18F-FACBC PET/MRI in diagnostic assessment and neurosurgery of gliomas

Purpose: This pilot study aimed to evaluate the amino acid tracer 18F-FACBC with simultaneous PET/MRI in diagnostic assessment and neurosurgery of gliomas. Materials and Methods: Eleven patients with suspected primary or recurrent low- or high-grade glioma received an 18F-FACBC PET/MRI examination before surgery. PET and MRI were used for diagnostic assessment, and for guiding tumor resection and histopathological tissue sampling. PET uptake, tumor-to-background ratios (TBRs), time-activity curves, as well as PET and MRI tumor volumes were evaluated. The sensitivities of lesion detection and to detect glioma tissue were calculated for PET, MRI, and combined PET/MRI with histopathology (biopsies for final diagnosis and additional image-localized biopsies) as reference. Results: Overall sensitivity for lesion detection was 54.5% (95% confidence interval [CI], 23.4–83.3) for PET, 45.5% (95% CI, 16.7–76.6) for contrast-enhanced MRI (MRICE), and 100% (95% CI, 71.5–100.0) for combined PET/MRI, with a significant difference between MRICE and combined PET/MRI (P = 0.031). TBRs increased with tumor grade (P = 0.004) and were stable from 10 minutes post injection. PET tumor volumes enclosed most of the MRICE volumes (>98%) and were generally larger (1.5–2.8 times) than the MRICE volumes. Based on image-localized biopsies, combined PET/MRI demonstrated higher concurrence with malignant findings at histopathology (89.5%) than MRICE (26.3%). Conclusions: Low- versus high-grade glioma differentiation may be possible with 18F-FACBC using TBR. 18F-FACBC PET/MRI outperformed MRICE in lesion detection and in detection of glioma tissue. More research is required to evaluate 18F-FACBC properties, especially in grade II and III tumors, and for different subtypes of gliomas