Toward clinical application of prompt gamma spectroscopy for in vivo monitoring of boron uptake in boron neutron capture therapy

In boron neutron capture therapy (BNCT) the absorbed dose to the tumor cell s and healthy tissues depends critically on the boron uptake. Pronounced in dividual variations in the uptake patterns have been observed for two boron compounds currently used in clinical trials. This implies a high uncertain ty in the determination of the boron dose component. Ln the present work a technique known as prompt gamma spectroscopy (PGS) is studied that potentia lly can be used for in vivo and noninvasive boron concentration determinati on at the time of the treatment. The technique is based upon measurement of gamma rays promptly emitted in the B-10(n, alpha)Li-7 and H-1(n, gamma)D-2 reactions. The aim of this work is to prepare the present setup for clinic al application as a monitor of boron uptake in BNCT patients. Therefore, a full calibration and a set of phantom experiments were performed in a clini cal setting. Specifically, a nonuniform boron distribution was studied; a s kin/dura, a larger blood vessel, and tumor within a head phantom was simula ted. The results show that it is possible to determine a homogeneous boron concentration of 5 mug/g within +/-3% (1 standard deviation). In the nonuni form case, this work shows that the boron concentration can be determined t hrough a multistep measurement procedure, however, with a somewhat higher u ncertainty (similar to 10%). The present work forms the basis for a subsequ ent clinical application of the PGS setup aimed at in vivo monitoring of bo ron uptake. (C) 2001 American Association of Physicists in Medicine.