Dr. Steven E. Nissen’s most important medical contribution is his pioneering work in using ultrasound images to measure fatty plaque inside the walls of coronary arteries. And so, his supporters say, pharmaceutical companies — whatever they may think of Dr. Nissen’s drug safety crusades — come to him to conduct industry-sponsored research on the heart effects of their medicines. “He has technology that he’s good at that they need access to,” said Dr. Mehmet C. Oz, a well-known heart surgeon at NewYork-Presbyterian Hospital. The technology — known as intravascular ultrasound, or IVUS — involves attaching miniature probes to the tip...