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In a typical catalytic trickle bed type of process reactor, capturing representations of steady-state flow features as well as situations like channelling or bypassing is a challenging task. Transmission-type industrial process tomography (PT) based on gamma radiation can be employed in many chemical and process industries as a tool for localizing the problem area for quick and economical troubleshooting. Industrial PT technology often makes use of either penetrating radiation like radioisotope based gamma rays, X-rays, microwaves or ultrasonic waves. We have developed a new gamma-ray transmission tomography system in collaboration with the Indian Oil Corporation Ltd. (IOCL R&D Unit, Faridabad, India). The system makes use of thirty two scintillator based gamma-ray detectors in addition to a host of other sub-systems. This paper evaluates the performance of the system considering systematic and automated data acquisition, capabilities of the reconstruction software as well as experimental verification using actual flow dynamics in the process column to map the steady state three phase liquid gas flow distribution across a plane in the presence of catalyst.

The measurement of volume fractions of different components in multiphase flows is of great interest in many industrial applications. Ultrasound process tomography is especially well-suited for the differentiation of gaseous and liquid phases. This paper presents a measurement system, which was developed for real-time ultrasound process tomography, utilizing a ring of 32 ultrasound transducers on a measurement pipe. Simulations and measurements were conducted, and a reflection-mode reconstruction technique was used to obtain the system's point spread function and examine the performance on inhomogeneous configurations of water containing multiple gaseous objects. Furthermore, the possibility of increasing the measurement rate by reducing the number of excitations and its effects on the quality of the reconstructed images is investigated.

We investigate the potential of using ultrasonic diffraction tomography technique for characterization of biological tissues. Unlike most of other studies where ultrasonic tomography operates at frequencies higher than 1 MHz, low-frequency tomography uses lower frequencies on the order of 0.3–0.5 MHz. Such a choice is due to low attenuation at these frequencies, resulting in higher precision of input data. In this paper we explore transmission and reflection schemes for both 2D (layer-by-layer) and 3D tomography. We treat inverse tomography problems as coefficient inverse problems for the wave equation. The time-domain algorithms employed for solving the inverse problem of low-frequency tomography focus on the use of GPU clusters. The results obtained show that a spatial resolution of about 2–3 mm can be achieved when operating at the wavelength of about 5 mm even using a stationary 3D scheme with a few fixed sources and no rotating elements. The study primarily focuses on determining the performance limits of ultrasonic tomography devices currently designed for breast cancer diagnosis.

This study describes the development of a multisource computed tomography (CT) system that proved to be a useful tool to study multiphase systems. In this CT system, two different radioisotope sources, 192 Ir (317 keV and 448 keV) and 137 Cs (662 keV), were placed in a single lead collimator and several tomography measurements carried out. The multisource CT system was capable of determining as well as differentiating the attenuation coefficients of materials with two phases (gas and liquid). It was also able to provide important information concerning the hydrodynamics occurring inside a multiphase column.

Oil-water biphasic medium widely existed in mining and transportation process of petroleum industry, where visualized measurement processes vital importance in production increase, state monitoring and fault prognosis. Ultrasonic Tomography (UT) is a non-invasive and non-radioactive sensing modality in industrial Process Tomography, which is demonstrated as a competitive monitoring technique with great potential. However, facing the refraction effect of Ultrasound wave at oil-water interfaces, the accuracy of reconstruction algorithm is with large error and serious artifacts. To address the issue, a modified ray-tracing image reconstruction algorithm is proposed. The amplitude attenuation during ultrasound propagation in nonhomogeneous medium is quantitatively modeled to form absolute UT model. With ray tracing strategy applied and improved, the nonlinear refraction effect is characterized in the form of iterative update of sensitivity matrix, followed by which the sound speed mapping transfers reconstructed attenuation images to sound speed distribution for ray tracing computation. Numerical tests indicate that the proposed method significantly improves reconstruction accuracy through projection-based, regularization-based and algebraic-based inverse algorithms, which demonstrate its benefits in conducting oil-water biphasic medium imaging.

