Raman-shifted alexandrite laser for soft tissue ablation in the 6- to 7-µm wavelength range

Prior work with free-electron lasers (FELs) showed that wavelengths in the 6- to 7-µm range could ablate soft tissues efficiently with little collateral damage; however, FELs proved too costly and too complex for widespread surgical use. Several alternative 6- to 7-µm laser systems have demonstrated the ability to cut soft tissues cleanly, but at rates that were much too low for surgical applications. Here, we present initial results with a Raman-shifted, pulsed alexandrite laser that is tunable from 6 to 7 µm and cuts soft tissues cleanly—approximately 15 µm of thermal damage surrounding ablation craters in cornea—and does so with volumetric ablation rates of 2–5 × 10−3 mm3/s. These rates are comparable to those attained in prior successful surgical trials using the FEL for optic nerve sheath fenestration

Detection of colonic inflammation with Fourier transform infrared spectroscopy using a flexible silver halide fiber

Persistent colonic inflammation increases risk for cancer, but mucosal appearance on conventional endoscopy correlates poorly with histology. Here we demonstrate the use of a flexible silver halide fiber to collect mid-infrared absorption spectra and an interval model to distinguish colitis from normal mucosa in dextran sulfate sodium treated mice. The spectral regime between 950 and 1800 cm−1 was collected from excised colonic specimens and compared with histology. Our model identified 3 sub-ranges that optimize the classification results, and the performance for detecting inflammation resulted in a sensitivity, specificity, accuracy, and positive predictive value of 92%, 88%, 90%, and 88%, respectively

Infrared Spectroscopic Studies of Cells and Tissues: Triple Helix Proteins as a Potential Biomarker for Tumors

In this work, the infrared (IR) spectra of living neural cells in suspension, native brain tissue, and native brain tumor tissue were investigated. Methods were developed to overcome the strong IR signal of liquid water so that the signal from the cellular biochemicals could be seen. Measurements could be performed during surgeries, within minutes after resection. Comparison between normal tissue, different cell lineages in suspension, and tumors allowed preliminary assignments of IR bands to be made. The most dramatic difference between tissues and cells was found to be in weaker IR absorbances usually assigned to the triple helix of collagens. Triple helix domains are common in larger structural proteins, and are typically found in the extracellular matrix (ECM) of tissues. An algorithm to correct offsets and calculate the band heights and positions of these bands was developed, so the variance between identical measurements could be assessed. The initial results indicate the triple helix signal is surprisingly consistent between different individuals, and is altered in tumor tissues. Taken together, these preliminary investigations indicate this triple helix signal may be a reliable biomarker for a tumor-like microenvironment. Thus, this signal has potential to aid in the intra-operational delineation of brain tumor borders. © 2013 Stelling et al