Optical coherence tomography is a novel imaging technique providing potentially high resolution tri-dimensional images
of tissue microstructure up to 2-3mm deep. We present pre-clinical data from a novel miniaturised OCT probe utilised
for endoscopic imaging of laryngeal mucosa. A 1300nm SS-OCT probe was passed in tandem with a flexible fibreoptic
nasoendoscope into the larynx of a manikin. Ex vivo OCT images were acquired using a desktop 1300nm TD-OCT
imaging system. The feasibility, robustness and safety of this set-up was demonstrated as a preliminary step to extending
the use of this assembly to a clinical patient cohort with varying laryngeal pathologies.
Larynx cancer is one of the most common primary head and neck cancers. For early-stage laryngeal cancer, both
surgery and radiotherapy are effective treatment modalities, offering a high rate of local control and cure. Optical
coherence tomography (OCT) is an established non-invasive optical biopsy method, capable of imaging ranges of 2-
3 mm into tissue. By using the principles of low coherence light interferometry, OCT can be used to distinguish
normal from unhealthy laryngeal mucosa in patients. Two forward-looking endoscope OCT probes of different sizes
in a sweeping frequency OCT (SS-OCT) configuration were compared in terms of their performances for ex-vivo
laryngeal cancer imaging.
The setup configuration of the first OCT probe unit was designed and constructed at the Institute of Applied Physics
RAS, Russia (diameter of 1.9 mm and the rigid part at the distal end is 13 mm long). The second OCT endoscope
probe was constructed at the Department of Biomedical Engineering at Johns Hopkins University, USA, using a
tubular piezoelectric actuator with quartered electrodes in combination with a resonant fiber cantilever (diameter of
2.4 mm, and rigid part of 45 mm).
Cross-sectional images of laryngeal lesions using the two OCT configurations were aquired and compared with
OCT images obtained in a 1310 nm SS-OCT classical non-endoscopic system. The work presented here is an
intermediate step in our research towards in-vivo endoscopic laryngeal cancer imaging.
A miniature endoscope probe for forward viewing in a 50 kHz swept source optical coherence tomography (SS-OCT)
configuration was developed. The work presented here is an intermediate step in our research towards in vivo
endoscopic laryngeal cancer screening. The endoscope probe consists of a miniature tubular lead zirconate titanate
(PZT) actuator, a single mode fiber (SMF) cantilever and a GRIN lens, with a diameter of 2.4 mm. The outer surface
of the PZT actuator is divided into four quadrants that form two pairs of orthogonal electrodes (X and Y). When
sinusoidal waves of opposite polarities are applied to one electrode pair, the PZT tube bends transversally with
respect to the two corresponding quadrants, and the fiber optic cantilever is displaced perpendicular to the PZT tube.
The cantilever's resonant frequency was found experimentally as 47.03 Hz. With the GRIN lens used, a lateral
resolution of ~ 13 μm is expected. 2D en face spiral scanning pattern is achieved by adjusting the phase between the
pairs of X and Y electrodes drive close to 90 degrees. Furthermore, we demonstrate the imaging capability of the
probe by obtaining B-scan images of diseased larynx tissue and compare them with those obtained in a 1310 nm SS-OCT
classical non-endoscopic system.
Optical coherence tomography (OCT) is a potentially useful 'optical biopsy' tool in medicine. To realize this potential doctors must be able to interpret OCT images with at least the same accuracy as conventional histology. It is therefore important that some accurate method of comparing OCT images with conventional histology be found. Despite numerous OCT vs. conventional histology studies in the literature the methods used for comparison have, by necessity, been approximate because it is not possible to cut a physical tissue section in the same plane as the OCT optical section (partly due to histology processing artefacts). In this paper we present a method of rendering solid tissue volumes with semi-transparency using the Virtual Reality Modelling Language (VRML) and devise a VRML script which allows any two volume data sets to be manipulated within the same region of virtual space. This allows the structure of a whole volume of tissue imaged with OCT to be directly compared with the serial section reconstruction of the conventionally stained histology. As the whole volume is visualized any corresponding tissue regions can be more easily identified despite tissue processing artefacts. We demonstrate the effectiveness of our method usng an ex vivo biopsy of human breast carcinoma.
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