A catheter assembly for an ultrasound system includes an elongated catheter for insertion into the cardiovascular system of a patient. The catheter includes a sheath that defines a lumen extending along the sheath. The catheter assembly also includes an imaging core for inserting into the lumen of the catheter. The imaging core includes an elongated, rotatable driveshaft and an imaging device coupled to the distal end of the driveshaft with rotation of the driveshaft causing a corresponding rotation of the imaging device. The imaging device includes at least one transducer for transforming applied electrical signals to acoustic signals and also for transforming received echo signals to electrical signals. The imaging core further includes a swellable material disposed on at least the at least one transducer and configured and arranged to rotate with rotation of the driveshaft and to swell upon exposure to a fluid.
