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ITER is the first worldwide international project aiming to design a facility to produce nuclear fusion energy. The technical requirements of its plant systems have been established in the ITER Project Baseline. In the project, the Reliability, Availability, Maintainability and Inspectability (RAMI) approach has been adopted for technical risk control to help aid the design of the components in preparation for operation and maintenance. A RAMI analysis was performed on the conceptual design of the ITER Central Safety System (CSS). A functional breakdown was prepared in a bottom-up approach, resulting in the system being divided into 2 main functions and 20 sub-functions. These functions were described using the IDEF0 method. Reliability block diagrams were prepared to estimate the reliability and availability of each function under the stipulated operating conditions. Initial and expected scenarios were analyzed to define risk-mitigation actions. The inherent availability of the ITER CSS expected after implementation of mitigation actions was calculated to be 99.80% over 2 years, which is the typical interval of the scheduled maintenance cycles. This is consistent with the project required value of 99.9 ± 0.1%. A Failure Modes, Effects and Criticality Analysis was performed with criticality charts highlighting the risk level of the different failure modes with regard to their probability of occurrence and their effects on the availability of the plasma operation. This analysis defined when risk mitigation actions were required in terms of design, testing, operation procedures and/or maintenance to reduce the risk levels and increase the availability of the main functions.

ITER is the first worldwide international project aiming to design a device that proves the physics and technological basis for fusion power plants to produce nuclear fusion energy. In the project, the RAMI approach (reliability, availability, maintainability and inspectability) has been adopted for technical risk control to guide the design of components in preparation for operation and maintenance. RAMI analysis of the ITER central interlock system (CIS), which shall provide investment protection for the ITER systems was performed on the conceptual design. A functional breakdown was prepared in a bottom-up approach, resulting in the system being divided into 5 main functions and 7 sub-functions which are described using the IDEFO method. Reliability block diagrams (RBDs) were prepared to estimate the reliability and availability of each function under stipulated operating conditions. Initial and expected scenarios were analyzed to define risk-mitigation actions. The inherent availability of the ITER CIS expected after implementation of mitigating actions was calculated to be 99.86% over 2 years, which is the typical interval of the scheduled maintenance cycles. A failure modes, effects and criticality analysis (FMECA) was performed to initiate risk mitigation action. Criticality matrices highlight the risks of the different failure modes with regard to the probability of their occurrence and impact on operations. It was assessed that the availability of the ITER CIS, with appropriate mitigating actions applied, meets the project availability requirement for the system.

Most of ITER's diagnostics will be provided with viewing lines (optical, microwave, spectroscopic) for the monitoring of key characteristics of the plasma or for the achievement of physical measurements inside the vacuum vessel. For many of them the nature of the physical signal transmitted through the viewing lines requires the implementation of window assemblies incorporating either Glass/Ceramic or Beryllium window. The main requirements of the Diagnostic Window Assemblies are the transmission of the signals without attenuation or disturbances, the containment of vacuum, the confinement of in-vessel radioactive materials. Although they are generally not in direct viewing of the plasma, they are exposed to severe environmental conditions in normal and accidental conditions. The concept chosen for ITER Diagnostic Window Assemblies is based on a system of two windows with a monitored interspace, largely inspired from previous large machine solutions. Such a system is able to satisfy the transmission and vacuum requirements. Although this capability has previously proven a high reliability level, ITER conditions, which are more stringent, impose the requirement for improvement of existing designs and even the development of novel solutions, in particular to assure the radioactive material confinement function, which must be met in all circumstances including all off-normal conditions. Moreover the qualification of these concepts shall meet the nuclear safety requirements, although non metallic and beryllium components are not covered by existing codes and standards. This paper presents designs of window assemblies for different diagnostics. It gives an update of the current R&D programme implemented to solve several technical issues specific to ITER. Finally it presents the approach to the demonstration that safety requirements will be met by these components, involving the development of ITER Practice for replaceable non-metallic windows.

ITER will have a set of 45 diagnostics to ensure controlled operation. Many of them are integrated in the ITER ports. This paper addresses the integration process of the diagnostic systems and the approach taken to enable coordinated progress. An overview of the Port Integration hardware introduces the various structures needed for hosting tenant systems inside ITER diagnostics ports. The responsibilities of the different parties involved (ITER Organization and the Domestic Agencies) are outlined. The main challenges for diagnostic port integration engineering are summarized. The plan for a common approach to design and manufacture of the supporting structures, in particular the Port Plug is detailed. A coordinated design including common components and a common approach for neutronic analyses is proposed. One particular port, the equatorial port 11, is used to illustrate the approach.

