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Introduction to the Physics and Technology ofExtracorporeal Shock Wave Therapy (ESWT/CSWT)

STORZ MEDICAL AG, Kreuzlingen, Switzerland

Kreuzlingen, October 2003

Physics and Technology of ESWT/CSWT

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Table of contents

Definition of Shock Waves .........................................................................................................................3

Generation of Shock Waves .......................................................................................................................3

Requirements for Shock Waves for Medical Applications ...........................................................................5 Power...................................................................................................................................................................6

The properties of shock wave energy ...............................................................................................................7 Cavitation........................................................................................................................................................9

Dynamic Range, Reproducibility and Dosing Capability ........................................................................................10 Localization ........................................................................................................................................................10

Design Concept of MODULITH® SLX .......................................................................................................12 X-Ray Localization...............................................................................................................................................12 Ultrasound Localization.......................................................................................................................................13 Versatility............................................................................................................................................................13

Design Concept of MODULITH® SLK .......................................................................................................13 Therapy Source...................................................................................................................................................14 Ultrasound Localization.......................................................................................................................................14 X-Ray Localization...............................................................................................................................................14 Multifunctional Workstation ...............................................................................................................................15

Design Concept of MINILITH® SL1...........................................................................................................15

Design Concept of MODULITH® SLC (Cardio)..........................................................................................16 Therapy Source...................................................................................................................................................17 Ultrasound Localization.......................................................................................................................................17 Energy Release...................................................................................................................................................17 ECG Synchronization ..........................................................................................................................................17


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Definition of Shock Waves In physical terms, shock waves are high-energy waves with a high amplitude, characterized by extremely short build-up times. Acoustic shock waves used for medical applications are generated by processes that are similar to explosions, displacing the mass sur-rounding them, such as detonations of explosives. In nature, such processes can be observed in lightning, for instance, which is characterized by the instantane-ous heating of a spark channel, thus displacing the surrounding air similar to an explosion. The distur-bance of the uniform ambient pressure is radiated in the form of blast waves or shock waves (thunder).

Shock waves are characterized by a surge-type pres-sure distribution. Similar surges in the distribution of pressure can also be obtained by generating steep-flanked high-amplitude sound waves within a me-dium. This process can be compared, even if only to a limited extent, to a sine sea wave, which, initially mildly swinging, grows increasingly steeper on a flat, sandy beach until it eventually breaks. However, this is where the comparison ends. Admittedly, the shock waves currently used for medical applications are generated and propagated in water; contrary to transverse waves occurring on the surface of the sea, however, shock waves are longitudinal waves and cannot break. Whether the shock waves used for medical applications are shock waves in the strict physical sense of the word, still remains unanswered.

Fig. 1: Sine wave and steep-flanked shock wave

Be that as it may, medical shock waves are pulse-shaped acoustic waves with a high amplitude and thus correspond to the established definition of the term "shock wave".

Interestingly, the first shock waves used for medical purposes were generated by a spark discharge apply-ing the aforementioned principle of the lightning stroke. In view of the fact that shock waves, contrary to natural lightning strokes, are intended to develop their effects in the human body, they are normally generated in water, as the acoustic properties of water are similar to those found in living tissue. The high-energy waves can thus be introduced into the body without any significant reflection losses.

Generation of Shock Waves

A patent application for the first shock wave genera-tor to be used for the treatment of brain tumours was filed in the United States by F. Rieber as long ago as 1947.

Fig. 2: Patent application filed by F. Rieber

In the early 1960s, research into shock waves gained fresh impetus from material analysis. Industry and the medical profession started collaborating. In February 1980, the first kidney stone was successfully disinte-

grated at the Großhadern Hospital in Munich1. Owing

to the astonishing success of this method of treat-ment, extracorporeal shock wave therapy soon be-came the number one choice in the treatment of

1 Chaussy, C., Schmiedt, E., Jocham, D., Brendl, W., Forssmann, B., Walther, V. (1982): "First clinical experience with extracorporeally induced destruction of kidney stones by shock waves"; Journal of Urology, 1982/127, pp. 417-420


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kidney and ureter stones and was also used to disin-tegrate gallstones as well as pancreatic stones and stones in the salivary glands.

Early lithotripters required the patient to be immersed in a misshapen bath tub surrounded by a mass of technical apparatus. Today, the patient is positioned on a comfortable patient table and not in direct con-tact with the water. In fact, the shock waves are generated in water inside the therapy head which is attached to the patient's body by means of a closed water cushion, i.e. also "dry", simply applying some contact gel or a thin film of water.

