A lithotripsy assembly includes a target positioned inside a body that has an external surface. A lithotripsy dry head shock wave transducer is aimed at the target. A gel enclosure is defined at least partially by the body and the lithotripsy transducer. A volume of acoustic coupling fluid is positioned in the gel enclosure, which is fluidly connected to a vacuum pump. The vacuum pump draws air bubbles out of the gel enclosure to reduce attenuation of shock waves.
