• Proceedings of the KIEE Conference
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• 2004.11c
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• pp.538-540
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• 2004

Electrical currents generated by human heart activities create magnetic fields represented by MCG(MagnetoCardioGram). Since an MCG signal acquisition system requires precise and stable operation, the system adopts hundreds of SQUID(Superconducting QUantum Interface Device) sensors for signal acquisition. Such a system requires fast real-time data acquisition in a required sampling interval, i.e., 1 mili-second for each sensor. This paper presents designed hardware to acquire data from 256-channel analog signal with 1 ksamples/sec speed, using 12-bit 8-channel ADC devices, SPI interfaces, parallel interfaces, 8-bit microprocessors, and a DSP processor. We implemented SPI interface between ADCs and a microprocessor, parallel interfaces between microprocessors. Our result concludes that the data collection can be done in $168{\mu}sec$ time-interval for 256 SQUID sensors, which can be interpreted to 6 ksamples/sec speed.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.11a
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• pp.444-447
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• 2004

A heart diagnosis system adopts hundreds of Superconducting Quantum Interface Device(SQUID) sensors for precision MCG(Magnetocardiogram) or MEG(Magnetoencephalogram) signal acquisitions. This system requires correct and real-time data acquisition from the sensors in a required sampling interval, i.e., 1 mili-second. This paper presents our hardware design and test results, to acquire data from 256 channel analog signal with 1-ksample/sec speed, using 12-bit 8-channel ADC devices, SPI interfaces, parallel interfaces, and 8-bit microprocessors. We chose to implement parallel data transfer between microprocessors as an effective way of achieving such data collection. Our result concludes that the data collection can be done in 250 ${\mu}sec$ time-interval.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.902-905
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• 2004

A heart diagnosis system adopts Superconducting Quantum Interface Device(SQUID) sensors for precision MCG signal acquisitions. Such system is composed of hundreds of sensors, requiring fast signal sampling and precise analog-digital conversions(ADC). Our development of hardware board, processing 64-channel 12-bit 1ks/s, is built by using 8-channel ADC chips, 8-bit microprocessors, SPI interfaces, and parallel data transfers between microprocessors to meet the 1ks/s, i.e. 1 ms speed. The test result shows that the signal acquisition is done in 168 usuc which is much shorter than the required 1 ms period. This hardware will be extended to 256 channel data acquisition to be used for the diagnosis system.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.54 no.11
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• pp.643-649
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• 2005

A heart diagnosis system adopts Superconducting Quantum Interface Device(SQUD) sensors for precise MCG(MagnetoCardioGram) signal acquisitions. Such system needs to deal with hundreds of sensors, requiring fast signal sampling md precise analog-to-digital conversions(ADC). Our development of hardware board, processing 64-channel 12-bit in 1 ks/s speed, is built by using 8-channel ADC chips, 8-bit microprocessors, SPI interfaces, and specially designed parallel data transfers between microprocessors to meet the 1ks/s, i.e. 1 mili-second sampling interval. We extend the design into 256-channel hardware and analyze the speed .using the measured data from the 64-channel hardware. Since our design exploits full parallel processing, Assembly level coding, and NOP(No Operation) instruction for timing control, the design provides expandability and lowest system timing margin. Our result concludes that the data collection with 256-channel analog input signals can be done in 201.5us time-interval which is much shorter than the required 1 mili-second period.

• Journal of Biomedical Engineering Research
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• v.27 no.4
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• pp.154-163
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• 2006

A 64-channel magnetocardiogram (MCG) system using low-noise superconducting quantum interference device (SQUID) planar gradiometers was developed for the measurements of cardiac magnetic fields generated by the heart electric activity. Owing to high flux-to-voltage transfers of double relaxation oscillation SQUID (DROS) sensors, the flux-locked loop electronics for SQUID operation could be made simpler than that of conventional DC SQUIDs, and the SQUID control was done automatically through a fiber-optic cable. The pickup coils are first-order planar gradiometers with a baseline of 4 em. The insert has 64 planar gradiometers as the sensing channels and were arranged to measure MCG field components tangential to the chest surface. When the 64-channel insert was in operation everyday, the average boil-off rate of the dewar was 3.6 Lid. The noise spectrum of the SQUID planar gradiometer system was about 5 fT$_{rms}$/$\checkmark$Hz at 100 Hz, operated inside a moderately shielded room. The MCG measurements were done at a sampling rate of 500 Hz or 1 kHz, and realtime display of MCG traces and heart rate were displayed. After the acquisition, magnetic field mapping and current mapping could be done. From the magnetic and current information, parameters for the diagnosis of myocardial ischemia were evaluated to be compared with other diagnostic methods.