Nor Muzakkir Nor Ayob

Advancements in Transmitters and Sensors for Biological Tissue Imaging in Magnetic Induction Tomography

Magnetic Induction Tomography (MIT), which is also known as Electromagnetic Tomography (EMT) or Mutual Inductance Tomography, is among the imaging modalities of interest to many researchers around the world. This noninvasive modality applies an electromagnetic field and is sensitive to all three passive electromagnetic properties of a material that are conductivity, permittivity and permeability. MIT is categorized under the passive imaging family with an electrodeless technique through the use of excitation coils to induce an electromagnetic field in the material, which is then measured at the receiving side by sensors. The aim of this review is to discuss the challenges of the MIT technique and summarize the recent advancements in the transmitters and sensors, with a focus on applications in biological tissue imaging. It is hoped that this review will provide some valuable information on the MIT for those who have interest in this modality. The need of this knowledge may speed up the process of adopted of MIT as a medical imaging technology.

The Front-End Hardware Design Issue in Ultrasonic Tomography

This paper explains the front-end hardware design for ultrasonic tomography. The ultrasonic tomography system presented in this paper uses a noninvasive sensing technique with transmission-mode approach for investigating gas bubbles in an experimental column. Several explanations regarding the common tomography technique and the hardware preparation are also discussed. The sensory parts consist of 32 units of ultrasonic transceivers to form the fan-shaped beam projections. A low voltage of 20 V has been used to generate the ultrasonic burst tones. The electronic circuitry details, including the signal generator, the signal conditioning, and the signal acquisition strategy, are also presented. The results from this paper are useful for further development in ultrasonic tomography design.

Segmented Capacitance Tomography Electrodes: A Design and Experimental Verifications

A segmented capacitance tomography system for real-time imaging of multiphase flows is developed and presented in this work. The earlier research shows that the electrical tomography (ECT) system is applicable in flow visualization (image reconstruction). The acquired concentration profile obtained from capacitance measurements able to imaged liquid and gas mixture in pipelines meanwhile the system development is designed to attach on a vessel. The electrode plates which act as the sensor previously has been assembled and fixed on the pipeline, thus it causes obscurity for the production to have any new process installation in the future. Therefore, a segmented electrode sensor offers a new design and idea on ECT system which is portable to be assembled in different diameter sizes of pipeline, and it is flexible to apply in any number due to different size of pipeline without the need of redesigning the sensing module. The new approach of this sensing module contains the integration intelligent electrode sensing circuit on every each of electrode sensors. A microcontroller unit and data acquisition (DAQ) system has been integrated on the electrode sensing circuit and USB technology was applied into the data acquisition system making the sensor able to work independently. Other than that the driven guard that usually placed between adjacent measuring electrodes and earth screen has been embedded on the segmented electrode sensor plates. This eliminates the cable noise and the electrode, so the signal conditioning board can be expanded according to pipe diameter.

Novel Adjacent Criterion Method for Improving Ultrasonic Imaging Spatial Resolution

In this letter, we present a novel approach for improving spatial resolution in ultrasonic tomography. The proposed technique modifies a Back-projection (BP) algorithm in reconstructing tomography images. We used 32-ultrasonic transducer on a liquid column to perform the imaging process. Two phantoms were used to evaluate the proposed technique and compared with BP technique. The results showed that the proposed technique improves the spatial resolution and exhibits more accurate tomograms.

Detection of small gas bubble using ultrasonic transmission-mode tomography system

This paper presents the development of an ultrasonic transmission-mode tomography system for the detection of small gas bubble using higher frequency ultrasonic sensors. The selection of the sensors is important and must be suitable to the application design. Consideration on the natural limitation of ultrasonic wave is also noted as the higher the frequency of the ultrasonic transducer, the better the sensitivity but lower penetration depth. 16-pairs of these ultrasonic sensors are installed and fixed inside a sensor jig which is designed to hold all the sensors. The sensor jig is also mounted on the circumference of a vertical column which will be used as the investigated process vessel. The developments presented also include the non-invasive fabrication techniques, the electronic measurement circuits, image reconstruction technique, and finally on the imaging results of the proposed system.

Design and Development of Ultrasonic Process Tomography

Real-time reconstruction of the flow image is needed in order to estimate the flow regime when it is continuously evolving. This flow image is important in many areas of industry, and scientific research concerning liquid/gas two-phase flow. The operation efficiency of such a process is closely related to accurate measurement, and control of hydrodynamic parameters such as flow regime, and flow rate (Rahiman et al., 2010). Commonly, the monitoring in the process industry is limited to either visual inspection or a single-point product sampling assuming the product is uniformed. This approach for the determination of fluid flow parameters of two-component flow is also known as flow imaging.

Improving gas component detection of an ultrasonic tomography system for monitoring liquid/gas flow

The development of an ultrasonic transmission tomography system is described. The system is intended for the imaging of two component flows (such as gas/water) inside pipes of industrial processes. Transmission-mode approach has been used for sensing the gas/liquid two-phase flow, which is a kind of strongly inhomogeneous medium. A prototype fixture of vertical column and a mobile prototype design of sensors jig for ultrasonic tomography imaging are used. The fixture of the vertical column is designed to hold the sensors jig that will have the 16-pairs of ultrasonic sensors attached to it. The investigations were based on the transmission and the reception of ultrasonic sensors that were mounted circularly on the surface of experimental vessel. This paper also explains the hardware and circuitry design for the Ultrasonic Tomography System. Detailed explanations are presented on relationship of the smallest resolution the system are able to detect with the characteristics of the installed ultrasonic sensor.

Evaluation of square type electromagnetic field screen implementation on interference effects in magnetic induction tomography modality

This paper discusses and evaluates the implementation of square type electromagnetic screen on the excitation coil of Magnetic induction tomography (MIT) through real experiment. By using electromagnetic screen, interference phenomena due to scattered primary field can be reduced, hence reducing the sources of errors in the measurement data. In this experiment, two types of screen with different thickness of 2 mm and 25 mm had been evaluated. The measurements have shown that relative to without screen, 2 mm thickness screen reduces the field at about 84.31% at the back area while increased the field strength up to 19.45% in the front region. Excitation screen with 25 mm thickness provides better reduction of 98.43% at the back, however there is also reduction at about 9.82% of the field strength at the front region. The result from this experiment provides valuable information on the specification needed when applying electromagnetic screen to the individual excitation coil in the MIT system.

Simulation on using cross-correlation technique for two-phase liquid/gas flow measurement for Ultrasonic Transmission Tomography

Combining Ultrasonic Transmission Tomography (UTT) with the cross-correlation flow measurement technique can provide more information on the flow than usual. A simulated dual-plane UTT system for use on laboratory and plant-scale process equipment has been developed on the basis of this idea. This paper focuses on the correlator used to cross-correlate the tomogram images between the downstream and upstream plane of the simulated dual-plane ultrasonic transmission tomography system. This paper proposed the use of 2D correlation coefficient for the correlator and the result of its use is discussed. The principle of measurement of the local gas velocity distribution in a bubbly gas/liquid pipe flow which is based on cross-correlation of two plane images is also described. Initial experimental results illustrate the feasibility of the method presented here.