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In a conventional carbon-ion radiotherapy facility, a carbon-ion beam is typically accelerated up to an optimum energy, slowly extracted from a synchrotron ring by a resonant slow extraction method, and ultimately delivered to a patient through a beam-delivery system. At Japan’s Gunma University, a method employing slow-beam extraction along with beam-acceleration has been adopted. This method slightly alters the extracted-beam’s energy owing to the acceleration component of the process, which subsequently results in a residual-range variation of approximately 2 mm in water-equivalent length. However, this range variation does not disturb a distal dose distribution with broad-beam methods such as the single beam-wobbling method. With the pencil-beam 3D scanning method, however, such a range variation disturbs a distal dose distribution because the variation is comparable to slice thickness. Therefore, for pencil-beam 3D scanning, an energy compensation method for a slow extracted beam is proposed in this paper. This method can compensate for the aforementioned energy variances by controlling net energy losses through a rotatable energy absorber set fixed between the synchrotron exit channel and the isocenter. Experimental results demonstrate that beam energies can be maintained constant, as originally hypothesized. Moreover, energy-absorber positions were found to be significantly enhanced by optimizing beam optics for reducing beam-size growth by implementation of the multiple-scattering effect option.

We report our studies in various fields of Physics through nuclear moments utilizing the β-NMR technique, including material sciences, nuclear structures and fundamental symmetries. Especially, we focus on the recent progress in the studies on the electronic structure in Pt through Knight shifts of various impurities, lattice locations of impurities, electric field gradients, the analysis of nuclear spin in terms of its components, anomaly in the spin expectation value for 9C-9Li mirror pair, the G-parity conservation law, and the Ramsey resonance on UCN for future neutron EDM measurements.

Facilities for heavy ion therapies are steadily increasing in number worldwide. One of the advantages of heavy ions is their high relative biological effect (RBE). In a model used at NIRS (National Institute of Radiological Sciences), linear energy transfer (LET) spectra are required to estimate biological dose (physical dose × RBE). The CR-39 plastic charged-particle detector (CR-39) is suitable for measurement of LET. For the present study, done at the Gunma University Heavy Ion Medical Center (GHMC), we measured LET spectra at 11 depths in spread-out Bragg peak (SOBP) irradiation by a 12C beam of 380 MeV/u. The lower threshold of the CR-39 to measure LET was about 5 keV µm-1 due to poor sensitivity for low LET. Then we calculated biological dose and survival fraction distributions and compared them with treatment planning results at GHMC. We used Monte Carlo simulation (Geant4) to calculate LET spectra. The simulation results were in good agreement with the experimental spectra. Moreover, the biological dose and survival fraction distributions estimated from the CR-39 reproduced the treatment planning. The CR-39 is suitable for estimating biological dose in carbon ion therapy.

We report recent situation of anomaly in spin expectation value found in 9 C- 9 Li mirror pair, recent analysis of the nuclear spin in terms of orbital or intrinsic and proton or neutron, and a result from the study of the G -parity conservation law through β -ray angular correlation in terms of its nuclear orientation.

Information on electron density is important for radiotherapy treatment planning in order to optimize the dose distribution in the target volume of a patient. At present, the electron density is derived from a computed tomography (CT) number measured in x-ray CT scanning; however, there are uncertainties due to the beam hardening effect and the method by which the electron density is converted from the CT number. In order to measure the electron density with an accuracy of +/-1%, the authors have developed dual-energy x ray CT using monochromatic x rays. They experimentally proved that the measured linear attenuation coefficients were only a few percent lower than the theoretical ones, which led to an accuracy within 2% for the electron density. There were three factors causing inaccuracy in the linear attenuation coefficient and the electron density: the influence of scattered radiation, the nonlinearity in the detector response function, and a theoretical process to derive the electron density from the linear attenuation coefficients. The linear attenuation coefficients of water were experimentally proved to differ by 1%-2% from the theoretical one even when the scattering effect was negligible. The nonlinearity of the response function played an important role in correcting the difference in the linear attenuation coefficient. Furthermore, the theoretical process used for deriving the electron density from the linear attenuation coefficients introduces about 0.6% deviation from the theoretical value into the resultant electron density. This deviation occurs systematically so that it can be corrected. The authors measured the electron densities for seven samples equivalent to soft tissue in dual-energy x-ray CT, and finally obtained them with an accuracy of around +/-1%.