Shock waves can be generated in different ways; however, they all have one thing in common and that is an electric storage capacitor with variable high voltage which is charged and subsequently rapidly discharged by means of various electroacoustic trans-ducers. The four methods employed in the generation of shock waves for medical applications are the elec-trohydraulic, the piezoelectric and the electromag-netic mechanism, with the latter being subdivided into systems employing flat coils and acoustic lenses and systems using cylindrical coils and paraboloidal-type reflectors.

Fig. 3: Generation principles of shock waves

The electrohydraulic system shown on the left in Fig. 3 employs a spark gap. High voltage is applied to two opposing electrodes positioned inside the water bath about one millimetre apart. The spark arcing across causes the surrounding water to evaporate. The pressure wave induced by the steam bubble is reflected by an ellipsoidal acoustic mirror. Even today, this system is still employed with considerable success. However, the disadvantage of this method is that substantial pressure fluctuations (approx. 50%) may occur between individual shock waves. In addition to

this drawback, the spark discharge becomes increas-ingly uncontrollable due to the consumption of the electrodes. This leads to substantial fluctuations in the average value of the generated pressure, thus limiting the service life of this system to a few thousand shock waves.

Piezoelectric systems make use of the fact that polycrystalline piezoelectric ceramic elements expand or, depending on the high-voltage polarization, con-tract when subjected to a high-voltage pulse. Due to the spherical arrangement of a great number of pie-zoelectric crystals, the waves thus generated are fo-cused on the centre, i.e. the focus, of the spherical arrangement. The advantages offered by this system of shock wave generation are its focusing accuracy, its long service life and the fact that due to the relatively low acoustic power treatment can generally be per-formed without anaesthetic. Its disadvantage lies in the insufficient power it often produces despite the mass of sophisticated technical equipment involved. The patient thus has to be subjected to repeated treatments to obtain the desired effect. In addition to this, X-ray localization systems are rather difficult to integrate into piezoelectric systems.

The first of the two electromagnetic systems shown in Fig. 3 is characterized by a strong pulsed current flowing through a flat coil, thus generating a rapidly changing magnetic field. An opposing magnetic field is induced in the metal membrane above the coil, thus causing the membrane to be pushed away from the coil. The initially flat waves are focused by means of a lens that is arranged above the coil.


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The cylindrical source2 patented by STORZ MEDICAL and shown on the right in Fig. 3 also employs the electromagnetic principle of shock wave generation. The heart of this system is a cylindrical coil. The cylin-drical membrane is pushed away from the coil by the induction of a magnetic field and accelerated radially outwards by a pulsed current, thus initially generating a cylindrical wave perpendicular to the cylinder axis. The cylindrical wave is reflected by the paraboloidal-type reflector and transformed into a spherical wave that is focused concentrically onto the focal point.

Fig. 4: Patented STORZ MEDICAL cylindrical source

The use of the cylindrical source described above has brought about significant benefits in clinical practice. Firstly, the cylindrical design offers sufficient space for the integration of an in-line localization unit. Sec-ondly, the required energy is introduced into the patient's body over a large skin area, thus reducing pain to a minimum. The particular geometry of this system allows a precisely defined focal point with high energy densities to be obtained. The cylindrical source can be built in such a way that the focal point is lo-cated well clear of the therapy head. This allows the shock waves to penetrate deep into the tissue, and thus the treatment of obese patients as well – particu-larly important in urology.

2 Wess, O., Marlinghaus, E.H., Katona, J. (1990): "A new Design of an Optimal Acoustic Source for Extracorporeal Lithotripsy"; in: Burhenne, Joachim (ed.): Biliary Lithotripsy II; Year Book Medical Publishers, Inc.; Chicago, pp. 211-214; ISBN 0-8151-1375-7

Fig. 5: Treatment of an obese patient

The cylindrical source is easily adapted also for cardiac indications.

Fig. 5a: Cardiac treatment

Today's lithotripters are increasingly equipped with electromagnetic sources.

Requirements for Shock Waves for Medical Applications

As with any drug or medication employed in the treatment of diseases, it is the dosage that determines the success of the therapy. On the one hand, the effects produced have to be vigorous enough to obtain the desired result. On the other hand, how-ever, possible side effects are to be minimized or, where possible, excluded. On the basis of these condi-tions, the technical requirements to be met by shock wave systems will be examined in detail.

• The power of the source has to be suffi-cient.

• Adequate measures have to be taken to minimize side effects.

• It must be possible for the dynamic range, the reproducibility and the dosing capa-bility to be tailored to the clinical condi-tions.