Electrical resistance tomography (ERT) and electrical capacitance tomography (ECT) are two established process tomography techniques that can be applied into various indsutries. ERT can monitor the electrical conductivity changes in the process whereas ECT can detect the electrical dielectric materials. Due to their high-speed and low cost features, they are particularly attractive to industrial applications which require real time conditional monitoring. For the past decades, 2D linear back projection (LBP) has been the standard technique for both commercialised ERT and ECT systems because of its simplicity and fast reconstruction speed. In this paper, ITS Plc has released a 'Reconstruction Tool-Suite' software that allows industrial users to utilise different reconstruction algorithms to further understand their processes. Different algorithms are integrated into this software package including the single step Tikhonov method and the iterative Landweber method. In the latest version of the software, the full-field 3D tomography reconstruction scheme is also included, which allows the users to perform 3D reconstruction for their processes. A series of experiments are conducted to validate the pros and cons of different methods.

Three-phase flow imaging is a very challenging problem in industrial process tomography. A particular interest here is three phase flow including both conductive and non-conductive phases. Currently there is no robust solution to this problem. Electrical capacitance tomography (ECT) has been applied to visualize the permittivity distribution by measuring inter-capacitance between electrodes around sensing area. Magnetic inductance tomography (MIT) is a technique to image the conductivity distribution through the inductance measurements over the coils around the sensing area. In this paper, the three-phase flow is classified into two scenarios: air background and water background. A dual-modality method of ECT and MIT is proposed to image both the conductive and dielectric components under test. As a result of this experiment, the dual-modality method is able to solve air-background three-phase flow imaging, but a problem has been raised in the water-background scenario. The static experiment results are promising for such contactless three phase flow imaging.

Electrical capacitance tomography (ECT) is a well-established industrial process tomography technique. The application of ECT is generally limited to imaging insulating objects with permittivity contrast. Although ECT imaging for grounded conductors are studied earlier, there is not a systematic study of imaging floating metals using ECT. To broaden the application of the ECT, imaging of suspended metallic samples is studied in this paper. Placing a metallic conductor between electrodes has an effect of shortening the spacing between the electrodes, thus the capacitances are increased. This increment in capacitances can be regarded as placing a dielectric sample with higher permittivity than the reference data. An ECT image of the floating metallic samples can be reconstructed using traditional sensitivity based image reconstruction, which is in the same way as imaging dielectric permittivity. In this paper, both metallic and dielectric samples are tested, and the results show the feasibility of ECT imaging for floating metals.

Process tomography (PT) techniques have been developed rapidly for visualizing the internal behavior of industrial processes, e.g. multi-phase flow measurement. Most of tomography systems employ a single measurement technique, such as computerized tomography (CT), optical tomography (OT), electrical resistance tomography (ERT) or electrical capacitance tomography (ECT). It is now possible to fit two or more tomographic systems to an industrial process. Detailed information from different modalities can be gained by inspection of separate tomographs, and the advantage of the strongest features provided by each unit can be taken. A combined tomogram can be produced of superior quality to any of the separate tomograms. To maximize the information available from the combined tomographic system, data fusion is the better option. In this paper, a dual-mode tomography system based on capacitance sensor and gamma sensor was developed to capture oil–gas two-phase flow. The two modalities can work at the same time. Two fusion methods, namely image fusion method and data fusion method, are proposed. Both simulation and static experiments for oil–gas two-phase flow were conducted. The reconstruction results of different fusion methods and modalities were compared and discussed.

Various tomographic techniques such as electrical capacitance, electrical resistivity, MRI, X-ray/gamma-ray tomography have been reviewed with special emphasis on applicability for the industrial set-ups are discussed. It was found that gamma-ray tomography is most suitable technique which could be used for industrial set-ups. Gamma-ray tomography was also applied for variety of industrial equipment, such as paddle bed dryer, packed distillation column, to explore the possibility of their use for diagnosis of unidentified problems. From the preset work it is recommended to undertake tomographic scanning of critical equipments periodically to enhance the efficiency and reduce possible downtime.