ITER is currently the most ambitious project on nuclear fusion research. Its objective is to demonstrate the feasibility of fusion as an energy source for the future. The complexity of the systems required to meet this challenge present many opportunities for omissions or incorrect assumptions. System engineering allows the engineer to deal with such a complexity by developing a Functional Breakdown Structure (FBS). Unlike a Plant Breakdown Structure (PBS), the FBS is a function-oriented tree, not a product-oriented tree. It details operations or activities that have to be performed as needed functions of the architecture, allowing identification of any missing elements, defining the personnel skills required to operate the architecture and managing the machine availability.

In the ITER project, Reliability, Availability, Maintainability and Inspectability (RAMI) approach has been adopted for technical risk control to guide the design of components and the preparation for operation and maintenance. RAMI analysis of the ITER CODAC System, the central plant control system, was performed in the current design available in the conceptual design phase. A functional breakdown was prepared, resulting in the system being divided into 5 main functions themselves divided into sub-functions. The Failure Modes, Effects and Critical Analysis were performed to initiate risk mitigation actions. Criticality matrices highlight the risks of the different failure modes with regard to their probability of occurrence and the impact on the availability. Identified risks exist on the effect on data storage hardware and for computer software. Reliability block diagrams were prepared to estimate the reliability and availability of each function under stipulated operating conditions. The inherent availability of the mandatory functions for the control of plasma experiments with mitigations was calculated to be 99.2% that is higher than the project required value of 98.8%. Compensating provisions are advocated in terms of design, testing, operation procedure and maintenance requirements in order to reduce risk levels.

ITER is the first fusion device designed to continuously process DT (Deuterium–Tritium) plasma exhaust and supply recycled fuel in a closed loop, using a FCS (Fuel Cycle System) which includes tritium plant, vacuum system, and fuelling and wall conditioning systems. In addition, as an important step towards the commercially viable power plant, ITER has an ambitious inherent availability target of 60% for plasma production. To be able to achieve this objective, the potential technical risk which may impact the machine operation was assessed by means of RAMI (Reliability, Availability, Maintainability and Inspectability). Firstly, a functional breakdown of the FCS was performed and critical components associated with its basic functions were identified. Secondly, FMECA (Failure Mode, Effects and Criticality Analysis) was performed to evaluate potential causes of failures and their consequences for the plasma operation. The analysis highlighted two critical functions in the tritium plant, namely storage and distribution performed by SDS (Storage and Distribution System) and isotopic separation performed by ISS (Isotope Separation System). Since the system involves various active components, inherent availability of the system has been finally estimated to be around 74% in DT phase.

The ITER availability objective is to reach for the machine operation in H phase an inherent availability of 60% and an operational availability of 32% assuming three 8 h plasma shifts operating mode and typically 8-month major shutdown after each 16-month experimental campaign. A functional analysis of the overall ITER machine from highest level functions down to main operational functions has been developed. The inherent availability ( A I ) objective of ITER has been defined on the basis of a bottom-up approach and using the results of reliability, availability maintainability and inspectability (RAMI) analyses. The ITER strategy in terms of operational availability ( A O ), Plasma pulse availability ( A P ) and fluence objectives is not only to improve reliability by optimizing the design but also to gain the maximum of operation time by decreasing the scheduled downtime for preventive maintenance and increasing the maintainability of the operational functions, thus decreasing the frequency and the time to maintain or/and to repair.

As the next step in the development of fusion energy, ITER has to be safe, reliable and available whenever needed to produce the experimental data as defined by the scientific program. To ensure th...

