Talk:Optical coherence tomography

Comment
08-29-06: Any chance of someone in the know adding a layperson definition or brief explanation? I'm editing a consent form for a research study that will use OCT for an investigational purpose. Federal regulations (45 CFR 46.116) require that the information given to a research subject be in language understandable to the subject. Unless the OCT researcher decides to confine recruitment to MIT grad students (unlikely to have the disease in question!), that regulation is going to be pretty hard to meet.

Growmac (talk) 15:28, 30 January 2008 (UTC) I have just added a laypersons section. Should be a start for people to work from anyway. HTH. Gordon.

Hi all, new here. I manage a Youtube channel, and we have a video on this topic that I'm told provides a good lay introduction to the topic. Leaving it here in case it could be worked into external links or something. https://www.youtube.com/watch?v=J014Q5z7rJg 98.228.52.175 (talk) 23:15, 27 January 2014 (UTC)

patrickyip 10:50, 03 March 2012 I did not find the fig 5 as described in the section of Time encoded frequency domain OCT (also swept source OCT) — Preceding unsigned comment added by Patrickyip (talk • contribs) 02:52, 3 March 2012 (UTC)

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Are there large blank areas for other people that are viewing this page or is it just my browser? I'm not sure how to fix that. Jackkoho 20:18, 20 April 2006 (UTC)
 * I got it all fixed. Just needed to realign the figures.Aboosh 18:40, 7 November 2006 (UTC)

There is much more material on the german page of OCT - So a translation might improve the situation on the english pages... On the other hand there was more on this page which was lost somehow. --BoP 15:10, 2 Jan 2005 (UTC)

This article is kind of complicated with a lot of intra-OCT community lingospeak which is great for publishing but may not work for an outsider (say a physician). For example, "ultra high resolution" doesn't really have any meaning if one's reference for high resolution is electron microscopy. I'm going to try to make it a little more palatable.

Anyone else find it moderately terrifying that physicians research their surgical procedures on wikipedia? 128.239.220.80 13:02, 11 May 2006 (UTC)

Reference
There was no link to the following footnote in the article, so I have saved it here:
 * 9.    J. M. Herrmann, M. E. Brezinski, B. E. Bouma, S. A. Boppart, C. Pitris, J. F. Southern and J. G. Fujimoto, "Two- and three-dimensional high-resolution imaging of the human oviduct with optical coherence tomography," Fertility and Sterility, vol. 70, no. 1, pp. 155--158, 1998. Available: sciencedirect.com.

-AED 07:01, 21 November 2006 (UTC)

Commercial links
Growmac (talk) 15:09, 30 January 2008 (UTC)

I have noticed that all the links to the commercial groups operating in OCT have been removed. I should preface this post by highlighting my interest as a Founding Director of Michelson Diagnostics, the UK based OCT company.

Having read the external link guidelines, I think that this removal is not appropriate. OCT is a commercially young field, and none of the groups operating are working at a 'shifting boxes' stage of R&D. We are still very much at the stage of interacting with potential users and informing the clinical and research community at large about OCT.

Because of these reasons, I believe the links to all the OCT Commercial Organisations were both appropriate and useful. There has been universal care not to allow any commercial advertising or peddling on the page, and I don't think any companies have an interest in abusing the page.

I intend to undo the removal of commercial links because of the above reasons. I am easily contactable via my companies website - search for Michelson Diagnostics on Google if you wish to do so.

Dr Gordon McKenzie, 30th Jan 08

It would seem that the links have been removed again without comment. Would Montco please respond to the points above.

Growmac (talk) 10:27, 14 April 2008 (UTC)


 * OK Doc, not a problem,


 * Please refer to external links guidelines point 14 under links to be avoided.


 * "Lists of links to manufacturers, suppliers or customers."


 * You assert that "We are still very much at the stage of interacting with potential users and informing the clinical and research community at large about OCT."


 * Well good. I think you should include any relevant information about the field in the article, not simply slapping links for these firms on the page.  That's not what Wikipedia is here for.  If you want to include a list of companies involved in the field, not a problem.  You see, if I let your company's link on the page, I have to let them all in and then the page becomes a linkfarm.  Also bad.  If you want, do something over at Open_Directory_Project and we will ad a single link to the open directory.


 * Bottom line is that we aren't here to help every company get their name out. If there is an article about the company, then we put a link to that company on that page.  I realize that you think that your field is special and due to this we should make an exception from all the rules.  I am afraid it isn't.  Everybody thinks that their company is special, that their field is special and that this justifies their inclusion.  Please don't put it back, I'll just take it back down.Montco (talk) 13:43, 14 April 2008 (UTC)

A useful response, and I think that the ODP suggestion is a good one. I will get it organised and then place a single link. I wasn't campaigning for special treatment, and was careful not to be anonymous. Growmac (talk) 10:01, 21 April 2008 (UTC)

Confusing
This article appears confusing to me. Does anybody else have trouble understanding it?