A multislit collimator was designed and fabricated for basic studies on microbeam radiation therapy (MRT) with an x-ray energy of about 100 keV. It consists of 30 slits that are 25 {mu}m high, 30 mm wide, and 5 mm thick in the beam direction. The slits were made of 25 {mu}m-thick polyimide sheets that were separated by 175 {mu}m-thick tungsten sheets. The authors measured the dose distribution of a single microbeam with a mean energy of 125 keV by a scanning slit method using a phosphor coupled to a charge coupled device camera and found that the ratios of the dose at the center of a microbeam to that at midpositions to adjacent slits were 1050 and 760 for each side of the microbeam. This dose distribution was well reproduced by the Monte Carlo simulation code PHITS.

Based on more than 10 years of experience with HIMAC, we have proposed a new treatment facility for the further development of therapy with HIMAC. The new facility, as an extension of the existing one, has been designed and the related R&D work has been carried out. The following descriptions give a summary account of the design study and the related R&D work for this new treatment facility at HIMAC.

The magnetic moment of short lived β-emitter 24mAl (426 keV, Iπ = 1 + , T1/2 = 131 ms) has been measured by means of β-NMR technique, for the first time. From the β-NMR spectrum, the magnetic moment was determined as \(\left| {\upmu}\left( ^{\rm 24m}{\rm Al} \right) \right|=\left( {2.99\pm 0.09} \right){\upmu}_{\rm N}\). Combined with the known magnetic moment of the mirror partner 24mNa, the expectation value of is obtained to be (0.08 ± 0.12). These values are reproduced well by the shell model calculation.

Dual energy X-ray CT was carried out with synchrotron radiation at BL20B2 beam line of JASRI/SPring-8. The X-ray beams were vertically magnified by employing an asymmetry Bragg reflection geometry. The field size was about 25 mm×250 mm at the end of the beam line. Porcine eyes and brain and water were used as samples. The DXCT provided the highly accurate information on an electron density; the electron density of water was in agreement of about 0.6% with the theoretical value. Images of the electron density and an effective atomic number had good quality sufficient for medical applications.

Since 1994, the clinical trial for cancer therapy with HIMAC has successfully progressed, and more than 2100 cancer patients have been treated with a carbon beam. Based on the development of the accelerator and irradiation technologies for 10 years, we have designed a new carbon-therapy facility for widespread use in Japan, and key technologies for the new facility have been developed. We describe the conceptual design of the new facility and the status of development for the key technologies.

Based on 10 years experience of carbon therapy at HIMAC, new facility project is in progress at NIRS. In this paper, the design of the synchrotron and its transport system dedicated for carbon therapy based on the machine study at HIMAC and the results of the studies are presented. © 2001 Elsevier Science. All rights reserved

In order to define the optical parameters of a slowly extracted beam at the entrance of the extraction channel and to realize optical matching with the beam line, the outgoing separatrix was measured at HIMAC. Modifying the lattice parameters of the ring model according to the measurement result, the simulation result makes it possible to predict the optical parameters at the extraction channel. As a result, it was experimentally verified that optical matching of the slowly extracted beam with the transport line was realized. The measured beam size and dispersion functions were in good agreement with the calculation result at each monitor in the transport line. Particle tracking also predicts the beam profile at each profile monitor in the beam line. Further, a quasi-parallel beam was demonstratedb by changing the beam optics in the beam line.

The momentum dependences of the nuclear spin polarization P and alignment A of 13B(I π = 3/2+, T 1/2 = 17.36 ms) produced in the 100A MeV 15N + Be collisions have been measured by detecting β-ray asymmetry. Because both the P and A were significantly smaller than the prediction from a simple kinematical model, some relaxation mechanisms must be take into account. Comparing the signs of the observed alignment of 12B, the sign of the quadrupole coupling constant eqQ of 13B in TiO2 was determined to be positive.

