2.1. Ultrasound Examinations

The B-TUS examinations were performed with an ACUSON SEQUOIA 512 GI ultrasound machine (Siemens, Erlangen, Germany). A 4C1 curved array transducer with frequencies between 3.5 and 4.5 MHz was used. The CEUS examinations were performed with the same transducer in 1.5 MHz contrast-specific mode according to the EFSUMB guidelines [17]. A bolus injection of 2.4 mL of SonoVue^® (Bracco Imaging S.p.A., Milan, Italy) contrast medium was given via peripheral venous access, followed by 10 mL NaCl 0.9%. During the first 30 s, PEs and thoracic pathologies were continuously examined. Subsequently, several short examinations in 30 s intervals, up to 3 min, were conducted. The pathologies presented in CEUS imaging were saved as images. All the patients were examined in an upright sitting position. All the ultrasound examinations were performed standardised and prospective by a German Society for Ultrasound in Medicine (DEGUM)-qualified Level-III examiner (C.G.). The ultrasound data were obtained during general clinical procedures and according to the hospital’s guidelines.

The following B-TUS data and CEUS parameters were retrospectively analysed by two independent, experienced investigators (E.S., C.G.). In the event of a discrepancy between the two investigators, the final decision was made by a third experienced investigator (C.T.). Cohen’s kappa statistics were applied to measure interrater reliability.