A study method using early dynamic acquisition of [F]fluorodopa positron emission tomography for the differential diagnosis between progression and radionecrosis of brain metastases after radiotherapy.

BACKGROUND

It is difficult to distinguish between the brain metastasis progression (BMP) and brain radionecrosis (BRN) on the basis of F-3,4-dihydroxyphenylalanine positron emission tomography/computed-tomography (F-FDOPA PET/CT) data. The advent of silicon photomultiplier (SiPM) PET technology makes it possible to study dynamic volumes and potentially improve diagnostic accuracy. We developed a method for processing F-FDOPA PET/CT in the differential diagnosis between BMP and BRN. The method involves a short (3-second) sampling time during a 4-minute acquisition on a SiPM-PET/CT machine. We prospectively included 15 patients and 19 metastases. All acquisitions were performed in list mode acquisition for 25 min on a four-ring SiPM PET/CT system. We calculated the ratios between the maximum activity in the lesion's voxel and the mean activity in the contralateral region (VOImax/CLmean) or the mean activity in the white matter (VOImax/WMmean).

RESULTS

Seven lesions were classified as BMP and twelve were classified as BRN. Statistically significant intergroup differences in the VOImax/CLmean and VOImax/WMmean activity ratios were observed for both the clinical volume and the early acquisition. The best performing quantitative variable was the VOImax/CLmean ratio on early acquisition, with a diagnostic accuracy of 94.7%, a sensitivity of 100%, and a specificity of 91.7%.

CONCLUSION

The F-FDOPA PET/CT data acquired a few minutes after the bolus injection confirms its value in differentiating between BMP and BRN, compared to the much longer classic clinical protocol.