Assessment of histotripsy-induced liquefaction with diagnostic ultrasound and magnetic resonance imaging < i > in vitro < /i > and < i > ex vivo < /i > .

In this study, magnetic resonance (MR) and diagnostic ultrasound imaging were combined to assess histotripsy treatment in vitro and ex vivo. Mechanically ablative histotripsy pulses were applied to agarose phantoms or porcine livers. Bubble cloud emissions were monitored with passive cavitation imaging (PCI), and hyperechogenicity via plane wave imaging. Changes in the medium structure due to bubble activity were assessed with diagnostic ultrasound using conventional B-mode imaging and T1-, T2-, and diffusion-weighted MR images acquired at 3 Tesla. Liquefaction zones were correlated with diagnostic ultrasound and MR imaging via receiver operating characteristic (ROC) analysis and Dice Similarity Coefficient (DSC) analysis. Diagnostic ultrasound indicated strong bubble activity for all samples. Histotripsy-induced changes in sample structure were evident on conventional B-mode and T2-weighted images for all samples, and were dependent on the sample type for T1- and diffusion-weighted imaging. The greatest changes observed on conventional B-mode or MR imaging relative to baseline in the samples did not necessarily indicate the regions of strongest bubble activity. Areas under the ROC curve for predicting phantom or liver liquefaction were significantly greater than 0.5 for PCI power, plane wave and conventional B-mode grayscale, T1, T2, and ADC. The acoustic power mapped via PCI provided a better prediction of liquefaction than assessment of the liquefaction zone via convention...
Source: Physics in Medicine and Biology - Category: Physics Authors: Tags: Phys Med Biol Source Type: research