Fig. 1

[¹⁸F]BBPA histogram distinguishes neoplastic lesions and non-neoplastic lesions. A Flowchart of histogram plotting demonstrated that the [¹⁸F]BBPA PET was first co-registered to contrast-enhanced T1-weighted thin slice MRI, and the region of interest (ROI) was defined by the gross total resection (GTR) area on MRI. The ROI was subsequently applied to [¹⁸F]BBPA PET, and the voxel value within the ROI was documented. A histogram of voxel values was plotted, which reflected the distribution of values within ROI (X-axis ranged 0–4, Y axis ranged according to the number of voxels). B A newly diagnosed glioblastoma (WHO grade IV, IDH wild-type) displayed significant MRI contrast enhancement, and the ROI was semi-automatically defined (blue area) and applied on [¹⁸F]BBPA PET. Histogram of voxels within ROI revealed a pattern similar to normal distribution. C Similarly, the ROI (blue area) in a recurrent glioblastoma (WHO grade IV, IDH wild-type) patient was defined and the histogram can also be fitted as a normal distribution. D On the other hand, a gross resected pathological confirmed radiation necrosis also displayed BBPA activity with SUVmax of 2.97, but the histogram from the ROI (red area) was positively skewed and the SUVmean was 0.56. E Similarly, a viral encephalitis whose lesion completely remission after anti-viral therapy was also contrast-enhanced and [¹⁸F]BBPA active, and the histogram of lesion (red area) was also positively skewed (SUVmax 2.55, SUVmean 0.94)