1 cm x 1 cm Bounded output mask for TI measurement
The bounded output mask provides a means of ensuring that measurements of TI according to IEC 62359 can satisfy the requirement of only determining the ultrasonic output through an area of 1 cm x 1 cm.
A novel precision-formed mask that provides both high absorption of ultrasonic signals incident upon the flat surface of the mask, and high level of reflections from the internal surfaces of the aperture.
This enables accurate the determination of P1x1 as required in IEC 62359 during the determination of TI.
- The mask is fabricated from the NPL HAMA absorber material to provide high absorption and high echo reduction.
- Precision machined aperture with dimensions 1cm by 1 cm
- Edges of the mask aperture have highly reflective metal lining
To use, the NPL apertures are simply placed in front of the physiotherapy treatment head, with the resulting reduction in power being measured using the radiation force balance.
The method is described in the paper, A new method for measuring the effective radiating area of physiotherapy treatment heads (Bajram Zeqiri and Mark Hodnett, Ultrasound in Medicine & Biology, Vol. 24:5, 1998, pp. 761-770), and also in the, Guidelines for the testing and calibration of physiotherapy ultrasound machines, (IPEM Report No. 84, Institute of Physics and Engineering in Medicine, 2001).