Abstract
1039
Objectives: In the current BNCT, the accurate estimation of 10B concentration in the tumors and normal tissues is important to enhance therapy effect and to avoid side effects. Four-borono-2-[18F]-fluoro-phenylalanine (FBPA) PET has been employed to estimate the accumulation of 10B concentration in the tumors and normal tissues. The tumor/normal tissue ratio (T/N ratio) and the tumor/blood ratio (T/B ratio) by FBPA PET have been used to select candidates of BNCT. Patients with T/N ratio more than 2.5 and/or T/B ratio more than 2.0 were the candidate of BNCT according to the guideline by Japanese Society of Neutron Capture Therapy. The values of T/N ratio and/or T/B ratio may not be accurate due to the deformation and extirpation cavity formation after previous surgical or chemoradiotherapy.This study evaluated the relationship between T/N ratio and SUV max and between T/B ratio and SUV max.
Methods: Twenty-seven consecutive patients with suspected local recurrence or residual tumors (male/female, 11/25; age, 57 years (range, 18 to 78)) had FBPA PET study during October 2013 - April 2016. Fourteen cases of brain tumor, 12 cases of head and neck cancer, and 1 case of malignant melanoma were included. Written informed consent was obtained from all patients. After fasting for at least four hours, patients received an intravenous injection of FBPA (3.7MBq/kg for PET/CT). Whole-body images were acquired 60 min after injection by means of PET/CT system (Eminence SOPHIA SET-3000 BCT/X; Shimadzu, Japan). Spherical volumes of interest (VOI) were manually set by encompassing tumor margin. The 1cm diameter VOI were set in contralateral normal tissue and left ventricle. The SUV max values were determined by the same VOI for tumors. These data were obtained using PMOD software, ver.3.6. Statistical analysis was done by linear regression and spearman’s correlation tests.
Results: There was a correlation between T/N ratio and SUV max (correlation coefficient 0.75, slope 1.48, and intercept 0.05). T/N ratio of 2.5 corresponded to SUV max of 3.74. There was a correlation between T/B ratio and SUV max (correlation coefficient 0.90, slope 1.02, and intercept 0.19). T/B ratio of 2.0 corresponded to SUV max of 2.24.
Conclusion: The threshold value of BNCT candidates can be measured in the SUV max images by setting VOI for tumor alone in stead of taking the count ratio of tumor to normal tissue and/or blood in FBPA PET. Research Support: