Optical projection tomography is a form of

tomography Tomography is imaging by sections or sectioning that uses any kind of penetrating wave. The method is used in radiology, archaeology, biology, atmospheric science, geophysics, oceanography, plasma physics, materials science, astrophysics, quantu ...

involving

optical microscopy Optics is the branch of physics that studies the behaviour and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behaviour of visible, ultraviole ...

. The OPT technique is sometimes referred to as Optical Computed Tomography (optical-CT) and Optical Emission Computed Tomography (optical-ECT) in the literature, to address the fact that the technique bears similarity to

X-ray computed tomography An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10 picometers to 10 nanometers, corresponding to frequencies in the range 30 ...

(CT) and

single-photon emission computed tomography Single-photon emission computed tomography (SPECT, or less commonly, SPET) is a nuclear medicine tomographic imaging technique using gamma rays. It is very similar to conventional nuclear medicine planar imaging using a gamma camera (that is, ...

(SPECT). It is in many ways the optical equivalent of

or the medical CT scan. OPT differs in the way that it often uses ultraviolet, visible, and near-infrared photons as opposed to X-ray photons. However, essential mathematics and reconstruction algorithms used for CT and OPT are similar; for example,

radon transform In mathematics, the Radon transform is the integral transform which takes a function ''f'' defined on the plane to a function ''Rf'' defined on the (two-dimensional) space of lines in the plane, whose value at a particular line is equal to the l ...

iterative reconstruction Iterative reconstruction refers to iterative algorithms used to reconstruct 2D and 3D images in certain imaging techniques. For example, in computed tomography an image must be reconstructed from projections of an object. Here, iterative recons ...

based on projection data are used in both medical CT scan and OPT for 3D reconstruction. Both medical CT and OPT compute 3D volumes based on transmission of the photon through the material of interest. Given that the tissue is typically opaque in the ultraviolet, visible, and near-infrared spectrum, the tissue must first be made clear with an optical clearing agent, so that the light can pass through. Common optical clearing agents include BABB and methyl salicylate (wintergreen). OPT can assume two primary forms - transmission mode and emission mode. In transmission mode, where light is passed through an optically cleared sample, one can obtain structural information about the sample of interest. In emission mode, where the sample is exposed to excitation light, one can obtain functional information about the sample of interest. In tandem with organs harvested from

genetically modified mouse A genetically modified mouse or genetically engineered mouse model (GEMM) is a house mouse, mouse (''Mus musculus'') that has had its genome altered through the use of genetic engineering techniques. Genetically modified mice are commonly used for ...

that express fluorescent proteins such as

green fluorescent protein The green fluorescent protein (GFP) is a protein that exhibits bright green fluorescence when exposed to light in the blue to ultraviolet range. The label ''GFP'' traditionally refers to the protein first isolated from the jellyfish ''Aequorea ...

s, the emission mode of OPT can yield 3D genetic expression images of the mouse organ. The technique has already contributed to a large number of studies aimed at addressing a broad range of biological questions in diverse systems such as human, mice, chicken, fly, zebrafish, and plants. More recent adaptations have further enabled the use of the technique for studies of specimens on the adult mouse organ scale, individual cell nuclei, and longitudinal assessments of

organ culture Organ culture is a development from tissue culture methods of research, the organ culture is able to accurately model functions of an organ in various states and conditions by the use of the actual ''in vitro'' organ itself. Parts of an organ or ...

s. Fluorescence optical projection tomography visualises the distribution of dyes in the specimen.

References

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External links

*https://web.archive.org/web/20101105182544/http://genex.hgu.mrc.ac.uk/OPT_Microscopy/optwebsite/frontpage/index.htm
Video I: Optical Projection Tomography of a mouse left lateral liver lobe.Video II: Optical Projection Tomography of an embryonic stomach, intestine and pancreas of a mouse.Inner World of carnivorous plants from the John Innes Centre
Tomography Articles containing video clips

See also

References

External links