Ultrasound Histotripsy on a Viable Perfused Whole Porcine Liver: Histological Aspects, Including 3D Reconstruction of the Histotripsy Site.

Non-invasive therapeutic-focused ultrasound (US) can be used for the mechanical dissociation of tissue and is described as histotripsy. We have performed US histotripsy in viable perfused ex vivo porcine livers as a step in the development of a novel approach to hepatocyte cell transplantation. The histotripsy nidus was created with a 2 MHz single-element focused US transducer, producing 50 pulses of 10 ms duration, with peak positive and negative pressure values of P+ = 77.7 MPa and P- = -13.7 MPaat focus, respectively, and a duty cycle of 1%. Here, we present the histological analysis, including 3D reconstruction of histotripsy sites. Five whole porcine livers were retrieved fresh from the abattoir using human transplant retrieval and cold static preservation techniques and were then perfused using an organ preservation circuit. Whilst under perfusion, histotripsy was performed to randomly selected sites on the live. Fifteen lesional sites were formalin-fixed and paraffin-embedded. Sections were stained with Haematoxylin and Eosin and picro-Sirius red, and they were also stained for reticulin. Additionally, two lesion sites were used for 3D reconstruction. The core of the typical lesion consisted of eosinophilic material associated with reticulin loss, collagen damage including loss of birefringence to fibrous septa, and perilesional portal tracts, including large portal vein branches, but intact peri-lesional hepatic plates. The 3D reconstruction of two histotripsy sites was successful and confirmed the feasibility of this approach to investigate the effects of histotripsy on tissue in detail.