Scientists at UK measurement institute the Nation Physical Laboratory (NPL) have developed a device that allows physiotherapists to check whether ultrasound treatment equipment is sending out sound waves in a uniform pattern.
The device is a tile which contains thermochromic crystals that lose their colour when heated. This can reveal any ‘hot spots’ where the ultrasound treatment head is focusing the sound waves in a way that could make a patient’s muscle strain or ligament damage worse.
This should allow therapists to quickly check for treatment head damage or asymmetric beam-patterns and either adjust the head or avoid using it, improving the quality of physiotherapy ultrasound treatments in the process.
Bajram Zeqiri, the NPL science fellow who led the project, said, ‘In clinical practice the new ‘imager’ tiles would be used in much the same way you would treat a patient: by applying coupling gel to the treatment head, coupling it to the tile, switching on for typically 10 seconds, and then removing and observing the resulting image.’
The tool consists of two layers: a bottom layer made of thermochromic crystals embedded in a polyurethane rubber matrix which absorbs sound, and a colourless top layer that is used to trap the heat within the tile.
The acoustic energy from the treatment head heats up the tile and turns the crystals white when they reach a certain temperature. Within seconds, this produces a pattern on the tile that represents how the ultrasound waves are distributed by the treatment head.
The device is being manufactured through a licence agreement with UK company Precision Acoustics.