title: Medical ultrasound
context: A contrast medium for medical ultrasonography is a formulation of encapsulated gaseous microbubbles[30] to increase echogenicity of blood, discovered by Dr Raymond Gramiak in 1968[31] and named contrast-enhanced ultrasound. This contrast medical imaging modality is clinically used throughout the world,[32] in particular for echocardiography in the United States and for ultrasound radiology in Europe and Asia.
question: When was ultrasound first used in medicine?
answers: 1968