We proposed dual-energy X-ray CT for direct measurement of electron densities to make treatment planning for heavy ion radiotherapy more accurate. The accuracy was proved to be about 1% using synchrotron radiation in previous experiments carried out at SPring-8 and PF-AR. The electron densities of some porcine organs were measured in this method at SPring-8, and compared with data of ICRU Report. Besides, the atomic number of the object is also obtained as a byproduct. Comparing the CT-number given in conventional CT scanning is an important information. Images of the electron density and atomic number may give new information to medical diagnosis.

We have developed dual-energy X-ray CT (DXCT) using monochromatic X-ray beams. From the DXCT, we can obtain distributions of an electron density and an effective atomic number in a human body. Especially, the electron density is very important for the heavy-ion radiotherapy. Now, we adopted the CdTe array to this detector system to know the energy of incident photons as well as detect the position and the number of photons. We carry out the experiment of the DXCT with CdTe array at the beamline of KEK. The preliminary result of the experiments and the feasibility of a quantitative polychromatic X-ray CT as an advanced method of this method are shown in this study.

Secondary beam courses have been constructed at HIMAC. There are two beam courses, SB1 and SB2, which were designed as branches from the PH2 (a primary beam course) at the same point. The SB1 course is used mainly for medical applications with a positron emitter beam, where an irradiation system was installed for this purpose. The SB2 course is expected for general experiments. In this paper, the current status of the secondary beam courses in HIMAC is presented.

The magnetic moment of 33 Cl ( I π = 3 / 2 + , T 1 / 2 = 2.51 s ) has been re-measured precisely by β -NMR method. The obtained magnetic moment | μ | = 0.7549 ( 3 ) μ N is consistent with the old value 0.7523 ( 16 ) μ N , but is 5 times more accurate. The value is well reproduced by the shell model calculation, μ S M = 0.70 μ N . Combined with the magnetic moment of the mirror partner 33 S, the nuclear matrix elements 〈 l p 〉 , 〈 l n 〉 , 〈 S p 〉 , and 〈 S n 〉 were derived.

The nuclear moments of 13B(Iπ = 3/2−, T1/2 = 17.36ms) have been re-measured precisely in order to establish the spin manipulation technique for the study of the alignment correlation term in mass system A = 13. From the β-NMR on 13B in Pt, the magnetic moment was determined as |μ(13B)| = 3.1778(5)μN. From the β-NQR on 13B in TiO2, the Q moment has been determined as |Q(13B)| = 36.6(8)mb. We have measured the alignment correlation term α_E for 13B β decay for the first time and obtained a preliminary result as α−(13B) = 0.15(12)%/MeV.

The momentum dependences of the nuclear spin polarization P and alignment A of 12 B ( I π = 1 + , T 1 / 2 = 20.20 ms) [ 13 B ( I π = 3 / 2 − , T 1 / 2 = 17.36 ms)] produced in 100 A MeV 13 C [ 15 N] + Be collisions have been measured by detecting the β -ray asymmetry. Because both the P and A were significantly smaller than the prediction from a simple kinematical model, some depolarization mechanisms must be taken into account related with the collision process itself. Comparing the signs of the observed alignment of 12 B and 13 B, the sign of the quadrupole moment Q ( 13 B) was determined to be positive.

Knowledge of electron densities for materials is important for treatment planning for proton and heavier-ion radiotherapy. In order to obtain the electron densities with high precision, we have developed dual-energy X-ray computed tomography using synchrotron radiation. Two monochromatic X-rays with different energies generated from synchrotron radiation enables tomographic imaging which produces a cross sectional image based on electron density plus an additional image based on effective atomic number. Experiments for the dual-energy X-ray CT were made on the BL20B2 beamline at SPring-8. An image intensifier system and a CCD camera were used as the 2-D detectors. The measured electron densities were agreement to within 2% of the theoretical ones. Electron density and effective atomic number provide different contrast in images. Dual-energy X-ray CT can be used for quantitative measurement of the material.

