A 12 × 12 pixel detector has been developed and used in a laboratory experiment for lost fast-ion diagnostics. With gamma rays in the MeV range originating from nuclear reactions (9)Be(α, nγ)(12)C, (9)Be(d, nγ)(12)C, and (12)C(d, pγ)(13)C, a high purity germanium (HPGe) detector measured a fine-energy-resolved spectrum of gamma rays. The HPGe detector enables the survey of background-gamma rays and Doppler-shifted photo peak shapes. In the experiments, the pixel detector produces a gamma-ray image reconstructed from the energy spectrum obtained from total photon counts of irradiation passing through the detector's lead collimator. From gamma-ray image, diagnostics are able to produce an analysis of the fast ion loss onto the first wall in principle.