The dean who was hired less than three years ago to fix problems at the University of Missouri School of Medicine has resigned as the school faces a federal fraud investigation. Dr. Robert Churchill will leave the university in October to prevent further distractions surrounding the investigation of two of the school's radiologists, according to MU officials. The radiologists, Dr. Kenneth Rall and Dr. Michael Richards, were dismissed Friday after an internal audit found the doctors illegally billed Medicare for services performed by resident doctors in training.