|
Photodynamic diagnosis (PDD) has become popular in bladder cancer detection. Several studies have however shown
an increased false positive biopsies rate under PDD guidance compared to conventional cystoscopy. Raman
spectroscopy is an optical technique that utilizes molecular specific, inelastic scattering of light photons to interrogate
biological tissues, which can successfully differentiate epithelial neoplasia from normal tissue and inflammations in
vitro.
This investigation was performed to show the feasibility of NIR Raman spectroscopy in vitro on biopsies obtained under
guidance of 5-ALA induced PPIX fluorescence imaging. Raman spectra of a PPIX solution was measured to obtain a
characteristic signature for the photosensitzer without contributions from tissue constituents.
Biopsies were obtained from patients with known bladder cancer instilled with 50ml, 5mg 5-ALA two hours prior to
trans-urethral resection of tumor (TURT). Additional biopsies were obtained at a fluorescent and non-fluorescent area,
snap-frozen in liquid nitrogen and stored at -80 °C. Each biopsy was thawed before measurements (10sec integration
time) with a confocal Raman system (Renishaw Gloucestershire, UK). The 830 nm excitation (300mW) source is
focused on the tissue by a 20X ultra-long-working-distance objective. Differences in fluorescence background between
the two groups were removed by means of a special developed fluorescence subtraction algorithm. Raman spectra from
ALA biopsies showed different fluorescence background which can be effectively removed by a fluorescence
subtraction algorithm. This investigation shows that the interaction of the ALA induced PPIX with Raman spectroscopy
in bladder samples. Combination of these techniques in-vivo may lead to a viable method of optical biopsies in bladder
cancer detection.
|