The aim of this paper is to provide a comprehensive review of the current measurement technologies available for on-line monitoring of the performance of the gas/oil/water separators, which are commonly used as the first stage of crude oil processing. Firstly, a short overview is given of the fluid physics governing the separation processes and the design of separation vessels. Simple theoretical models of separation physics are briefly reviewed and the process challenges outlined. This is followed by the description of existing measurement systems, those entering the market and likely future developments. The measurement systems are broadly divided into three categories: (1) those based on the assumption of a complete phase separation within the vessel; (2) those based on the concept of an array of sensors distributed across the heterogeneous layers, hence not requiring any assumptions regarding the actual phase distribution; and (3) more complex systems enabling cross-sectional imaging in the industrial process tomography sense.

Neutron computed tomography is an important imaging tool in the field of non-destructive testing and in fundamental research for many engineering applications. Contrary to X-rays, neutrons can be attenuated by some light materials, such as hydrogen, but can penetrate many heavy materials. Thus, neutron computed tomography is useful in obtaining important three-dimensional information about a sample's interior structure and material properties that other traditional methods cannot provide. The neutron computed tomography system at the Pennsylvania State University's Radiation Science and Engineering Center is being utilized to develop a water quantification technique for investigation of water distribution in fuel cells under normal conditions. A hollow aluminum cylinder test sample filled with a known volume of water was constructed for purposes of testing the quantification technique. Transmission images of the test sample at different angles were easily acquired through the synthesis of a dedicated image acquisition computer driving a rotary table controller and an in-house developed synchronization software package. After data acquisition, Octopus (version 8.2) and VGStudio Max (version 1.2) were used to perform cross-sectional and three-dimensional reconstructions of the sample, respectively. The initial reconstructions and water quantification results are presented.

A new neutron tomography imaging system was developed in order to realize high-quality three-dimensional (3D) and four-dimensional (4D) visualizations by fusing the high-frame-rate neutron radiography and computed tomography (CT) techniques. The fundamental idea is that the object is revolved with high rotating speed and the neutron radiography images are recorded with a high-speed video camera and an image intensifier, and then the consecutive images are processed by a 3D CT technique. The 4D dynamic images of the sand flow in the sandglasses could be visualized clearly. This new technique has also an advantage in that it can reduce radio-activation of the object materials remarkably.

The present work describes the development of a new detection technology for medical imaging using the method of Single-Photon Emitted Computed Tomography (SPECT) combined with X-rays Computed Tomography (CT). Our ultimate goal is to advance disease detection by imaging quantitatively molecular agents and localizing their distribution in tissues and organs by SPECT simultaneously with the anatomical CT image. To assess the imaging characteristics of the imaging agents developed, we tested and advanced a detection technique first developed for high-energy physics: Gas Electron Multipliers (GEMs).

This paper describes the design and modelling of ultrasonic tomography for two-component high-acoustic impedance mixture such as liquid/gas and oil/gas flow which commonly found in chemical columns and industrial pipelines. The information obtained through this research has proven to be useful for further development of ultrasonic tomography. This includes acquiring and processing ultrasonic signals from the transducers to obtain the information of the spatial distributions of liquid and gas in an experimental column. Analysis on the transducers' signals has been carried out to distinguish between the observation time and the Lamb waves. The information obtained from the observation time is useful for further development of the image reconstruction.

The amelioration of present X-ray imaging systems especially in computed tomography to resolutions below 1 μm necessitates very precise equipment details such as the manipulators, focus size and stability of the tube and the detector adjustment. In this paper, we present an experimental setup of a computed tomography system with sub-micrometer resolution. The requirements on and characteristics of the components and their influence on the measurements are discussed and exemplary results of different test objects in the field of non-destructive testing with sub-micrometer resolution are presented.

Process tomography (PT) techniques have been developed rapidly for visualising the internal behaviour of industrial processes. Most tomography systems employ a single measurement technique, such as Electrical Resistance Tomography (ERT) or Electrical Capacitance Tomography (ECT). Although single-modality process tomography systems provide sufficient information for some applications, in other applications, e.g. three-phase flow, additional information is required. In fact, many industrial processes are complex and contain multiple components, which require multiple measurement techniques to individually quantify them. To facilitate this process, a multi-modal process tomography system must allow individual modality data to be collected and combined effectively. This paper describes opportunities for rationalisation and sharing of resources that have been exploited to create a dual-modality tomography system.

