The boron distribution in cells from a rat brain, into which a boron compound (BOPP) had been injected in the context of Boron Neutron Capture Therapy (BNCT), was analyzed with a nuclear microprobe by Nuclear Reaction Analysis. The 11B(p,α)Be ∗ reaction was utilized at the resonance at 0.63 MeV. Boron images and Scanning Transmission Ion Microscopy (STIM) images were recorded and evaluated by various methods. The sample preparation was straightforward and introduced only a minimum of steps which could potentially interfere with the result. Methods to to compare different boron compounds for BNCT are suggested. The boron was distributed fairly evenly in the cells. The average boron concentration was about 7 ppm dry weight, and the variation over individual cells small.