Ex vivo optical coherence tomography imaging of larynx tissues using a forward-viewing resonant fiber-optic scanning endoscope

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. © 2012 SPIE

Spatial compounding algorithm for speckle reduction of dynamic focus OCT images

Optical coherence tomography is capable of imaging the microstructures within tissues. To preserve the transverse resolution at all imaging depths, we implement a dynamic focusing scheme. To improve the quality of images further, a simple speckle reduction scheme is employed which uses the vibration introduced by the translation stage used for axial scanning. A spatial compounding technique is developed based on co-registration followed by an averaging algorithm. We conclude that the degree of speckle reduction achieved is worth the expense of more complicated processing required. © 1989-2012 IEEE

Phantom testing of a novel endoscopic OCT probe: A prelude to clinical in-vivo laryngeal use

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. © Copyright SPIE

Ex-vivo endoscopic laryngeal cancer imaging using two forward-looking fiber optic scanning endoscope probes

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

3-D optical coherence tomography of the laryngeal mucosa

Laryngeal carcinoma is one of the commonest primary head and neck malignancy and the need for early identification is very important for successful treatment. Outpatient fibreoptic examination of the larynx is unreliable in differentiating benign, pre-malignant and malignant lesions, and therefore surgeons have to rely on biopsies for a definitive diagnosis. This is an invasive procedure requiring general anaesthesia and may have a detrimental effect on the patient's voice. Conventional imaging modalities (ultrasound, computed tomography and magnetic resonance imaging) have a limited resolution and hence cannot give sufficient information on the extent or nature of laryngeal lesions. The aim of our study is to investigate the feasibility of optical coherence tomography (OCT) in imaging the normal larynx, to lay the foundations for an investigation of its ability to differentiate between benign and malignant disease. Ten tissue specimens from normal larynges were imaged with an 850 nm OCT system that was capable of providing both B-scan (longitudinal or cross-section) images as well as C-scan (en-face or images at constant depth). The en-face OCT mode allowed us to reconstruct 3-D OCT images of the tissue examined. Imaged specimens were processed with standard histopathological techniques and sectioned in the plane of the B-scan OCT images. Haematoxylin-eosin stained specimens were compared with the OCT images thus collected. Preliminary results showed good correlation between OCT images and histology sections in normal tissue