Monochromatic x-ray computed tomography (CT) at two different energies provides information about electron density of human tissue without ambiguity due to the beam hardening effect. This information makes the treatment planning for proton and heavy-ion radiotherapy more precise. We have started a feasibility study on dual energy x-ray CT by using synchrotron radiation. A translation-rotation scanning CT system was developed for quantitative measurement in order to clarify what precision in the measurement was achieved. Liquid samples of solutions of K2HPO4 and solid samples of tissue equivalent materials were used to simulate human tissue. The experiments were carried out using monochromatic x-rays with energies of 40, 70 and 80 keV produced by monochromatizing synchrotron radiation. The solid samples were also measured in a complementary method using high-energy carbon beams to evaluate the electron densities. The measured electron densities were compared with the theoretical values or the values measured in the complementary method. It was found that these values were in agreement in 0.9% on average. Effective atomic numbers were obtained as well from dual-energy x-ray CT. The tomographic image based on each of the electron densities and the effective atomic number presents a different feature of the material, and its contrast drastically differs from that in a conventional CT image.

The RF-knockout (RF-KO) slow-extraction method with frequency modulation (FM) and amplitude modulation (AM) has brought high-accuracy irradiation to the treatment of a cancer tumor moving with respiration, because of a quick response to beam start/stop. However, a beam spill extracted from a synchrotron ring through RF-KO slow-extraction has a huge ripple with a frequency of around 1 kHz related to the FM. The spill ripple will disturb the lateral dose distribution in the beam scanning methods. Thus, the source of the spill ripple has been investigated through experiments and simulations. There are two tune regions for the extraction process through the RF-KO method: the extraction region and the diffusion region. The particles in the extraction region can be extracted due to amplitude growth through the transverse RF field, only when its frequency matches with the tune in the extraction region. For a large chromaticity, however, the particles in the extraction region can be extracted through the synchrotron oscillation, even when the frequency does not match with the tune in the extraction region. Thus, the spill structure during one period of the FM strongly depends on the horizontal chromaticity. They are repeated with the repetition frequency of the FM, which is the very source of the spill ripple in the RF-KO method.

The magnetic moment of the short-lived β emitter 35Ar ( I π =3/2 + , T 1/2 =1.77 s) has been remeasured by means of the combined technique of polarized nuclear beams and β-NMR. The obtained magnetic moment is 0.6322(2) μN. This value is consistent with the old data, but is one order of more magnitude precise. The value is well reproduced by the shell model calculation.

In cancer treatment with heavy ions, verification of the ion range in the patient's body is important. For this purpose, a positron emitter beam provides the possibility of range verification. To use the positron emitter beam, we have constructed a secondary beam course and its irradiation system. In this paper the constructed system is presented together with some results of beam experiments.

The magnetic dipole (μ) and electric quadrupole (Q) moments of short-lived nucleus 22F ( I π = 4 + , T 1 / 2 = 4.2 s ) have been measured for the first time by means of the β-NMR technique. A spin polarized 22F beam was produced through the charge exchange reaction of 22Ne and was implanted into single crysltals of NaF and MgF2 for μ and Q measurements, respectively. As a result, | μ ( F 22 ) | = ( 2.69443 ± 0.00039 ) μ N and | Q ( F 22 ) | = ( 3 ± 2 ) mb was obtained. These values are well reproduced by the shell model calculations.

The spin lattice-relaxation rates of short-lived unstable nuclei Al 25 and P 28 in Pt has been measured by means of the β-NMR technique, in order to study the electronic structure of dilute impurities in Pt. From the obtained spin-lattice relaxation rates, Knight shifts K c were estimated to be K c [ Al in Pt ] = ( 0.45 ± 0.09 ) × 10 − 3 and K c [ P in Pt ] = ( 4 − 4 + 2 ) × 10 − 3 using the Korringa relation. These values were evaluated by comparing to the first principle calculations.