イチゴ炭疽病菌の地下部からの侵入感染の可能性を検討するために，病原菌の浸根接種，灌注接種と噴霧接種による子苗の発病を比較した．その結果，浸根接種や灌注接種では，葉の汚斑症状や葉柄の黒斑症状が見られず，葉柄基部が黒変して株全体が萎凋枯死した．これらの株では新根の発生が少なく，根の部分的褐変や黒変が認められた．発病程度は浸根接種株で最も激しく，噴霧接種株がこれに次ぎ，灌注接種株では弱く，病勢進展もやや遅れた．発病株から炭疽病菌を分離した結果，噴霧接種株は葉，葉柄から高率に分離されたのに対し，浸根接種株は葉，葉柄，根冠部および根から高率に分離された．以上の結果から，炭疽病菌は葉や葉柄などの地上部感染だけでなく，根冠部や根からも侵入して感染すると考えられた．育苗培養土としてピートモス，オガクズ，砂土および土壌を入れた鉢をイチゴ発病株に隣接して置き，頭上灌水で管理したところ，ピートモスやオガクズなどの鉢土表面から炭疽病菌が高率に検出され，これらの鉢土に子苗を植え付けると苗が発病した．発病株は葉や葉柄の黒斑症状は認められなかったが，いずれも萎凋症状を呈した．このことから，鉢土中の病原菌が伝染源となり，苗に発病を引き起こすことが示唆された．イチゴ炭疽病菌の分生子で汚染した土壌は，ジエトフェンカルブ・チオファネートメチル水和剤の1000倍液を灌注することにより，高い防除効果が認められた．

Diagnostics play a very important role in the modern Tokamak where optimum performance is essential. To achieve this, the device must be equipped with reliable and robust sensors and instrumentation that allow the operation envelope to be fully explored. Development of these diagnostics to maintain this reliability is necessary. Further to the development, the systems must be integrated in a way that maintains their performance while simultaneously satisfying the key requirements needed for safety and tokamak operation. ITER will have 50 diagnostics; almost all of which are utilized primarily for the real-time operation of the tokamak. While there is still much work to do, to date, significant progress has been made in the development of these systems. The work load for the developments is shared across all the ITER partners. This paper focuses on the challenges for the integration of the systems.

Stiff-man syndrome (SMS) is characterized by fluctuating muscular rigidity and spasm. Recently, antibodies against glutamic acid decarboxylase (GAD), the enzyme catalyzing the synthesis of y-amino butyric acid (GABA), have been detected in SMS patients. An autoimmune mechanism against GAD was thus proposed for the suppression of GABAergic inhibitory interneurons, resulting in rigidity and spasm. We conducted quantitative investigations on the ventral horn of the spinal cord and its GAD immunoreactivity, post mortem, in a SMS patient and four controls. In the spinal cord of the SMS patient, we found a 70%, 33% and 27% reduction (P0.05) in the density of neurons with somal areas of 1000-1500 microm2, 500-1000 microm2, and 0-500 microm2, respectively. The density of neurons with a somal area greater than 1500 microm2 was not reduced, although some neurons in this class showed central chromatolytic changes. The affected muscles exhibited neurogenic atrophy. GAD-like immunoreactivity in the spinal gray matter was not significantly decreased. The density of Purkinje cells, known to contain high amounts of GAD, was not significantly reduced. While the co-occurrence of elevation of anti-GAD antibody in the serum and reduction in the density of small spinal neurons was confirmed, that of smaller alpha-motor neurons and gamma-motor neurons, the qualitative changes in larger alpha-motor neurons, and the preservation of spinal GAD-like immunoreactivity and non-spinal GAD-containing neurons suggest the involvement of factors other than autoimmune mechanisms through anti-GAD antibodies. More diverse mechanisms may be associated in the pathogenesis of SMS.

ITER will explore a plasma parameter envelope currently not available in tokamaks. This will require a set of diagnostics that can follow this envelope. To implement these diagnostics in a reliable and robust way requires development of current techniques in many areas to make them applicable to ITER: they need to be operable in the ITER environment and satisfy the physics and engineering requirements. In some cases, the exploitation of new techniques will be required. While much work has been carried out in this area, significant further work remains to bring the system to implementation.

A RAMI (Reliability, Availability, Maintainability, Inspectability) analysis has been performed for the heating (& current drive) neutral beam (HNB) and diagnostic neutral beam (DNB) systems of the ITER device [1–3]. The objective of these analyses is to implement RAMI engineering requirements for design and testing to prepare a reliability‐centred plan for commissioning, operation, and maintenance of the system in the framework of technical risk control to support the overall ITER Project. These RAMI requirements will correspond to the RAMI targets for the ITER project and the compensating provisions to reach them as deduced from the necessary actions to decrease the risk level of the function failure modes. The RAMI analyses results have to match with the procurement plan of the systems.