The DarkArcher was here (talk) 01:14, 14 September 2008 (UTC)
 * No, I find the article good, but the topic is complex. --Kipmaster (talk) 15:42, 10 May 2011 (UTC)

Dubious: Light losing its coherence when being scattered
Hi. I notice in the "laymans description" a claim that light taht is scattered loses its coherence. I have access to several scientific articles that show this is not the case. I would like to know if someone is willing to back up the claim in question with a source, or if I should change it and source my change. Cuardin (talk) 09:39, 29 March 2010 (UTC)

The comment about coherence is subtle, but, as worded in the article, I would say that it is wrong. The word "coherent" in the context of OCT describes two waveforms that produce an interference signal when added together in an interferometer. If they are not coherent, only the constant mean intensity and no interference fringes are observed as the reference mirror is moved in the interferometer. In the case of OCT, light that has traveled twice the the distance of the sample arm + a given distance into the material is coherent with light that has traveled twice the reference arm, plus or minus the coherence length of the light source. Because this coherence length is small, interference fringes are observed when the penetration depth of the light roughly satisfies the relation 2*(penetration depth) + 2*(sample arm length) = 2*(reference arm length). Thus, the penetration depth is encoded onto the mirror displacement, or equivalently the reference arm length. The reflectivity at this depth is encoded onto the strength of the interference signal.

As for the comment about scattered light losing its coherence, it is not generally true. If a plane wave scatters off of a sphere, the scattered light is still coherent with the incoming plane wave. This is what produces the interference pattern observed in the far field of the sphere. Kmdouglass 19:48, 23 June 2010 (UTC) —Preceding unsigned comment added by Kmdouglass (talk • contribs)

I agree with both of the comments above: light does not lose its coherence on scattering. Coherence is lost when *multiple* scattering occurs, so that the phase relationship between the multiply-scattered wave (which is split many times and encounters many scattering events) and the original input beam becomes statistically equivalent to a random relationship. --NathanHagen 12:57, 09 Nov 2010 —Preceding unsigned comment added by NathanHagen (talk • contribs)

Light might not lose its coherence when scattered, but isn't it true that all the scattered light returning to the same point as the reflected light has neccesarily been multiply scattered and thus is not coherent? —Preceding unsigned comment added by 195.37.186.62 (talk) 10:00, 1 December 2010 (UTC)

Wording is too elitist
Example of what i mean: "In time domain OCT the pathlength of the reference arm is translated longitudinally in time" Which, of course, is technically correct. But in no way does it help understanding what time-domain-OCT is about.

I get that medical professionals want to, well, sound professional, but wordings like that are just douchebaggery. Just say what you want to say, something like "reference arm moves from left to right and back repeatedly." doesn't sound fancy, but everyone will instantly know what it means. — Preceding unsigned comment added by 93.196.90.54 (talk) 13:06, 12 August 2015 (UTC)
 * Yes we had an expert come through and do a lot of work, which was great, but it was too technical, per WP:TECHNICAL.... Jytdog (talk) 14:00, 12 August 2015 (UTC)

Theory: Figures are for different techniques
Hello,

I noticed that each of the four figures in the Theory section is for a different type of OCT (well, two are "SD-OCT", one is TD-OCT, and another is SS-OCT). Since these come before the descriptions of each separate technique (TD, spatially-encoded fourier-domain aka. SD, time-encoded fourier-domain aka. SS), these figures are rather confusing, since a different explanation is needed to understand each technique.

If, instead, the figures are moved into their respective technique heading, they might make a lot more sense. Also, it would be helpful if the figures included the name of the technique (eg. the 1st figure sounds like the technique is called "full-field OCT", but the OCT technique appears to correspond to "spatially encoded fourier-domain OCT", although it is admittedly acquiring a full-field view).

Thanks for the article. DeminJanu (talk) 20:38, 24 August 2016 (UTC)

Origin
The origin of the technology lay with MIT scientists, who (it is said) applied an application from outer space research after a project was canceled. The layers of imaging that the light has to pass through are the same layers in principle that light passes through cloud that were pursued for military purposes. Reference Fujimoto, J., & Swanson, E. (2016). The Development, Commercialization, and Impact of Optical Coherence Tomography. Investigative Ophthalmology & Visual Science, 57(9), OCT1–OCT13. http://doi.org/10.1167/iovs.16-19963, makes mention of initial support from Air Force Office of Scientific Research (Arlington, VA, USA)Fred114 21:44, 26 September 2018 (UTC) — Preceding unsigned comment added by Fred114 (talk • contribs)

Coherence
There's a problem with the description of the light sources having low coherence. Ultra-broadband laser sources can be used for OCT because they can produce very short pulses. These pulses create an interference pattern only within a very short distance (given by ~ "speed of light"/bandwidth). If the laser is phase-stabilized, then one pulse can create a stable shot-to-shot interference pattern with the next if they can be set up to overlap each other. In this case, the coherence is typically very high, and the coherence time is determined by the bandwidth of any particular cavity mode, not the entire bandwidth of the laser.

This interference, which possible in principle, is unlikely in practice as the distance between pulses is given by "speed of light"/"repetition frequency", which for an 80MHz source gives a distance of about 4 metres. However, to insinuate that these lasers have a low degree of coherence is misleading.

2607:FEA8:F1E0:725:D5B3:1C10:16E7:7F7C (talk) 22:12, 30 November 2019 (UTC)

Resolution
Comment "verification needed|reason=confocal microscopy typically has a resolution of about 1 um and it is stated earlier that confocal microscopy has better resolution than OCT, so need to substantiate this claim|date=June 2015" removed. Confocal microscopy has a resolution limit described by the Rayleigh criterion amounting to ~250 nm 131.181.27.227 (talk) 01:05, 16 August 2022 (UTC)

Equation of Complex Coherence citation
"Due to the coherence gating effect of OCT the complex degree of coherence is represented as a Gaussian function expressed as" cites a paper, which does not appear to have the given equation in it. Ionsme2 (talk) 22:29, 30 March 2023 (UTC)