Nuclear structure of proton-rich unstable nucleus 28P has been studied by measuring its g-factor for the first time. The g-factor of 28P (Iπ = 3+, T1/2 = 270.3 ms) was measured by means of β-NMR technique combined with the new polarization technique for charge exchange reaction product in the intermediate energy heavy ion collisions. The obtained g-factor of g = 0.1028(27) is very much quenched from the Schmidt value, but is well reproduced by the shell model (+0.102). In connection with the magnetic moment of the mirror partner and the β-ray transition probability, the orbital angular momenta and intrinsic spins of protons and neutrons have been determined as 〈lp〉 = 0.43(29), 〈ln〉 = 1.85(29), 〈Sp) = 0.28(4), and 〈Sn〉 = 0.44(4).

Heavy-Ion Medical Accelerator in Chiba (HIMAC) provides ion beams for radiotherapy of cancers and for other basic researches. High-energy beam transport lines deliver the beams to three treatment rooms and two experiment rooms with the aid of 41 beam monitor units. Each monitor unit consists of a wire grid as a profile monitor, or a combined unit in which the wire grid and a parallel plate ionization chamber are united for an additional measurement of a beam intensity. They are operated in a mixed gas of 80% Ar and 20% CO2. The gas gain of the wire grid achieves about 8000 at an applied voltage of −2700 V. Dynamic ranges of the wire gird and the parallel plate ionization chamber were measured to be 8×105 and 1×106 in test using ion beams, respectively. A control system of these monitor units offers easy operation, so that operators are almost free from miss-operations. The monitor units are interlocked with a system which protects patients from the undesired irradiation. Five wire grids are used for continuously monitoring the beam during treatments, which play a role in keeping qualities of the treatments. The monitor system has been designed to meet requirements for medical uses, and works in a stable and reliable manner and satisfies the requirements.

ions has been observed through measurements of the surviving charge state of Arions planar channeled in a Si crystal. We experimentally demonstrate trajectory-dependent, i.e., impactparameter dependent resonant-coherent-excitation phenomena by measuring the energy deposition incoincidence with the charge state of emerging ions. The resonant-coherent-excitation transition energyreflects spin-orbit

Researchers explore the use of Bragg Ionization Peak in radiotherapy for tumors. Considerations for the production of a high quality radioactive beam include secondary beam production efficiency, primary beam survival, and multiple scattering. A Positron Emitting Beam Analyzing camera was developed and tested at BEVALAC using a neon-19 beam stopping point. Results indicate that in homogeneous brain tissues, CT measurements and radioactive beam measurements are between 1-2 mm; there can be substantial difference between CT measurements and radioactive beam estimates if the beam stopping point crosses the fossae; random coincidences due to detector activation also appear as diffused images in the image plane of the beam stopping point; and further enhancements are necessary to make reliable measurements in the human trunk and complex brain regions.

A beam extraction method using a transverse rf electric field with amplitude and frequency modulation has been studied in order to develop an irradiation method which is synchronized with the breathing of a patient for high-quality charged particle therapy. The dependence of the extracted beam intensity on the voltage, the frequency band width and the center frequency of the transverse rf electric field has been investigated. The extracted beam intensity was slightly increased from that of the ordinary slow extraction method with a third order resonance. The response of the extracted beam intensity to the applied transverse rf electric field was as prompt as within 1 ms. The horizontal emittance of beams extracted by the present method was reduced by about 70% compared with that by the ordinary one due to utilizing a constant separatrix. Amplitude modulation can control the global beam spill structure. The frequency modulation reduced the effect of the current ripple of the main quadrupole magnets.

The NIRS heavy-ion two-synchrotron medical facility, HIMAC, was approved in the 1987 fiscal year and clinical trials were started in late June 1994 as previously arranged. The operation experiences show that the entire HIMAC facility can work well with high stability and excellent reproducibility. For example, the intensity of beam extracted slowly from the rings can be reduced as low as 500 particles per pulse because stable and reproducible acceleration can be achieved in the rings in spite of no beam feedback. This performance enables direct counting of the beam and its fragments in the preparatory experiments toward clinical treatments and provides a promising basis for acceleration and storage of radioactive beams toward simultaneous treatment and diagnosis in future.

