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 ∼10–12 mm 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 ∼4–6 mm. 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 (∼18 mm). For stone breakage experiments the DoLi was fired at ...
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