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The NIRS has carried out carbon-ion radiotherapy (RT) with HIMAC since 1994. On the basis of their ten-year HIMAC experience, NIRS has developed a standard-type CIRT facility in order to boost availability of carbon-ion RT in Japan. Work has been carried out at its pilot facility at Gunma University since 2010. The current projects of the pilot facility include Saga-HIMAT and i-ROCK, promoted by the Kanagawa prefectural cancer center. Toward the further sophisticated conformal carbon-ion RT with HIMAC, the NIRS has since 2006 been developing new treatment technologies, such as a fast 3D rescanning with a pencil beam and a compact rotating gantry.

On the basis of more than 10 years of experience with HIMAC, we proposed and designed a new treatment research facility, as an extension of the existing facility, for the further development of radiotherapy with HIMAC. The new facility employs a 3D rescanning technique developed at NIRS. Its building construction was completed in March 2010 and the devices are being installed. A beam commissioning and a pre-clinical study will be initiated from this October. Here, we report recent progress for this new treatment facility project at HIMAC.

The power supplies for the main bending and quadrupole magnets of the Heavy-Ion Medical Accelerator (HIMAC) in Chiba are controlled by preset current and voltage patterns, which are created by a pattern-creation program. It has been observed that a deviation between the preset current and the actual one becomes very large when newly created patterns are applied to the power supplies. This deviation is attributed to the incorrect parameters used for calculations of the voltage pattern in the pattern-creation program. In order to reduce the deviation, we have analyzed the values of resistance and inductance using the actual data of the current and voltage patterns. As a result, more than 10% difference was found between the conventional and newly calculated parameters. By applying the new parameters to the pattern-creation program a reduction of the deviation was confirmed.

Purpose: A project to construct a new treatment facility, as an extension of the existing HIMAC facility, has been initiated for the further development of carbon-ion therapy at NIRS. This new treatment facility is equipped with a 3D irradiation system with pencil-beam scanning. The challenge of this project is to realize treatment of a moving target by scanning irradiation. To achieve fast rescanning within an acceptable irradiation time, the authors developed a fast scanning system. Methods: In order to verify the validity of the design and to demonstrate the performance of the fast scanning prior to use in the new treatment facility, a new scanning-irradiation system was developed and installed into the existing HIMAC physics-experiment course. The authors made strong efforts to develop (1) the fast scanning magnet and its power supply, (2) the high-speed control system, and (3) the beam monitoring. The performance of the system including 3D dose conformation was tested by using the carbon beam from the HIMAC accelerator. Results: The performance of the fast scanning system was verified by beam tests. Precision of the scanned beam position was less than {+-}0.5 mm. By cooperating with the planning software, the authors verified the homogeneity of the deliveredmore » field within {+-}3% for the 3D delivery. This system took only 20 s to deliver the physical dose of 1 Gy to a spherical target having a diameter of 60 mm with eight rescans. In this test, the average of the spot-staying time was considerably reduced to 154 {mu}s, while the minimum staying time was 30 {mu}s. Conclusions: As a result of this study, the authors verified that the new scanning delivery system can produce an accurate 3D dose distribution for the target volume in combination with the planning software.« less

Carbon ion radiotherapy has been conducted since 1994 at National Institute of Radiological Sciences, Japan, with beams from Heavy Ion Medical Accelerator in Chiba. Accumulated number of patients treated will become more than 5,000 by the end of this year. The tumor sites with more than 200 treated patients include Prostate, Lung, Head and Neck, Bone and Soft Tissue, and Liver. The experience of 15 years can be summarized as that carbon ion therapy has established efficacy in treatment of tumors, especially so-called ‘radio-resistant’ ones and including ‘inoperable’ cases. Reduction of fractionation, and thus treatment period, is another important achievement which can benefit patients in many ways. Recent development of the therapeutic system in order to advance more efficient and patient-friendly treatments will be presented also.

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.

