A Magnetic Induction Tomography system with sub-millidegree phase noise and high long-term phase stability

Wee, H. C.; Watson, S.J.; Patz, R.; Griffiths, Huw; Williams, Robert J.

doi:10.1007/978-3-540-89208-3_178

Cited by 18 publications

(19 citation statements)

References 6 publications

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“…Recent work has shown [5] that with this phase noise level, images of the three strokes can be reconstructed. Furthermore, a phase noise level of 1 m°should be achievable in the next datacollection hardware currently under development [32].…”

Section: Mit Signalsmentioning

confidence: 99%

Forward modelling of magnetic induction tomography: a sensitivity study for detecting haemorrhagic cerebral stroke

Zolgharni

Ledger

Griffiths

2009

Med Biol Eng Comput

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For a magnetic induction tomography (MIT) system operating at 10 MHz, the signals produced by a haemorrhagic cerebral stroke were computed using an anatomically realistic, multi-layer, finite element (FE) head model comprising 12 tissues. The eddy-current problem was approximated using the commercial FE package, Comsol Multiphysics, and the numerical techniques employed were validated using a benchmark test. Mesh convergence for the head model was investigated for first- and second-order elements. MIT signals were computed for strokes of different sizes and locations in the brain to judge the sensitivity of the MIT configuration. The results revealed that for a large peripheral stroke (volume 50 cm(3)), 27% of the signals were above the phase noise level achievable in our current data-collection hardware (approximately 20 m degrees). In order to detect the same percentage of the signals due to a centrally located small stroke, a reduction in phase noise to 1 m degrees was necessary.

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Section: Mit Signalsmentioning

confidence: 99%

Forward modelling of magnetic induction tomography: a sensitivity study for detecting haemorrhagic cerebral stroke

Zolgharni

Ledger

Griffiths

2009

Med Biol Eng Comput

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“…They also reconstructed image of leg in vivo and the accuracy of system in phase detection reached 17m°. H.C. Wee et al employed phase tracking technology in EMT system design with 14 channels, operation frequency ranged from 0.5MHz to 14MHz of the same year [10,11]. Place 1-turn small coils near the 4-turn transmitters and 2-turn receivers respectively to eliminate the phase error.…”

Section: Introductionmentioning

confidence: 99%

Phase detection for conductivity based on electromagnetic measurement system

Dong

2013

2013 IEEE International Conference on Imaging Systems and Techniques (IST)

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In electromagnetic tomography, phase of measurements from receivers contain the significant information of conductivity for target to test. The quality of reconstruction image mainly depends on the precision of phase detection. To discuss the effects in this aspect, simulate the relative conditions by the finite element simulation software, COMSOL Multiphysics. Conduct simulations for the target in object field with different conductivity and simulate the conditions when the target place at different positions in object field. To verify the validity of the results from simulations, design a prototype EMT system. This system utilizes NI PXI-5105 board to collect the high frequency signal directly, which could guarantee the precision and simplify the complexity of hardware. Based on the prototype EMT system, use the salt solution with different conductivities as target and conduct a series of relevant experiments. Results from simulations and experiments show the same variation tendency for each condition. It makes foundation for the system developing and optimization in future.

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“…The first experimental multi‐channel MIT system was designed by Korjenevsky et al () for biomedical applications with the system frequency of 20 MHz. Watson et al () designed a lower frequency (10 MHz) 16‐channel MIT system for use in low conductivity samples. A similar annular‐array 16‐channel MIT system was developed by Vauhkonen et al () using down‐conversion methods with the capability of simultaneous parallel readouts for cerebral stroke applications.…”

Section: Introductionmentioning

confidence: 99%

“…Watson et al () designed a lower frequency (10 MHz) 16‐channel MIT system for use in low conductivity samples. A similar annular‐array 16‐channel MIT system was developed by Vauhkonen et al () using down‐conversion methods with the capability of simultaneous parallel readouts for cerebral stroke applications. Multifrequency MIT systems were designed by Scharfetter et al () using planar gradiometers and a high‐resolution phase detector (PD), and by Wee et al () using a new phase stabilization scheme to reduce phase drift of the system.…”

Section: Introductionmentioning

confidence: 99%

“…A similar annular‐array 16‐channel MIT system was developed by Vauhkonen et al () using down‐conversion methods with the capability of simultaneous parallel readouts for cerebral stroke applications. Multifrequency MIT systems were designed by Scharfetter et al () using planar gradiometers and a high‐resolution phase detector (PD), and by Wee et al () using a new phase stabilization scheme to reduce phase drift of the system. Inverse problems also have been studied including edge‐preserving regularization, level‐set, artificial neural networks and total variation (Dorn et al, ; Korjenevsky, ; Casanova et al, ; Merwa et al, ; Soleimani et al, ).…”

Section: Introductionmentioning

confidence: 99%

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Imaging of hemorrhagic stroke in magnetic induction tomography: An in vitro study

Mamatjan

2014

Int J Imaging Syst Tech

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Magnetic Induction Tomography (MIT) has the potential of providing an inexpensive medical device for regular screening and monitoring of patients. MIT could be used to detect hemorrhagic stroke, if high measurement accuracy and spatial resolution can be reached to allow significant contrast between normal brain tissues and hemorrhaged areas. However, this can be challenging because spatial resolution in MIT is limited due to the small number of independent measurements, the inverse problems are severely ill-posed, and erroneous data cause large artefacts in reconstructed images and lower the detectability threshold of bleeding. The noise components degrading signal and image quality may be caused by thermal drift and noise from acquisition systems, environment or by body movements. The objective of the article is to empirically investigate hemorrhagic stroke in MIT based on in vitro study and to improve stroke detectability and visibility to help monitoring stroke patients. The following approaches were evaluated: (i) level setting, (ii) improved spatial filtering, (iii) averaging of multiple measurements, (iv) the combinations of these three approaches, and (v) wavelet denoising. They were evaluated with an in vitro phantom resembling a cerebral stroke in a pig brain. The results showed that these approaches enhanced stroke visibility, lowered stroke detectability threshold from 15 ml to 5 ml, and improved the localization of phantom hemorrhages such that their combination produced the best results. These methods may make it easy to the estimation of actual stroke volume, and clinical interpretation, and it can be used to longterm monitoring of stroke progression.

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A Magnetic Induction Tomography system with sub-millidegree phase noise and high long-term phase stability

Cited by 18 publications

References 6 publications

Forward modelling of magnetic induction tomography: a sensitivity study for detecting haemorrhagic cerebral stroke

Forward modelling of magnetic induction tomography: a sensitivity study for detecting haemorrhagic cerebral stroke

Phase detection for conductivity based on electromagnetic measurement system

Imaging of hemorrhagic stroke in magnetic induction tomography: An in vitro study

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