For a study, it was determined that Fluorescence was induced by 5-aminolevulinic acid (5-ALA) in high-grade glioma (HGG), which was used for resection. However, in low-grade glioma (LGG), the usefulness of 5-ALA–induced fluorescence was unknown. Time kinetics and time dependencies were yet to be investigated. The work determined the real-time kinetics of protoporphyrin IX (PpIX) in LGG using hyperspectral fluorescence measurements to determine what parameters predict fluorescence. Patients with grade II gliomas who had imaging that could not rule out HGGs were given 5-ALA at a dose of 20 mg/kg body weight four hours before surgery. Researchers used a hyperspectral camera to measure the fluorescence intensity (FI) and PpIX concentration (CPpIX) in tumor tissue. The role of 18F-fluoroethyl-l-tyrosine (18F-FET) PET values in predicting fluorescence was investigated using apparent diffusion coefficient (ADC)–based tumor cell density, Ki-67/MIB-1 index, chromosomal 1p/19q codeletion, and 18F-fluoroethyl-l-tyrosine (18F-FET) PET values.

A total of 81 biopsies from 25 patients were included in the study. FI and CPpIX maxima were seen in fluorescence-positive tissues between 7 and 8 hours following injection. Regardless of any MRI gadolinium contrast enhancement, peaks of FI and CPpIX were found throughout this 7- to 8-hour time window when visible fluorescence was recorded. Gadolinium enhancement (P=0.008), Ki-67/MIB-1 index (P<0.001), 18F-FET PET uptake ratio (P=0.004), and ADC-based tumor cellularity (P=0.017) were all substantially different between fluorescing and non-fluorescing tissue, although 1p/19q codeletions were not. The uptake of 18F-FET PET and the Ki-67/MIB-1 index was independently associated with fluorescence using logistic regression. The fluorescence-based evaluation of CPpIX in human LGG tissues about 18F-FET PET uptake and Ki-67/MIB-1 is described in this paper. Fluorescence in LGGs peaked between 7 and 8 hours after 5-ALA application, similar to HGGs, which has implications for administration time.