Hybrid Retargeting for High-Speed Targeted Optical Biopsies
With the increasing maturity of optical biopsy techniques, routine clinical use has become more widespread. This wider adoption of the technique demands effective tracking and retargeting of the biopsy sites, as no visible markers are left following exami
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The Hamlyn Centre for Robotic Surgery, Imperial College London, UK 2 Mauna Kea Technologies, Paris, France {a.mouton,menglong.ye11}@imperial.ac.uk
Abstract. With the increasing maturity of optical biopsy techniques, routine clinical use has become more widespread. This wider adoption of the technique demands effective tracking and retargeting of the biopsy sites, as no visible markers are left following examination. This study presents a high-speed framework for intra-procedural retargeting of probe-based optical biopsies in gastrointestinal endoscopy. A probe tip localisation method using active shape models and geometric heuristics, which eliminates the traditional dependency on shaft visibility, is proposed for automated initialisation. Partial occlusion and tissue deformation are addressed by exploiting the benefits of indirect and direct tracking through a novel combination of geometric association and online learning. Robustness to rapid endoscope motion and improvements in computational efficiency are achieved by restricting processing to the automatically detected video content area and through a feature-based rejection of non-informative frames. Performance evaluation in phantom and in-vivo environments demonstrates accurate biopsy site initialisation, robust retargeting and significant improvements over the state-ofthe-art in processing time and memory usage.
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Introduction
Gastrointestinal (GI) endoscopy together with histopathological tissue examination is the gold-standard for the diagnoses of pathologies in the digestive tract. Endoscopy-guided probe-based optical biopsies, however, allow for in-vivo visualisation of tissues at a cellular level, forgoing the need for tissue excision. Macroscopic retargeting of previously examined sites in this context is challenging due to the absence of physical scars at the biopsy sites [1]. Traditional retargeting, performed by tattooing the examined tissue with ink or Argon Plasma Coagulation (APC), is limited as the ink tends to diffuse and APC causes tissue damage. This study proposes a non-invasive alternative for automated intraprocedural retargeting using purely vision-based techniques, seeking high-speed performance and robustness to rapid endoscope movements, natural tissue deformation and partial site occlusion. Mountney et al. [6] perform intra-procedural retargeting using a visual SLAMbased approach (assuming large-scale rigidity) to generate a 3D model of the c Springer International Publishing Switzerland 2015 N. Navab et al. (Eds.): MICCAI 2015, Part I, LNCS 9349, pp. 471–479, 2015. DOI: 10.1007/978-3-319-24553-9_58
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Fig. 1. Tip localisation: (a) Orientation constraint. (b) Major landmarks computation.
tissue surface. Initialisation is automated by a probe detection technique which exploits the achromatic properties of the probe shaft. Atasoy et al. [2] address tissue deformation using a geometrically-constrained MRF model, while Allain et al. [1] propose retargeting based on epipolar lines, derived from multiple views of a give
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