Edinburgh Napier University

  Quantitative ulltrasound (QUS) analyzes unprocessed radio frequency data from an ultrasound transducer or array and infers properties about tissue microstructure. Whilst it has shown success in diagnosing various soft tissue diseases, there have been limited reports of application to the brain. Due to the difficulty of obtaining freshly-excised human tissue, fresh-frozen and fixed samples are attractive alternatives. However, their use makes it imperative to understand the effects of freezing and fixation in order to assess whether preserved samples can give reliable results. As chicken liver and gizzard muscle have been shown previously to be valid acoustic phantoms for brain and brain tumour respectively, we have used them in a preliminary step to assess these effects. QUS measurements of scatterer size, acoustic concentration, the parameters κ and α from the homodyned K-distribution, were made using a research ultrasound system (Vantage 128, Verason-ics Inc, WA, USA) from fresh, fresh-frozen and fixed samples of both tissue types. A confidence interval of 95% was used to evaluate whether these parameters were significantly altered by preservation method. The results showed that scatterer size and homodyned K distribution parameters were mostly unaffected but the acoustic concentration was significantly affected. This preliminary study suggests that QUS parameters measured from frozen or fixed tissue could be reliable as a guide for some in vivo clinical diagnostic measurements.