A 70-year-old man on antiplatelet therapy developed sudden severe back pain in his neck with numbness and weakness in his extremities. On admission, he presented with complete quadriplegia, hypoesthesia, and anuria. Magnetic resonance imaging (MRI) revealed cervical cord compression due to an epidural hematoma posterior to the spinal cord and intramedullary hyperintensity. Surgical evacuation was performed about 12 hours after the onset, but the recovery of neurological deficits was poor. After performing 2 additional administrations of steroid pulse therapy, the patient's motor dysfunction began to improve and spinal MRI showed a recovery as well. These observations suggest that steroid administration should be considered as a post-operative additional therapy for cases with severe neurological deficits even after surgery.

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

X-rays emitted from Ar 17+ , Fe 24+ and Kr 35+ ions of about 400 MeV/u transmitting through a thin Si crystal of about 20 μm thickness have been measured in a planar channeling condition and compared with those in a random incident condition. We have found that the X-ray yield from Ar 17+ ions is larger for the channeling condition than for the random incidence, while those from Fe 24+ and Kr 35+ ions are rather smaller. Such tendencies are explained by considering the projectile dependences of excitation and ionization probabilities together with X-ray emission rates. A crude simulation has qualitatively reproduced these experimental results. When the crystal thickness is small, the X-ray yield is smaller in the channeling condition than in the random incident condition, because excitation is depressed. However, for thicker crystals, the X-ray yield is larger, since the survived population of projectile-bound electrons is larger due to small ionization probabilities under the channeling condition. This inversion occurs at a specific crystal thickness depending on projectile species. Whether the thickness of the used crystal is smaller or larger than the inversion thickness determines enhancement or depression of the X-ray yield in the channeling condition.

The time structure of extracted beams has been improved in synchrotron rings with resonant slow-extraction including RF-knockout extraction. In order to control the global spill structure in the RF-knockout slow-extraction method, it is necessary to improve the amplitude modulation (AM) function of the transverse RF-field. For this purpose, a scheme with a simple model of the extraction process has been proposed. Using this simple model, an analysis was carried out for determining the parameter relevant to the diffusion process in the separatrix. With this parameter, the new AM function obtained by the analytical approach could provide a flat spill within ±23% in both a simulation and an experiment at the HIMAC synchrotron. Cooperating with the feedback system, the global spill structure was significantly suppressed to be less than ±5%.

Energetic ions traveling through a single crystal are excited by an oscillating crystal field produced by a periodic arrangement of the atomic strings/planes, which is called Resonant Coherent Excitation (RCE). We have observed enhancement of convoy electron yields associated with RCE of 1s electron to the n=2 excited states of 390 MeV/u hydrogen-like Ar17+ ions passing through a Si crystal in the (2 2 0) planar channeling condition. Lost electrons from projectile ions due to ionization contribute to convoy electrons emitted in the forward direction with the same velocity as the projectile ions. With combination of a magnet and a thick Si solid-state detector, we measured the energy spectra of convoy electrons of about 200 keV emitted at 0°. The convoy electron yield as a function of the transition energy, i.e. the resonance profile, has a similar structure to the resonance profile observed through the ionized fraction of the emerging ions. It is explained by the fact that both enhancements are due to increase in the fraction of the excited states from which electrons are more easily ionized by target electron impact in the crystal than from the ground state.

A resonant slow-extraction method from synchrotron rings has been successfully developed in order to deliver a beam for a period of over several seconds. In the resonant slow-extraction method, an optimization of the parameters is necessary in order to keep the beam size and position constant during the extraction for sufficient use of the extracted beam. For this purpose, a simple method to measure the outgoing separatrix was proposed and verified at the HIMAC synchrotron. In this method, two tantalum rods each with diameter of 1 mm are used as internal probes located near the extraction channel. By observing the extracted beam under the rods inserted into the ring, the outgoing separatrix can be measured. This technique will significantly contribute to the operation of a synchrotron employing resonant slow-extraction.

