Clinical trials are the essential mechanism through which new medical imaging devices and methods are tested. However, with the growing number of such medical solution, clinical trials are proven to be too slow and too costly. Computational resources and modeling technologies have brought us to a place that we can consider computational alternatives to clinical trials: virtual trials where the trial take place in silico. This course provides an essential introduction to virtual clinical trials, focused primarily on imaging. Topics covered include models of human anatomy and physiology, models of imaging processes primarily CT and breast imaging, models of interpretation processes, standardization of the VCT pipeline, and regulatory prospects of VCT. The course will include applications of VCT in designing and affirming new medical imaging equipment and methods, the use VCT data for prototyping and/or complementing the conduct of real clinical trials, and near-hands-on experience in conducting a few example mini-trials as a part of the class.