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 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° (TRANS-FUSIMO project) and n° (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: [2] Thiel W. An arterial substance for subsequenct injection during the preservation of the whole corpse. Ann Anat 1992;174: [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: [4] Gueorguieva MJ, Yeo DTB, Eisma R, Melzer A. MRI of Thiel-embalmed human cadavers. J Magn Reson Imaging 2014;39: 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.