X-rays emitted from resonant coherently excited (RCE) n =2 states of 390 MeV/amu hydrogen-like Ar 17+ ions were observed under planar channeling in a Si crystal. The resonance profiles for X-ray emission consisting of two peaks for j =1/2 and j =3/2 are characterized by suppression of the j =1/2 peak. The degeneracy of the n =2 states are removed by Stark effect due to the static crystal field. The RCE probability of these Stark splitted substates differs, reflecting the polarization of the oscillating crystal field. However, the associated alignment was not clearly observed. It is explained by the fact that both polarization of the oscillating crystal field and the wave functions of Stark-mixed n =2 states depend on the distance from the channel center, and the X-ray emission is preferred in a channel center in a crystal.

Two advanced RF-knockout (RF-KO) slow-extraction methods have been developed at HIMAC in order to reduce the spill ripple for accurate heavy-ion cancer therapy: the dual frequency modulation (FM) method and the separated function method. As a result of simulations and experiments, it was verified that the spill ripple could be considerably reduced using these advanced methods, compared with the ordinary RF-KO method. The dual FM method and the separated function method bring about a low spill ripple within standard deviations of around 25% and of 15% during beam extraction within around 2 s, respectively, which are in good agreement with the simulation results.

Our previous study revealed that the use of radiological technology in medicine was spreading in Japan. For example, in 1991, the economic scale was about 10b$ (billion dollars, 1$=121¥) corresponding to 4% of the national health expenditures (240b$) or 0.24% of the nominal GDP (gross domestic products, 4,231b$). This time, the economic scale was compared between Japan and the U.S.A. within limited parameters. (1) For the TDHE (total domestic health expenditures) base, it was 981b$ in the U.S.A. and 219b$ in Japan, implying that the American people spent rather much money for their health. (2) For the economic scale estimated by studying parameters (ESP), approximately 49b$ for the U.S.A. and 12b$ for Japan. ESP in the former is large in magnitude by a factor of 4, implying that U.S.A. people do not hesitate to use radiological technologies for curing their diseases. This tendency was clearly observed by the expenditures on prostate cancer and the FDG-PET and so on. (3) The ratio between ESP and GDP withi...

A non-destructive beam-profile monitor employing micro-channel plates and a resistive anode that can be applied to a detector has been developed. The monitor works by a method of charge division to determine the spatial position for an event of residual gas ions on a detector. Two monitor units for measuring the transverse horizontal and vertical density distributions of a circulating beam were installed in the HIMAC synchrotron. The monitor has been used for an electron-cooling experiment with a spatial resolution of less than ±0.38 mm, as well as for studies of beam dynamics under routine operation in the synchrotron. The design and reliability of the monitor as well as some results of the performance are described.

We measured the emerging charge-state distribution of hydrogen-like 390 MeV/u Ar 17þ ions planar channeled in a silicon surface barrier detector for the DE measurement, and observed their energy deposition in the detector simultaneously. We simulated the energy loss spectrum of specific emerging charge state, and succeeded in reproducing it with an adjusting parameter for the cut-off momentum transfer between close and distant collisions. 2002 Elsevier Science B.V. All rights reserved.

A prospective sequential MRI study was done to investigate the morphologic changes of the lumbar disc hernia (LDH). We also studied the relationship between the MRI changes and the type of LDH and the clinical outcome. MRI was performed every 3 months from the onset for a maximum of 24 months in 42 patients with radicular leg pain and symptoms definitely diagnosed as caused by LDH. The size of the herniated mass was determined by the ratio of the anteroposterior diameter of the spinal canal to the maximum diameter of the LDH mass on T2-weighted axial images. The clinical outcome was evaluated as excellent, good, or poor depending on leg pain and physical findings. The JOA (Japanese Orthopaedic Association) score for LDH was also used to assess the outcome. Thirty-seven (88%) of the 42 patients showed >50% reduction of the hernia on MRI 3–12 months after onset, and the morphologic changes of the herniated mass were well correlated with the clinical outcome.

