Development of an Imaging Technique for Boron Neutron Capture Therapy.

The development of 4-B-borono-2-F-fluoro-L-phenylalanine (FBPA) for use in positron emission tomography (PET) has contributed to the progress of boron neutron capture therapy (BNCT). FBPA has shown similar pharmacokinetics and distribution to 4-B-borono-L-phenylalanine (BPA) under various conditions in many animal studies. FBPA PET is useful for treatment indication. A higher FBPA accumulation ratio of the tumor to the surrounding normal tissue (T/N ratio) indicates that a superior treatment effect is expected. In clinical settings, a T/N ratio of higher than 2.5 or 3 is often used for patient selection. Moreover, FBPA PET is useful for predicting the B concentration delivered to the tumor and surrounding normal tissues, enabling high-precision treatment planning. Precise dose prediction using FBPA PET data has greatly improved the treatment accuracy of BNCT. However, the methodology used for the data analysis of FBPA PET findings varies; thus, data should be evaluated using a consistent methodology so as to be more reliable. In addition to PET applications, the development of FBPA as a contrast agent for magnetic resonance imaging that combines gadolinium and B is also in progress.