various incident ions using an experimental approach to reveal these physical qualities of the beams. Polymethyl methacrylate, as a substitute for the human body, was used as a target. A deltaE-E counter telescope with a plastic scintillator and a BGO scintillator made it possible to identify the species of fragments based on differences of various elements. By combining a gas-flow proportional counter with a counter telescope system, LET spectra as well as fluence spectra of the fragments were derived for each element down from the primary particles to hydrogen. Among them, the information on hydrogen and helium fragments was derived for the first time. The result revealed that the number of light fragments, such as hydrogen and helium, became larger than the number of primaries in the vicinity of the range end. However, the greater part of the dose delivered to a cell was still governed by the primaries. The calculated result of a simulation used for heavy-ion radiotherapy indicated room for improving the reaction model.

Ions↗

PubMed2003

A CT calibration method based on the polybinary tissue model for radiotherapy treatment planning.

A method to establish the relationship between CT number and effective density for therapeutic radiations is proposed. We approximated body tissues to mixtures of muscle, air, fat and bone. Consequently, the relationship can be calibrated only with a CT scan of their substitutes, for which we chose water, air, ethanol and potassium phosphate solution, respectively. With simple and specific corrections for non-equivalencies of the substitutes, a calibration accuracy of 1% will be achieved. We tested the calibration method with some biological materials to verify that the proposed method would offer the accuracy, simplicity and specificity required for a standard in radiotherapy treatment planning, in particular with heavy charged particles.

Adipose Tissue↗

PubMed2000

[Fundamental Study on Heavy Ion CT Using Pencil Beam Scanning Method]

The feasibility of heavy ion computed tomography was investigated. A cylindrical polyethylene sample of 50 mm in diameter was used to establish the pencil beam scanning method and estimate the performance of the system. The sample was irradiated with carbon ions of 290 MeV/u and 400 MeV/u, and helium ions of 150 MeV/u. The residual beam energy was measured by a BGO scintillator in coincidence with two small plastic scintillators placed in front of and behind the sample to restrict the beam path and improve the spatial resolution in the CT reconstruction. The projection data were obtained by moving the sample only in the transverse direction because of its symmetrical structure. A Lucite sample with many holes of different diameters was used to demonstrate the spatial resolution of this CT system. From the reconstructed images the spatial resolution was estimated to be less than 2 mm under the conditions in this work. The electron density ratios of ethyl alcohol, water, and Lucite to polyethylene were obtained, which are in good agreement with the calculated values.

Journal Article↗