This paper reviews the foundation of gamma-ray transmission tomography methods in industry. There are two categories of industrial tomography systems; those using a single source and automatic scanning, and those using multiple sources and no mechanical scanning. The main purpose of the latter is to reveal the dynamics of industrial processes. Compared to medical tomography temporal resolution is more important for these systems than spatial resolution. Such systems have also been realised using electronic scanning of multiple X-ray sources. Examples on different systems are given. Future developments include dual energy and multiple modality configurations enabling component fraction measurements on multiphase systems. Tomographic methods are also being implemented in permanently installed gauges with a limited number of projections, a priori information and parametric description of the process rather than reconstructed images.

Summary Computed tomography utilises a rotating X-ray source combined with multiple detectors in the latest scanners. This data can then be processed in numerous ways to provide axial, multi-planar and 3D images for diagnostic purposes. This modality has rapidly developed since its inception in direct relationship to the exponential increase in computer technology with a corresponding increase in its range of applications.

Dual-modality imaging is a technique in which computed tomography (CT) or magnetic resonance imaging is combined with positron emission tomography or single-photon emission CT to acquire structural and functional images with an integated system. The data are acquired in a single procedure; the patient remains on the scanner table while undergoing both x-ray and radionuclide studies to facilitate correlation between the structural and functional images. The resulting data can aid in localization, enabling more specific diagnosis than can be obtained with a conventional imaging study. In addition, the anatomic information can be used to compensate the correlated radionuclide data for physical perturbations such as photon attenuation, scatter radiation, and partial volume errors. Thus, dual-modality imaging provides a priori information that can improve both the visual quality and the quantitative accuracy of the radionuclide images. Dual-modality imaging systems are also being developed for biologic research involving small animals. Small-animal dual-modality systems offer advantages for measurements that currently are performed invasively with autoradiography and tissue sampling. By acquiring data noninvasively, dual-modality imaging permits serial studies in a single animal, enables measurements to be performed with fewer animals, and improves the statistical quality of the data.

Gas/solids flow measurement presents many challenges to academics and engineers. Although this subject has been investigated for many years, it still remains a notorious task. The main difficulty is that all existing multi-phase flow meters are flow-regime-dependent and suffer from severe non-linearity problems. Industrial process tomography is based on measuring a subject, such as a gas/solids flow, from many different viewing angles and reconstructing cross-sectional distributions, i.e. tomographic images. From the images the flow regime can be identified, the solids fraction and velocity profiles be derived, and the volumetric flow rate be measured. This paper discusses these possibilities, in particular with electrical capacitance tomography (ECT). Some new results are presented.

Pixel-based tomography has been used with great success for medical applications where it is most appropriate but this approach does not always transfer easily to industrial applications. For example pixel-based image reconstruction from electrical impedance tomography measurements is well known to be an ill- posed problem and with high noise levels such tomograms cannot be reliable. An alternative approach is to use a parametric representation of the tomogram for which reconstruction can be better posed. The primary reason for parametric modelling however is interpretatio n. This paper compares parametric modelling to other methods and then gives an example of the method for an application to a hydrocyclone. Two tomographic modalities are discussed and the results from parametric modelling are validated. This example demonstrates the great power achievable from a parametric modelling approach to tomographic imaging of industrial processes.

In contrast to X-rays, neutrons can penetrate most metals easily. Neutron attenuation is strongly isotope dependent, and a high contrast is possible for many light-weight elements. Especially their high sensitivity for hydrogen makes them a valuable tool for the detection of organic materials like lubricants, plastics or sealants within metal housings. Neutron radiography and tomography complement the application of X-rays for the inspection of complex and critical components like in automotive and aerospace applications. However, the requirements for beam geometry are much higher for tomography than for simple radiography because the sample cannot be close to the detector, as the sample has to be rotated in the beam, usually by 180°. This paper gives an overview on tomography requirements and limitations, applications and future prospects.

