View source for Biology:Optical tomography

{{Infobox interventions |
  Name        = Optical tomography |
  Image       = Diffuse Optical Tomography - fiber-optic array - journal.pone.0045714.g001.png|
  Caption     = A fiber-optic array for breast cancer detection by way of Diffuse Optical Tomography.|
  ICD10       = |
  ICD9unlinked = |
  MeshID      = D041622 |
  OPS301      = |
  OtherCodes  = |
}}
'''Optical tomography''' is a form of computed tomography that creates a [[Digital data|digital]] volumetric model of an object by reconstructing images made from light transmitted and scattered through an object.<ref>{{MeshName|Optical+Tomography}}</ref> Optical tomography is used mostly in [[Medicine:Medical imaging|medical imaging]] research. Optical tomography in industry is used as a sensor of thickness and internal structure of semiconductors.<ref>^ Wojtek J. Walecki and Fanny Szondy, "[https://dx.doi.org/10.1117/12.797541%20 Integrated quantum efficiency, reflectance, topography and stress metrology for solar cell manufacturing]", [http://www.zebraoptical.com/Publications.html Sunrise Optical LLC], Proc. SPIE 7064, 70640A (2008); {{doi|10.1117/12.797541}}</ref>

==Principle==
Optical tomography relies on the object under study being at least partially light-transmitting or translucent, so it works best on [[Physics:Soft tissue|soft tissue]], such as breast and [[Biology:Brain|brain]] tissue.

The high scatter-based attenuation involved is generally dealt with by using intense, often pulsed or intensity modulated, light sources, and highly sensitive light sensors, and the use of [[Physics:Infrared|infrared]] light at frequencies where body tissues are most transmissive. Soft tissues are highly scattering but weakly absorbing in the near-infrared and red parts of the spectrum, so that this is the wavelength range usually used.

==Types==
===Diffuse optical tomography===
{{main|Medicine:Diffuse optical imaging}}
In near-infrared diffuse optical tomography (DOT), transmitted [[Physics:Photon diffusion|diffuse photons]] are collected and a [[Diffusion equation|diffusion equation]] is used to reconstruct an image from them.<ref>{{Cite journal|last1=Hoshi|first1=Yoko|last2=Yamada|first2=Yukio|date=2016-07-13|title=Overview of diffuse optical tomography and its clinical applications|journal=Journal of Biomedical Optics|language=en|volume=21|issue=9|pages=091312|doi=10.1117/1.JBO.21.9.091312|pmid=27420810 |bibcode=2016JBO....21i1312H |issn=1083-3668|doi-access=free}}</ref>

===Time-of-flight diffuse optical tomography===
A variant of optical tomography uses optical time-of-flight sampling as an attempt to distinguish transmitted light from scattered light.<ref>{{Cite journal|last1=Lyons|first1=Ashley|last2=Tonolini|first2=Francesco|last3=Boccolini|first3=Alessandro|last4=Repetti|first4=Audrey|last5=Henderson|first5=Robert|last6=Wiaux|first6=Yves|last7=Faccio|first7=Daniele|date=August 2019|title=Computational time-of-flight diffuse optical tomography|url=http://www.nature.com/articles/s41566-019-0439-x|journal=Nature Photonics|language=en|volume=13|issue=8|pages=575–579|doi=10.1038/s41566-019-0439-x|arxiv=1808.01135 |bibcode=2019NaPho..13..575L |s2cid=118707188 |issn=1749-4885}}</ref> This concept has been used in several academic and commercial systems for breast cancer imaging and cerebral measurement. The key to separation of absorption from scatter is the use of either time-resolved or frequency domain data which is then matched with a diffusion theory based estimate of how the light propagated through the tissue. The measurement of time of flight or frequency domain phase shift is essential to allow separation of absorption from scatter with reasonable accuracy.{{citation needed|date=August 2015}}

===Fluorescence molecular tomography===
In '''fluorescence molecular tomography''', the fluorescence signal transmitted through the tissue is normalized by the excitation signal transmitted through the tissue, and so many of the fluorescence tomography systems do not require the use of time-resolved or frequency domain data, although research is still ongoing in this area. Since the applications of fluorescent molecules in humans are fairly limited, most of the work in fluorescence tomography has been in the realm of pre-clinical cancer research. Both commercial systems and academic research have been shown to be effective in tracking tumor protein expression and production, and tracking response to therapies.{{citation needed|date=August 2015}}

===Confocal diffuse tomography===
'''Confocal diffuse tomography''' uses a powerful laser to illuminate a sample through a [[Physics:Scattering|scattering]] medium, followed by [[Deconvolution|deconvolution]] with a calibrated [[Diffusion equation|diffusion operator]] to estimate a volume without the effects of diffusive scattering and subsequent application of a [[Confocal|confocal]] [[Inverse filter|inverse filter]] to recover the sample image.<ref>{{Cite journal|last1=Lindell|first1=David B.|last2=Wetzstein|first2=Gordon|date=December 2020|title=Three-dimensional imaging through scattering media based on confocal diffuse tomography|url= |journal=Nature Communications|language=en|volume=11|issue=1|pages=4517|doi=10.1038/s41467-020-18346-3|issn=2041-1723|pmc=7481188|pmid=32908155|bibcode=2020NatCo..11.4517L }}</ref><ref>{{Cite web|title=Confocal Diffuse Tomography {{!}} Nature Communications 2020 - YouTube|url=https://www.youtube.com/watch?v=uyuCyzV0pdM|access-date=2021-02-10|website=www.youtube.com}}</ref>

==See also==
*[[Physics:Optical coherence tomography|Optical coherence tomography]]
*[[Medicine:Diffuse optical imaging|Diffuse optical imaging]]
*[[Physics:Computed tomography laser mammography|Computed tomography laser mammography]]

==References==
{{reflist}}

==Further reading==
*{{Cite journal | last1 = Haisch | first1 = C. | doi = 10.1146/annurev-anchem-062011-143138 | title = Optical Tomography | journal = Annual Review of Analytical Chemistry | volume = 5 | pages = 57–77 | year = 2012 | pmid =  22524216| bibcode = 2012ARAC....5...57H }}

==External links==
*[https://web.archive.org/web/20051125154108/http://www.imperial.ac.uk/research/photonics/research/topics/tomog/tomog.htm Optical tomography at Imperial College, London]
*[http://www.ucl.ac.uk/medphys/research/borl/imaging Optical tomography at University College, London]
*[http://www.physics.org/featuredetail.asp?NewsId=25 "Boobs, Babes and Blood" - Article on physics.org]

{{Medical imaging}}

[[Category:Neuroimaging]]

{{Sourceattribution|Optical tomography}}