located or occurring within a blood vessel, or operating from within a blood vessel
Nissen is best known for pioneering intravascular ultrasound, a method of exploringarteries from within and measuring the amount of sludge clogging them up.
intravascular in American English
(ˌɪntrəˈvæskjulər)
adjective
Anatomy
in, or directly into, a vessel, esp. a blood vessel