Jun Ikebe

An articulated neurosurgical navigation system using MRI and CT images

Neurosurgical operations sometimes involve difficulties in finding out the real positions of small-size neoplasms shown on tomographical images. The articulated navigation system, with the aid of a computer, gives ongoing positional correspondence between the position in the patients brain and the one in the tomographic images to assist neurosurgery.<<ETX>>

A Simulation Study of Intracranial Pressure Increment Using an Electrical Circuit Model of Cerebral Circulation

An electrical circuit model of the cerebral circulation is presented. Changes of pulsatile waves of the intracranial pressure (ICP) and the cerebral blood volume (CBV) with ICP increment were investigated by simulation of the cerebral blood flow using this model. The simulation is performed by a small signal approximation using the pulsatile component. The results obtained are able to explain the phenomenon of changes in pulsatile wave of ICP with ICP increment. With regard to the CBV, the modeling results are useful for application to rheoencephalography (REG) using electrical impedance method for noninvasive ICP monitoring.

Computer Aided Analysis of Cell-Cycle Phase from Cytophotometric Histogram

A method for estimating, from cytophotometric data, the proportion of cells in three different phases of the cell cycle is proposed. Computation is done by means of determining seven parameters in the approximate function for the fluorescence intensity histogram. The proportion of cells in the GI, S, and G2-M phases, obtained by this method, was found to be reliable.

Detection and Analysis of Cranial Bruit

A method of detecting cranial bruits produced by turbulent blood circulation in the head is presented. The acoustic properties of the head were examined in order to design and evaluate a direct-contact-type phonodetector using an accelerometer. The detection apparatus described here can be applied to any part of the head and is able to detect weak bruits over the frequency range of 100 Hz-3 kHz. It has fairly simple frequency characteristics. Spectral and coherence analyses made on bruits recorded by the detection apparatus indicated the possibility of noninvasive diagnosis of intracranial vascular lesions, especially for detecting aneurysm in mass examinations.

New tetrapolar circuit method using magnetic field for measurement of local impedance change in biological substances

A tetrapolar circuit and method using a magnetic field is proposed for measuring the local electric impedance change in living tissue. On the basis of this method, the authors designed an apparatus that can detect impedance changes in two closely situated parts of living tissue, simultaneously and independently. Using this apparatus, they showed the effectiveness of the proposed method by an in vitro experiment and by an in vivo measurement of pulsatile waveforms in the forearm arteries. The detection sensitivity for a local impedance change was confirmed to be higher than that of the conventional tetrapolar method. Pulsatile impedance waveforms measured in the radial and the ulnar parts of the forearm were consistent with those estimated from the anatomical structure.<<ETX>>

Quantitative Evaluation of Saccadic Eye Movement Disorders Under Random Visual Stimuli on CRT

A computer aided saccadic disorder examination system for clinical use is presented. Eye movements are stimulated by an M-sequence-controlled moving target on a CRT and the degree of saccadic disorder is evaluated by estimating a linear discriminant function, via procedures of cross-correlation analysis and age compensation.

ICP Measurement of Hydrostatic Pressure Balance Method

The hydrostatic pressure balance method was developed and introduced in the present monitor for high precision epidural measurement of the ICP. To eliminate any potential errors caused by tension on the dura mater, we have developed a completely new pressure transmission method by using a coplanar contact, which has been created with a soft and thin detector pouch. In addition, we have utilized a separately installed pressure transducer which is connected to the detector through a non-elastic tube. This makes the measurement accurate, as it is not affected by the rotation of the patient’s head as conventional monitors were. We also confirmed experimentally that this measurement is hardly affected by the existence of small Particles or blood clots between the contacting surfaces of the dura mater and the pouch. What has to be emphasized finally is that the detector pouch is inexpensive, disposable and thereby infection-free, and after usage, is easily extractable without the necessity of any surgical procedure.

New tetrapolar method using magnetic field for local impedance measurement

The tetrapolar circuit method has been used to detect physiological events as changes in electrical impedance. However, it is still difficult to obtain more meaningful information of local events because of the expanse of current distribution. In order to measure the local impedance change in living tissue, the authors propose a tetrapolar circuit method using a magnetic field. In this method, an eddy current generated in the living tissue by the magnetic field is used in addition to the constant current. The current distribution can be restricted to a local area by combining the eddy current with the constant current. The effectiveness of this method was confirmed by in-vivo measurement of pulsatile waveforms due to the arterial blood flow in the forearm.<<ETX>>

Intracranial measurements for neurosurgical aid

The authors point out that although computed tomography (CT) techniques have changed diagnostic procedures in neurosurgery extensively, complementary technologies covering CTs weak points are needed to treat to overcome intracranial diseases. They report on two areas they have been working in that are related to intracranial measurements: measurement of cranial bruit and computer-assisted surgical navigation. In the measurement of cranial bruit the authors tested their new detectors on eleven patients, including five aneurysm cases and four AVM (arteriovenous malformation) cases, and detected the bruit in six patients. The detectors showed better performance, especially at the low-frequency range, than displacement-type detectors. Since the bruit measurement is completely noninvasive, it can be easily introduced into health care examinations. The navigation system developed consists of an articulated pointer, a display apparatus and a personal computer which calculates the position of the pointer on the brain and overlays this position on the tomographic images.<<ETX>>

Noise elimination procedure for scale bed signals using a microcomputer

透析患者の体内水分量をモニターするのにスケールベッド方式は輸液や不感蒸泄分も包括的に測定しうるという長所を持つが, 反面ベッド上に不用意に載せられる衣類, 器具等による偏差や, 術者の接触, 患者の体動によるノイズ等を含むために, 臨床上の信頼度は必ずしも高いものではなかった. 特に前者の偏差は通常のフィルタ操作では取り除くことのできないものである. 今回, 我々はこれらのノイズ信号の単位時間当りの変化量が生体自身の体重変化量に較べて著しく大であり, しかも全透析時間に比べてごく短時間にしか混入しないという事実を利用して, 信号の変化量の大小によってゲートを開閉する雑音除去機構を提案し, Differential Limitterと名付けた.本機能ブロックはマイクロコンピューターのソフトウェアで容易に実現することができるがこの場合に必要なパラメーターの設定方法について考察し, サンプリング間隔の短縮はかえって雑音と信号との識別を悪化させること, 長い時定数の低域濾波回路を前段に挿入するのが不利なことなどを示した. 試作装置は8ビットマイクロコンピューター8085と信号入力用のA/D変換器, ペンレコーダー出力用のD/A変換器から構成され, 実際の臨床使用では数%の誤差で安定な出力信号を得ることができた.本方法によれば患者の体動による瞬時的雑音だけではなく, ベッド上の雑物による定常的誤差をも自動的に除去でき, より正確な体内水分量管理が行える.