Benefits, Open questions and Challenges of the use of Ultrasound in the COVID-19 pandemic era. The views of a panel of worldwide international experts - Piscaglia, Fabio; Stefanini, Federico; Cantisani, Vito; Sidhu, Paul S.; Barr, Richard; Berzigotti, Annalisa; Chammas, Maria Cristina; Correas, Jean-Michel; Dietrich, Christoph Frank; Feinstein, Steven; Huang, Pintong; Jenssen, Christian; Kono, Yuko; Kudo, Masatoshi; Liang, Ping; Lyshchik, Andrej; Nolsøe, Christian; Xie, Xyaoyan; Tovoli, Francesco (Ultraschall in der Medizin - European Journal of Ultrasound, 2020)