• A localization method is to be used to al-low shock waves to be applied to precisely defined regions of the patient's body.


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Power

Discussions dealing with the efficiency of different shock wave apparatus generally concentrate on the energy and energy flux density as these two parame-ters are considered to determine the power of a shock wave source. However, no universally valid definition of the underlying criteria has been published so far. This issue thus needs to be dealt with in greater de-tail, and investigations need to be carried out into the characteristic physical parameters of the shock wave field. The temporal and spatial pressure distribution is the most important of all criteria, as all other quanti-ties can be derived from this parameter. Therefore, this will be dealt with first.

Fig. 6: Temporal pressure distribution

The above graph shows a typical temporal pressure distribution. Such a curve is obtained by introducing a suitable pressure probe, a so-called hydrophone, into the shock wave field and triggering a single pressure pulse. Optical glass-fibre hydrophones are nowadays state-of-the-art measurement probes for shock waves. Only with this complex and expensive equipment a sufficiently accurate recording of the extremely high pressures, the short rise and fall times, and also the negative tensile parts can be achieved. Sometimes values obtained with the older needle of membrane hydrophones made of PVDF can still be found.

The pressure increases from the ambient pressure up to several hundred or thousand bar and subsequently decreases within one microsecond. This is followed by post-pulse oscillations, i.e. tensile components, which need to be minimized as they are considered to be one of the major causes of pain and possible tissue damage. The amplitude of the shock wave can be changed by varying the amount of electric energy

supplied. However, the general form of the temporal pressure distribution remains virtually unaffected by these changes.

Fig. 7: Spatial pressure distribution

The spatial pressure distribution varies according to the geometry of the shock wave source. As can be seen in Fig. 7, the pressure field can be illustrated in the form of a three-dimensional area. The peak of this 3-D area corresponds to the focal point. Moving away from the focus, the pressure decreases more or less steeply, which shows that a considerable amount of pressure can still be measured outside the actual focus. Owing to the acoustic energy contained in these areas, these pressures cannot be ignored.

In physical terms, the focus corresponds to the peak pressure. The pressure values that are higher than half the peak pressure constitute the focal zone, which means that only the top of the three-dimensional area cut off at half the peak pressure is taken into consid-

eration. In case of the MODULITH® SLX, the focus size

as defined above is 6 mm lateral and 28 mm in axial

direction. With the MODULITH® SLK dimensions of

4 mm (lateral) and 50 mm (axial) can be found. Even-tually, the MINILITH SL1 features a diameter of 2.4 mm and an axial extension of 25 mm. Cardiac

application (MODULITH® SLC) utilizes a specialically

matched focal zone.

However, the definition of a focal zone alone does not furnish a satisfactory description of the shock wave field as the measuring procedure simply uses the pressure values down to half the peak pressure, regardless of the absolute peak pressure.


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The other important parameters of shock wave fields used for medical applications are the acoustic energy contained in tissue and the tissue-specific energy flux

density or the shock wave intensity in the focal zone3.

The properties of shock wave energy

In view of the fact that shock waves can be generated by using different methods (Fig. 3), parameters such as kilovolt (kV) figures or specific settings on the ap-paratus employed are not suitable for defining the shock wave energy. Regrettably, kV values are still widely encountered in this context due to the lack of knowledge of meaningful parameters.

dt(t)pc

AE ⋅

⋅= ∫ 2ρ

Unit of measurement: Millijoule

A = wave surface

p = pressure

ρ = density of the propagation medium

c = propagation speed in said medium

t = time

The above formula defines the total energy contained in the shock wave, without explaining, however, whether this energy is concentrated on a small area (focus) or spread over a large surface.

3 Wess, O., Ueberle, F., Dührssen, R.-N., Hilcken, D., Krauss, W., Reuner, Th., Schultheiss, R., Staudenraus, I., Rattner, M., Haaks, W., Granz, B.: "Working Group Technical Developments – Consensus Report in High Energy Shock Waves in Medicine", Thiem Verlag, Stuttgart, Germany, 1997

Fig. 8: Focusing of a shock wave

As shown in Fig. 8, the shock wave spreads out as it is radiated from the therapy head and is subsequently concentrated onto the focus. The distribution of the shock wave energy over a large entry area allows unnecessary pain and side effects to be reduced and the effects to be confined to the focal zone. Damage to skin and tissue layers situated in front of the actual therapy zone can thus be avoided, without reducing the efficacy of the shock wave energy in the area to be treated.

