Even before the discovery of X-rays, attempts at non-invasive medical imaging required an understanding of fundamental principles of physics. Students frequently do not see these connections because they are not taught in beginning physics courses. To help students understand that physics and medical imaging are closely connected, we have developed a series of active learning units. For each unit we begin by studying how students transfer their knowledge from traditional physics classes and everyday experiences to medical applications. Then, we build instructional materials to take advantage of the students' ability to use their existing learning and knowledge resources. Each of the learning units involves a combination of hands-on activities, which present analogies, and interactive computer simulations. Our learning units introduce students to the contemporary imaging techniques of CT scans, magnetic resonance imaging (MRI), positron emission tomography (PET), and wavefront aberrometry. The project's web site is http://web.phys.ksu.edu/mmmm/.