Assessment of proton microbeam analysis of 11B for quantitative microdistribution analysis of boronated neutron capture agents in biological tissues

The B-11(p,alpha)Be-8* nuclear reaction was assessed for its ability to quantitatively map the in vivo subcellular distribution of boron within gliosarcomas treated with a boronated neutron capture therapy agent. Intracranial 9L gliosarcomas were produced in Fischer 344 rats. Fourteen days later, the majority of the rats were treated with f-boronophenylalanine and killed humanely 30 or 180 min after intravenous injection. Freeze-dried tumor cryosections were imaged using the B-11(p,alpha)Be-8* nuclear reaction and proton microbeams obtained from the nuclear microprobe at Lawrence Livermore National Laboratory. The B-11 distributions within cells could be imaged quantitatively with spatial resolutions down to 1.5 mum, minimum detection limits of 0.8 mg/kg, and acquisition times of several hours. These capabilities offer advantages over alpha-particle track autoradiography, electron energy loss spectroscopy, and secondary ion mass spectrometry (SIMS) for, quantification of B-11 in tissues. However, the spatial resolution, multi-isotope capability, and analysis times achieved with SIMS are superior to those achieved with B-11(p,alpha)Be-8* analysis. When accuracy in quantification is crucial, the B-11(p,alpha)Be-8* reaction is well suited for assessing the microdistribution of B-11. Otherwise, SIMS may well be better suited to image the microdistribution of boron associated with neutron capture therapy agents in biological tissues. (C) 2003 by Radiation Research Society.