The following rule applies to the focus: the better the energy can be concentrated over a small target area, the greater will be the effect. Consequently, the effi-cacy of the shock wave at the focus is dependent on the intensity of the energy flux density at this point. The energy flux density, also referred to as energy density, is the energy per unit area and is defined by dividing the energy by the area:

dt(t)pcA

E⋅

⋅= ∫ 21ρ

Unit of measurement: Millijoule per square millimetre (mJ/mm2)

As shown in Fig. 8, the energy flux density can be increased dramatically by focusing the shock wave, provided that the shock wave energy, which initially spreads over a large surface, is concentrated on a very small area. The energy flux density or intensity can be drawn upon as one of the parameters – though not the only one – that determine the efficacy of shock waves used for medical applications.


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The qualities of shock waves produced by various lithotripters used in urology were compared in a re-

search study4 commissioned by the Italian Department

of Health. Among other things, to describe the shock wave quality this study drew upon the peak pressure and the maximum intensity (i.e. energy flux density) obtained at the focus with the maximum energy level.

Fig. 9: Focus pressure

Fig. 10: Shock wave intensity at the focus

The chart above clearly illustrates that the cylindrical source developed by STORZ MEDICAL stands out from all other tested sources in that it has led to the best results with regard to both the aforementioned pa-rameters.

4 Buizza, A., Dell’Aquila, T., Giribona, P., Spagno, C. (1995): "The performance of different pressure pulse generators for extracorporeal lithotripsy: a comparison based on commercial lithotripters for kidney stones"; Ultrasound in Medicine & Biology, 21:2, pp. 259-272

Side effects

As mentioned above, a successful treatment can only be performed if the desired efficacy of the shock waves is not accompanied by intolerable side effects. In the field of urology, for example, side effects such as different types of haematomata or, occasionally, interactions with the cardiac rhythm (extrasystoles) have occurred. Tests carried out on animals have revealed that the application of shock waves may lead to serious damage to the lungs. This is due to the fact that shock waves are almost entirely reflected and hence develop destructive forces when they reach boundary layers (tissue/air), at which the acoustic properties change drastically. However, when shock waves reach the boundary layer of a kidney stone, it is precisely these forces which cause the stone to be disintegrated without damaging the surrounding tissue unacceptably.

Side effects can be kept within acceptable limits if users make sure that the high intensity zones of the shock wave field are not targeted on vulnerable tissue (e.g. the lungs), and that the energy flux density and the total energy applied reach therapeutic values only in the zones to be treated. In all other zones, these values have to be kept below the permissible values to avoid damage. The generally accepted maximum value is at present 0.03 mJ/mm². This value has been

measured on blood-filled umbilical cords.5

From a technical point of view, a favourable distribu-tion of the shock wave field is obtained by producing sources with large apertures that distribute the energy entering the body over a large skin surface. Another positive feature of these large-aperture sources is that they are characterized by an astonishing focusing accuracy and thus ensure the best possible energy flux densities or intensities. It should be mentioned, how-ever, that the energy density and intensity are limited by technical and, to a certain extent, anatomical fac-tors. Shock wave sources should be used that feature a maximum aperture and a maximum aperture angle at which the shock waves converge towards the focal point in order to optimize the efficacy of the shock waves while at the same time minimizing undesired side effects. Again, the cylindrical source developed by STORZ MEDICAL stands out from other sources in

5 Steinbach, P., Hofstaedter, F., Nicolai, H., Roessler, W., Wieland, W. (1993): "Determination of the energy-dependent extent of vascular damage caused by high-energy shock waves in an umbilical cord model"; Urological Research, 21, pp. 279-282


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that it meets these requirements better than any other shock wave generator.

This is clearly shown in Fig. 11, which is taken from the aforementioned study. The diagram below con-firms that the STORZ MEDICAL source features the highest ratio between the focus pressure and the pressure at the point of entry into the body (in this case 50 mm in front of the focus).

Fig. 11: Focus pressure and pressure at the skin surface

Being rapid pressure fluctuations occurring in water, shock waves are not visible. However, they can be made visible by using suitable Schlieren photography apparatus. The images in Fig. 13 show the shock waves on their way to the focal point at various times after leaving the source. These images show a two-dimensional sectional view of the three-dimensional, spherical segment-shaped wave surface illustrated in schematic form in Fig. 12.

Fig. 12: Propagation of waves

The wavefronts have a thickness of about 1 mm and propagate in the direction of the focal point at a velocity of approx. 1500 m/s. After having passed through the focal point, the wavefronts diverge and dissipate, their amplitude gradually weakening.