The microwave absorption properties of M-type hexagonal ferrite BaFe/sub 12-X/(Ti/sub 0.5/Mn/sub 0.5/)/sub X/O/sub 19/ composite have been investigated. It was found that the complex permeability and /spl mu/'/sub r/ and /spl mu/"/sub r/ induced by the ferrimagnetic resonance can be controlled both in amplitude and along the frequency axis by changing the substitution amount x and the powder mixture ratio. The complex permeability of TiMn substituted ferrite composite was successfully adjusted to the calculated absorption condition, and exhibited a wide absorption bandwidth /spl Delta/f/f=47% in the X-band with a homogeneous single-layer configuration. The mixture of two kinds of ferrite powder exhibited a wider bandwidth of 53% and a simulated model indicates that it should be possible to obtain a further increase.

The microwave absorption properties of M-type hexagonal ferrite BaFe/sub 12-x/(Ti/sub 0.5/Mn/sub 0.5/)/spl times/O/sub 19/ composite have been investigated. An optimized TiMn substituted ferrite composite exhibited a wide absorption bandwidth nearly double that of conventional spinel ferrite composites in the X-band for both normal and 30/spl deg/ oblique incidence. The composite sheet exhibited exactly the expected absorption characteristics and this demonstrated the advantage of utilizing the ferrimagnetic resonance of M-type hexagonal ferrite for microwave absorbers.

The authors discuss the design and implementation of the authentication system called SPLICE/AS in the WIDE (widely integrated distributed environment) Internet environment. SPLICE/AS is designed based on the public-key encryption, and the authentication scheme originally proposed by R.M. Needham and M.O. Schroeder (1978). In order to manage a large-scale network like WIDE Internet, the hierarchical domain-based management scheme is introduced. Currently, the prototype of SPLICE/AS is working on the 4.3 Berkeley UNIX system. To improve the reliability and robustness of SPLICE/AS, the authors are modifying SPLICE/AS and developing a new protocol for database propagation which is discussed. >

Cardiac autonomic neuropathy can be a cause of sudden death in patients with diabetes mellitus. Clinical evaluation methods for diabetic cardiac sympathetic neuropathy have not been established. Using 125I-metaiodobenzylguanidine (MIBG) and streptozotocin (STZ)-induced diabetic rats, we evaluated cardiac sympathetic neuropathy and the effects of aldose reductase inhibitor (ARI).Myocardial MIBG uptake was measured 4 hr after injection in the following groups: control rats, rats treated with insulin or ARI (epalrestat, 100 mg/kg/day) from immediately to 4 wk after STZ injection and rats treated with insulin or ARI from 4-8 wk. Myocardial MIBG distribution and norepinephrine content were evaluated in the control and diabetic rats with or without ARI therapy started immediately after STZ injection.Myocardial MIBG uptake was significantly lower in diabetic rats than in control rats; the reduction was marked in the subendocardial myocardium. Myocardial norepinephrine content was increased significantly in diabetic rats compared with control rats. Decreased MIBG uptake and increased norepinephrine content in diabetic myocardium were completely prevented by insulin therapy started immediately after STZ injection and partially, but significantly, by ARI administered from immediately after STZ injection. Heterogeneous MIBG distribution also disappeared with the ARI therapy. In contrast, diabetic rats treated with insulin or ARI therapy started 4 wk after STZ injection showed no improvement in MIBG uptake.These results suggest that MIBG abnormalities observed in diabetic rats may reflect diabetic cardiac sympathetic neuropathy independently of cardiomyopathy, nephropathy or coronary heart disease secondary to diabetes and that MIBG imaging may be useful for clinical assessment of cardiac sympathetic neuropathy.

Sympathetic nervous system activation is important in the pathophysiology of congestive heart failure. However, little about how the treatment for heart failure may influence myocardial sympathetic nervous activity has been established. In this study, we evaluated effects of cilazapril (CLZ) and verapamil (VER) on myocardial sympathetic nervous activity in cardiomyopathic BIO 53.58 hamsters using [125I]metaiodobenzylguanidine ([125I]MIBG).We used BIO 53.58 hamsters aged 3, 6 and 10 mo and age-matched normal F1b hamsters. We divided BIO 53.58 hamsters into untreated, CLZ- and VER-treated groups. We measured myocardial [125I]MIBG uptakes and norepinephrine concentrations and evaluated the extent of fibrosis and the distribution of [125I]MIBG.The myocardial [125I]MIBG uptake was significantly lower in BIO 53.58 hamsters aged 6 and 10 mo than in age-matched F1b hamsters. Myocardial [125I]MIBG uptake was significantly correlated to myocardial norepinephrine concentration in BIO 53.58 hamsters. Myocardial [125I]MIBG uptake was significantly higher in both of the treated groups than in the untreated group. The extent of myocardial fibrosis was significantly lower in both of the treated groups than in the untreated group. The myocardial [125I]MIBG uptake showed a significant inverse correlation with the extent of fibrosis. Myocardial [125I]MIBG distribution was highly heterogeneous in the untreated BIO 53.58 hamsters, whereas it was homogeneous in the F1b hamsters aged 6 mo and the treated BIO 53.58 hamsters.In BIO 53.58 hamsters, myocardial [125I]MIBG uptake decreased with the progression of cardiomyopathy, and the decreased uptake was improved by treatment with CLZ and VER. Thus, myocardial [125I]MIBG uptake can reflect the effects of treatment on cardiomyopathy, as well as the progression of cardiomyopathy.

