Real time evaluation of the liver microcirculation by whole organ machine perfusion within an MRI system
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Objectives
Machine perfusion of organs outside of the body is a growing area of research with significant applications in the fields of organ preservation and transplantation, but more widely it offers a new approach to study disease processes and to evaluate new therapeutics and devices. Magnetic Resonance Imaging (MRI) allows for non-invasive assessment of organ structure and function, enabling quantitative measurement of tissue perfusion and microstructure. In this study, we demonstrate that MR imaging sequences can be obtained from machine-perfused porcine livers using a modified perfusion rig for MR compatibility and highlight the quantitative measures that can be obtained through this methodology.
Materials and Methods
7 porcine livers were retrieved fresh from the abattoir using a previously published protocol and following transport in cold preservative underwent perfusion with oxygenated autologous blood inside a 3T clinical MRI scanner using a custom modified perfusion rig. Multiple MR imaging sequences were acquired: T2-weighted imaging, Diffusion Weighted Imaging and Dynamic Contrast Enhanced imaging following injection of Gadolinium dye into the portal vein and hepatic artery. Histological analysis was performed to assess preservation injury to the liver. Control samples for histology were obtained from livers with similar preservation periods but preserved in standard cold storage on ice (Static Cold Storage).
Results
Concurrent MR imaging and machine perfusion were successfully performed, allowing dynamic measurement of tissue perfusion to be obtained in ex vivo livers, including calculation of gadolinium contrast enhancement curves and Apparent Diffusion Coefficient maps. Segmentation of vessels down to a radius of 0.45mm allowed detailed morphological analysis of the vascular network, including extraction of clinically relevant parameters such as vessel tortuosity. Histological evaluation showed better preservation of the hepatic acinar structure in perfused than non-perfused livers.
Conclusions
Our results demonstrate that MR imaging of machine-perfused organs enables high-resolution quantitative evaluation of whole-organ vascular morphology and flow dynamics. This platform provides opportunities to study vascular pathology in diseased human organs and evaluate novel therapeutic interventions, with particular relevance for drug-delivery strategies.
