A catheter assembly for an intravascular ultrasound system includes a catheter, an imaging core, and a shield-coupling capacitor. The catheter defines a lumen extending along a longitudinal length of the catheter. The imaging core is configured and arranged for inserting into the lumen. The imaging core includes a rotatable driveshaft, one or more transducers, one or more conductors, and a conductive shield. The one or more transducers are mounted to the rotatable driveshaft. The one or more conductors are coupled to the one or more transducers and extend along the driveshaft. The conductive shield is disposed around the one or more conductors. The shield-coupling capacitor is electrically coupled to the conductive shield and includes one or more rotating capacitors. The one or more rotating capacitors include one or more rotating plates and one or more stationary plates. The shield-coupling capacitor is configured and arranged for coupling to a system ground.