Fig. 13: Propagation of waves – schlieren photographs

Cavitation

On closer inspection of the last few images in Fig. 13, cavitation bubbles can be seen on the centre line of the images. Cavitation occurs when shock waves are followed by tensile waves, which blow open the fluid. Bubbles are formed around microscopically small cavitation centres and expand within a few microsec-onds to different maximum diameters (about 1 mm). Having reached their maximum size, they generally collapse within 100 microseconds, merging with the original cavitation bubble and sending out a secon-dary spherical shock wave.

Cavitation bubbles contribute to the disintegration of kidney stones. However, they are also considered to be responsible for tissue damage. Bubbles located near acoustic boundary layers (stone surface, vascular walls, pulmonary alveoli, etc.) cannot collapse point-symmetrically. The initially spherical bubble is dented and forms an intensive fluid jet with a diameter of a few tenths of a millimetre which impacts on the boundary surface at a velocity of several hundred metres per second. This jet can erode stone surfaces and puncture the walls of smaller vessels (formation of microhaemorrhages). This again calls for the use of shock wave sources with large apertures. Using such sources, the cavitation threshold values are only ex-ceeded near the focus zone, whereas the skin surface is exposed to cavitation only to a limited degree or not at all.


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Dynamic Range, Reproducibility and Dosing Capability

A generous dynamic range is essential in order to be able to handle different indications and to take into account patients' differing pain thresholds. It must be possible for the energy levels and energy flux densities to be adjusted to specific conditions within generous limits. Experts often refer to 'high-energy' and 'low-energy' shock waves. However, so far no precise definition has been established stating which energy flux densities are covered by these two terms. Various study groups have suggested the following classifica-

tion for orthopaedic applications6:

Mainz7:

low energy: 0.08 mJ/mm2

medium energy: 0.28 mJ/mm2

high energy: 0.6 mJ/mm2

Kassel8:

low energy: < 0.12 mJ/mm2

high energy: > 0.12 (bis 0,38) mJ/mm2

For different fields of shock wave applications (cardi-ology, urology) specific energy settings may be re-quired.

In order to tailor the treatment to be performed to the target zone and the patient's tolerance to pain, the doctor needs to know how much energy is ap-plied throughout the entire duration of the treatment. This means that it must be possible for every emission of shock waves to be precisely dosed and reproduced. The description of the individual methods employed in the generation of shock waves has shown that not all systems are equally effective in this respect. In fact, the study commissioned by the Italian Department of Health has confirmed that it is the electromagnetic shock wave generators that produce the most stable values, even in the higher pressure range.

6 The energy levels that can be set when using the MINILITH cover both the high-energy and the low-energy values listed in the above classifi-cation. In the lower energy range, which generally does not require any anaesthetic, the energy levels can be precisely adjusted. When using higher energy levels, the energy supplied by the MINILITH is vigorous enough to allow even pseudarthrosis to be treated successfully.

7 Rompe, J. D., Universität Mainz, auf dem Süddeutschen Orthopäden-kongress, 25. - 28. April 1996 in Baden-Baden

8 Siebert, W., Orthopädische Klinik Kassel, auf dem Süddeutschen Orthopädenkongress, 25. - 28. April 1996 in Baden-Baden

Fig. 14: Stability at focus

Localization

The use of a reliable localization system is absolutely essential when performing shock wave therapy, all the more so as serious side effects produced by shock waves cannot always be excluded.

Today, there are really only two systems suitable for this purpose: ultrasound or X-ray localization systems. It is up to the doctor to decide which system to use. However, this decision should always be dependent on the specific indication to be treated. Various local-ization methods, which are independent of the type of system used, are offered by the individual manu-facturers. A distinction is usually made between off-line and in-line localization, the latter being character-ized by the fact that localization is performed through the therapy head.

Fig. 15: Off-line/in-line localization

When using off-line ultrasound localization systems, the targeted zone may not correspond to the zone

actually subjected to shock waves9. Just like optical

9 Wess, O., Stojan, L., Rachel, U.K. (1995): "Untersuchungen zur Präzision der Ultraschallortung in vivo am Beispiel der extrakorporal induzierten Lithotripsie" [Investigations into the accuracy of in vivo ultrasound localization on the basis of extracorporeally induced li-thotripsy] in: Chaussy, Christian (ed.): Die Stoßwelle, Forschung und Klinik [Shock waves, research and clinical applications]; Attempto Verlag, pp. 37-44; ISBN 3-89308-228-X


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boundary surfaces, the boundary layers between different types of tissue may refract the ultrasonic waves. The deviations from the linear direction of propagation of the ultrasonic waves, which is an indispensable requirement to ensure precise localiza-tion, are not so small that they can be neglected. In the case of penetration depths of about 100 mm, which are quite common in the treatment of kidney stones, deviations of 10 mm and more may occur. These difficulties can be almost entirely excluded when using in-line localization systems. It goes with-out saying that none of the systems available today can guarantee a 100% localization accuracy. How-ever, in-line systems allow deviations to be reduced to a minimum, as the shock waves propagate through the same tissue areas as the in-line ultrasonic waves and thus undergo similar refraction. This is of utmost importance for cardiac applications.

