Dietmar A Neisius is the Chief ofthe Department of Urology at theHospital of ‘Barmherzige Brüder’inGermany since July 1998 and hasbeen a Professor of Urology at theUniversity of Saarland in Homburg,Germany since November 2000. Heis member of the GermanUrological Societies (DGU), SociétéInternationale d'Urologie (SIU) andAmerican Urology Association (AUA)and co-worker of DGU workingparties “Urolithiasis” and “Sectionof Operative Techniques”. In 1985he started the first treatment ofhuman stones with the piezoelectricextracorporeal shockwave lithotripsySystem in Homburg.

a report by

D i e tma r A N e i s i u s

Chief of the Department of Urology, Hospital of ‘Barmherzige Brüder’

In recent years a number of review articles have beenpublished on the current status of extracorporealshockwave lithotripsy (ESWL) and the lithotriptertechnology used alongside it.1–3 However, well-founded statements on the current piezoelectricESWL systems can be missed entirely or areinaccurate, or the statements made are based on thepiezoelectric systems of the first- and second-generation. In the meantime the piezoelectricshockwave technique, especially with the Piezolith3000 from Richard Wolf, has developed to becomeone of the most innovative and flexible shockwavesystems the ESWL market has to offer. Therefore itpays to consider this system and its efficiency moreclosely. Clinical results for the Piezolith 3000 and thefirst practical experience with its new triple-focus arepresented in this report.

T h e A pp l i e d P i e z o e l e c t r i c E SWLS y s t em

Figure 1 shows the Piezolith 3000 with treatmenttable, ultrasound unit and X-ray unit with therapysource. A very compact piezoelectric shockwavesource (SW) with an aperture diameter of 27cm sitsin its centre. The SW source offers 165mmpenetration depth and is therefore suitable for thetreatment of deep-lying stones and adipose patients.A variety of settings offers the user the freedom ofadapting to different treatment requirements. TheSW source can be brought both into over- andunder-table position by an isocentric swivel device.This means the best treatment access can becombined with the advantageous supine position ofthe patient, irrespective of what body calculi comeinto question. The supine position is clearly morepleasant for the patient and leads to a clear reductionof unwanted respiratory and patient movementsduring the treatment. With a peak pressureamplitude Pmax of 120MPa and a maximum energyE5Mpa of 115mj the SW source makes the sufficient

power reserves available to guarantee a highdisintegration efficiency. The use of innovativedouble-layer piezo technology is responsible for this.The triple-focus (F1, F2, F3), with 20 cadjustableenergy levels each, grants the user full freedom foroptimum dosage of the SW energy to the differentrequirements of the treatment situation such as hardureteral stones, kidney stones of different size,salivary calculi, stones in children and SW therapy(ESWT) with a single ESWL unit. Fixed adaptationof the SW source to the X-ray unit ensures stable andprecise assignment of the therapy focus to the X-rayisocentre and guarantees, for instance, optimumaccuracy even for the small ureteral stones. Anultrasound probe, which can be rotated and shiftedaxially, is arranged in the centre of the SW source forrealtime ultrasound localisation. Kidney stones in anyposition are localised without difficulty andeffectively with inline ultrasound localisation, sincethe direction of view and therapy direction coincide.

C l i n i c a l R e s u l t s

In a clinical study 254 patients with renal andureteral stones were treated at the UrologicalDepartment of the Hospital of ‘Barmherzige Brüder’with the Piezolith 3000 (focus setting F1). Thesewere 148 renal stone treatments (58%) and 106ureteral stone treatments in situ (42%). The stoneswere in the range less than 1.5cm. The localisationwas performed for the kidney stones primarily byultrasound. The ureteral stones were localised inaddition with the integrated X-ray C-arm and, ifvisible with ultrasound, treated further underultrasound control. All treatments were performedwithout analgesia or sedation. The average energydose in 20 energy levels lays between level 12 and15. Good fragmentation could be achieved in thisway without essential sensations of pain beingcaused. Two thousand to 4,000 shockwaves wereapplied per session with a repetition rate of 3Hz.

C l in i ca l Exper ience wi th the Lates t Generat ion P iezoe lec t r i cExt racorporea l Shockwave L i thot r ipsy Sys tem

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1. Köhrmann K U, “Comparison of Lithotripters”, European Pharmacotherapy, (2005);pp. 90–93.2. Rassweiler J J, Tailly G G, Chaussy C, “Progress in Lithotriptor Technology”, EAU Update Series, (2005);3: pp.

17–36.3. Teichman J M H, Portis A J, Cecconi P P et al., “In vitro comparison of shock wave lithotripsy machines”, J. Urology,

(2000);164: pp.1,259–1,264. .

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The duration of the treatment was between 15 and30 minutes and electrocardiogram (ECG)monitoring was not necessary.

Out of 106 ureteral stones, 77 (73%) were treated insitu. In 29 patients (27%) a double-J stenting or apushback of the stones was performed initially before

the ESWL treatment took place because of acuteobstruction. In this group 20 out of 29 patients (69%)were free of stones in the three-month follow-up. Inthe 77 patients with ureteral stones treated in situ, 52patients (67%) were free of stones one week aftertreatment had taken place. Auxiliary measures wereapplied without further ESWL treatment to patientswho were not free of stones.

