1. MR-guided Focused Ultrasound Ablation in a Preclinical Thiel Model Ioannis Karakitsios,Xu Xiao, Markus Domschke, Andreas Melzer Institute of Medical Science and Technology, University of Dundee, Dundee, United Kingdom E-mail: i.karakitsios@dundee.ac.uk Introduction Magnetic Resonance guided Focused Ultrasound Surgery (MRgFUS) is a non-invasive method that can reduce the tumour size by thermally ablating it [1]. The Thiel-embalmed preservation model can provide insight in treatment of moving/perfused organs and can facilitate simulation of liver surgery with MRgFUS [2-4]. The purpose of our work was to demonstrate a pre-clinical experimental setup, based on explanted Thiel embalmed ovine liver, filled with contrast-enhanced agar gel, fixed in an agar/gelatine phantom. Materials and methods Contrast-enhanced (Gadolinium 1:50 doped in agar/gelatine mixture) agar gel was injected in the organ. The organs were fixed in agar gel phantom and scanned on a 1.5T scanner (Signa HDx, GE Medical Systems, USA) using a three- dimensional Time-Of-Flight (3D-TOF) sequence: TE: 11 ms, Flip Angle: 30°, Acquisition Matrix: 360×224, 44 Locations per Slab. The MR scans were reconstructed using three-dimensional Maximum Intensity Projection (3D-MIP). The livers were heated with FUS for 20 s on a patient system table (ExAblate 2000,InSightec Ltd.,Israel) with following acoustic energies: 300 J, 600 J and 900 J. Proton Resonance Frequency (PRF) Thermometry was used to calculate the maximum temperatures achieved. Results The temperature feedback was assessed via post-treatment PRF thermal maps and themperature graphs (Fig. 2). 3D MIP reconstructed MR images of the liver vasculature were generated (Fig. 3). For the Thiel-embalmed ovine liver, maximum temperature increase (±SD) of 51.7°C (0.2), 71.7°C (0.5) and 87°C (0.4) was achieved for heating with 300 J, 600 J and 900 J respectively. Identical values were found for fresh organ. Conclusion The results demonstrated high enough temperatures to achieve ablation (>57°C) at acoustic energies:700 J and 900 J. The comparison between the temperature output from FUS treatments of the fresh and embalmed organs showed low difference (<0.5°C). A satisfactory vasculature was observed. Overall, the explanted Thiel embalmed organ, embedded into agar/gelatine block, constitutes a reliable model to study MRgFUS. Acknowledgements; The research leading to these results has also received funding from the European Union's Seventh Framework Programme (FP7) under grant agreement n°611889 (TRANS-FUSIMO project) and n°611963 (FUTURA).. Fig 1 – Experimental description showing:(A) Thiel embalmed liver fixed in agar/gelatine,(B) MRgFUS treatment system table,(C) 3D TOF MR image showing vasculature in the liver. Fig 3 – Reconstructed (3D-MIP) MR images showing the vasculature of (A) fresh ovine,(B) Thiel-embalmed ovine liver. References [1] Bradley GW. MR-guided focused ultrasound: a potentially disruptive technology. J Am Coll Radiol 2009;6:510-513. [2] Thiel W. An arterial substance for subsequenct injection during the preservation of the whole corpse. Ann Anat 1992;174:197-200. [3] Eisma R, Mahendran S, Majumbar J, Weihe S, Teintra C, Deppe H, Wolff KD. Thiel embalming technique: a valuable method for teaching oral surgery and implantology. Clin Implant Dent Relat Res 2009;14:121-126. [4] Gueorguieva MJ, Yeo DTB, Eisma R, Melzer A. MRI of Thiel-embalmed human cadavers. J Magn Reson Imaging 2014;39:576-583. A C B Fig 2 – Post-treatment PRF thermal map and graph showing the maximum (red line) and the average (green line) temperature achieved on the targeted area.