Prompt γ-ray imaging in hadron therapy is a novel approach for range verification. Due to the high energy of prompt γ-rays emitted during therapeutic irradiation in the order of MeV, Compton imaging is a feasible method. In this work, an imaging prototype together with the corresponding data handling and an image reconstruction framework are presented. Data and reconstructed images from laboratory measurements are shown and evaluated. A spatial resolution of 7 mm full width at half maximum in a distance of 7 cm has been achieved. More importantly, current limitations were identified for further work. It has been shown that an assumption on the unknown initial photon energy can considerably improve the imaging result.