A model for beam customization with collimators and a range-compensating filter based on the phase-space theory for beam transport is presented for dose distribution calculation in treatment planning of radiotherapy with protons and heavier ions. Independent handling of pencil beams in conventional pencil-beam algorithms causes unphysical collimator-height dependence in the middle of large fields, which is resolved by the framework comprised of generation, transport, collimation, regeneration, range-compensation, and edge-sharpening processes with a matrix of pencil beams. The model was verified to be consistent with measurement and analytic estimation at a submillimeter level in penumbra of individual collimators with a combinational-collimated carbon-ion beam. The model computation is fast, accurate, and readily applicable to pencil-beam algorithms in treatment planning with capability of combinational collimation to make best use of the beam-customization devices., 16 pages, 5 figures

We measured the polarization of the β‐emitting 23Ne (Iπ = 5/2+, T1/2 = 37.24 s) and 25Al(Iπ = 5/2+, T1/2 = 7.18 s), produced through the one nucleon pickup reactions in the intermediate energy heavy ion collisions, and was compared with those from the projectile fragmentation process. The larger polarization which seems to persistently be positive throughout the momentum distribution, and sharper momentum distributions suggest nuclear friction mechanism to be responsible for the polarization phenomena. Using such a large polarization, magnetic moment of 23Ne and the quadrupole moment of 25Al were measured. The obtained values are |μ(23Ne)| = 1.0817(9) μN and |Q(25Al)| = (240 ± 20) mb.

Numerical studies on the effect of a superconducting wiggler (SCW), which was developed at National Institute of Radiological Sciences (NIRS), to Saga light source (SAGA-LS) have been performed. The three dimensional magnetic field of the SCW was calculated to evaluate the effect on beam optics. It was found that the tune correction was needed to reduce a deformation of the vertical beta function. The dynamic aperture shrank to about 70 % on horizontal plane. However these effects are considered to be tolerable at the SAGA-LS.

β‐NMR spectra have been observed for 33Cl, 23Al and 23Ne. As a result, the magnetic moment of 33Cl was determined as |μ(33Cl)| = 0.7549(3) μN. Combined with the known magnetic moment of 33S and the ft‐value of the 33Cl β decay, the orbital angular momenta and the intrinsic spins for proton and neutron groups, are deduced separately as 〈lp〉 = 1.3, 〈n〉 = 0.3, 〈Sp〉 = −0.12 and 〈Sn〉 = −0.02. The magnetic moment of 23Al, and that of 23Ne were determined as |μ(23Al)| = 3.89(22) μN and |μ(23Ne)| = 1.0817(9) μN, respectively. As a result, the orbital angular momentum 〈lz〉 and the intrinsic spin 〈Sz〉 were deduced to be 2.09(29) and 0.41(29), respectively. Combined with the ft‐value of the β transition from the ground state of 23Al to the excited state of 23Mg, proton and neutron contributions are separated. The obtained expectation values 〈lp〉, 〈ln〉, 〈Sp〉 and 〈Sn〉 are compared with the shell model predictions.

Monochromatic x-ray CT at two different energies provides information about electron density without ambiguity due to the beam hardening effect. This information makes the treatment planning for heavy-ion radiotherapy more precise. We have started a feasibility study on the dual-energy x-ray CT by using synchrotron radiation. We developed a linear scanning CT system(1D-CT) in order to evaluate what precision in the measurement was achieved. Comparison fo measured electron densities with the theoretical values proved that these values were in afreement in 0.9 % on average. We haave developed a 2D-CT system with a two-dimensional scintillator array to take images in a short time. At present, it has been proved that the electron density is measured in the precision of about 1 %. Effectove atomic numbers are obtained as well from the dual-energy x-ray CT. They present a different feature of an object, and the contrasts in the images differ from that in a conventional CT image. The feature of the images may help distinguish more clearly tissues or organs with aid of difference contrast from the conventional CT images., International Symposium on Portable Synchrotron Light Sources and Advanced Applications

