Objectives. To study the in vivo tissue effects of synchronous twin pulse technology. Recently, the concept of a synchronous twin pulse technique for shock wave therapy has been introduced with the development of the Twinheads' unit. Methods. In 10 pigs (20 kidneys), one of three sites was targeted: the renal pelvis (2 pigs), the mid-zone parenchyma (5 pigs), or the lower pole parenchyma (3 pigs). The treatment parameters were 1000 twin shock waves at 14 kV with a 90° angle between the shock wave reflectors using a rate of 60 shock waves/min in 17 kidneys and 120 shock waves/min in 3 kidneys. To study the effect of an increasing number of twin shock waves, 4 animals (8 kidneys) were used; the mid-zone parenchyma was subjected to 2000 and 3000 twin shock waves in 4 kidneys each, using a rate of 60 shock waves/min at 14 kV and a 90° angle in all of them. For comparison with the use of a single head, another 3 animals (6 kidneys) were treated with the use of the single under-table head; all of them received 2000 single shock waves at 14 kV focused on the mid zone of the kidney parenchyma. Within 1 hour of treatment, the treated kidneys were harvested, inspected, and sectioned at the focal site, as well as at 1 and 2 cm distant to the focal site. Results. No gross lesions of the surrounding organs, subcapsular hemorrhage, or parenchymal damage were found at the outer surfaces of the kidneys undergoing twin head shock wave lithotripsy even after 3000 twin shocks. The coronal section revealed minimal gross lesions in 4 of 28 kidneys. Microscopically, the parenchymal changes were minimal. In vivo study of the use of the single under-table head revealed that 5 of 6 kidneys had large subcapsular hematomas at both anterior and posterior surfaces and on coronal section extending into the parenchyma. Microscopically, the changes were significant. Conclusions. Synchronous twin pulse shock waves induced minimal damage compared with single pulse standard shock waves. Of note, even after 3000 twin pulses (ie, a total of 6000 shock waves), the renal damage remained minimal.
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