physics

Optical projection tomography

Optical projection tomography is a physics topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Optical projection tomography rather than just read about it. In short: Optical projection tomography is a form of tomography involving optical microscopy. 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 (CT) and single-photon emission computed tomography (SPECT).

Key takeaways

Optical projection tomography belongs to physics; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Optical projection tomography to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Optical projection tomography from memory before moving on to harder problems.

Reference excerpt

Optical projection tomography is a form of tomography involving optical microscopy. 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 (CT) and single-photon emission computed tomography (SPECT). It is in many ways the optical equivalent of X-ray computed tomography 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 or iterative reconstruction 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 that express fluorescent proteins such as green fluorescent proteins, 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 cultures. Fluorescence optical projection tomography visualises the distribution of dyes in the specimen.

See also Diffuse optical imaging Optical coherence tomography Optical tomography

References

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 Archived 2020-06-10 at the Wayback Machine

Worked examples

Example 1 — a first encounter with Optical projection tomography

Start with the simplest possible case. Write down what Optical projection tomography claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In physics, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Optical projection tomography before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Optical projection tomography ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Optical projection tomography

In research: Optical projection tomography appears in physics research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Optical projection tomography in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Optical projection tomography is common in secondary-school and first-year university syllabi. It links to neighbouring topics Tomography, so understanding it makes those chapters shorter.
In everyday life: Look for Optical projection tomography outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Optical projection tomography in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Optical projection tomography means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Optical projection tomography out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Optical projection tomography in simple terms?

Why does Optical projection tomography matter?

Because it connects several physics ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Optical projection tomography?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Optical projection tomography.