Evaluation of synchronous twin pulse technique for shock wave lithotripsy: determination of optimal parameters for in vitro stone fragmentation.
OBJECTIVE
The Twinheads extracorporeal shock wave lithotriptor (THSWL) is composed of 2 identical shock wave generators and reflectors. One reflector is under the table and the other is over the table with a variable angle between the axes of the 2 reflectors. The 2 reflectors share a common second focal point, making it possible to deliver an almost synchronous twin pulse to the targeted stone. We studied the optimal parameters for in vitro stone fragmentation.


METHODS
Two types of 1 cm artificial stones were used, namely Bon(n)-stones of 3 compositions (75% calcium oxalate monohydrate [COM] plus 25% uric acid, struvite and cystine) and plaster of Paris. The parameters tested were shock wave number (100, 500 and 1,000), shock wave power (8, 11 and 14 kV) and angle between the reflector axes (67, 90 and 105 degrees). After the optimal parameters were determined we studied the disintegrative efficacy of THSWL for 3 types of human urinary calculi, including COM, calcium hydrogen phosphate (brushite) and cystine. Each stone received 1,000 twin shock waves at 14 kV with an angle of 90 degrees between the reflectors. All experiments were done using a rate of 60 twin shock waves per minute. Following lithotripsy stone fragments were processed and sized. The ratio of the weight of fragments greater than 2 mm-to-total weight of all fragments was calculated.


RESULTS
Optimal stone fragmentation results for THSWL were obtained with the maximum number of shock waves (1,000) and full power (14 kV). There was no significant statistical difference in fragment size or the ratio of fragments greater than 2 mm with the use of different angles except for cystine and plaster of Paris calculi, for which the right angle was most effective. At application of the optimal parameters to human stones THSWL produced small fragment size for COM and cystine stones, while brushite stones were not fragmented to the same extent.


CONCLUSIONS
The efficacy of synchronous twin pulse technology improves as the number of shock waves and power increase. A 90-degree angle between the shock wave reflectors is advantageous for certain stones (that is cystine and plaster of Paris) but it is not a factor for other stone compositions. THSWL has satisfactory disintegrative efficacy for human stones, especially COM and cysteine calculi.
Sheir
Khaled Z
KZ
Department of Urology, Urology and Nephrology Center, Mansoura University, Egypt. kzsheir@hotmail.com
Zabihi
Nasim
N
Lee
David
D
Teichman
Joel M
JM
Rehman
Jamil
J
Sundaram
Chandru P
CP
Heimbach
Dirk
D
Hesse
Albrecht
A
Delvecchio
Fernado
F
Zhong
Pei
P
Preminger
Glenn M
GM
Clayman
Ralph V
RV
D002129:Calcium Oxalate; D002130:Calcium Phosphates; D002133:Calcium Sulfate; D003553:Cystine; D006801:Humans; D066298:In Vitro Techniques; D008096:Lithotripsy / Q000295:instrumentation / Q000379:methods*; D017616:Magnesium Compounds; D010316:Particle Size; D010710:Phosphates; D000069877:Struvite; D013673:Technology Assessment, Biomedical; D014527:Uric Acid; D014545:Urinary Calculi
D002130:Calcium Phosphates; D017616:Magnesium Compounds; D010710:Phosphates; D002129:Calcium Oxalate; D014527:Uric Acid; D003553:Cystine; D000069877:Struvite; C494366:calcium phosphate, dibasic, dihydrate; D002133:Calcium Sulfate