Neurosurgical microscopic solid laser-based light inhibits photobleaching during fluorescence-guided brain tumor removal with 5-aminolevulinic acid

Background: Fluorescence image guided surgery (FIGS) with 5-aminolevulinic acid for malignant gliomas improves surgical outcome. One of the problems during FIGS is photobleaching under surgical microscopic white light. A solid laser-based white light source for neurosurgery that we developed does not include light with a wavelength of around 405 nm, which is strongly absorbed by protoporphyrin IX. In the present study, we examined the efficacy of this light source to prevent the photobleaching of protoporphyrin IX-induced fluorescence. Methods: Filter papers transfused with protoporphyrin IX solution and a coronally sectioned F98 glioma rat model pretreated with 50 mg/kg 5-aminolevulinic acid were continuously exposed to white light. One group was exposed to conventional xenon-based white light and another group was exposed to laser-based white light. Fluorescence at a wavelength of 635 nm was measured with a radiospectrometer (in vitro study) and the relative fluorescence brightness was also measured in digital images (in vivo study) under excitation from violet blue light emitted from diodes every 5 min. Results and conclusion: Estimated time for 50% photobleaching was prolonged about two times in the laser-based white light exposure group compared with that in the xenon-based white light exposure group (9.1/18.7 min). In the brain tumor rat model, it was also prolonged about 2.7 times (15.1/40.7 min). A laser-based white light source may inhibit photobleaching during FIGS for malignant gliomas. This light source for neurosurgical microscopy has the potential to prolong the prognosis of malignant glioma patients.