The electron density is one of the most important elements for the treatment planning in the radiotherapy, because this information is used for the range estimation of the heavy‐ion beam. In order to measure more precise electron density, we have developed the dual‐energy x‐ray CT system using synchrotron radiation. The x‐ray detector consists of 256 × 96 scintillator‐array. It can take more than a hundred projection images per second. The response of the detector to x‐rays was proved to be linear up to at least 1013 photon/pixel. The experiments were carried out using two monochromatic x‐rays of 40 keV and 70 keV at the beam‐line BL20B2 of SPring‐8. As the results from samples of water, ethanol and solutions of dipotassium hydrogenphosphate with five concentrations, the electron densities measured in the dual‐energy x‐ray CT method were in agreement with the theoretical values by about ± 1%. This is almost the same level as that achieved by the one‐dimensional CT system we developed previously. In addition, a sample of kidney of a pig fixed by formalin neutral buffer solution was used to distinguish the tissues in the CT images based on the electron density and the effective atomic number that was additionally obtained in the dual‐energy x‐ray CT. It suggested that renal pelvis was enriched with adipose tissue, and it was difficult to distinguish renal cortex and renal medulla.

The relationship between resolution of human vessels and radiation dose in micro‐angiography was evaluated. The radiation dose required to visualize vessels increased as a function of the −4th power of the resolution of vessel images. Since vessels are overlapped in angiograms, resolution of the target vessel is poor. We discuss resolution of 1 mm vessels in selective angiography.

A synchrotron light source dedicated to medical applica- tions has been designed at National Institute of Radiological Sciences. The storage ring, with circumference of 80 m, is designed for accel- eration of 2.3 GeV and a stored current of 420 mA. It is equipped with two multipole wigglers to produce sufficient photon flux in a hard x-ray region required for medical applications. The purposes of the synchrotron light source are clinical performance of medical diag- noses clinically and research and development relating with medical applications. One of the most interesting applications for us is dual- energy x-ray computed tomography (CT). It gives the information about electron density of human tissue. The information plays an im- portant role in advancing heavy-ion radiotherapy of cancers. Electron density can be derived from attenuation coefficients measured by dif- ferent energy x rays. In this paper, a practical method of the dual- energy x-ray CT with synchrotron radiation is proposed with the theoretical consideration. The primitive experiment using monochro- matic x rays emitted from radioisotopes proved the procedure of analysis mentioned here effective to derive electron densities from linear attenuation coefficients for two x rays of a different energy. The beamline dedicated to dual-energy x-ray CT is also proposed. It has a multipole wiggler as a light source and it mainly consists of a dual crystal monochromator and a rotating filter for attenuating photon flux of x rays and two-dimensional detector. © 2001 Society of Photo-Optical In

A synchrotron light source dedicated to medical applications is designed at NIRS. The synchrotron ring accelerates electrons up to 1.8 GeV and stores them with about 400 mA, and is equipped with two superconducting multipole wigglers to generate sufficient photon flux for medical diagnoses. One of the most interesting applications for us is monochromatic x-ray computed tomography (CT). It plays an important role in advancing heavy ion radiotherapy of cancers which is being performed at NIRS. The radiotherapy is carried out based on a treatment planning which is a protocol for irradiation of the heavy ion beam on a target to maximize dose distribution and a biological advantage. The treatment planning converts CT-number of tissues along paths of the heavy ion beam to electron densities in order to calculated end-of-range of the heavy ion beam. The conventional x-ray CT introduces uncertainty into the CT- numbers due to beam hardening effect. While the monochromatic x-ray makes the CT-scan free from the beam hardening effect. Furthermore, dual energy x-ray CT-scans give the electron density directly without conversion from the CT-number. We focus on the x-ray CT using two monochromatic x-rays, and outline its beamline and the compact ring.

A synchrotron light source dedicated to medical applications is required to be compact for installation in limited spaces at hospitals. The NIRS storage ring, with a circumference of 44.8 m, is designed to accelerate electrons up to 1.8 GeV and to store a beam of 400 mA. The ring is composed of superconducting bending magnets for downsizing. A beam of 300 MeV is injected into the ring from a microtron operated at an L-band RF frequency. There are two superconducting multipole wigglers with nine poles and a maximum field of 8 T, which can produce a photon flux of about 1.4 × 1013 photons s−1 mrad−1 (0.1% bandwidth)−1 at 33 keV used for coronary angiography.