This study aimed to survey the effects of removable partial denture (RPD) wearing on periodontal conditions of both abutment and non-abutment teeth. The periodontal conditions changed in the 5 years following RPD placement. Tooth mobility of non-abutment teeth improved despite poor oral hygiene. This improvement might be related to the RPD placement.

We studied myocardial accumulation and clearance of [123I]metaiodobenzylguanidine (MIBG) along with measurements of plasma norepinephrine concentrations.Myocardial imaging with MIBG and plasma norepinephrine concentration measurements were performed in 21 patients with chronic renal failure on dialysis and 11 control subjects. Dynamic acquisitions, begun immediately after MIBG injection, and planar images 15 and 150 min after injection were used to measure early and late myocardial uptake and clearance rates of MIBG from the heart.Early and late MIBG uptake was not significantly different from that in controls but MIBG clearance was significantly more rapid in controls. Based on echocardiographic findings, the patients were divided into three subgroups: those without left ventricular hypertrophy and dysfunction (n = 10), with hypertrophy (n = 4) and with dysfunction (n = 7). Among controls and the three patient subgroups, MIBG clearance was significantly higher in all the subgroups and also was significantly higher in patients with dysfunction than in those without hypertrophy and dysfunction. Plasma norepinephrine levels were significantly higher in patients than in controls and correlated significantly with the clearance rate.MIBG clearance from the heart was rapid in patients with chronic renal failure on dialysis, particularly those with left ventricular dysfunction or hypertrophy, suggesting cardiac sympathetic overactivity in these patients.

The patient was a 35-year-old man with confusional state and headache. Analysis of cerebrospinal fluid (CSF) showed 1,383/mm3 cell count, the protein level of 300mg/dl and glucose level of 42 mg/dl. Cryptococcus neoformans was disclosed by India ink preparation. The cryptococcal antigen test was positive at 1:125 by latex agglutination. The diagnosis of cryptococcal meningoencephalitis was determined. Antifungal treatment with amphotericin B resulted in improvement of neurologic signs, CSF findings and cryptococcal antigen test. But two months later, brain MRI demonstrated low intensity areas on T1 weighted image and high intensity areas on T2 and proton weighted images in the cerebral cortical region. Gd-DTPA MRI showed enhanced areas in the cerebral leptomeninges. It was considered that these MRI lesions corresponded to pseudocysts and Gd-DTPA enhanced lesion indicated dilated vessels or destructed blood-brain barrier. After administration of larger doses of amphotericin B, these lesions on MRI disappeared. It is suggested that brain MRI is useful in diagnosis of cryptococcal meningoencephalitis to detect pseudocysts at the cortical region which may imply the early stage of procrastinating process.

The transplantation of the human T-cell acute lymphoblastic leukaemia (T-ALL) cell line HSB-2 into severe combined immunodeficient (SCID) mice was found to produce a disseminated pattern of leukaemia similar to that seen in man. The intravenous injection of 10(7) HSB-2 cells was associated with a universally fatal leukaemia. Histopathological examination of animals revealed the spread of leukaemia initially from bone marrow to involve all major organs including the meninges. An immunotoxin (HB2-Sap) was constructed by conjugating the anti-CD7 MAb HB2 to the ribosome-inactivating protein saporin. An in vitro protein synthesis inhibition assay revealed specific delivery of HB2-Sap immunotoxin (IT) to CD7+ HSB-2 target cells with an IC50 of 4.5 pM. When SCID mice were injected with 10(6) HSB-2 cells and then treated 8 days later with a single intravenous dose of 10 micrograms of immunotoxin there was a significant therapeutic effect evidenced by the numbers of animals surviving in the therapy group compared with untreated controls (chi 2 = 5.348, P = 0.021). These results demonstrate the useful application of human leukaemia xenografts in SCID mice and the potential therapeutic effect of an anti-CD7 immunotoxin in human T-ALL. Images Figure 1

