Exploration of new concepts for sensor based tissue specific laser surgery
Final Report Abstract
Summarizing the results from work packages A-G, diffuse reflectance and auto-fluorescence turned out to be suitable for tissue discrimination. Auto-fluorescence and diffuse reflectance spectroscopy are adequate techniques for nerve identification in the vicinity of bone. Also salivary gland was reliably identified by both measurement methods. PCA with non-scaled spectral data in combination with multiclass QDA showed the best classification results. However, the differentiation performance during laser ablation was slightly reduced. To monitor the ablated tissue during the laser pulses a process emission based analysis was conducted. However, the investigation of process emissions during Er:YAG laser ablation was not fully satisfying: the process emissions produced by the Er:YAG laser turned out to be not fully suitable for a precise tissue discrimination. Hence, to optimize the monitoring of laser-processing we propose to use laser induced breakdown spectroscopy (LIBS). First preliminary tests with LIBS in an open setup (no vacuum chamber) were done. The results of these LIBS tests yielded very promising results. Our workgroup positively evaluated the prospects of diffuse reflectance and auto-fluorescence as a remote controlled feedback system for laser surgery in ex vivo as well as in in vivo studies. However, the crucial nerve/fat and nerve/salivary gland tissue pairs showed reduced discrimination abilities due to the bio-morphological similarity of the two tissue types in ex vivo experiments. An additional reason for the implementation of a remote measurement of auto-fluorescence parameters is the extension of the feedback method for laser surgery of pathological tissue. Here, the method of auto-fluorescence is well investigated in both ex vivo and in in vivo studies. Research in this area suggests an enhancement in the identification of pathologies when combining auto-fluorescence and diffuse reflectance spectroscopy. These studies focus on the pre-therapeutically detection of cancer tissues as a diagnostic instrument and do not yield on the transfer of this data to an intra-operative environment. In contrast, our aim was to evaluate the viability of tissue identification in a highly time efficient and precise way by using diffuse reflectance and the uncorrected (raw) auto-fluorescence spectra for a real-time process control for intra-operative laser surgery as a therapeutically tool. Other works have yet demonstrated the feasibility of an intra-operative diagnostic and therapeutic instrument concerning brain tumors. These studies however, work with the pre-operative application of 5-aminolevulinic acid-induced protoporphyrin IX fluorescence. The present study, however, focuses on an optimization of this method for an identification of tissues without the local or systemic application of optical enhancers. This will account for an easy and practicable implementation in a real-time laser ablation feedback mechanism without any potential additional harm for the patient.
Publications
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Diffuse reflectance spectroscopy for optical soft tissue differentiation as remote feedback control for tissue-specific laser surgery. Lasers Surg Med; 42:319-325, 2010
Stelzle F, Tangermann-Gerk K, Adler W, Zam A, Schmidt M, Douplik A, Nkenke E
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Optical Nerve Detection by Diffuse Reflectance Spectroscopy for Feedback Controlled Oral and Maxillofacial Laser Surgery. Journal of Translational Medicine 2011, 9:20
Stelzle F, Zam A, Adler W, Tangermann-Gerk K, Douplik A, Nkenke E, Schmidt M
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In Vivo Optical Tissue Differentiation by Diffuse Reflectance Spectroscopy: Preliminary Results for Tissue-Specific Laser Surgery. Journal of Surgical Innovation, 19(4): 385-93, 2012
Stelzle F, Zam A, Adler W, Tangermann-Gerk K, Knipfer C, Douplik A, , Schmidt M, Nkenke E
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The Impact of Laser Ablation on Optical Soft Tissue Differentiation for Tissue Specific Laser Surgery - An Experimental Ex Vivo Study. Journal of Translational Medicine, 10:123, 2012
Stelzle F, Terwey I, Knipfer C, Adler W, Tangermann-Gerk K, Nkenke E, Schmidt M
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Qualitative tissue differentiation by analysing the intensity ratios of atomic emission lines using laser induced breakdown spectroscopy (LIBS): prospects for a feedback mechanism for surgical laser systems. J Biophotonics. 2013 Dec 23
Kanawade R, Mahari F, Klämpfl F, Rohde M, Knipfer C, Tangermann-Gerk K, Adler W, Schmidt M, Stelzle F
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Tissue discrimination by uncorrected autofluorescence spectra: a proof-of-principle study for tissue-specific laser surgery. Sensors (Basel). 2013 Oct 11;13(10):13717-31
Stelzle F, Knipfer C, Adler W, Rohde M, Oetter N, Nkenke E, Schmidt M, Tangermann-Gerk K
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Optical nerve identification in head and neck surgery after Er:YAG laser ablation. Lasers Med Sci. 2014 Sep;29(5):1641-8
Stelzle F, Knipfer C, Bergauer B, Rohde M, Adler W, Tangermann-Gerk K, Nkenke E, Schmidt M
