A sub-millimetre Raman biopsy probe fabricated by femtosecond laser writing and chemical etchingThursday (25.06.2020) 13:10 - 13:50 Room 3
A common clinical route to diagnosing cancer in the body is to perform a surgical biopsy followed by histopathology, where suspect tissue is removed and inspected by histology. The procedure has several shortcomings: Often, cancerous lesions are visually indistinguishable from healthy tissue, and so biopsy sampling is performed “blind”. Additionally, the time between taking a biopsy and delivering a diagnosis can be several weeks, leading to a delay in the onset of treatment. Finally, histology is complex, requiring a trained specialist to make an often subjective classification. A relatively new procedure with the potential to aid traditional biopsies is a Raman-based optical biopsy. A Raman biopsy is a medical procedure that uses Raman spectroscopy to classify tissue in situ in the body. The technique has the potential to offer real-time classification of tissue at a molecular level – allowing tissue health to be determined quantitatively without delay. To perform a Raman biopsy in hard-to-reach areas of the body, such as the oesophagus, optical signals are transported via optical fibres. Raman spectroscopy relies on the collection of very weak signals, and therefore miniaturised optics are often needed at the distal end to guide light onto the relevant tissue area and then return Raman scattered light back for spectral analysis. The manufacture of these optical systems remains a critical challenge in translating the technique into routine clinical pathways.
To address this challenge, we have applied ultrafast laser assisted etching (ULAE) to fabricate a novel miniature Raman probe. ULAE relies on focused femtosecond laser pulses to drive non-linear absorption processes in transparent materials such as fused silica. After laser inscription, the laser modified material exhibits an enhanced chemical etching rate, allowing this material to be selectively removed. Several components can be written on a single substrate, facilitating passive optical alignment which reduces traditionally labour-intensive micro-assembly. We have designed a Raman probe which makes full use of the fabrication capabilities of ULAE. The probe has a sub-millimetre diameter – suitable for deployment within the bore of standard surgical needles – and a confocal sensing cone with a 0.8 numerical aperture. At the conference we will present the design, fabrication and characterisation of our Raman probe as well as the results from proof-of-concept Raman analysis.
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