2006 Fiscal Year Final Research Report Summary
Detection of emboli in-vivo using high accuracy electrical impedance measurements
| Project/Area Number |
16500300
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Biomedical engineering/Biological material science
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| Research Institution | Kitasato University |
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Principal Investigator |
SATORU Nebuya Kitasato University, School of Allied and Health Sciences, Clinical Engineering, Lecturer, 医療衛生学部, 講師 (00276180)
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| Co-Investigator(Kenkyū-buntansha) |
NOSHIRO Makoto Kitasato University, School of Allied and Health Sciences, Clinical Engineering, Professor, 医療衛生学部, 教授 (80014231)
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| Project Period (FY) |
2004 – 2006
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| Keywords | electrical impedance / the common carotid artery / clot / non-invasive measurement / the finite element method / emboli detection / high accuracy |
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| Research Abstract |
Doppler ultrasound has been used for the detection of emboli passing into the brain in order to forecast transient ischemic attacks, brain infarction and stroke. However, the Doppler ultrasound method has some disadvantages such as the attachment of an ultrasound transducer and maintenance of its direction. Electrical impedance measurement is a possible method for the in vivo detection of emboli and may overcome some of the disadvantages of the Doppler ultrasound method. However, the change in impedance caused by a bubble is expected to be very small and of short duration so that in vivo detection will be difficult. In this study, we had developed measurement techniques to detect emboli in vitro. The results of our study are as follows.
1. Development of an optically isolated impedance measurement system with high accuracy and speed.
We had suggested an optically isolated impedance measurement system. The system can measure real and imaginary components at 1.25MHz during 1ms. Transfer im
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pedance measurement accuracy was 0.1% at 1.25MHz. In addition, communication performance of Bluetooth module was also evaluated. The communication error was 0% at less than 30m of communication distance that is feasible for clinical use.
2. Development of electrical phantom of the neck and detection of emboli at the carotid model within the phantom.
The neck phantom consisted of materials to simulate the conductivity of skin, fat and muscle layers and a tube mimicking the common carotid artery. The whole model was a cube, 250x250x250 mm. Two disc drive electrodes of 3.5 mm in diameter were located 70 mm apart in a vertical linear array and two receive electrode were located 10mm apart in contact with the top of the skin layer. The measurement frequency was set at 100 kHz. Whole of Bovine blood had been filled into the carotid model and a 5mm cubic clot had also insulated into the center of the carotid model. The maximum impedance change was 0.12±0.16%.
3. Estimation of impedance change by passing through emboli using the lead field theory
The lead field theory developed by Geselowitz (1971) was used to calculate the theoretical impedance change as a function of the distance between the emboli and the electrode array for a homogenous phantom. We had also measured frequency characteristics of conductivity between whole of blood and clot of ten pigs to estimate absolute impedance change by passing thorough emboli with the theoretical function. Using the lead field theory and experimental results, the fundamental limit on the detectable size of emboli has been estimated for the common carotid artery. The theoretical results showed that a 0.5mm diameter emboli is detectable at a depth of 25mm, similar to the depth of the common carotid artery. Less
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