A prototype non-destructive beam-profile monitor employing tandem-type MCPs has been designed and tested at HIMAC. The monitor can measure the vertical beam profile of a circulating ion beam in the synchrotron. In a series of tests, however, it was found that the monitor had a defect in the accuracy of the measured profiles. It was caused by an electric field distortion in the work area. The electric field was improved so as to create a uniform equipotential distribution with the aid of a 3D-field simulation code. The field-shaping electrodes were replaced to longer ones, and the applied voltages of each electrode were changed to the optimum values. The monitor has been successfully used for studies of electron cooling as well as monitoring the beam under normal-mode operation in the HIMAC synchrotron.

Resonant coherent excitation (RCE) of 390 MeV/u hydrogen-like Ar 17a ions planar channeled in a Si crystal was investigated through measurements of the de-excitation X-rays as well as the charge state distribution of the transmitted ions. We observed enhancements of both the fraction of ionized Ar 18a ions and the intensity of the de-excitation X-rays under the RCE condition. The na 2 states of Ar 17a in the crystal are split into four energy levels due to spin‐orbit interaction and Stark eAect induced by the planar potential of the crystal. The intensities of the X-rays from the lower two levels were found to be smaller compared with those from the higher two levels, which is explained by the dominance of the 2s component not decaying via a single photon emission. The diAerence between the resonance profiles of the charge state and the X-ray reflects the nature of na 2 states in the crystal field. ” 2000 Elsevier Science B.V. All rights reserved.

An RF acceleration system, in which digital control with a direct digital synthesizer (DDS) is applied, has been developed for the Heavy Ion Medical Accelerator in Chiba (HIMAC) synchrotron. This digital system allows us to obtain stable operation of the acceleration system over a wide frequency range from 1.04 to 7.9 MHz. In this paper the designed digital RF control system and its performance are described.

High-intensity, high-quality beams originating from the electron-cooling method will be utilized for medical and other application at HIMAC. As a first step, an electron cooler with an adiabatic expansion factor of 10 has been designed and is under construction at HIMAC. So far, field measurements of the cooler have been completed. In this paper, the present status of the electron cooler under construction is described, and plans of medical and other application by using the electron-cooling method at HIMAC are presented.

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.

Resonant coherent excitation of the 1s electron to na 2 states in a hydrogen-like ion was studied through measurements of the survived fraction of 390 MeV/u Ar 17a planar channeled in a Si crystal. Adopting a totally depleted Si surface barrier detector as a target crystal, the charge state of the individual emerged ion was measured in coincidence with the energy deposition in the target. By changing the incident direction along theO2 20 U ,O 004 U, andO1 11 Uplanes, a series of clear resonances were observed as the decrease in the survived charge fraction due to higher electron loss probability for the excited state. Each resonance profile reflects energy splitting of the na 2 manifold originated from l‐ s interaction and Stark eAect due to the crystal field. From the correlation between the energy loss and survived charge fraction, transition energy as a function of the ion trajectory amplitude is deduced which is in good agreement with calculated results. ” 1998 Elsevier Science B.V. All rights reserved.

Continuum X-rays emitted from Be- and C-targets bombarded with 75-290 MeV/u C6+ ions were observed with an HPGe detector placed at 90\(\) to the beam direction. In all spectra two components could be clearly distinguished: Radiative Electron Capture into Continuum (RECC) forming a characteristic edge, and Secondary Electron Bremsstrahlung (SEB) which dominates at high photon energies. The shape of the spectra was compared to a theoretical description. A special emphasis was given to the details of the RECC edge. It has been found that at the highest projectile energy of 290 MeV/u, in opposite to the lower beam energies, the detailed structure of this edge cannot be reproduced satisfactory within the approach applied.