From the Department of Radiology, Division of Neuroradiology,a and Division of Musculoskeletal Imaging,b Indiana University School of Medicine. Reprint requests: Karen S. Caldemeyer, MD, Indiana University School of Medicine, University Hospital, Room 0279, 550 N University Blvd, Indianapolis, IN 46202-5253. J Am Acad Dermatol 1999;41:768-71. Copyright © 1999 by the American Academy of Dermatology, Inc. 0190-9622/99/$8.00 + 0 16/1/98499 C omputed tomography (CT) and magnetic resonance imaging (MRI) are the most widely used cross-sectional imaging methods used in medicine. CT was a revolutionary development of the 1970s. The term computed tomography derives from computed (with computer), tomo (to cut), and graph(y) (pictures). CT uses ionizing radiation, or x-rays, coupled with an electronic detector array to record a pattern of densities and create an image of a “slice” or “cut” of tissue. The x-ray beam rotates around the object within the scanner such that multiple x-ray projections pass through the object (Fig 1). The internal structure of the object can then be reconstructed from the multiple projections of that object.1 As x-rays pass through the patient, they are attenuated. The amount of attenuation depends on the type of tissue through which the x-ray beam passes. X-ray imaging contrast is generated as a consequence of differences in attenuation between adjacent tissues. The higher the attenuation of the x-ray beam, the brighter the tissue on CT images, and the lower the attenuation, the darker the tissue on CT images. Therefore bone and calcification that significantly attenuate the x-ray beam are white. Fat, being rich in carbon, is more transparent than water containing oxygen, which attenuates x-rays to a greater degree.1 Therefore fat is blacker than water on CT. Air causes little attenuation of x-rays and is very black (Figs 2 and 3). Regional or focal deviations from the normal CT appearance will be

This paper describes an investigation into the use of optical-fibre sensors in a tomographic measurement system, designed to measure the flow of dry solids in gravity-drop and pneumatic conveyors. A simple model of the system is provided and used to predict the response of both individual sensors and the full system. Results are provided which show that the model is acceptable. The system is used to provide tomographic images of solid concentration within a gravity conveyor.

Radioisotope emission tomographic methods, as developed in nuclear medicine, are reviewed with reference for their suitability for process tomography. The most promising techniques appear to be positron emission tomography and its offshoot positron emission particle tracking.

Improvements in the control of minerals processing plant may be possible by using tomographic techniques to measure the quantity and spatial distribution of material at certain points in the process. Electrical tomography can provide real-time (100 frames/sec) distribution maps with a resolution of 1 in 20 lines (400 pixels over cross-section) which can be used for i) model verification, ii) measuring material concentrations at critical locations within process vessels as part of an overall control scheme. Case studies are presented on i) electrical capacitance tomography for non-conducting process fluids (e.g. for use in pneumatic conveyors), ii) electrical resistance tomography for electrically conducting fluids (e.g. for use in hydrocyclones).

A first generation translate-rotate industrial computerized tomograph (CT) was designed and built. The tomograph features a single Nal(Tl) detector, 74 GBq 137Cs radioactive source, a computer-controlled mechanical rig, data acquisition and reduction, and advanced image processing capability. Objects up to 20 cm in diameter and 70 kg in weight can be imaged. High quality images were obtained for the various test objects, demonstrating the applicability of CT to metallic as well as ceramic material. A differential tomography technique was developed to detect lack of penetration by the electron beam in the welding process as applied to the welding of pressure vessels.

x-Ray computed axial tomography (CT) provides cross-sectional views of materials, components, and assemblies for industrial non-destructive evaluation. We have applied CT imaging to quantitatively measure the 3-D distribution ogf x-ray attenuation at reasonably high resolutions. In our industrial x-ray CT-studies, we have centered on two technical approaches: a first-generation translate/rotate CT system that consist of well-collimated (∼ 0.55 mm) photon source detector, and a third-generation scanner that uses a fluoroscopy detector.

The general features and advantages of radionuclide computer tomography systems are discussed. Application of such systems, coupled with emission tomography, to automated examination of spherical and rod fuel elements is described.

Film based projection acquisition in industrial computerized tomography imaging has the potential for increasing spatial resolution performance by a factor of ten to one hundred. Utilizing microdensitometric evaluation of radiographic projections, effective detector sizes of a few microns may be achieved. An experimental scanning system has been built using a modular multifunctional approach, and a few preliminary reconstructions are presented.