Abstract
Using high intensity focused ultrasound (HIFU) to locally perform thermalablation has shown its potential in auxiliary excision surgery, especially inthermal ablation of tumor. However, it is challenging for clinical physicians tolocate the region being under HIFU thermal ablation and determine the appliedablation level only by conventional ultrasound B-mode images, causing dangers intherapy. In this study, we propose an ultrasonic Nakagami imaging technique tomonitor HIFU thermal ablation in real time. It has been demonstrated thatultrasonic Nakagami imaging is capable of characterizing tissues with differentscatterer concentration and distribution. Because in histological sections withand without HIFU thermal ablation, there are differences in scattererconcentration and distribution, we hypothesize that Nakagami parameters oftissues being HIFU thermal ablated will change, accordingly, thus potentiallyenabling Nakagami visualization of HIFU-induced thermal lesions. Ex vivo thermalablation experiments of porcine livers were conducted to demonstrate our idea.Experiment results showed that Nakagami images could reveal the HIFU-inducedthermal lesion, which was difficult to be located in conventional B-mode imagesbecause of no appearance of bubbles. Moreover, in the cases with apparent bubbleformation, both of B-mode images and Nakagami images could locate the positionof the thermal ablation area, while Nakagami images owned higher contrast. Insummary, we experimentally demonstrated the feasibility of monitoring HIFUthermal ablation by Nakagami imaging. The contrast of the ablated regionsbetween the Nakagam images before and after thermal ablation outpeform that ofB-mode images. Because the complexity of the Nakagami imaging algorithm is low,it can be easily integrated as part of post processing in current array systemsindicating that real-time visualization of HIFU thermal lesion with Nakagamiimaging is possible. © 2010 IEEE.