Industrial tomography

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There is growing interest in using realtime tomography to monitor complex industrial processes. It is often important to know what is happening within a pipe, a vat, or a reaction vessel, and tomography provides a convenient and non-invasive way of doing this. We are particularly interested in novel techniques, such as tomography based on the electrical or magnetic properties of an object, or tomography using cosmic rays.

Electrical and magnetic tomography

(Key people: Manuchehr Soleimani, Allen Yao, Kent Wei, Elle Ma)

For industrial tomography, the emphasis is usually on high speed data acquisition, rather than resolution. This lends itself to electrical tomography techniques, which although lacking the resolution of X-ray and MRI tomography, are nearly instantaneous. Examples of electrical tomographic imaging methods are:

  • Electrical Impedance Tomography (EIT), in which measurements of resistance between different combinations of electrodes, are used to determine the internal resistivity of an object.
  • Electrical Capacitance Tomography (ECT), in which multiple measurements of capacitance between different combinations of metal plates placed around the object, are used to determine the internal dielectric permittivity of an object.
  • Magnetic Permeability Tomography (MPT), in which multiple measurements of coupling between different combinations of magnets and magnetometers are used to determine the internal magnetic properties of an object.
  • Magnetic Induction Tomography (MIT), in which multiple measurements of coupling between magnetic excitation and sensing coils are used to determine the internal resistivity of an object.

Invert is currently constructing a range of imaging devices, many of which are based on these principles. See the Engineering Tomography Laboratory page for more information.

Prototype magnetic induction tomography device.

Cosmic ray muon tomography

(Key people: Nathan Smith, Christopher Benton)

When cosmic rays (high energy particles originating from deep space) strike the Earth's atmosphere, they create showers of secondary particles. These showers include muons (particles similar to electrons, but unstable and much heavier). By measuring how these muons are absorbed or scattered by an object, it is possible to use tomographic techniques to determine the object's internal composition.

Muon tomography is particularly sensitive to the presence of very heavy elements, such as uranium or plutonium. It has therefore been proposed as a way of rapidly checking shipping crates for the presence of smuggled nuclear materials. Muon tomography has also been used by geophysicists, to look inside mountains and volcanoes.

Calculated most-likely trajectories for muon paths through a medium, for known input and output trajectories.

When muons pass through a solid object, only the input and output trajectories can be directly measured. We are developing techniques to infer the most likely trajectory taken through the object for given input and output measurements. A better understanding of the muon trajectories should lead to higher quality imaging.

Ultrasound Tomography

(Key people: Manuchehr Soleimani)

In Ultrasound Tomography (UST), pulses of very high frequency sound (typically in the order of megahertz) are fired into the object to be observed. Ultrasound detectors are used to measure the time-of-flight to different locations on the objects surface. This time-of-flight depends on the physical properties of the intervening material, and so contains information about the object's interior. Multiple measurements can be used to reconstruct the object's internal composition.

Invert is developing a UST device to measure the internal composition of a fluid filled vessel. It can measure velocity throughout the fluid, and detect the presence of solid objects, or gas bubbles.