Comparison of measurement techniques for the determination of ultrasonic power of high-intensity ultrasound transducers

Project Description

The development of efficient treatment methods against cancer is one of the greatest challenges in current medical research. On 1 April 2008, the European Metrology Research Programme project "External Beam Cancer Therapy" (EBCT) was formally launched with the involvement of nine National Metrology Institutes. The central objective of this project is to provide reliable measuring techniques for all forms of cancer therapy based on external radiation. As well as established cancer therapies which use ionizing radiation, such as particle and Intensity Modulated Radiation Therapies (IMRT) employing high-energy photon radiation, this project includes the emerging technique of High Intensity Therapeutic Ultrasound.

One of the key elements of the project is the development and comparison of measurement techniques for the determination of acoustic output power generated by high-intensity ultrasound transducers. Because there has been no experience of such methods in any world laboratory, comparison between different techniques is essential for the establishment of a reliable basis for measurement. The four institutes involved in the WP 2 of the EBCT project will organise a comparison of power measurement methods under the conditions given by the BIPM guidelines for key comparisons. Two transducers will be circulated among participants and measurements following an agreed protocol will be carried out. PTB, as coordinator of the comparison, will collect and process the data. By suitable presentation of the data describing agreement and important differences in measurements, the key results of the comparison will be documented. On the basis of these results, the measurement techniques will be improved and definitive uncertainty budgets developed and validated.

Final Report 2011-05-02

The project has been completed and the final report can be downloaded here:

The inter-laboratory comparison of power measurement capabilities and procedures in the frequency range 0.5 to 3 MHz up to at least 150 W was part of a European Metrology Research Programme project: JRP7/TP2 “External Beam Cancer Therapy (EBCT)”. The task was to measure the acoustic radiation conductance G of two HITU transducers at three frequencies excited at four power levels within a usual power range. Fulfilling the task it was required to measure the time-averaged, ultrasonic output power and the applied rms voltage used for excitation of the transducers.
Two HITU transducers, used as transfer standards, circulated between the participants (INRIM – Italy, NPL – UK, PTB – Germany, UME – Turkey) within 7 months, including the remeasurements at the pilot laboratory (PTB). A final report describes the measurement setups applied, the results obtained and the associated uncertainties. The participants relative expanded uncertainties for the radiation conductance at the various combinations of transducer type, frequency and excitation level range from 4.5 % to 15.2 %. Reference values and degrees of equivalence are given.
The obtained agreement between the results of the participants can generally be considered satisfactory. Based on experience of this comparison a new comparison under the auspice of BIPM is recommended.

Acoustics, Ultrasound and Vibration (AUV)
Coordinating Institute
PTB (Germany)