1 Department of Internal Medicine, Fondazione Istituto di Ricovero e Cura a Carattere Scientifico Policlinico San Matteo, University of Pavia, Pavia, Italy.
2 Department of Information Engineering and Computer Science, Ultrasound Laboratory Trento, University of Trento, Trento, Italy.
3 Pulmonary Medicine Unit, Department of Medical and Surgical Sciences, Fondazione Istituto di Ricovero e Cura a Carattere Scientifico Policlinico Universitario Agostino Gemelli, Rome, Italy.
4 Diagnostic and Interventional Ultrasound Unit, Valle del Serchio General Hospital, Lucca, Italy.