Spectrally agile endoscopic fluorescence imaging

Thesis

During minimally invasive (keyhole) tumour resection surgery, the sentinel node is typically visualized by injecting an opaque dye into the tumour and monitoring uptake in the node via endoscopy. Conventional illumination methods for sentinel node mapping are limited to shallow penetration depths causing nodes below fat tissue to be overlooked. This paper reports on the development of novel optical techniques for the implementation of a spectrally-agile laparoscopic system capable of identifying near-infrared fluorescence from clinically-approved fluorescent dyes. The construction of a tuneable illumination unit is described; this combines a series of near-infrared laser diodes with conventional visible light for fluorescence excitation and sample illumination respectively. Additionally, a methodology based on a micro-lens approach for separating near-infrared fluorescence images from conventional colour images at the laparoscope's eyepiece with minimal distortions is presented. Near-infrared detection methods based on optical multichannel analyzers are discussed, with special consideration given to their commercial availability and potential for endoscopic applications in the abdominal, gastrointestinal and gynaecological cavities. In order to determine maximum penetration depths achievable with our system, Monte Carlo and analytic methods have been implemented to model photon transport through mammary fat tissue at visible and near-infrared wavelengths, revealing imaging sensitivity. Specifically, expected optical penetration depths at 690 nm, 732 nm, 785 nm and 830 nm are 2.27 mm, 2.90 mm, 3.15 mm and 3.26 mm respectively. In essence, laparoscopic assisted spectroscopy based on tuneable excitation and emission can be employed to increase sensitivity and specificity of sentinel node detection and may provide the additional benefit of differentiation between normal and cancerous tissue.

Authors: Quinn, SD

• Publication date: 2012
• DOI: 10.5287/ora-j2vyre4qw
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English
• Keywords: endoscopy; fluorescence imaging
• Subjects: Physics