Purpose: This work is aimed to improve the computational model of the beam‐customization devices for treatment planning of radiotherapy with heavy charged particles, where only a single collimator and a compensator have been commonly handled with inaccuracy of unphysical collimator dependence in the middle of large fields. Method and Materials: The phase‐space theory is applied to the beam transport through the beam‐customization devices to enable handling of multiple collimators and a compensator in any order. The theoretical model was experimentally tested with a carbon‐ion beam, where two jaw and a multileaf collimators, a 3‐cm PMMA half plate for a range compensator, and an 8‐cm square aperture for a patient collimator were concurrently used. In the model, a matrix of pencil beams was transported through the devices and a two‐dimensional in‐air dose distribution on the isocenter plane was computed within ten seconds. For comparison, the penumbra sizes at the field edges formed by the effective collimators were analytically estimated and the dose profiles along four axes on the isocenter plane were experimentally measured. Results: The model computation agreed with the measurement and analytic estimation at a submillimeter level in penumbra size and reproduced the measured dose fluctuation in the middle of the field due to the range‐compensator scatter. Conclusion: The model computation is fast, accurate, and readily applicable to pencil‐beam algorithms in treatment planning to enable combinational collimation for the best use of beam‐customization devices.

For medical irradiation, beams with a uniform distribution have been required. We have proposed a method to control the beam profile using an octupole magnet. We have installed an octupole magnet and confirmed its effectiveness at the Heavy Ion Medical Accelerator in Chiba (HIMAC) beam-transport line. A beam efficiency of 91% can be realized with a flatness of ±4% over the range of ±15 mm. The beam offset at the position of the octupole magnet is required to be within ±0.2 mm to realize this condition. This method is expected to have a beam efficiency higher than that of the ordinary method using wobbler magnets and a scatterer system.

The energy distribution of pions produced from 16 O bombarded with 200 MeV electron was measured. The angular distribution of 16 O(γ,π + ) 16 N was deduced for the pions leading to the sum of the four lowest lying residual levels. The cross section integrated over angles is compared with the previous data deduced from the photopion yield curve. Experimental cross sections are compared with the shell model and Helm model predictions. The shell model results with configuration mixing approximately reproduce the present experimental results. The Helm model results are also similar to the experimental angular distribution pertterns.

The information on the electron densities of bodies is important for the treatment planning of radiotherapy. In order to obtain the electron densities directly, we have developed dual-energy X-ray computed tomography (CT) using synchrotron radiation. It was experimentally proved that the electron density was deduced with about 1% accuracy from two linear attenuation coefficient. However, the linear attenuation coefficient were measured by a few percent lower than the theoretical ones. We assumed that the less accurate linear attenuation coefficients were caused by the influence of scattered radiation and the non-linearity in the response of the detector. In comparison of the scattered radiation to the simulation results, the scattered radiation contributed at the most 0.5% to the linear attenuation coefficients. Correcting the non-linearity in the detector response functions, the values of linear attenuation coefficient were improved drastically.

We have developed a parallel beam suitable for channeling experiments with relativistic heavy ions at HIMAC (Heavy Ion Medical Accelerator in Chiba). To observe channeling phenomena, we used a silicon surface barrier detector (SSD) as a sample crystal and as a detector for the energy loss in itself. Further, we measured the angular spread of the beam transmitted through the SSD by a position sensitive detector (PSD) placed downstream of the SSD. Under axial and (111), (220) and (004) planar channeling conditions, we observed that the energy loss of the channeled ions in the SSD became almost a half and their angular spread was also reduced.

The momentum distributions of projectile-like fragments produced in the 40 Ar+ 9 Be reaction at E / A =90 MeV and the 16 O+ 12 C reaction at E / A =290 MeV were observed. A correlation between the width of the transverse momentum distribution and the velocity was found at E / A =90 MeV. Coulomb final-state interaction and AMD calculation cannot explain this correlation. A good agreement between EPAX2 and the production cross sections derived from observed momentum distribution of the fragments was found.