When shock waves are applied in orthopaedics to treat disorders concerning human postural or locomo-tor systems, it will hardly ever be possible to detect and localize structures sited in the centre of the shock wave field if the ultrasound transducer is located outside the shock wave axis (off-line arrangement). Unfavourable anatomical conditions and bone struc-tures that interfere with the target area and cannot be penetrated by ultrasonic waves render the localiza-tion of the target area difficult or even impossible if a lateral transducer is used. Consequently, none of the shock wave apparatus currently available for ortho-paedic applications are equipped with off-line local-ization units. Despite the fact that after having per-formed an anatomically oriented localization of the treatment zone, minor corrections are frequently carried out after consultation with the patient, a precise localization is still indispensable.

Furthermore, for various indications, such as calcare-ous tendinopathy or pseudarthrosis, it may be advis-able to use an X-ray localization system instead of or in addition to ultrasound localization. Again, in-line fluoroscopic X-ray localization offers considerable advantages compared with an off-line arrangement. This system ensures an axial projection of the target area sited in a central position on the shock wave axis and allows deviations from the cross hairs to be de-tected and corrected with maximum accuracy.

Again, the central opening of the electromagnetic cylindrical source, which can be attributed to the design, offers ideal conditions for an in-line X-ray localization, which would be difficult or impossible to perform with other types of systems.

Fig. 16: In-line Ultrasound and X-ray localization

The following chapter takes a closer look to the different concepts of shock waves de-vices of STORZ MEDICAL.

• MODULITH® SLX ................. Page 12

• MODULITH® SLK ................. Page 13

• MINILITH® SL1 ..................... Page 15

• MODULITH® SLC .................. Page 16


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Design Concept of MODULITH® SLX The MODULITH® SLX is a modular system that is com-

prised of a therapy unit with cylindrical source, a patient table and an X-ray and/or ultrasound localiza-

tion unit. The MODULITH® SLX is available in three

different versions:

• MODULITH® SLX-MX featuring a highly

versatile, high-quality X-ray system

• MODULITH® SLX-MX/F featuring an aston-

ishingly compact X-ray system

• transportable MODULITH® SLX featuring a

mobile X-ray C-arm

Therapy Unit

The patented STORZ MEDICAL cylindrical source stands out from other systems in that it uses the best technology for the generation of shock waves avail-able today. Energy flux densities of between 0.2

mJ/mm² and 2.0 mJ/mm² make the MODULITH® SLX

ideally suited both for the gentle treatment of chil-dren and for the vigorous disintegration of ureter stones, which are generally difficult to crush, or ex-tremely hard kidney stones and gallstones.

In addition to this, the MODULITH® SLX is equipped

with a unique patient table specially developed to meet the highest demands in terms of ease of opera-tion and comfortable patient positioning. An ex-tremely resistant supporting sheet that is transparent to X-rays, ultrasound and shock waves ensures that not only normal weight patients but also obese pa-tients and small children are held in a comfortable and safe position. The patient table has a generous range of movement (both motor-driven and manual) in three directions, which allows treatment to be performed without having to move the patient. How-ever, the use of this versatile patient table is not lim-ited to the field of lithotripsy. In fact, it is equally suited for a variety of diagnostic examinations and therapeutic applications.

Fig. 17: MODULITH® SLX energy flux densities / energy levels

X-Ray Localization

All apparatus are characterized by the fact that X-ray localization is carried out in-line directly through the source. This is done by using the proven TTS tech-nique (Through The Source) which allows the target area to be localized much more quickly and reliably. Any focusing inaccuracies are detected immediately throughout the treatment and can be corrected with-out having to interrupt the therapy. Two airbags are used to force the water out of the X-ray path during localization, thus ensuring an optimum image quality.

Fig. 18: STORZ MEDICAL MODULITH® SLX-MX/S

Apart from in-line (p.a.) fluoroscopy, the compact X-ray system of the MODULITH SLX-AX is equally suited for 30° projections. In addition to this, the highly flexible X-ray system of the MODULITH SLX-UX allows +/-45° projections in lateral direction and 0° to 45° projections in cranio-caudal direction to be per-formed.


