DIFFERENTIAL DIAGNOSIS OF BRAIN GLIOMAS: THE POSSIBILITIES OF DYNAMIC PET-CT WITH 18F-FLUORODEOXYGLUCOSE

Abstract

Purpose. The aim of this prospective study, which included the analysis of data from 52 patients with primary brain gliomas, was to look for additional PET-CT biomarkers determined on the basis of the analysis of the first minute of dynamic PET scanning in order to increase the specificity and sensitivity of differential diagnosis of gliomas. 18F-FDG was administered simultaneously with the data collection began. Materials and methods. The study group included data of 52 patients, 27 men, 25 women, age 18-80 years, median 48 years + 12. Histologically, these were glioblastomas (n= 19), anaplastic astrocytomas (n=9), anaplastic oligodendrogliomas (n= 6), benign oligodendrogliomas (n= 6), and diffuse astrocytomas (n=9). Each patient underwent a standard brain MR- study (T2, T2-FLAIR, T1, 3D T1 with contrast enhancement). The selected patients then underwent PET-CT examination (Siemens Truepoint scanner, Siemens Medical Solutions, USA) with radiopharmaceutical 18F-FDG according to the dynamic protocol developed in the our department. Data collection started simultaneously with intravenous administration of radiotracer for the next 40 minutes. 34 frames of 6X10 sec, 6x20 sec, 6x30 sec, 4x60 sec and 12x150 sec were reconstructed. Results. Among the proposed new PET parameters, T/N60s (accumulation index averaged over the first 60 seconds after the administration of 18 F-FDG) turned out to be the most successful, which made it possible to statistically reliably separate glioblastomas from all other histological subtypes of gliomas. Thus, for glioblastomas, T/N60s = 1.6 ± 0.4, and for anaplastic oligodendrogliomas, it was 1.1 ± 0.2, p<0.01. Moreover, T/N60s made it possible to reliably differentiate not only Gr. II from gliomas Gr.III + Gr.IV, but also to differentiate glioblastomas from anaplastic astrocytomas (p<0.01) and glioblastomas from anaplastic and benign oligodendrogliomas (p<0.05 and p<0.01, respectively). All types of gliomas had an T/N60s>1.0, while its final accumulation could be lower than in intact tissue. A possible reason for this phenomenon may be tumor neoangiogenesis, which develops even in the case of low-grade gliomas. Conclusion. The use of the proposed technique for studying patients with brain gliomas and analyzing the data obtained with the new PET biomarkers significantly improves the quality of differential diagnosis of gliomas using 18F-FDG. It also allows reducing the study time for one patient without losing the specificity and sensitivity of diagnosis.