He also spent a great deal of time learning how to do echo cardiography.
From the stltoday.com
Echo cardiography uses standard ultrasound techniques to image two-dimensional sections of the heart.
From the stltoday.com
Before the widespread application of technetium-99m in nuclear medicine, the radioactive isotope thallium-201, with a half-life of 73 hours, was the main substance for nuclear cardiography.