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Fig. 19: STORZ MEDICAL MODULITH® SLX transportable

Ultrasound Localization

All apparatus can be equipped with an optional in-line ultrasound localization unit which can be easily in-serted into the central cylindrical opening of the ther-apy source. Ultrasound and X-ray localization can be performed simultaneously. Furthermore, it is possible for the 3.5 MHz ultrasound transducer to be removed

from the MODULITH® SLX and used as an independ-

ent diagnostic unit.

Fig. 20: Ultrasound localization

Versatility

The apparatus that are included in the MODULITH®

SLX series are more than just optimum lithotripters. They can equally be used as versatile urological work-stations. For this purpose, the apparatus can be com-bined with various accessories, among which the Trendelenburg cushion, leg supports, urosink or infu-sion rod.

Fig. 21: STORZ MEDICAL MODULITH® SLX/MX

Design Concept of MODULITH® SLK The MODULITH® SLK follows a completely new and revolutionary design: A medium sized shock wave source offering a wide energy range for all indications of shock waves is mounted on a flexible, easy-to-move, articulated arm.

Fig. 22: MODULITH® SLK workstation

Different components of the treatment set-up like uro table, X-ray C-arc, ultrasound device etc. can be cho-sen from a variety of brands and models according to the specific needs and requirements of the hospital.

These components can not only be used for ESWL! Diagnostics and urological procedures can also be performed utilising parts of the ESWL set-up. An endoscopic tower completes the urolgical work-station. And a detached use of X-ray C-arc or ultra-sound device for example is also easily possible.

For stone treatment the different components are simply regrouped — no mechanical connections are to be made.


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Due to its flexibility the MODULITH® SLK allows also

interdisciplinary utilisation. Besides urology, shock wave therapy in Rheumatology/Orthopaedics is just as well possible as stone disintegration in Gastroentero-logy and ENT.

Therapy Source

MODULITH® SLK is equipped with the STORZ

MEDICAL proprietary shock wave source with cylindri-cal coil and parabolic reflector.

This allows complete control over the shock wave application. The desired energy is accurately gener-ated and precisely reproduced from shock to shock.

With a penetration depth of between 0 and 150 mm the MODULITH® SLK is prepared to tackle any chal-lenge the patient’s pathology and anatomy may con-front it with.

With this source it realises an energy range un-equalled in the world of shock wave technology. From pain treatment in rheumatology to treatment of uret-eric stones in urology or pseudarthrosis in orthopae-dics — the MODULITH® SLK offers the proper energy settings for every shock wave therapy.

The uncompromising avoidance of disposable materi-als, the absence of an energy absorbing lens and continuous water conditioning evades time consum-ing service breaks between treatments, results in low running costs and guarantees the MODULITH® SLK is always ready for action.


Ultrasound localization is the fastest way to localize a target and to ensure permanently that the right target is hit — without any exposure to radiation.

The STORZ MEDICAL cylinder source allows an ultra-sound transducer to be integrated within the shock wave source: localization and therapy follow the same path. This is what we call "in-line". Osseous struc-tures or tissues with gas inclusions are easily detected. When moving the therapy head the ultrasound trans-ducer moves as well. So, the perfect path towards the target is easily found — both for diagnostic ultrasonic waves and for shock waves.

Examining the anatomy of a human body with ultra-sound not only means choosing the proper orienta-tion of the transducer but also to perform a searching motion on the skin to find the best place to scan through. Only by finding this ‘keyhole’ can a good ultrasound image be obtained.

The therapy head of the MODULITH® SLK can be

adjusted to this keyhole almost like a hand-held trans-ducer!

X-Ray Localization

When utilising shock waves in medical applications, the path of the pressure pulse towards its target is always of great importance. Obstacles such as bones or gas filled intestines will diminish the energy trans-ferred to the target and thus affect the treatment success. For most targets there is a path which is free of obstacles and it can be used as long as the shock wave source can be placed wherever required by the patient’s anatomy. For this reason, STORZ MEDICAL

has invented the Lithotrack® positioning system —

the key technology to computer-aided shock wave therapy (CAST).

Fig. 23: Working principle of Lithotrack® positioning system

An optical link between the C-arm and therapy head is established. The camera ‘looks’ at the shock wave source and in doing so can determine the position and orientation of the shock wave head. On the basis of this data the processing and display module gener-ates a virtual reality scenery.


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Fig. 24: Lithotrack® display

By moving the therapy head and watching the corre-

sponding movements of the focus on the Lithotrack®

display, the physician can adjust the focus of the shock wave to the centre of the X-ray with a sure and quick hand.

