title: Exploiting thermochromic materials for the rapid quality assurance of physiotherapy ultrasound treatment heads.
abstract: Significant nonuniformities in the acoustic intensity distribution generated by physiotherapy ultrasound treatment heads are not uncommon, potentially leading to significant localised temperature rises and tissue damage. An acoustic absorber tile containing a thermochromic pigment has been developed to provide rapid quality assurance of physiotherapy ultrasound treatment heads by virtue of a thermochromic colour change, indicating the time-averaged intensity distributions generated by these devices. As a bench-top device, the use of the tile is designed to mimic the nature of the physiotherapeutic application, requiring minimal training. Two designs where thermochromic pigments are added to the various polymeric layers of the tile are presented. Testing has been conducted with two physiotherapy treatment heads of differing performance, one of them notably exhibiting a strong "hot-spot" in localised acoustic time-averaged intensity. Findings show good qualitative agreement with classical hydrophone scans. Techniques are explored for the correction of nonlinearities in the thermochromic relationship, to enhance the accuracy of quantitative assessment.
authors.affiliation: National Physical Laboratory, Teddington, United Kingdom. ian.butterworth@npl.co.uk
authors.forename: Ian
authors.initials: I
authors.lastname: Butterworth
authors.forename: Jill
authors.initials: J
authors.lastname: Barrie
authors.forename: Bajram
authors.initials: B
authors.lastname: Zeqiri
authors.forename: Gordana
authors.initials: G
authors.lastname: Žauhar
authors.forename: Benjamin
authors.initials: B
authors.lastname: Parisot
mesh_terms: D004867:Equipment Design; D019544:Equipment Failure Analysis; D026741:Physical Therapy Modalities / Q000295:instrumentation* / Q000592:standards*; D011785:Quality Assurance, Health Care / Q000379:methods; D011829:Radiation Dosage; D011874:Radiometry / Q000295:instrumentation* / Q000592:standards*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014464:Ultrasonic Therapy / Q000295:instrumentation* / Q000592:standards*; D006113:United Kingdom