An optical biopsy system that combines diffuse reflectance spectroscopy and fluorescence lifetime measurements can distinguish between cancerous and healthy tissue in the liver. The technology could make it easier to diagnose liver cancer, which is the sixth most common cancer globally. Researchers from Orel State University in Russia developed the system, which combines the two light-based techniques to evaluate markers that relate to cellular metabolism — which differs between healthy and cancerous tissue cells. To perform their technique, the researchers designed a device to be compatible with the needles that are currently used for liver biopsies. Prior to the design process of the instrument, surgeons with whom the researchers were consulted on the work noted the difficulty of performing needle biopsies in the right location. The location of early-stage tumors can be difficult to pinpoint when inserting a tiny needle into the liver to acquire a tissue sample. The instrument developed by the team aims to overcome the difficulty and, as a result, prevent incorrect diagnoses. “It could thus one day help surgeons more precisely navigate the biopsy instrument to decrease the number of errors in taking tissue samples that are used for diagnosis,” said Evgenii Zherebtsov, a member of the research team. Researchers developed a new optical biopsy system that is compatible with a needle biopsy system and can distinguish between cancerous and healthy liver tissue. Courtesy of Evgenii Zherebtsov, Orel State University. Where diffuse reflectance spectroscopy reveals tissue properties based on how they reflect light, fluorescence lifetime analysis exposes tissues to a wavelength of light that induces fluorescence, and then measures how long that fluorescence takes to fade. The timing of the fluorescence decay depends on the presence of molecules that influence metabolism. “Although our team as well as others have previously used fluorescence intensity for tissue assessment, studies performed in other parts of the body have shown that fluorescence lifetime is less dependent on experimental conditions,” said Elena Potapova, co-first author of the study with Zherebtsov. “Fluorescence lifetime measurements remain more consistent in the presence of blood, when there is nonuniform illumination, or if the contact between the probe and tissue changes due to movement.” For the device, the team selected compact components. The instrument’s probe is 1 mm in diameter, which is compatible with a standard biopsy needle and has separate optical channels for diffuse reflectance spectroscopy and fluorescence lifetime measurements. To assess the sensitivity of the system, the researchers measured known solutions of molecules that influence metabolism. Once they obtained results, they performed experiments in a mouse model with liver cancer and preliminary measurements in patients with suspected liver cancer. The researchers found that their instrument and the parameters that they measured could reliably distinguish liver cancer tissue, healthy liver tissue, and the metabolically changed liver tissues that surround a tumor. Though the system was designed specifically for use in abdominal surgery, the research team believes that its results show that similar technologies could be useful for other medical applications. The researchers also said that their results from tests performed on human patients were reproducible. The team plans to continue measuring fluorescence lifetime parameters in patients with different types of tumors at different stages to generate real-time diagnostic classifiers. This will also make it possible to apply advanced machine learning methods that could help surgeons make clinical decisions during a biopsy procedure. The research was published in Biomedical Optics Express (www.doi.org/10.1364/BOE.447687).
