A novel leuco phenoxazine color former containing L-phenylalanine at the protecting group was prepared for radiation detection systems. It forms elongated self-assembled fibers in common organic solvents, leading to that efficient gelation. FE-SEM and FT-IR of the xerogel showed the color former formed a three-dimensional net-like structure. The color former organogel showed sufficient sensitivity to gamma rays that it can be used for imaging in heavy particle radiotherapy and has good potential for three-dimensional radiation detection systems.