Abstract
Fluorescence guided neurosurgery based on 5-aminolevulinic acid (5-ALA) has significantly increased maximal safe resections. Fluorescence lifetime imaging (FLIM) of 5-ALA could further boost this development by its increased sensitivity. However, neurosurgeons require real-time visual feedback which was so far limited in dual-tap CMOS camera based FLIM. By optimizing the number of phase frames required for reconstruction, we here demonstrate real-time 5-ALA FLIM of human high- and low-grade glioma with up to 12 Hz imaging rate over a wide field of view (11.0 x 11.0 mm). Compared to conventional fluorescence imaging, real-time FLIM offers enhanced contrast of weakly fluorescent tissue.
Highlights
Intraoperative fluorescence guidance using 5-aminolevulinic acid (5-ALA) induced protoporphyrin IX (PpIX) has made a strong impact in the field of neurosurgery since its first clinical use in 1998 [1]
PpIX fluorescence lifetime imaging of 5-ALA labeled glioma samples has shown the potential to differentiate tumorous from non-tumorous tissue. [21,26]
We inspected a solution of 1 μg/ml PpIX dissolved in dimethyl sulfoxide (DMSO) and acquired images for exposure times from 1 ms to 110 ms while sampling with 4, 8 and 16 phase frames
Summary
Intraoperative fluorescence guidance using 5-aminolevulinic acid (5-ALA) induced protoporphyrin IX (PpIX) has made a strong impact in the field of neurosurgery since its first clinical use in 1998 [1]. While high-grade gliomas (HGG) emit strong fluorescence which can be seen by the surgeon, low-grade gliomas (LGG) as well as parts of infiltration zones of HGG do not exhibit sufficient visible fluorescence, limiting the range of applications [5,6] To overcome this problem, quantification of PpIX concentration via spectroscopic methods has been proposed with promising results [7,8,9]. Hyperspectral wide-field fluorescence imaging has demonstrated the ability to quantify low PpIX emissions and can be considered state of the art for detecting LGG [10,11] This technology can readily be implemented with surgical instrumentation and has shown to achieve image acquisition rates of 0.5 to 1 Hz [11]. Blood layers reduce the fluorescence signal excited at 405 nm [15], stressing the need for alternative visualization solutions which are less dependent on fluorescence intensity
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