A Preliminary Investigation with ¹⁸F-NaF Dynamic PET/CT Brain Imaging for Primary Intracranial Tumors

Purpose: ¹⁸F-NaF is a highly sensitive tracer for the detection of bone metastases and involvement; however, little is known regarding its efficiency in detecting primary intracranial tumors. The aim of this study was to evaluate the feasibility and diagnostic efficiency of ¹⁸F-NaF dynamic PET/CT (dPET/CT) for primary intracranial tumors.

Methods: Sixty-six patients with primary intracranial tumors, who underwent preoperative routine MRI, ¹⁸F-NaF dPET/CT and ¹⁸F-FDG static PET/CT (sPET/CT) brain scans were consecutively enrolled. ¹⁸F-NaF dPET/CT was performed using a 35-minute (7 frames × 300 sec) list mode protocol simultaneously with the ¹⁸F-NaF bolus injection. The first and the last frame (5-min) were used for reconstruction. Qualitative and quantitative analysis (SUVmax; TBR, the tumor-to-background ratio; SCR, SUVmax change ratio) were performed, and the diagnostic performance of ¹⁸F-NaF dPET/CT was compared with routine MRI and ¹⁸F-FDG sPET/CT.

Results: In total, 53 of 66 patients were histopathologically confirmed, and a total of 53 tumors (5/48, malignant/benign tumors) were identified. In total, 51/53 lesions (96.2%) were detected with ¹⁸F-NaF dPET/CT vs. 52/53 lesions (98.1%) with routine MRI sequences (P > 0.05); 50/53 lesions (94.3%) were detected with the first frame vs. 46/53 lesions (86.8%) with the last frame of ¹⁸F-NaF dPET/CT (P > 0.05). Twenty-four patients were also diagnosed via ¹⁸F-FDG sPET/CT. In total, 13/24 lesions (54.2%) were detected with ¹⁸F-FDG sPET/CT vs. 23/24 lesions (95.8%) with ¹⁸F-NaF dPET/CT and 24/24 lesions (100%) with routine MRI sequences (P < 0.05, respectively).There was a statistically significant difference in SCR, SUVmax, and TBR at the first frame between benign and malignant tumors (P < 0.05). The ROC curve demonstrated that AUCs of TBR and SUVmax of the first frame were higher than 0.80 (AUC = 0.93 and 0.84, respectively, P < 0.05). TBR ≥ 3.86 and SUVmax ≥ 3.35 of the first frame were chosen as the optimal cut-off values, corresponding to a maximum Youden’s index of 0.83 and 0.75.

Conclusions: The present results demonstrate that ¹⁸F-NaF dPET/CT is superior to static ¹⁸F-FDG PET/CT for detecting primary intracranial tumors and could provide additional diagnostic information. The first frame of ¹⁸F-NaF dPET/CT is more valuable than the last frame.