Multifunctional Workstation

A full featured uro table and a fluoroscopic X-ray C-arc form the nucleus of a multi-purpose urological workstation.

An ultrasound device for diagnostic purposes and therapy (punctures) further extends the possibilities for the attending physician.

The addition of the shock wave device

MODULITH® SLK with its Lithotrack® system and its

support for in-line ultrasound creates a fully featured treatment unit for extracorporeal shock wave therapy.

Combining endoscopic devices by Karl Storz GmbH, Tuttlingen, with this treatment unit ends up in a state-of-the-art urological workstation meeting all profes-sional and economic challenges of today’s health care.

Design Concept of MINILITH® SL1 The MINILITH® developed by STORZ MEDICAL is the

result of many years of extensive experience in the field of kidney stone lithotripsy and the successful implementation of the specific requirements to be met by orthopaedic apparatus for extracorporeal shock wave therapy, as has been outlined above. The

MINILITH® is characterized by its compact size and

astonishing mobility, which allow the system to be transferred to different locations. The apparatus sim-ply has to be plugged in and does not require any further installation procedures.

Fig. 25: STORZ MEDICAL MINILITH® SL1

The unrestricted movement of the therapy head is due to it being suspended on gimbals on a lockable, articulated arm. It comprises a 7.5 MHz in-line integral ultrasound transducer with an infinitely adjustable scanning plane that can be rotated through 360°. When performing general ultrasound examinations, the transducer can be easily removed from the central therapy head opening and used independently of the therapy unit itself.

In addition to this, the therapy head has a precise adjustment feature which allows the focal point to be precisely moved in two directions without having to disconnect the therapy head.


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Fig. 26: Therapy head

Owing to its astonishing mobility and manoeuvrabil-ity, the therapy head can be positioned for use on the most diverse regions of the patient's body and is thus suitable for an almost unlimited variety of indications. One application is shown in the following figure.

Fig. 27: MINILITH® SL1

Finally, the MINILITH® SL1 provides well dosaged

uniform energy pulses with a wide dynamic range of 0.005 to 0.50 mJ/mm² in 20 steps. Very gentle treat-ments as well as consequent powerful applications in case of pseudarthrosis are matching all different medical needs. Fig. 28 illustrates the available energy

range of the MINILITH®.

Fig. 28: MINILITH® SL1 energy flux densities / energy levels

Furthermore, the MINILITH® stands out from other

apparatus in the same category because its in-line ultrasound localization system can be complemented by a standard mobile C-arm to perform in-line X-ray localization in the treatment of pseudarthrosis, for example.

Design Concept of MODULITH® SLC (Cardio)

Fig. 28: MODULITH® SLC

For shock wave therapy in cardiology a stringent control of the shock wave field parameters is manda-tory. The delicate cardiac system and vital functions of the heart require total control of all shock wave pa-rameters to provide medical efficiency without caus-ing serious side effects.


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The concept of the MODULITH® SLC is technically

matched to the following medical requirements:

• Precise control of spatial shock wave field dimensions

• Precise targeting and simultaneous position control by ultrasound

• Precise control and reproducibility of energy release

• Precise synchronisation with cardiac cycle

Therapy Source

As all shock wave devices of STORZ MEDICAL the

MODULITH® SLC is equipped with its proprietary

shock wave source with cylindrical coil and parabolic reflector. The focal distance and aperture configura-tion is matched to cardiac anatomy. The shock wave focus is precisely defined to provide shock wave agita-tion on only predetermined areas of the heart muscle. Targeting is controlled by manual fine adjustments within millimetre precision.

Fig. 29: Fine adjustment


Inline ultrasound co-axially integrated in the centre of the shock wave source provides continuous position control during shock wave treatment.

Fig. 30: In-line ultrasound

Energy Release

Special care is taken for incremental adjustment of shock wave energy in order to guaranty exactly the amount of shock wave exposure required.

Fig. 31: Dynamic range

ECG Synchronization

As known from kidney stone treatment shock waves may interfere with cardiac cycle and cause arrhythmia and premature heart beats. Exact synchronisation of shock wave release and refractory phase of the car-diac cycle is guaranteed by aid of ECG triggering

Fig. 32: ECG control

STORZ MEDICAL AG ∙ UNTERSEESTR. 47 ∙ CH-8280 KREUZLINGEN ∙ TELEFON: +41/71/677 45 45 ∙ TELEFAX: +41/71/677 45 05 E-MAIL: [email protected] ∙ INTERNET: WWW.STORZMEDICAL.COM

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