applications optical coherence tomography
Getting under your skin
nadya anscombe fi nds out about a pan-european research project that aims to get the most out of optical coherence tomography
O ptical coherence
tomography (OCT) is an imaging technology that is often described as the
optical equivalent to ultrasound. While this analogy is broadly correct, it does not convey the fact that OCT can do so much more than ultrasound. While it cannot penetrate as deeply into tissue as ultrasound, it has a higher resolution and can be combined with many other optical techniques to give a vast amount of information.
In ophthalmology, OCT can no longer be described as an ‘emerging’ technology – it is now accepted as a clinical standard for diagnosing and monitoring the
treatment of a number of retinal diseases. OCT’s use in other medical areas has been limited by its poor penetration depth, which, in typical biological samples, is usually only a few millimetres. However, the development of endoscopic probes means OCT can be used to image hollow organs such as the gastrointestinal tract, the bladder and the heart. In cardiology, intravascular OCT can resolve signifi cantly smaller details than the conventional technique of intravascular ultrasound. This makes OCT a valuable technique for visualising plaque lesions or checking the outcome of a stent deployment. The fi rst commercial systems for intravascular OCT in cardiology have recently entered the market and intravascular OCT is now so mature that large-scale commercialisation is expected in the next few years.
OCT has also shown great
an ultra-wide fi eld image of the internal surface of the eye (fundus) reconstruction from an ultra-wide fi eld oct data set. Images courtesy of LMU
12 electro optics l December 2011/January 2012
promise in dermatology. Because skin is the most easily accessible part of the human body and OCT has a limited penetration depth, dermatology was one of the fi rst applications investigated when OCT was fi rst developed. However, the differentiation between benign and malignant lesions in a clinical
setting is a huge challenge, because benign lesions often show the same structure in OCT images as malignant ones.
adding functionality It is in cases such as this where functional OCT could help. While OCT can reveal the morphology (thicknesses of different layers) of a sample, combining OCT with other techniques can reveal much more information. For example, polarisation-sensitive OCT can reveal the different structures of each layer; Doppler OCT can reveal blood fl ow in a sample; multiphoton tomography can add chemical specifi city to the structural imaging capability of OCT; and combining OCT with photoacoustic tomography can give a detailed map of blood vessels – valuable for diagnosing tumours.
It is this idea of combining
different techniques to create functional OCT that has been the focus of a pan-European research project for the last three years. Called FUN OCT, the project includes six partners from Denmark, Germany and Austria. ‘The aim of FUN OCT is to expand the non-invasive optical biopsy capability of OCT and
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