B-scan ultrasound imaging of thermal coagulation in bovine liver: Log envelope slope attenuation mapping

Thermal therapy is an experimental procedure to treat localised tumours in the prostate, liver, kidney or breast. Monitoring is important to ensure complete tumour destruction while sparing adjacent sensitive structures, Previous work demonstrated that, when biological tissues are heated above 65 degreesC, ultrasound (US) attenuation increases due to thermal coagulation of tissue. This study examined the feasibility of a B-scan, envelope-based attenuation estimation method to monitor thermal therapy. The slope of the log of the signal envelope was used to estimate attenuation. It is shown that this method is able to demonstrate, from simulated and phantom data, a limited ability to differentiate attenuation levels that correspond to thermally coagulated and uncoagulated beef liver. In ex vivo bovine liver, however, issues due to signal-to-noise ratio (SNR) of the signal envelope prevented the visulisation of a 2-cm diameter thermally coagulated inclusion. The limitations of this method are extended to the multinarrow-band (MNB) technique. (C) 2001 World Federation for Ultrasound in Medicine & Biology.