To evaluate the relationship between regional wall motion and 99mTc-methoxy-isobutyl-isonitrile (MIBI) uptake, ECG-gated single-photon emission computed tomography (SPECT) with 99mTc-MIBI was performed in 20 patients with prior myocardial infarction. The left ventricular images at end-diastole (ED) and end-systole (ES) were divided into 39 segments, respectively. Based on circumferential profile analysis, relative uptake (%EDc, %ESc), percent count increase (% delta C), and normalized percent count increase (% delta Cn) were analyzed in each segment and compared with regional wall motion indices assessed by echocardiography and left ventriculography. ECG-gated SPECT with 99mTc-MIBI provided high contrast tomograms of the left ventricular myocardium. %EDc and %ESc showed good correlations with regional wall motion indices. % delta C and % delta Cn, however, showed lower correlations compared with %EDc and %ESc. In conclusion, high-quality left ventricular images were obtained with 99mTc-MIBI ECG-gated SPECT, but quantitative analysis based on only percent count increase (% delta C) have limitations for evaluation of regional wall motion.

CT findings in primary low spinal fluid pressure syndrome are studied on the basis of 3 cases. Case 1 was a 43-year-old male with a complicated bilateral isodense subdural hematoma (SDH). Case 2 was a 45-year-old female with a complicated bilateral high dense SDH. Case 3 was a 36-year-old female discharged without any complications after spinal fluid pressure normalized. Slight downward displacement of the brain under low spinal fluid pressure is shown as the narrowing of with a Sylvian fissures and infratentorial cisterns on CT. On the other hand in this syndrome with a complicated bilateral isodense SDH, in addition to this finding CT reveals distortion and narrowing of body of lateral ventricles, which may be the differential findings from this syndrome without complicated SDH. Under low spinal fluid pressure, bridging veins are more stretched by a downward displacement of the brain. And consequently they are easily insured and SDH is developed.

A 43-year-old man with no history of trauma or neurosurgical procedure was admitted our hospital because of orthostatic headache made worse in upright position. Spinal fluid pressure was 0 mmH2O, and CT scan revealed wide cortical sulci and ventricles. In the 26th hospital day he had severe headache and CT scan revealed bilateral subdural hematoma, then neurosurgical procedure was done. About 2 months later, he was relieved of the headache and spinal fluid pressure returned to normal. We performed lumbar isotope cisternography and isotope choroid plexography in our case when low spinal fluid pressure and normalized pressure. Isotope cisternography revealed the radioactivity counts decreased rapidly in low pressure and normal in normal pressure. On the other hand isotope choroid plexography was almost no difference between low and normal pressure. Our data suggest that primary low spinal fluid pressure syndrome is not caused by hypoproduction, but by an undetectable leak from a minute tear in a spinal root sleeve or hyperabsorption at the spinal arachnoid membrane.

It has been well established that acquired lesions of the corpus callosum such as surgical section bring about disturbances of interhemispheric transfer of visual information. In contrast, patients with callosal agenesis do not display these specific deficits. The mechanisms of this compensation have been postulated as follows; (1) bilateral development of language function, (2) exploitation of extracallosal commissure fibers such as the anterior commissure. Several studies have reported, however, minor disturbances of interhemispheric visual transfer in callosal agenesis, such as less efficient interhemispheric transfer of complex visual stimuli (GottSaul, 1978), slower reaction time in interhemispheric comparison of visual stimuli (SauerweinLassonde, 1983), or deficits in spatial localization in the right hemi-field (Martin, 1985). In order to settle these issues, we have administered four kinds of tachistoscopic visual recognition tests on 4 patients with complete agenesis of the corpus callosum confirmed by magnetic resonance imaging (MRI). This technique enabled us to see the mid-sagittal plane of the corpus callosum and diagnose its total absence with much higher certainty and precision than previous studies employing computed tomography (CT) or pneumoencephalography. Case 1: A 41-year-old right-handed man visited us because of recurrent numbness in the four extremities. Neurological examination revealed no abnormalities. MRI has confirmed that the corpus callosum was totally lacking, and that the anterior commissure was normally visualized. Case 2: A 31-year-old right-handed man was referred to us for the treatment of partial complex seizure. Total agenesis and lipoma of the corpus callosum was diagnosed by MRI and reconstructed sagittal view of CT scan.(ABSTRACT TRUNCATED AT 250 WORDS)