MRI-derived synthetic [¹⁸F]FET PET in neuro-oncology: evaluation in glioma grading and differentiation from solitary brain metastasis.

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Abstract

O-(2-[18F]fluoroethyl)-L-tyrosine positron emission tomography ([¹⁸F]FET PET) is clinically useful in neuro-oncology but limited by cost and availability. We assessed the clinical utility of magnetic resonance imaging (MRI)-derived synthetic [¹⁸F]FET PET. A total of 489 patients with histologically confirmed gliomas or brain metastases were retrospectively analyzed. A deep learning model generated synthetic PET images from multimodal MRI in the overall cohort and subgroups. Synthetic PET was evaluated against reference PET for image similarity by peak signal-to-noise ratio (PSNR) and structural similarity index (SSIM), standardized uptake value ratio (SUVR) analysis by Pearson correlation and Bland-Altman analysis, and blinded reader assessment for glioma grading and high-grade glioma (HGG) versus solitary brain metastasis (SBM) differentiation using receiver operating characteristic analysis with area under the curve (AUC). Synthetic PET showed high similarity to reference PET in the overall, glioma, and metastasis groups (PSNR, 34.7-35.5 dB; SSIM, 0.90-0.96), and SUVR correlations were strong (r = 0.77-0.93, all P < 0.001), with minimal bias and narrow limits of agreement. Compared with MRI alone, MRI with synthetic PET improved glioma grading and HGG-SBM differentiation, increasing AUC from 0.815 to 0.941 and from 0.816 to 0.901 for glioma grading and from 0.731 to 0.871 and from 0.784 to 0.872 for HGG-SBM differentiation across the 2 readers (all P < 0.05). No significant differences were found between MRI with synthetic and reference PET for either task (all P > 0.05). MRI-derived synthetic [¹⁸F]FET PET may enhance glioma grading and HGG-SBM differentiation, providing a PET-like alternative when FET PET is unavailable.

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