Image based renal stone tracking to improve efficacy in extracorporeal lithotripsy.

PURPOSE: We describe a method to reduce the number of shocks necessary to fragment renal stones during extracorporeal shock wave lithotripsy by automatically taking into account stone movements. MATERIALS AND METHODS: Echotrack computer software was developed and implemented on a lithotriptor. One software module uses image processing to detect instantaneous stone location based on ultrasound images generated by the lithotriptor. A second module uses the detected location to control the shock wave generator position, and automatically adjusts it to improve coincidence between the focal volume and stone. The reliability of the tracking algorithm was clinically tested in 65 patients with renal stones. These in vivo tests were qualitative and the goal was to assess software ability to track stones during actual treatments. A quantitative evaluation of the reduction in shocks necessary for fragmentation was performed in vitro. Artificial stones were moved according to computer generated trajectories. Each trajectory was applied once with and once without automatic adjustment of the generator position. RESULTS: The in vivo tests demonstrated software ability to track stones as far as they were visible in the images. During in vitro tests automatic adjustments of the generator position reduced the number of shocks necessary to fragment stones completely by a factor of 1.64. CONCLUSIONS: Image based renal stone tracking software that automatically adjusts the shock wave generator position according to the displacement of renal stones is useful during extracorporeal shock wave lithotripsy. Treatment time was significantly shorter with this software.

[Electroconductive extracorporeal lithotripsy with Sonolith 4000+. A prospective study of the ECG desynchronization using a fixed-rhythm simulator]. / Lithotritie extracorporelle électroconductive avec le Sonolith 4000+. Etude prospective de la désynchronisation de l'ECG par l'utilisation d'un simulateur à rythme fixe.

INTRODUCTION: Electrohydraulic lithotripters use a R-wave triggering system as episodes of cardiac arrhythmia were observed during early clinical experiments. This study was designed to assess the safety of non triggered shock wave treatments using an external fixed rate device (120/min) on the Sonolith 4000 Plus (*), a non bathtub electroconductive lithotripter. METHODS: Our study is the first prospective evaluation of non-EKG-gated lithotripsy where the patient under continuous Holter monitoring served as his own control during a randomized alternation of periods with or without R-wave triggering. This design allowed for a direct comparison of the effect of EKG-gated and non-EKG-gated lithotripsy respectively. The sequence of the different periods was randomly assigned. The recordings were compared to a pre-treatment recording, the cardiologist ignoring the randomization. RESULTS: 25 consecutive patients without cardiac history have been treated for urinary stones. Ventricular and supraventricular excitability disorders have been noted in 7 patients, always during a non-EKG-triggered period. There was no correlation with stone location. No cardiac rhythm disturbances have been observed during triggered periods in the 25 patients. Auricular extrasystoles (0.1-0.5/min) were observed in 6 patients, and auricular couplets (0.5/min) in one. Ventricular extrasystoles were noted in 4 patients, and ventricular couplets in one. One patient had an asymptomatic non sustained ventricular tachycardia which resolved spontaneously. No clinically significant disorder occurred. Treatment time and analgesics requirements were reduced by non-EKG-triggering. CONCLUSIONS: Non-EKG-triggering lithotripsy has a definite potential for cardiac disturbances, but appeared to be clinically safe in these patients with no cardiac history.

Electroconductive lithotripsy: principles, experimental data, and first clinical results of the Sonolith 4000.

The electroconductive lithotripter (ECL) is a new concept for shockwave generation in which a highly conductive solution channels the discharge between the anode and cathode. In vitro experiments showed a linear relation between the voltage setting and the pressure at F2. In vitro stone disintegration studies showed a considerable reduction in shockwave pressure variability, improved energy transfer to the stone, and a unique linear relation between fragmentation and electrode voltage without a saturation effect. This new concept has been used clinically in the Sonolith 4000 lithotripter. In 142 evaluable treatments with a 3-month follow-up, the overall stone-free rate was 82%, and the retreatment rate in stone-free patients was 10%. For stones equal or less than 10 mm, the 3-month stone-free rate, retreatment rate, and secondary procedure rate were 85%, 5%, and 0%, respectively. For stones between 11 and 20 mm, these figures were 83%, 4%, and 2%, respectively. The efficiency quotient was found to be 81% for stones equal or less than 10 mm and 78% for stones between 11 and 20 mm. These clinical results confirm the improvements in efficacy observed in vitro with very satisfactory tolerance.

[Electroconductive lithotripsy: experimental and clinical results with the Sonolith 4000]. / Lithotritie électroconductive: résultats expérimentaux et cliniques du Sonolith 4000.

Electroconductive lithotripsy uses a highly conductive liquid to bathe the electrodes rather than water. The effect is to channel energy between the electrodes and force it to pass directly from the anode to the cathode, exactly at F1. The Sonolith 4000 (Technomed Medical Systems) uses this new generation of "electroconductive" shock waves. Experimental and clinical results are presented. The typical electroconductive technique creates a linear relationship between energy level, in kilovolts, and the amplitude of the acoustic shock at F2 over a wide range of power. There is also a linear relationship between power and effectiveness of desintegration. More than 800 patients have been treated to date. Follow-up has reached 3 months in the 166 treatments reported here. Overall success rate without residual stone was 82%. The percentage of patients with residual stones smaller than 5mm was 5%. The rate of clinical success was 87%. The rate of retreatment in patients without residual stone was 10%. For 11 to 20 mm stones, the success rate (0 fragments), the rate of retreatment and the rate of auxiliary procedures were 83%, 4% and 2% respectively for stones < or = 10 mm and 78% for 11 to 20 mm stones. The electroconductive generator used in this study provided very satisfactory results, better than those generally obtained with classical generators. Tolerance was excellent.