The retreatment rate for kidney stones was 1.35. Nocomplications requiring therapy such as larger perirenalhaematoma, urosepsis or even loss of a treated kidneyoccurred. Of the 148 treated kidney stones, 141patients (95%) were free of stones in the three-monthfollow-up after the last treatment, however, in sevenpatients (5%) auxiliary measures such asureterorenoscopy and additional endourologicallithotripsy for ureteral stone fragments wereperformed. The Piezolith 3000 achieved in the kidneystone treatments an efficiency quotient (EQ) of 0.68,making it one of the best ESWL systems worldwide.2

T h e C o n c e p t o f t h e T r i p l e - f o c u s

A three-fold switchable focus zone was introducedin the latest generation of the Piezolith 3000 as areaction to the findings from the area of ESWLresearch. ESWL has been employed successfullysince the beginning of the 1980s, however, thefundamental mechanisms of the fragmentationeffect and side effect are still the object of currentresearch work. According to current thinking, it isgenerally recognised4 that the effect is connectedprimarily with the energy applied in the stone andsound field variables, such as maximum pressureamplitude or maximum energy density play only asecondary role. The side effects on the other handare linked directly with the sound field in the tissue,whereby high energy densities and cavitation effectsare considered to be mainly responsible. Thequestion as to whether a large focus or a small focusis better cannot be answered with general validity.Instead, an optimum form of treatment must beselected depending on the stone to be fragmentedand its size, hardness, composition and position.These general considerations should indicate theimportance of a controllable, flexible, focal soundfield for future optimised ESWL treatments.

The double-layer technology (DLT) that is used inthe Piezolith 3000 makes it possible to react todifferent and future sound field requirements.Figure 2 shows a sectional representation of thetherapy source. Two active piezoceramic layers, afront layer and a back layer, are applied to a metalbowl. Both the front layer and the back layer are

Figure 1: Piezolith 3000 – System Overview

Figure 2: The New Triple-focus and the Double-layer Technology of the

Piezolith 3000

All three settings (F1, F2, F3) use the same amount of radiated acoustic energy.

4. Chaussy C, Haupt G, Jocham D, Köhrmann K U, Wilbert D, Therapeutic Energy Applications in Urology – Standardsand Recent Developments, (2005)

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actuated through their own electronic circuit withcontrolled high-voltage pulses. The actuation forthe focal zone F1 is such that the single pulsesgenerated in the layers are superimposedconstructively on the surface of the SW source.The focal zone F1 is therefore characterised by finefocusing at high energy density (6dB zone 2mm,Pmax 120MPa). The DLT has enabled selectivemodification of the focal sound field parameters tobe acomplished. The guiding principle is toredistribute the focal acoustic energy spatially andin time under conservation of the total radiatedacoustic energy. In this way, through triggeringboth active layers offset relatively in time, areduction of the maximum occurring energydensities or pressure amplitudes and anenlargement of the focal zones is achieved. Thefocal zone F2 generated in this way has a 6dBdiameter of 4mm at a maximum pressure Pmax of80MPa and the focal zone F3 has a diameter of6mm at maximum 40MPa.

In vitro experiments confirm that it is expedient to usedifferent therapy focuses (F1, F2, F3) for differentstone hardnesses. For this purpose 15mm gypsum ballswere completely fragmented by a 3mm mesh.Gypsum balls of HMT served as substitute for softbody stones, gypsum balls made of Bego-Stone4 forhard stones. A slight rise in the required number ofshockwaves from F1 to F3 can be detected with theuse of soft stones. F3 is similarly effective at the sameenergy level despite reduced energy density incomparison with F1, but in practice it is moreconservative with a wider focal zone. Thefragmentation in F1 is more than twice as effective asin F3 with hard stones.

The first clinical experiences with the triple-focusshow that good disintegration capacities can beachieved even with the focus setting F3. Thesensation of pain for the patient is also reduced bythe sound field modification from F1 to F3.Whereas with the fine focus F1 at maximumapplied energy an acute sharp pain is felt, theperception with F3 is changed to a rather dull painthat is more tolerable by the patient. In treatmentswithout anaesthesia or sedation therapy could beperformed with focus setting F3 around three tofour energy levels higher. This is expected to leadto a further increase in effectiveness in comparisonwith the already good clinical results obtained withthe fine focus F1.

S umma r y

The piezoelectric shockwave technique, asimplemented in the Piezolith 3000, has developedfurther in recent years. The results of the clinicalstudy demonstrate that this progress is limited notonly to high-quality and long-life technology, butalso shows positive practical effects. With a stone-free rate of 95% for kidney stones and an EQ of 0.68,the Piezolith 3000 is numbered among the mosteffective units on the market. The fact that sedationand analgesia, as well as ECG monitoring, can bedispensed with when using this unit predestines itsuse in the out-patient and interventional area.Patients who could choose in our clinic between anspark-gap lithotripter and the Piezolith 3000 decidedin the majority for Piezolith treatment. Thanks to thenew triple-focus the Piezolith 3000 offers absoluteflexibility for therapy adapted individually to theneeds of the treatment. ■

5. Liu Y, Zhong P, Acoust J, “BegoStone- new a stone phantom for shock wave lithotripsy research”, Soc. Am.(2002);112/4: pp. 1,265–1,268.