Diffuse reflectance spectroscopy of epithelial tissue with a smart fiber-optic probe

Abstract

Diffuse reflectance spectroscopy (DRS) with a fiber-optic probe can noninvasively quantify the optical properties of epithelial tissues and has shown the potential as a cost-effective, fast and sensitive tool for diagnosis of early precancerous changes in the cervix and oral cavity. However, current DRS systems are susceptible to several sources of systematic and random errors, such as uncontrolled probe-to-tissue pressure and lack of a real-time calibration that can significantly impair the measurement accuracy, reliability and validity of this technology as well as its clinical utility. In addition, such systems use bulky, high power and expensive optical components which impede their widespread use in low- and middle-income countries (LMICs) where epithelial cancer related death is disproportionately high. In this paper we report a portable, easy-to-use and low cost, yet accurate and reliable DRS device that can aid in the screening and diagnosis of oral and cervical cancer. The device uses an innovative smart fiber-optic probe to eliminate operator bias, state-of-the-art photonics components to reduce size and power consumption, and automated software to reduce the need of operator training. The device showed a mean error of 1.4 ± 0.5% and 6.8 ± 1.7% for extraction of phantom absorption and reduced scattering coefficients, respectively. A clinical study on healthy volunteers indicated that a pressure below 1.0 psi is desired for oral mucosal tissues to minimize the probe effects on tissue physiology and morphology.

Real time evaluation of tissue optical properties during thermal ablation of ex vivo liver tissues

“…The fiber-optic probe includes two side-firing fibers (200/220 mm), spaced apart by 1 mm for DRS, a homemade extrinsic Fabry-Perot interferometric (EFPI) temperature sensor [21] and two forward firing fibers (200/ 220 mm) for self-calibration [22,23], all housed into a 17G hypodermic needle. One of the two side-firing fibers is connected to the white LED to illuminate the target tissue and the other to the visible spectrometer A (Vis Spec A) for detection of diffuse reflectance from the tissue.…”

“…The self-calibration records a calibration spectrum in concurrent with DRS measurement which is used to correct for instrument fluctuations and probe bending loss [22,23]. The EFPI sensor head was fabricated by laser fusion bonding of two multimode fibers, separated by a small air gap (L c ), to a borosilicate capillary tube with an outer diameter of 400 lm (Figure 1(c)).…”

“…Thermal expansion of the borosilicate tubing alters the optical path difference between the two interfering waves that are reflected by the end-faces of the two fiber tips, shifting the peak positions of the interferogram. The temperature is determined by tracking the temperature-dependent wavelength shift in the interferogram [23]. The temperature sensor was calibrated in a water bath and was found to have an accuracy of 1 C between 20 and 95 C. A laptop computer with a custom LabVIEW program and embedded MATLAB scripts was used for instrument control and data acquisition and analysis.…”

Review of diverse optical fibers used in biomedical research and clinical practice

“…[117][118][119] In an elastic scattering process, photons hit tissue components and are scattered without experiencing a change in their energy, which means without a change in wavelength. The relative intensity of the backscattered light that can be collected by an optical fiber probe depends on the sizes and concentrations in the tissue of scattering components (e.g., nuclei, mitochondria, and connective tissue) and absorbing components (e.g., hemoglobin).…”

Monitoring of tumor radio frequency ablation using derivative spectroscopy

“…However, the absolute magnitude of a reflectance spectrum is dependent on a subtle variation in probe-to-tissue coupling and pressure, making it difficult to obtain reproducible and reliable reflectance spectra from the measured tissue. [30][31][32] This study differs from previous studies in various ways. First, using derivative spectroscopy, we mainly focused on the spectral characteristics of metHb, while eliminating the magnitude difference and suppressing the background effects from scattering and other substances (e.g., oxyHb, deoxyHb, and bile).…”