Results are reported on precise measurements of the weak-decay processes of Λ 4 H and Λ 4 He hypernuclei formed via the 4 He (K stopped − , π − ) reaction. The lifetimes of Λ 4 H (194 −26 +24 ps) and Λ 4 He (256 ± 27 ps) were obtained. The π 0 and π − decay branching ratios of Λ 4 He (0.515 ± 0.035 and 0.322 ± 0.034, respectively) were precisely determined and they are compared with recent theoretical estimates and related experimental values. Our results favor a Λ-nucleus interaction with an inner repulsive core. The non-mesonic weak decay widths of Λ 4 H and Λ 4 He are reexamined on the basis of our measurements and updated knowledge of the mesonic decay processes. It is found that the non-mesonic decay of Λ 4 He predominantly takes place via the Λ + p → n + p process.

We observed resonant coherent excitation (RCE) of 1s electron to n=2 states in Ar17+ through measurements of the survived fraction of 390 MeV/u hydrogen-like Ar17+ channeled in a Si crystal. We adopted a totally depleted Si surface barrier detector as a target crystal as well as a probe of the energy deposition. The charge state of emerged ions was measured by a combination of a charge separation magnet and a 2D-position sensitive detector. We observed the RCE for planar channeled ions by tilting the target Si crystal from the direction of [1 1 0] axis in the (2 2 0) , (0 0 4) , and (1 1 1) planes. Prominent resonances at tilt angles under the resonance condition were observed. Moreover, each resonance profile is split into several lines due to the l·s interaction and the Stark effect originating in the static crystal field. The energy deposition in the crystal gives the information of the amplitude of the ion trajectory. The resonance peak position, intensity and width in the survived fraction of Ar17+ reflect the position dependent strength of the crystal field, the RCE and the electron loss probabilities. They are in good accord with our calculation of the transition energy and probability.

We have succeeded in observing the channeling of 290 MeV/u C 6+ ions in a Si crystal. Under 〈1 1 0〉 axial, and (0 0 4), (2 2 0) and (1 1 1) planar channeling conditions, energy loss of the channeled ion in the Si crystal was observed. We also calculated the trajectory dependent stopping power for planar channeling ions, which employs mean and local electron densities evaluated adopting the Moliere potential. Calculated energy loss spectra were found to reproduce the experimental results quite well.

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.

Continuum x rays originated from radiative electron capture into continuum states (RECC) of relativistic Ne{sup 10+} ions have been observed. It has been found that the intensities of x rays decrease as their energy increases and the observed spectra show a clear edge which corresponds to the maximum energy transferred to free electrons under energetic projectile-ion collisions. The edge becomes dramatically sharp as the incident projectile energy decreases from 290 to 75 MeV/amu, indicating that the cross sections for RECC sharply increase at low projectile energies, which is in agreement with the theoretical expectation. {copyright} {ital 1997} {ital The American Physical Society}

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.

Selective production of the doubly excited state in 464 MeV/u He-like Ar${}^{16+}$ ions was accomplished using three-dimensional resonant coherent excitation in a thin foil of silicon crystal. Through a coherent interaction with the periodic crystal field, the Ar${}^{16+}$ ions were resonantly excited sequentially from the ground state to the $1s2p$ (${}^{1}\phantom{\rule{-0.16em}{0ex}}P$) state and then $2{p}^{2}$ (${}^{1}\phantom{\rule{-0.16em}{0ex}}D$) state in a way analogous to two-color x-ray laser excitation. The periodic crystal fields of 10${}^{11}$ V/m in the projectile's frame are equivalent to the fields generated by x-ray lasers with photon energies of 3139.55 and 3286.95 eV and an energy flux of 10${}^{16}$ W/cm${}^{2}$. We confirmed the doubly excited state formation through observation of the subsequent collisional ionization, Auger ionization, and radiative deexcitation.

