Transfer standard device to improve the traceable calibration of physiotherapy ultrasound machines

A Buoyancy Method for the Measurement of Total Ultrasound Power Generated by HIFU Transducers

“…The total ultrasound output power of a HIFU system is a key quantity related to the delivered dose during clinical treatment. Traditionally, the use of a radiation force balance has been considered the most accurate method of measuring ultrasound power: it is described in detail in the literature (for example Greenspan et al 1978;Benjavic and Carson 1980;Stewart 1982;Tsciegg et al 1983;Livett 1984;Davidson 1991;Beissner et al 1996;Beissner 1999aBeissner , 1999bBeissner , and 2002Hekkenberg et al 2000;2001, Hekkenberg et al 2006Sutton et al 2003) and in IEC standard 61161 (IEC61161 (2006)). …”

“…One method to prevent excessive heat buildup is to use an absorbing fluid instead of a solid material so that heat is dissipated by convection and streaming currents within the target. A radiation force target filled with castor oil has been described previously by Shaw (2006) and calibrated against the portable power standard (Hekkenberg et al 2006) using unfocused physiotherapy transducers at applied power levels between 1 and 15 W. The ratio of measured power to applied power was 1.04 at 1 MHz and 0.99 at 3 MHz both with an uncertainty of Ϯ6%. The same target was also tested at incident powers up to 140 W at 1.08 MHz and shown to be linear to within Ϯ3% over this range.…”

Progress in developing a thermal method for measuring the output power of medical ultrasound transducers that exploits the pyroelectric effect

“…This was performed using two large diameter transducers, operating at 1 and 3 MHz forming part of the NPL Portable Power Standard (PPS) system [8]. This is a Continuous-Wave Check Source able to deliver well-defined acoustic powers at physiotherapy levels.…”

Calibration and measurement issues for therapeutic ultrasound

“…3. Comparison of target types and dimensions used to measure a transducer with a ka of 12.4 (reproduced from [43]). The radiation conductance is normalized to the value measured at 2 mm with the 100 mm absorbing target.…”