Extracorporeal Shock Wave Lithotripsy for Urinary Tract Stones Using MPL 9000 Spark Gap Technology and Ultrasound Monitoring

Abstract

Between November 7, 1988 and December 31, 1989, 881 treatments were given with the MPL 9000 lithotriptor to 513 sites in 510 renal units in 464 patients. Of the stones 447 (87.1%) were in the kidney, 64 (12.5%) in the ureter and 2 (0.4%) in the bladder. Stone size was up to 2 cm. in 58.5% of the cases, greater than 2 to 3 cm. in 25.8% and more than 3 cm. in 15.7%, including complete or partial staghorn, or multiple stones. Of the patients 54.2% received only 1 treatment, 17.6% received 2 treatments and 28.2% received more than 2 treatments (re-treatment was necessary in 45.8%). The number of shocks used varied from 610 to 4,000 at 14 to 24 kv., the usual energy used being 18 kv. Of the stones 30.2% were treated after Double-J stents were inserted. A patient was declared stone-free only when no stone particle was visible on a plain abdominal x-ray (or ultrasound if the stone was radiolucent). X-rays 3 months after extracorporeal shock wave lithotripsy (ESWL) were available for review in 397 patients (79.9%) and 72.8% were stone-free (with the aforementioned criteria) at 6 months (61.5% without ancillary procedures and 11.3% after ancillary procedures). Of a subset of 106 patients 84% were stone-free within 3 months when ESWL was restricted to a smaller stone burden, the number of shock waves administered was increased and energy was restricted to 14 to 18 kv. Over-all, 9.1% of the patients needed ancillary measures, including percutaneous nephrostomy in 1.6%, push-back for ESWL in 1.9%, ureterorenoscopy in 5.4%, percutaneous nephrolithotomy in 0.6% and pyelolithotomy/ureterolithotomy in 2.8%. The MPL 9000 device has the unique combination of electrohydraulic shock wave generation and ultrasound monitoring. The latter attribute has the distinct advantage of avoiding radiation to allow for visualization of nonopaque renal and gallbladder calculi. In addition, because there is continuous stone visualization during fragmentation accurate stone targeting can be maintained. The combination of ultrasound monitoring and spark gap technology allows for effective stone fragmentation.

Are microbubbles necessary for the breakdown of liquid water subjected to a submicrosecond pulse?

“…1 Practical applications of dielectric liquids include switching elements for pulsed power systems, 2 use in energy storage, as water-filled gaps for the design of acoustic equipment, 3,4 the insulation of high-voltage devices, 5 and as the medium in spark erosion machines. 1 Practical applications of dielectric liquids include switching elements for pulsed power systems, 2 use in energy storage, as water-filled gaps for the design of acoustic equipment, 3,4 the insulation of high-voltage devices, 5 and as the medium in spark erosion machines.…”

Microscopic analysis for water stressed by high electric fields in the prebreakdown regime

“…There is considerable interest in the study of electrical breakdown in water (and other liquids) for a variety of reasons. 1 Practical applications of dielectric liquids include water-filled gaps for the design of acoustic equipment, 2,3 the insulation of high-voltage devices, 4 as the medium in spark erosion machines, 5 and use in energy storage and switching elements for pulsed power systems. Generally, for highvoltage pulsed power systems, solids or gases at high pressure have been used as the dielectric material.…”

Reduction of radiation exposure to patients in the follow‐up of shockwave lithotripsy

“…Although patients were limited to those with upper urinary tract stones (to standardise the radiographs required) the patients were not selected for stone type, number or size, or associated variations in treatment. It was thus intended that the patients were representative of those usually presenting with stones, and comparable with patients in other parts of the world [12]. In the present analysis, common practice in radiation prevention was followed by using standardized dose-equivalents per patient [6,7]; these are known for most adult radiation procedures [13].…”