| dc.description.abstract | Cancer affects 1 in 2 people during their lifetime. Early diagnosis is critical for ensuring good prognostic outcomes for patients, enabling earlier intervention and informing patient care. The current ’gold standard’ of cancer diagnosis is histopathological analysis; visual assessment of morphological features within samples. This process is labour intensive, time consuming, and prone to inter- and intra- observer disagreements. Raman spectroscopy is a highly specific, real-time, chemical analysis tool with the ability to discriminate between cancerous and healthy tissue, and thus represents a potentially powerful diagnostic tool. Fibre optic Raman probes provide the flexibility and size required in order to facilitate in vivo diagnostics.
This study develops upon previous work investigating the use of Raman spectroscopy needle probes for the analysis of lymph node tissue. Raman needle probes can incorporate the chemical specificity of Raman spectroscopy into the existing diagnostic pathway, however issues with etaloning and silica background contributions were identified as areas for increasing performance. This work addresses both of these issues through the optimisation of the experimental setup, as well as the creation and testing of different fibre optic probe designs.
Analysis of the effect of different cameras on obtained etaloning signals determined that the use of a camera with an AR coating optimised for the spectral region of interest resulted in a significant reduction in etaloning signals. It was identified that the use of 200 𝜇m fibres leads to improvements in sampling volume, signal quality and silica contributions. The use of higher sampling volume in particular may prove beneficial when measuring lymph node samples, which are known to be highly heterogeneous and therefore prone to under sampling issues during diagnosis. The use of this fibre and the high performance camera within a final probe design obtained a higher diagnostic performance with measurements of ten lymph node samples than was achievable with the previous generation of probe design, indicating the strength of the optimisation of the design. The use of the final design also reduced the incidence of burning of the samples and overall levels of fluorescence and etaloning.
Further testing of Shifted Excitation Raman Difference Spectroscopy (SERDS) indicated that of 7 tested excitation wavelengths between 830.0 nm and 833.9 nm, a combination of 830.0 and 832.4 represents the best available performance in terms of both removal
of silica and etaloning signals. This shift was then tested on two lymph node samples for the first analysis of lymph node tissue measured with a Raman needle probe using the SERDS technique, and demonstrated a powerful reduction in etaloning signals in particular. This development of the probe design and optimisation of experimental setup lead
to measurements that indicate the strength of Raman spectroscopy needle probes as a potential tool for the in vivo assessment of lymph nodes. | en_GB |
