Iekado Shibata

Ruptured aneurysm at a duplicated middle cerebral artery with accessory middle cerebral artery

Summary.Although many cerebral vascular anomalies are widely recognized, others are less well known or unclassified. Accessory middle cerebral artery (MCA) and duplicated MCA are among uncommon anomalies. We present a very rare case of subarachnoid haemorrhage due to rupture of a saccular aneurysm arising from a duplicated middle cerebral artery which was associated with an accessory middle cerebral artery.

Neuropath planner–automatic path searching for neurosurgery

Abstract This paper describes an improvement of automatic neurosurgical path searching algorithm which incorporates the structure of blood vessels. We have proposed an automatic searching method for surgical path planning on neurosurgery to realize minimally invasive operations within the range of soft tissues. This path searching is based on importance values we defined, and an anatomical structure database generated from MRI images and surgeon experiences. This paper introduces blood vessels into the path searching because we cannot give them damages during operation. We first obtain the structure of blood vessels from MRA, then also give them importance values, and finally incorporate the structure into path searching. Experimental results show that the path obtained by the proposed method is better than searching without vessel structure.

Quantitative Cerebral Blood Flow Calculation Method Using White Matter Lambda in Xenon Ct

The objective of this work is to propose a quantitative cerebral blood flow (CBF) calculation method for xenon CT (Xe-CT) by logically estimating the time course change rate (rate constant) of the arterial xenon concentration from that of end-tidal xenon concentration. A single factor, gamma (&ggr;), which is considered to reflect the diffusing capacity of the lung for xenon, was introduced to correlate the end-tidal rate constant (Kend-tidal) with the arterial rate constant (Karterial). When an appropriate value is given to &ggr;, it is possible to calculate the arterial rate constant (calculated Karterial) from Kend-tidal. A procedure was developed to determine the &ggr; value utilizing the characteristics of white matter lambda (&lgr;). This procedure was applied to three healthy volunteers. The &ggr; &ggr;alues for the three subjects were consistent with those directly calculated from end-tidal and arterial (abdominal aorta) xenon data. Hemispheric CBF values with use of calculated Karterial (47.3 ± 10.3 ml/100 g/min) were close to the reported normative values. We conclude this method could make current Xe-CT examinations substantially reliable and quantitative in measuring CBF.

Quantitative multilevel mapping of hepatic blood flow by xenon computed tomography using aorta.

A noninvasive and quantitative technique has been developed to measure human hepatic blood flow by xenon computed tomography (Xe-CT). Accurate data on time-dependent xenon concentrations in the arterial blood are indispensable for Xe-CT to ensure quantitativeness of measured blood flow. A method has been established by our group to use both aorta and end-tidal data to obtain arterial xenon information. Multilevel (3 levels) maps of arterial blood flow (Fa), portal blood flow (Fp), and partition coefficient (&lgr;) were created for patients with chronic hepatitis. A method to objectively evaluate Fa, Fp, and &lgr; values for the whole liver has also been developed by our group.

Automatic path searching for minimally invasive neurosurgical planning

We are developing a neurosurgical planning system, and this paper presents a method of automatic path searching from skin surface of the head to tumor inside the brain. The path obtained by our system is an optimal one in minimally invasive neurosurgery and it is calculated automatically based on a 3D atlas. The 3D atlas is a voxel based 3D matrix, and consists of two parts, structural part and knowledge part. The structural part includes the geometrical information with respect to each tissue. The knowledge part is generated based on experiences of doctors, and numeric value is provided as importance value for each tissue. The path searching consists of two steps, path finding and path smoothing. Path finding is to select an optimal path from surface of the head to the affected part based on minimization of importance value integrating along with the path. We applied the algorithm into a head MRI data set. The path obtained by path finding is reformed smoothly to approach the natural path of surgeon.

Radiologic assay for carbonic anhydrase

Abstract Preliminary experiments with a newly developed radioassay for carbonic anhydrase activity were performed. The velocity of 14CO2 formation from sodium [14C]bicarbonate was determined at both the nonenzymatic and enzymatic stages, and the net 14CO2 formation from the labeled substrate by carbonic anhydrase was calculated from the difference between these velocities. The enzyme activity could be calculated from this net CO2 formation and the 14C specific activity of the substrate. A trial using rat blood homogenates as enzyme samples revealed that the new radioassay could precisely determine the activity of carbonic anhydrase even at the dilution of 1:2000.

Three-dimensional composite images of SPECT/MRI in hydrocephalus

Recently programmable valves have been used in many institutions to prevent complications such as subdural hematoma, subdural hygroma and cerebrospinal fluid (CSF) over-or underdrainage in hydrocephalic patients after shunting operation. However, the valves can’t be used for MRI, and for patients in whom frequent pressure adjustments are necessary or pressure setting is changeable. We investigated performance of three-dimensional (3D) MRI and SPECT for evaluation of therapeutic effects from morphological and functional aspects using the Orbis-Sigma valve system, a shunt system that automatically controls flow of CSF.

A template-based method of ventricle part classification and realistic texturing for virtual ventriculoscopy

A new method for automatic ventricle part subdivision, classification and realistic texturing is proposed to simplify navigation for virtual endoscopy (VE). The method is based on finding distance transformations for input surfaces to fit a template surface. After surface co-registration, each point of the input surface is classified in accordance with the class of the nearest template point and then class-specific textures are applied.

3D Image Based Collaboration System for Telemedicine

This paper described a 3D image based collaboration system for telemedicine. This system enables doctor to observe 3D images transferred from image database through network, and also has collaboration function which operate 3D position of viewing of each doctor by 3D image displaying and data transferring through network. It is constructed based on server client style, and the server has the function of transferring data from a 3D image database and a collaboration record database, and also has control unit of transferring data between doctors during operating the system. The client has a user interface including operation part for parameter selection of viewing and sending comments, and display part for displaying 3D image based on volume rendering and 3D position and direction of observer by suing avatar. Doctors can use this system to do collaboration work by sending comments with viewing 3D image each other. We implement this system in different platforms including UNIX workstation and PC, and also supply Web browser based user interface for considering various user environments. We applied the 3D images of MRI in head for examining the structure of soft tissues and tumor in detail. We also evaluated the performance of the system through network including LAN and Internet, and experimental result shows that this system is useful.