中川原 実 日本電気三栄(株), 北海道支店・医用電子機器製品本部基本技術部, 課長代理
HONMA Ken-ichi Hokkaido University School of Medicine, Professor., 医学部, 教授 (40113625)
FUKUDA Noriko Hokkaido University, College of Medical Technology, Instructor., 医療技術短期大学部, 助手 (20173354)
YAMAKOSHI Ken-ichi Hokkaido University, The Research Institute of Applied Electricity, Associate Pr, 応用電気研究所, 助教授 (40014310)
NAKAGAWARA Minoru NEC San-Ei, Hokkaido branch, MSD. Acting chief.
|Budget Amount *help
¥11,400,000 (Direct Cost : ¥11,400,000)
Fiscal Year 1991 : ¥900,000 (Direct Cost : ¥900,000)
Fiscal Year 1990 : ¥4,000,000 (Direct Cost : ¥4,000,000)
Fiscal Year 1989 : ¥6,500,000 (Direct Cost : ¥6,500,000)
Recently, polygraphic recordings of EEG together with other biological signals are needed to monitor several kinds of events in unrestricted patients. There is therefore a need to develop an ambulatory system which allows simultancous monitoring of various biological signals including EEG.
This study presents a new ambulatory monitoring system using a digital autio-tape recorder (DAT). The system consists of biomedical sensors, a preamplifier, a recording unit with DAT and a data playback unit. Silver-silver chloride electrodes, respiratory and/or temperature sensors are used to detect biological signals. These signals are amplified using a preamplifier (NEC San-ei, 6R21-KF). After monitoring, the digital data stored in the DAT are retrieved via a D/A converter to be displayed on the CRT monitor or can be recorded using a conventional EEG machine (Polygraph ; NEC San-ei, Synafit). At present, this reproduction is 4 times the recording speed. The playback unit can also be connected to a
personal computer system via an interface (RS232C) in order to analyze the data.
Eight analog signals are converted into digital ones, which are first stored in a RAM buffer (6Mbit) for 8 minutes and then transferred to a data controller within 4 seconds. The appropriately formated data from the controller PCM (Pulse code modulation) are written on to a magnetic tape via a magnetic head driver. This operation is successively and intermittently repeated to obtain a 24 -hour continuous recording.
Specifications of the recording unit thus designed are as follows : 1) frequency response ; DC-100 Hz, 2) sampling frequency ; 200 Hz per channel, 3) size and weight of the unit ; 210(W) x 122(H) x 40(D) mm, 1300 grams. 24-hour continuous recording can be made using two 9 V alkaline manganese batteries.
We have been applying this ambulatory system to normal subjects as well as patients with psychiatric or neurological disorders, for example, epilepsy, hypersomnia, sleep apnea syndrome, sleep wake cycle disorder. Using the ambulatory system, 24-hour monitorings of physiological information were successfully carried out both in the healthy subjects and in the patients at their homes. Sleep pattern and epileptiform abnormalities could be observed in addition to conventional EEG patterns.
The present system using the DAT appears to be an useful and helpful means in the diagnosis and treatment of psychiatric and neurological disorders. This digital recording method allows quite accurate and reliable recording as compared to a conventional analog magnetic recorder.
However, the system will be further improved for practical use in terms of its size and weight, number of recording channels, signal resolution, and speed of data reproduction. Recent advances in micro-electronic and micromachine technology will render to solve these problems. Less