Fig. 2

[¹⁸F]BBPA histogram for differential diagnosis in clinical scenario. A A 62/M patient displayed right frontal lesion with ring-like contrast enhanced on MRI, and the whole lesion (light blue area), contrast enhanced area (blue area) and non-contrast enhanced area (red area) were semi-automatically defined. The contrast enhanced (blue) area exhibited a BBPA uptake similar to normal distribution which is in accordance with tumor characteristics, while the central (red) region revealed a positive skewed [¹⁸F]BBPA activity that is corresponding to non-neoplastic lesion. The whole tumor displayed a dual-peaked histogram pattern (light blue line) that can be divided into two single peaks on the separate segmentations (red and blue area), and this metabolic characteristics was suggestive of glioblastoma. B A 71/F patient exhibited right frontal metastatic breast cancer and received cranial radiotherapy and tyrosine kinase inhibitor. Four months after treatment, the tumor was considered to have treatment response thanks to the slightly improved volume effect on MRI. However, the lesion displayed increased symmetric [¹⁸F]BBPA activity, suggesting there was remaining active tumor. The patient continued tyrosine kinase inhibitor treatment, and six months after [¹⁸F]BBPA PET, the patient progressed clinically and radiologically. C A 63/M patient with periventricular metastatic lung cancer received radiotherapy and achieved completed response on MRI. Fifteen months after radiotherapy, the patient developed regional abnormal signal on MRI that was initially considered as tumor recurrence. However, the lesion exhibited positive skewed [¹⁸F]BBPA distribution that was suggestive of non-neoplasms, and the lesion remained radiologically stable at 1-year follow-up (without anti-tumor treatment)