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                                                           Recommendation statement
                                                 of the Conjoint Physics Working Group
                                                               of ISMST and DIGEST
                                              on ESWT study design and publication

Edited by:
Dr. Matias de la Fuente RWTH Aachen University, Chairman of the Working Group
Dr. Vinzenz Auersperg DIGEST and ISMST
Kristin Dietz-Laursonn, M.Sc. RWTH Aachen University
Dr. Siegfried Ginter Richard Wolf
Christian Dorfmüller Nonvasiv
Dr. Whala Khaled Dornier
Prof. Friedrich Ueberle HAW Hamburg
Maxime Fournier EMS
Dr. Rainer Pecha RPacoustics
Peter Vallon Likamed
Dr. Werner Schwarze Jena MedTech
Ralph Reitmajer MTS


This statement is the final conclusion of the editors mentioned above as the result of a

conjoined meeting of the Physics Working Group of ISMST and DIGEST, which was held at
Berlin on October 21st, 2015.

The group has been called together under auspices of ISMST and DIGEST due to the ongoing
discussion about the physical parameters used for the description of ESWT setup.

The editors conclude, that the use of currently established shockwave parameters to
describe the physical conditions during in-vitro or clinical studies is insufficient as:

• We don‘t know yet the key effect of shock waves on tissue, the biological response is not
clear as well as the best “shape” (spatial and temporal pressure distribution) of the shock
waves to be the most effective.

• Therefore it is unclear, which shockwave parameters (as defined in IEC 61846) should
be used to describe the clinical efficacy and to compare devices or if even new
parameters need to be introduced.

• Currently only few parameters are used by the ESWT community, such as:

   o Peak positive and negative acoustic pressure
   o Derived pulse intensity integral (= ED)
   o Total energy (-6dB)
   o Focal extension in x-, y- and z-direction
   o Number of pulses
   o Pulse repetition rate (Hz)

But these usually don’t suffice to describe the sound field, because of the complex 3-
dimensional distribution of the sound pressures and the influence of the tissue..

• We have to be cautious as one has to know how to read and interpret the parameters.
Depending on the measurement setup and on the SW technology the meaning and
significance of the parameters may vary a lot.

• Without further investigation, it cannot be expected in near future, that there will be a way
to improve the comparability of different devices and techniques:

   o Electrohydraulic applicators versus electromagnetic or piezoelectric ones: The
      measurements at electrohydraulic devices are usually mean values because each
      spark varies a little, so that each spark produces different shock waves

   o Radial and focusing applicators: The sound fields are very different and the
      parameters are not defined in the same way, especially as most shockwave
      parameters from IEC 61846 refer to the focal point.

• We need a rating and ranking of all measurable parameters

   o Which parameters could be interesting (& should therefore be mandatory to be
      published in clinical studies)

   o At the moment not enough parameters are mentioned at the publications

• It should be investigated, which additional parameters could be helpful to improve the
physical description of what is used performing ESWT with all the different devices and
their different techniques (focal, radial,planar, and defocused ESWT).

• Device approval is one reason for the problems:

   o Currently, it is shown by “technical equivalence” or “substantial equivalence”
      based on few (unimportant?) technical parameters?

   o But safety alone does not show clinical effectiveness.

   o Clinical equivalence has to be shown.

The editors came to an agreement for the following recommendations:

1. For clinical studies and in-vitro studies:

    1.1.Get support from technicians of the device manufacturer from the beginning of the
          planning of the experimental study design until the interpretation of the outcome.

    1.2.Clinicians should perform studies in conformance with „good clinical practice“ and
          describe every variable which might influence the clinical outcome

          1.2.1. Description of indication
          1.2.2. Description of the target to be treated
          1.2.3. Measurement and documentation of the success including the definition of
          1.2.4. Documentation of all additional (non-shockwave) treatments (including anesthesia)
          1.2.5. Number of sessions
          1.2.6. Time between sessions
          1.2.7. Number of pulses per session
          1.2.8. Pulse repetition rate (my influence cavitation)
          1.2.9. Navigation technique (how to find the target, e.g. Ultrasound, focused shockwave
                    to find most painful spot, …)

    1.3.Furthermore specify all parameters for the treatment settings of their devices which
          influence the sound field:.

          1.3.1. Shockwave device
          1.3.2. Shockwave head / applicator (name, model number, physical principle,
          1.3.3. Intensity levels
          1.3.4. All material interfaces the sound has to penetrate during in-vitro experiments
                   (geometries and materials between the transducer head and a few cm behind the
                   focal point)
          1.3.5. Coupling medium used and how it was applied
          1.3.6. Penetration depth of focused device (skin to focal spot distance)
          1.3.7. Treatment protocol (e.g. changes of device settings over time, movement of

    1.4.If not device settings but shockwave parameters (according to IEC 61846) are
           published, the origin of the data has to be referenced.

2. For companies:

    2.1.Provision of sound field parameters (as well as information concerning their
          measurement) in a database, which will be created and published online by ISMST and
          DIGEST and support researches by interpretation of the parameters by direct contact.

    2.2.Support of researchers in planning of in-vitro and in-vivo studies (setup, execution) and
          interpretation of the sound field data, especially when results are compared to other

Berlin, October 21st, 2015                                         Dr.-Ing. Matias de la Fuente Klein
                                                                         Chairman ISMST Physics Workinggroup