A project to construct a new treatment facility, as an extension of the existing HIMAC facility, has been initiated for the further development of carbon-ion therapy at NIRS. This new treatment facility is equipped with a 3D irradiation system with pencil-beam scanning. The challenge of this project is to realize treatment of a moving target by scanning irradiation. To achieve fast rescanning within an acceptable irradiation time, the authors developed a fast scanning system.In order to verify the validity of the design and to demonstrate the performance of the fast scanning prior to use in the new treatment facility, a new scanning-irradiation system was developed and installed into the existing HIMAC physics-experiment course. The authors made strong efforts to develop (1) the fast scanning magnet and its power supply, (2) the high-speed control system, and (3) the beam monitoring. The performance of the system including 3D dose conformation was tested by using the carbon beam from the HIMAC accelerator.The performance of the fast scanning system was verified by beam tests. Precision of the scanned beam position was less than +/-0.5 mm. By cooperating with the planning software, the authors verified the homogeneity of the delivered field within +/-3% for the 3D delivery. This system took only 20 s to deliver the physical dose of 1 Gy to a spherical target having a diameter of 60 mm with eight rescans. In this test, the average of the spot-staying time was considerably reduced to 154 micros, while the minimum staying time was 30 micros.As a result of this study, the authors verified that the new scanning delivery system can produce an accurate 3D dose distribution for the target volume in combination with the planning software.

Results are reported on a lifetime measurement of Λ4H formed in 4He (stopped K−,π°) reaction. Decay of Λ4H was clearly identified by observing the monochromatic π− peak from the two-body decay ( Λ 4 H → 4 He + π − p x =132.9 MeV/c ). The lifetime of Λ4H was determined to be τ(Λ4H) = 194−26+24 ps from a distribution of time difference between the K− injection and π− emission.

A heavy ion synchrotron complex for medical use is being constructed at Chiba, Japan. General feature and present status of this project are described.

Proton knockout reactions on carbon isotopes, p(9–16C,2p)8‐15B, at 250MeV/A were performed for systematic information on weakly to strongly bound 1p valence protons and deeply bound 1s protons. Various information such as energy gap between 1s and 1p orbits, widths of momentum distributions for 1s and 1p orbits, relative (p,2p) yields are obtained.

We report on the selective production of the 2s metastable state of 390-MeV u−1 H-like Ar17+ ions by the resonant coherent excitation (RCE). The RCE to the 2s state was achieved by using Stark mixing of n = 2 states under planar channeling conditions in a 1-m thick Si crystal. The population of the 2s state was quantitatively estimated from the ionization probability in a stripper foil installed 50 mm downstream of the crystal. The 2s population was found to be 0.05 of the total number of Ar17+ ions at the stripper. The result is in good agreement with a theoretical calculation performed with the density matrix approach.

We have experienced acase of extradural cyst in the thoracolumbar resion. The case was a 61 year old female suffering from urinary disturbance and palsy of the perineal area. MRI and myelogram showed a cystic lesion located at the posterior part of the spinal canal and compressing the spinal cord at the Th12 L3 levels. Intra-operative findings, indicated that the cyst communicated with the subaracnoid space. After extirpating the cyst, it is necessary to clear the communicating fissure and repair the weakend or defected dura to prevent the recurrence of the cyst. The patient fully recovered from her palsy and urinary disturbance.

