A system including a catheter assembly, which can include a housing, a sheath, and a core wire disposed within a sheath lumen. The housing can include a retraction-extension mechanism configured to retract the sheath from a first, fully extended position of the sheath, in which position a distal portion of the core wire can be wholly disposed within the sheath lumen. The housing can accommodate a proximal length of the sheath, and the retraction-extension mechanism can be configured to retract the proximal length of the sheath into the housing and expose a working length of a distal portion of the core wire. The core wire can include a sonic connector at a proximal end of the core wire configured to connect to an ultrasound-producing mechanism for ultrasound-based modification of one or more intravascular lesions with the working length of the core wire.
