Dai J et al, 2013: Critical Analysis of a New Generation Electrohydraulic Lithotripter: A Single Institution Experience with the Medispec E3000TM
Dai J, Al Ekish S, Harisaran V, Thavaseelan S, Pareek G.
The Warren Alpert Med. Sch. of Brown Univ., Section of Minimally Invasive Urol. Surg., Providence, Rhode Island, United States
PURPOSE: The Medispec E3000TM is a new generation electrohydraulic lithotripter with a wider focal width comparable to the Dornier HM3TM. Herein, we evaluate the efficacy of this machine for treatment of urinary stones at our institution by shockwave lithotripsy (SWL).
MATERIALS AND METHODS: 168 urinary calculi were treated using the Medispec E3000TM lithotripter over a 14 month period (10/2010-12/2011). During the first six months (10/2010-6/2011), a low power ramping protocol of 11-12-17 kV was used, and for the remaining six months (6/2011-12/2011), stones were treated with a higher power ramping protocol of 15-17-22.5 kV. A subanalysis of these groups was performed, as well as for stone location. The major endpoint was stone-free rate (SFR), defined as fragments < 4 mm on follow-up imaging. Data was analyzed using Fisher's Exact test and 2-tailed student's t- test.
RESULTS: The study included 102 males and 66 females with an average age of 52.8. Mean stone size was 6.9 x 7.2 mm, which was significantly associated with SFR (p < 0.0010). The overall SFR was 64.9%, with no significant difference between stones treated with the low power protocol (61.3%) and the high power protocol (70%). SFR varied by location across the upper pole (64.9%), mid-pole (57.1%), lower pole (68.4%), renal pelvis (79.2%), proximal ureter (66.6%), mid-ureter (83.3%), and distal ureter (53.8%), but these differences were not significant (p = 0.59). Efficiency quotient for the Medispec E3000TM was 54%.
CONCLUSIONS: Overall, we achieved SFR of 64.9% in our initial experience with the Medispec E3000TM. Optimizing treatment parameters may further improve success rates, and further outcomes follow up may allow a more comprehensive evaluation of the lithotripter's overall efficacy.
J Endourol. 2013 Mar 6. [Epub ahead of print]
PMID:23461464 [PubMed - as supplied by publisher]
Recent physical studies on the properties of shock waves have indicated that improved disintegration of stones might be obtained with a wider focus. Such a design is assumed to be associated with a more effective squeezing effect than that obtained in lithotripters with a small focus. In order to achieve this effect the Medispec E3000 has a focal volume of 13 x 60 mm and a power pressure between 42.5 and 91 MPa.
In 168 cases reported in this article the stone size was measured in two dimensions, but the information was insufficient for more detailed conclusions on the stone burden. The efficiency of a lithotripter is best expressed in terms of disintegration that results in fragments ance for as successful disintegration.