Solitary Brain and Neck Lesions Enhancing at MR Imaging: Evaluation with¹⁸F-(2S, 4R) 4-fluoroglutamine PET

Purpose: To prospectively determine whether differences between benign and malignant lesions in brain and neck can be depicted with ¹⁸F-(2S, 4R) 4-fluoroglutamine (¹⁸F-FGln) PET. Materials and Methods: 24 patients (14 women, 10men; age range, 26-79 years) with solitary brain lesions that were enhanced at magnetic resonance (MR) imaging underwent dynamic or static whole-brain ¹⁸F-FGln PET/CT after giving informed consent in this institutional review board-approved. Histopathologic diagnoses were made in all cases (9 high-grade gliomas, 9 metastases to the brain, 2 primary brain lymphoma and 4 benign lesions). In four benign lesions, 1 was cerebral infarction, 1 was chromophobe cell pituitary adenoma, another was Warthin's tumor of the parotid gland and the last one was necrotic tissue of brain after radiotherapy. The maximum standardized uptake value (SUVmax) for lesion and peritumoral regions was measured on PET images was calculated. Differences were assessed with one-way analysis of variance, Fisher exact, and Student t tests.

Results: Differences in SUVmax between high-grade gliomas (5.18±1.14), metastases (3.11 ± 1.68), and primary brain lymphomas (7.01±1.39) were significant (P < 0.05). These differences were also significant at pairwise analysis. The time activity curve (TAC) of dynamic ¹⁸F-FGln PET/CT in the three groups of malignant tumors show that lymphomas with a rapid increase in the early phase (0~5min.pi), and a consistent in the middle (5~15min.pi) and late phase (15~30min.pi); the high-grade gliomas with a low level in the initial phase, a slow increase in the middle and late phase; the metastases with a slow increase in the first and middle phase, and a consistent in late phase. In four benign lesions, there was mild radioactive uptake in the lesion edge of cerebral infarction (SUVmax=2.17), no obvious uptake in Warthin’s tumor (SUVmax=0.88), and moderate uptake in pituitary adenoma and necrotic tissue after radiotherapy (the SUVmax were 3.67 and 4.86 respectively).

Conclusions: High-grade gliomas, metastases, and lymphomas may be distinguished on the basis of measured ¹⁸F-FGln uptake and TAC. Higher uptake of ¹⁸F-FGln is a significant feature of primary brain lymphomas. The uptake of ¹⁸F-FGln in some benign tumors, such as the pituitary adenoma, and in the necrotic tissues of brain tumors after radiotherapy requires special attention and further study.

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