The value of Augmented Reality in surgery - A usability study on laparoscopic liver surgery.

Augmented Reality (AR) is considered to be a promising technology for the guidance of laparoscopic liver surgery. By overlaying pre-operative 3D information of the liver and internal blood vessels on the laparoscopic view, surgeons can better understand the location of critical structures. In an effort to enable AR, several authors have focused on the development of methods to obtain an accurate alignment between the laparoscopic video image and the pre-operative 3D data of the liver, without assessing the benefit that the resulting overlay can provide during surgery. In this paper, we present a study that aims to assess quantitatively and qualitatively the value of an AR overlay in laparoscopic surgery during a simulated surgical task on a phantom setup. We design a study where participants are asked to physically localise pre-operative tumours in a liver phantom using three image guidance conditions - a baseline condition without any image guidance, a condition where the 3D surfaces of the liver are aligned to the video and displayed on a black background, and a condition where video see-through AR is displayed on the laparoscopic video. Using data collected from a cohort of 24 participants which include 12 surgeons, we observe that compared to the baseline, AR decreases the median localisation error of surgeons on non-peripheral targets from 25.8 mm to 9.2 mm. Using subjective feedback, we also identify that AR introduces usability improvements in the surgical task and increases the perceived confidence of the users. Between the two tested displays, the majority of participants preferred to use the AR overlay instead of navigated view of the 3D surfaces on a separate screen. We conclude that AR has the potential to improve performance and decision making in laparoscopic surgery, and that improvements in overlay alignment accuracy and depth perception should be pursued in the future.

Development and Characterization of a Porcine Liver Scaffold.

The growing number of patients requiring liver transplantation for chronic liver disease cannot be currently met due to a shortage in donor tissue. As such, alternative tissue engineering approaches combining the use of acellular biological scaffolds and different cell populations (hepatic or progenitor) are being explored to augment the demand for functional organs. Our goal was to produce a clinically relevant sized scaffold from a sustainable source within 24 h, while preserving the extracellular matrix (ECM) to facilitate cell repopulation at a later stage. Whole porcine livers underwent perfusion decellularization via the hepatic artery and hepatic portal vein using a combination of saponin, sodium deoxycholate, and deionized water washes resulting in an acellular scaffold with an intact vasculature and preserved ECM. Molecular and immunohistochemical analysis (collagen I and IV and laminin) showed complete removal of any DNA material, together with excellent retention of glycosaminoglycans and collagen. Fourier-transform infrared spectroscopy (FTIR) analysis showed both absence of nuclear material and removal of any detergent residue, which was successfully achieved after additional ethanol gradient washes. Samples of the decellularized scaffold were assessed for cytotoxicity by seeding with porcine adipose-derived mesenchymal stem cells in vitro, these cells over a 10-day period showed attachment and proliferation. Perfusion of the vascular tree with contrast media followed by computed tomography (CT) imaging showed an intact vascular network. In vivo implantation of whole intact nonseeded livers, into a porcine model (as auxiliary graft) showed uniform perfusion macroscopically and histologically. Using this method, it is possible to create an acellular, clinically sized, liver scaffold with intact vasculature in less than 24 h.