Ultrasonic probes for producing multiple cavitation volumes

A probe comprising:

• a shank including a proximal end, a distal end, and a shaft extending from the proximal end to the distal end, the proximal end of the shank configured to be coupled to a source of ultrasonic energy, and the shank being configured to propagate the ultrasonic energy from the proximal end to a tip at the distal end in a propagation direction parallel to a longitudinal axis of the shank;
• a first groove within the shaft, the first groove positioned proximate to the tip;
• and
• a second groove within the shaft, the second groove positioned along the shank between the first groove and the proximal end,
• wherein the shaft includes a non-grooved section between the first groove and the second groove, the first groove is spaced from the second groove by a first distance approximately equal to a first integer multiple of a half-wavelength of a resonance frequency of the shank in the propagation direction, and the first groove is located proximate to a first location at which the ultrasonic energy corresponds to a first odd integer multiple of a quarter wavelength of the resonance frequency.