A considerable degree of progress has been achieved in new and emerging tomographic imaging systems in the past few decades. These techniques include optical tomography (Gibson et al. 2005), electromagnetic tomography (Griffiths 2001), electrical impedance tomography (Bayford 2006), ultrasound tomography (Glide-Hurst et al. 2008), magnetoacoustic tomography (Xu & He 2005) and magnetic resonance electrical impedance tomography (Woo & Seo 2008), to name a few. On close examination, it is apparent that there are clear areas of overlap in the development of these imaging technologies. Methodologies developed in one technology can be transferred to others. From a mathematical prospective image, reconstruction can be considered in a common class of inverse problems (Kaipio et al. 2000; Soleimani 2008). Researchers in the two specific application areas of tomography do not always export the developments across disciplines. Similarly, theoretical mathematicians need to develop techniques in close collaboration with the system designers and the end users.
The objectives of this issue are to bring together in one publication a range of different application areas with the common aim of improving the quality of the reconstructed image. We have invited some of the well-known scientists and leading figures in their respective fields to present their findings. The combination of these papers covers a wide range of scientific approaches to imaging for different application areas.
In this special issue, various new methods and techniques have been presented. Gibson & Dehghani (2009) present an overview of recent developments in medical applications of diffuse optical tomography (DOT). The main advancements in DOT are in brain mapping and breast imaging. This is linked to the image reconstruction paper by Dehghani et al. (2009), which played a very important role in the development of optical tomography. In Dehghani et al. (2009), different aspects of the image reconstruction of optical tomography are presented. The paper presents some imaging results, demonstrating the current capabilities of single wavelength, spectral and spatial imaging in near infrared, using experimental and patient data. Microwave tomography (MWT), an important member of the new and emerging electromagnetic tomography, has been included. Semenov (2009) presents an expert overview on difficulties of using MWT for applications and presents results for MWT for various applications including breast cancer detection, diagnostics of lung cancer, brain imaging and cardiac imaging.
Multimodal and metaphysics imaging have potential for development in new and emerging tomography imaging. Most of these imaging techniques have some reduction in sensitivity, and a multimodal or metaphysics approach could provide complementary imaging results. Yuan & Jiang (2009) present photoacoustic tomography as one of the latest developments in multiphysics tomography, which shows promise for magnetic resonance electrical impedance tomography. The paper presents an in vivo experimental demonstration of the techniques in quantitative photoacoustic imaging. In all of these imaging techniques, image visualization is a key problem. Various new and emerging imaging techniques are providing images with four- and five-dimensional information. Zhang et al. (2009) examine image visualization techniques with reference to the images from electrical impedance tomography.
Alongside the medical imaging applications, industrial process tomography is developing by employing various new and emerging imaging techniques. Optical imaging, various electromagnetic imaging techniques and acoustic imaging have all found applications in industrial process monitoring (York 2001; Yang & Peng 2003) as well as non-destructive evaluation in material characterization. It is often the case that a development in a medical application can lead (or help) to a development in an industrial application and vice versa. A main feature of most industrial process tomography applications is the need for fast imaging techniques. For these reasons, dynamic imaging techniques are important for the successful use of these imaging techniques for process monitoring. Khambampati et al. (2009) present various methods of dynamic image reconstruction in electrical impedance tomography, a key technique in industrial process monitoring, which have been studied and the results are compared.
A search of the ISI web of Science for journal publications shows the level of research activities in some of these new and emerging imaging techniques. The search shows that ultrasound tomography has 111 papers, magnetic induction tomography 61 papers, electrical capacitance tomography 258, electrical impedance tomography 1033, magnetic resonance electrical impedance tomography 50, optical tomography 1159, optical coherence tomography 6115, near infrared tomography 69, DOT 318, photoacoustic tomography 108, magnetoacoustic tomography 9 and MWT 111.
This issue is by no means a complete account of research activities in new and emerging tomographic techniques; however, it does show an interesting snapshot of the present state of the research activities and demonstrates the need for further development across the disciplines.
One contribution of 7 to a Theme Issue ‘New and emerging tomographic imaging’.
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