For Measurement of ECG m Yumiko Kimezawa October 14, 2011RPS1
Outline Our Architecture Important Things in Measurement of ECG Signal Book Knowledge Question Requirements for Measurement of ECG Future Work October 14, 2011RPS2
Our Architecture October 14, 2011RPS3 A/D converter FilterRAM Processing Results From patient Sensor Processing results are sent through the Ethernet
Important Things in Measurement of ECG Signal Clinically-important frequency component of ECG signal - 0 ~ 250Hz October 14, 2011RPS4 Change in voltage in chest wall -Less than 3mV (very weak) Measurement in environments with much noise Change in voltage inside this range must be faithfully reproduced Voltage gain of high signal-to-noise ratio (250 to 1000 times) must be gained Signal-to-noise ratio: The ratio of signal power to the noise power
Book Knowledge October 14, 2011RPS5 Impedance converter Lead network Head amplifier Micro computer ADC Main amplifier Isolation circuit Output equipment Lead Code Power Circuit An example of block diagram illustrating cardiography equipment
Book Knowledge October 14, 2011RPS6 Impedance converter Lead network Head amplifier Micro computer ADC Main amplifier Isolation circuit Output equipment Lead Code Power Circuit An example of block diagram illustrating cardiography equipment This circuit prevents body’s impedance from being lower than input circuit’s impedance
Book Knowledge October 14, 2011RPS7 Impedance converter Lead network Head amplifier Micro computer ADC Main amplifier Isolation circuit Output equipment Lead Code Power Circuit An example of block diagram illustrating cardiography equipment Constitution of 12-lead from the combination of sensors A~J : Sensors Example - Ⅰ : Output between A and E -aVR: Output between A and F
Book Knowledge October 14, 2011RPS8 Impedance converter Lead network Head amplifier Micro computer ADC Main amplifier Isolation circuit Output equipment Lead Code Power Circuit An example of block diagram illustrating cardiography equipment ECG signal is very weak The signal must not be amplified suddenly Differential amplifier is used as head amplifier An amplifier is needed The signal is amplified in stages Noises are reduced signal-to-noise ratio is improved
Book Knowledge October 14, 2011RPS9 Impedance converter Lead network Head amplifier Micro computer ADC Main amplifier Isolation circuit Output equipment Lead Code Power Circuit An example of block diagram illustrating cardiography equipment For securing of security, impedance converter, lead network and head amplifier have to be isolated from main amplifier, power circuit and A/D converter
Question A/D converter (AD9254) is included in HSMC -Pipelined switched capacitor ADC -Sampling frequency: 150MHz -Resolution: 14-bit -Power: 430mW October 14, 2011RPS10 HSMC Performance is overmuch Clinically-important frequency component of ECG signal is from 0 to 250Hz 500Hz is enough for sampling frequency Using a lot of electricity Conversion process is complex Using A/D converter in HSMC is of questionable value
Requirements for Measurement of ECG An amplifier is needed Securing of security also have to be considered October 14, 2011RPS11
Future Work Studying cardiography equipment using digital filtering techniques October 14, 2011RPS12
October 14, 2011RPS13
心電計の回路を表すブロック 図の例 October 14, 2011RPS14 イン ピーダ ンス変 換器 誘導ネッ トワーク 前置 増幅器 マイクロコ ンピュータ AD 変換器 主増幅器 アイソ レーショ ン回路 出力装置
標準１２誘導を作るための 誘導ネットワークの原理 October 14, 2011RPS15 A BCD E F G H I J A~J の各点の出 力を組み合わ せる。 例えば、第Ⅰ誘 導は A と E 、 aVR は A と F を組み 合わせたもの となる。