We present a joint experimental and theoretical study of convoy-electron emission resulting from highly-charged-ion transport through carbon foils at moderately relativistic speeds. Energy spectra of electrons ejected at $0\ifmmode^\circ\else\textdegree\fi{}$ have been measured for 390 MeV/u hydrogen-like ${\mathrm{Ar}}^{17+}$ ions and 460 MeV/u $(\ensuremath{\beta}=v/c=0.74,\ensuremath{\gamma}=1.49)$ ${\mathrm{Fe}}^{25+}$ $(1s),$ ${\mathrm{Fe}}^{24+}$ ${(1s}^{2}),$ and ${\mathrm{Fe}}^{23+}$ ${(1s}^{2}2s)$ incident on carbon foils with thicknesses from 25 to $8700\ensuremath{\mu}{\mathrm{g}/\mathrm{c}\mathrm{m}}^{2}.$ Due to this unprecedented wide range of thicknesses, the sequential excitation and ionization of initially deeply bound electrons to highly excited states and continuum states can be followed in considerable detail. The analysis of the spectra is aided by simulations based on the classical transport theory which has been extended to relativistic energies and to multielectron projectiles. The motion of the projectile electron inside the solid target is calculated taking into account the Coulomb potential of the projectile ion and the multiple stochastic collisions with target cores and target electrons. Different phases of the convoy-electron emissions can be disentangled: direct ejection to the continuum, the transient buildup of an excited-state wave packet followed by ionization, and postionization modification of the continuum spectrum. We find good agreement between experiment and simulation for the evolution of charge states and the emission spectrum.

HIMAC, the Heavy Ion Medical Accelerator in Chiba, is the first heavy ion accelerator dedicated to medical applications. The two 800 MeV/u synchrotron rings are controlled by a computer system. Testing in part has been started and preliminary results are successful. The testing of the whole control system is scheduled to be completed by the end of October 1993.

An extremely-thin Germanium crystal (0.8 μm-thick) has been firstly exploited in the resonant coherent excitation (RCE) experiment. The 460 MeV/u H-like Fe25+ ions were incident on the Ge crystal under the (220) planar channeling as well as non-channeling conditions. The RCE from 1s to 2p1/2 and 2p3/2 states were successfully observed as an enhancement of the x-ray fluorescence.

We treated a patient with giant schwannoma of the back. The tumor measured 35 x 25 x 12 cm and weighted 1840 g. Histological diagnosis was benign schwannoma. To our knowledge, there is no previous report of such a large schwannoma of the back.

We studied the anisotropy of Ly-α x-rays from H-like Ar17+ ions excited by polarization-controlled resonant coherent excitation. The effects of fine-structure depolarization on the 2p1/2 and 2p3/2 states were experimentally demonstrated as a reduction in anisotropy of decay radiation.

We demonstrate the alignment of H-like and He-like heavy ions by three-dimensional resonant coherent excitation in a thin crystalline target. The projectile ions experienced a linearly polarized oscillating field in a crystal and were excited to a specific magnetic substate, forming the aligned 2P state. We prepared the different directions of the aligned states and observed the anisotropy of deexcitation x-ray emission, which was in good agreement with theoretical estimates.

We exploited the double resonance technique in three-dimensional resonant coherent excitation to the production of hollow He-like and Li-like heavy ions. The two K-shell electron were sequentially excited to the L-shell using two frequency components of the oscillating fields arising from the different arrays of atomic planes in a Si crystal.

Convoy electrons emitted from 416 MeV/u heliumlike Ar16+ ions excited by three-dimensional resonant coherent excitation (3D-RCE) have been explored. The 1s electron in the ground state was excited to the 2p state by a periodic crystal field during the passage through a Si crystal and released into the continuum by collisions with target atoms to form a cusp-shaped peak in the energy distribution, referred to as convoy electron. Under the resonance condition, we found not only enhancement of the convoy electron yield but also significant narrowing in the energy distribution, reflecting the initial bound state momentum distribution of the excited ions. This suggests that RCE is well-suited to study fast ion collisions involving the specific excited state.

We investigated resonant coherent excitation (RCE) of 445 MeV/u Li-like Ar15+ under the planar channeling and non-channeling conditions. The K-shell and L-shell excitations are observed as decreases in the survival fraction of the Ar15+ ions after passing through a thin Si crystal. RCE under the planar channeling condition provides the opportunity to study a strong static Stark effect on the Li-like system with K-shell or L-shell vacancy. Under the non-channeling conditions, the observed excitation energies and the reported theoretical calculations were in reasonable agreement.