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B Blad

Publications and source records attributed to B Blad.

6 recordsLinked to original sources

A current injecting device for electrical impedance tomography.

Electrical impedance tomography (EIT) has to be improved in order to become an accepted diagnostic technique in clinical use. The aim of this study is to improve the hardware of this technique and preferably upgrade the current injecting device. Instead of using a constant current generator the idea is to implement a voltage source and measure current accurately, in order to improve the resolution in the image. The performance of such a device is analysed, particularly concerning theoretical and practical limitations. The amplitude and phase accuracy, noise and settling time are measured and presented in diagrams. The results show that improvements are possible to achieve and that such a device will improve the stability of an EIT system and the image quality.

Electric Impedance

Quantitative assessment of impedance tomography for temperature measurements in hyperthermia.

The objective of this study is a non-invasive assessment of the thermal dose in hyperthermia. Electrical impedance tomography (EIT) has previously been given a first trial as a temperature monitoring method together with microwave-induced hyperthermia treatment, but it has not been thoroughly investigated. In the present work we have examined this method in order to investigate the correlation in vitro between the true spatial temperature distribution and the corresponding measured relative resistivity changes. Different hyperthermia techniques, such as interstitial water tubings, microwave-induced, laser-induced and ferromagnetic seeds have been used. The results show that it is possible to find a correlation between the measured temperature values and the tomographically measured relative resistivity changes in tissue-equivalent phantoms. But the uncertainty of the temperature coefficients, which has been observed, shows that the method has to be improved before it can be applied to clinical in vivo applications.

Body Temperature

Waveform generator for electrical impedance tomography (EIT) using linear interpolation with multiplying D/A converters.

This paper describes the implementation of a multiplying digital-to-analogue (D/A) converter as a programmable waveform generator to be used in an electrical impedance tomography (EIT) system. Different digital techniques of generation waveforms are considered and the advantages and disadvantages of the chosen slope-plus-pedestal technique are presented. A wire-wrapped prototype system has been designed, and from measured frequency spectra the total harmonic distortion can be calculated to values between 1.1 and 2.9% depending on frequency.

Analog-Digital Conversion