Proposed standard thermal test object for medical ultrasound

A general design for a thermal test object (TTO) is proposed. A number of n ovel features make the design particularly suitable for use as a standardis ed device for assessing the heating capability of diagnostic ultrasound bea ms, To assess performance, soft-tissue TTOs have been made containing thin- film thermocouples sandwiched between discs of tissue-mimicking gel. Instal led in an appropriate measurement system, these TTOs exhibit excellent ther mal and spatial resolution, allowing the ultrasound beam to be located rapi dly and reproducibly. The measured temperature rise after 3 minutes of heat ing has been compared with theoretical predictions based on measured pressu re distributions, and agreement is within 10%. Other studies have shown tha t soft-tissue- and bone-mimicking TTOs can be used to evaluate a wide range of ultrasound fields and that different physical tissue models can be simu lated. It is concluded that this design would be suitable for providing ref erence assessments of the thermal hazard posed by diagnostic ultrasound und er standardised conditions. Crown copyright. Reproduced by permission of th e Controller of HMSO.