NADH-fluorescence scattering correction for absolute concentration determination in a liquid tissue phantom using a novel multispectral magnetic-resonance-imaging-compatible needle probe

Abstract

In this report, a quantitative nicotinamide adenine dinucleotide hydrate (NADH) fluorescence measurement algorithm in a liquid tissue phantom using a fiber-optic needle probe is presented. To determine the absolute concentrations of NADH in this phantom, the fluorescence emission spectra at 465 nm were corrected using diffuse reflectance spectroscopy between 600 nm and 940 nm. The patented autoclavable Nitinol needle probe enables the acquisition of multispectral backscattering measurements of ultraviolet, visible, near-infrared and fluorescence spectra. As a phantom, a suspension of calcium carbonate (Calcilit) and water with physiological NADH concentrations between 0 mmol l−1 and 2.0 mmol l−1 were used to mimic human tissue. The light scattering characteristics were adjusted to match the backscattering attributes of human skin by modifying the concentration of Calcilit. To correct the scattering effects caused by the matrices of the samples, an algorithm based on the backscattered remission spectrum was employed to compensate the influence of multiscattering on the optical pathway through the dispersed phase. The monitored backscattered visible light was used to correct the fluorescence spectra and thereby to determine the true NADH concentrations at unknown Calcilit concentrations. Despite the simplicity of the presented algorithm, the root-mean-square error of prediction (RMSEP) was 0.093 mmol l−1.

NADH-fluorescence absorption correction to determine absolute fluorophore concentrations of a liquid tissue model

“…As shown in the previous study [9], the absorbance spectrum of NC overlaps with the fluorescence emission spectrum of NADH in the visible region from 420 to 650 nm. Consequently, the fluorescence emission intensity cannot be used to determine the NADH concentration of a matrix which contains NC.…”

“…Gardner et al claim that their model estimates the fluorophore concentration with an average standard deviation of 15% [7], and Chen et al are able to achieve an average relative error of 7% for the prediction of free Ca 2+ concentrations using Fura-2 [8]. The correction algorithm within this study is an extension of a previously published work [9]. It is based on differences between two integrals of the absorbance remission and the fluorescence emission spectrum, respectively.…”

“…Similar to the previous study [9], all experiments are carried out using a liquid tissue model. The solvent of this model is demineralised water, whose scattering, fluorescence and absorbance properties are similar to those of human skin.…”

“…A remission measurement setup with a multispectral needle probe is used to obtain UV/VIS-remission and fluorescence emission spectra. The experimental setup has already been reported in detail [9]. Briefly, the unit consists of a measuring probe [10], where two fibers act as emitting fibers and one fiber acts as a detecting fiber.…”

Design of a Multimodal Imaging System and Its First Application to Distinguish Grey and White Matter of Brain Tissue. A Proof-of-Concept-Study

“…However, the created images (Figure 3(2a,4a)) are based on reflectivity at 750 nm. The chosen wavelength lies in the optical window of tissue that ranges from 600 nm to 940 nm [69]. This spectral region is independent of the main absorber in blood-perfused tissue, hemoglobin [70].…”