Computer-Assisted Tomography and Magnetic Resonance Imaging

Until recently, techniques for direct measurements on roots and soil water in the rooting zone have been largely destructive, or simply lacked the spatial resolution necessary for meaningful definition of root and water content distributions. With advances in X-ray physics, detector technology and mathematical reconstruction theory, a solution to this problem was essentially achieved by Hounsfield (1972), who developed the technique known as computer-assisted tomography (CAT) or computed tomography (CT). In addition to X- and γ-rays (photons), tomographic imaging is also applicable to other types of energy such as electrons, protons, alpha particles, lasers, radar, seismic and nuclear magnetic resonance (NMR).

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