Intelligent Tutoring Systems (ITS) are increasingly breaking free of the lab and entering the classroom. These practice-based software systems promise significant learning gains over more traditional e-learning approaches. However, their widespread uptake is still hampered by the difficulty in building them. Over the past ten years we have developed ITS authoring tools that have evolved to the point that it is now feasible for teachers to build their own systems. We report on one such system, an ITS for medical imaging, built by the head of the Medical Imaging Department of a polytechnic institution using VIPER, an ITS authoring system we have developed. Despite requiring no specialist skills (other than domain knowledge) to build, an initial study provides evidence that the resulting ITS is effective at teaching the important concepts of this subject, and demonstrates that is it feasible for teachers to develop their own intelligent tutoring systems.