A Side-viewing Fluorescence Needle Probe for Brain Biopsy Guidance

This study presents a fiber-optic needle probe to detect malignant tissue prior to removal from the brain.

The probe comprises separate multimode optical fibers for excitation and detection of fluorescence. A higher numerical aperture was used in the collection fiber to provide a larger acceptance angle for fluorescence emission light. Using a dual-bore ferrule to simplify fabrication and ensure optical alignment, the fibers were angle-polished and silver-coated using Tollens' reagent to produce a side-facing needle probe, which was integrated into a 16-gauge needle (outer diameter 1.65 mm). Sensitivity of the probe was assessed using a tissue-mimicking fluorescent brain phantom, with optical scattering, absorption and fluorescence properties comparable to brain tissue. To demonstrate feasibility in a clinical environment, experiments were performed on fresh brain tissue obtained from patients undergoing surgical resection for glioblastoma.

When the tissue-mimicking fluorescent phantom was obscured by a thin layer of non-fluorescent material, sensitivity was found to be comparable to a free-space fluorescence surgical microscope. Fluorescence was detectable through an obscuring thickness of 0.4 mm of low absorption, non-fluorescent material, and 0.3 mm of high absorption, non-fluorescent material. When evaluated on fresh human brain tissue, the probe detected the characteristic fluorescence signal of protoporphyrin IX, with a stronger signal detected in tissue with an increased density of malignant cells.

These findings show feasibility of using a dual-fiber fluorescence needle probe to identify malignant brain tissue.

This work contributes to advancing the use of optical methods for surgical guidance.