Tissue characterization using high wave number Raman spectroscopy

TLDR

Raman spectroscopy is a powerful diagnostic tool for tissue identification, but in vivo use is hampered by intense Raman signals from fused silica fiber cores, requiring complex and costly filtering designs. Because fused silica produces no Raman signal in the 2400–3800 cm⁻¹ high‑wave‑number region, a single unfiltered fiber can both deliver laser light and collect scattered light without filtering. In vitro comparison of brain tumor and bladder tissue maps shows that the high‑wave‑number region yields diagnostic information equivalent to the fingerprint region, indicating that simple standard fibers could replace complex probes for many clinical applications.

Abstract

Raman spectroscopy is a powerful diagnostic tool, enabling tissue identification and classification. Mostly, the so-called fingerprint (~400–1800 cm–1) spectral region is used. In vivo application often requires small flexible fiber-optic probes, and is hindered by the intense Raman signal that is generated in the fused silica core of the fiber. This necessitates filtering of laser light, which is guided to the tissue, and of the scattered light collected from the tissue, leading to complex and expensive designs. Fused silica has no Raman signal in the high wave number region (2400–3800 cm–1). This enables the use of a single unfiltered fiber to guide laser light to the tissue and to collect scattered light in this spectral region. We show, by means of a comparison of in vitro Raman microspectroscopic maps of thin tissue sections (brain tumors, bladder), measured both in the high wave number region and in the fingerprint region, that essentially the same diagnostic information is obtained in the two wave number regions. This suggests that for many clinical applications the technological hurdle of designing and constructing suitable fiber-optic probes may be eliminated by using the high wave number region and a simple piece of standard optical fiber.