The characteristics of broad and narrow focal zone lithotripters

Yuri A. Pishchalnikov, James A. McAteer, R. Jason VonDerHaar, Irina V. Pishchalnikova, James C. Williams

Research output: Chapter in Book/Report/Conference proceedingConference contribution

3 Scopus citations

Abstract

The focal width of a lithotripter is a measure of the diameter of its focal zone, the region where acoustic pressures are at least half the maximum positive pressure generated at a given power level. Different lithotripters have different focal widths. The Dornier HM3, for example, has a focal width of ∼10-12mm and for many years this was the widest focal zone among clinical machines. Electromagnetic lithotripters tend to have narrower focal zones, in the range of ∼4-6mm. Recent studies suggesting that focal width plays an important role in stone breakage prompted this assessment of two electromagnetic lithotripters. Acoustical mapping using a fiber optic probe hydrophone (FOPH-500) and breakage of U-30 gypsum model stones were used to compare a conventional lithotripter (Dornier DoLi-50) and a broad focal zone device (XiXin XX-ES). FOPH mapping characterized the focal width of the DoLi to be about 5mm and that of the XX-ES to be much wider (∼18mm). For stone breakage experiments the DoLi was fired at power level 3 (mid-range) and the XX-ES was operated at the recommended clinical setting of 9.3 kV. Both lithotripters were fired at 60 SW/min. U-30 model stones held in a 2mm mesh basket were positioned at the clinical target point on the acoustic axis and at 5mm steps laterally, and the number of SW's to complete fragmentation was counted. Breakage onaxis was similar for the two machines (DoLi 676±105 SW's versus XX-ES 644±123 SW's, p>0.6), but at 15mm the DoLi required nearly twice the number of SW's as the XX-ES (DoLi 3006±780 SW's versus 1726±972 SW's, p<0.006). This demonstrates that a broad focal zone lithotripter is more effective in breaking stones off axis and supports the idea that focal width is an important feature, likely to be relevant in the clinical setting where respiratory motion may limit the effectiveness of narrow focal zone machines.

Original languageEnglish (US)
Title of host publicationRenal Stone Disease 2 - 2nd International Urolithiasis Research Symposium
Pages238-242
Number of pages5
DOIs
StatePublished - Oct 22 2008
Event2nd International Urolithiasis Research Symposium - Indianapolis, IN, United States
Duration: Apr 17 2008Apr 18 2008

Publication series

NameAIP Conference Proceedings
Volume1049
ISSN (Print)0094-243X
ISSN (Electronic)1551-7616

Other

Other2nd International Urolithiasis Research Symposium
CountryUnited States
CityIndianapolis, IN
Period4/17/084/18/08

Keywords

  • Local width
  • Peak pressure
  • Shock wave lithotripsy
  • Stone breakage efficiency

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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    Pishchalnikov, Y. A., McAteer, J. A., VonDerHaar, R. J., Pishchalnikova, I. V., & Williams, J. C. (2008). The characteristics of broad and narrow focal zone lithotripters. In Renal Stone Disease 2 - 2nd International Urolithiasis Research Symposium (pp. 238-242). (AIP Conference Proceedings; Vol. 1049). https://doi.org/10.1063/1.2998028