1. Department Medical Physics and Bioengineering, University College London, Torrington Place, London WC1E 7JE, UK
2. UCL Mechanical Engineering, University College London, Torrington Place, London WC1E 7JE, UK
3. Wellcome/EPSRC Centre for Interventional and Surgical Sciences, UCL Mechanical Engineering, University College London, Torrington Place, London WC1E 7JE, UK
4. Department of Electronics, Information and Bioengineering, Politecnico di Milano, Milano 20133, Italy
5. UCL Mechanical Engineering, University College London, Torrington Place, London WC1E 7JE, UK; Leeds Teaching Hospitals NHS Trust, Leeds LS1 3EX, UK
6. Cardiothoracic Surgery Unit, Great Ormond Street Hospital for Children, Holborn, London WC1N 3JH, UK
7. UCL Mechanical Engineering, University College London, Torrington Place, London WC1E 7JE, UK; Ri.MED Foundation, Via Bandiera, 11, Palermo 90133, Italy