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Minispectrometer with handheld probe for 5-ALA based fluorescence-guided surgery of brain tumors: Preliminary study
J F Cornelius1, J M Placke1, J Knipps1
1Klinik für Neurochirurgie, Universitätsklinikum Duesseldorf, Heinrich-Heine-Universität, Duesseldorf, Germany.
Introduction:
Recently a mini-spectrometer with a handheld probe quantifying 5-aminolevulinic acid (5-ALA) based fluorescence intensity of brain tumors was developped by Kim et al. to improve fluorescence-guided neurosurgery.
Objective:
To evaluate if this new tool is capable to discriminate nuances of fluorescence intensity of strongly fluorescing tumors (glioblastomas (GBM) and meningiomas (MM)). To study different modes of measurement (touch/no-touch). To determine protoporphyrin IX (PPIX) concentration in tumor tissue as compared to a laboratory spectrometer.
Material And Methods:
The tumor tissue was resected from patients operated in the neurosurgical department of University Hospital Duesseldorf, Germany between 01/2014 and 06/2014. Two spectrometers, one custom-built with a handheld probe ("mini-spectrometer") and one commercial laboratory spectrometer were employed. After calibration they were used to detect and compare fluorescence intensity of human brain tumor samples ex vivo under standardized conditions. The mini-spectrometer was tested at different distances to the tumor. PPIX concentrations of tumor lysates were determined by both spectrometers.
Results:
In total n=11 tumors (5 MM and 6 GBM) resulting in 17 tumor biopsies were studied. All GBM showed significant higher fluorescence intensity as compared to MM (Z=-3.123, p=0.001). The fluorescence signal was inversely proportional to the square of the distance (GBM: R2=0.226; F=4.683; p<0.5; MM: R2=0255; F=8.042; p<0.01). The mini-spectrometer recorded fluorescence signals up to 2mm ("no-touch"). Determination of PPIX concentration in tumor by the mini-spectrometer did not differ from a laboratory spectrometer.
Conclusion:
The mini-spectrometer was a very sensitive tool for detection of 5-ALA based fluorescence of human brain tumors. Fluorescence intensity of glioblastoma and meningioma were significantly different. A no-touch mode of measurement was possible. PPIX concentration in tumor tissue could be determined as precisely as with a laboratory spectrometer. In future clinical trials the practicability of using such a tool in vivo has to be further evaluated.
