Endoscopic ultrasound (EUS) - a combination of endoscopy and ultrasonography
Endoscopic ultrasound combines the advantages of the two medical disciplines endoscopy and ultrasonography. The ultrasound transducer is integrated in the distal end of the endoscope which allows the close positioning of the transducer at the region of interest, one important factor of the unrivalled resolution of the EUS image.
Competing techniques are computed tomography (CT) and magnetic resonance imaging (MRI), but both technologies are offering a lower image resolution – and therefore detection rate - of small lesions when compared with EUS. Additionally the CT & MRI technology is limited to imaging only and do not offer the option to directly collect tissue samples in case a suspicious region was found during the examination. EUS provides this option and is even free of radiation.
The high image resolution allows the diagnosis and staging of various lesions which are located in and around the GI tract. Typically EUS examinations follow the standard endoscopy whenever additional, more detailed information about tissue characteristics, blood flow dynamics or tumor invasion depths are required. Especially a very precise definition of the tumor invasion depth (TNM-staging) is of major importance to guarantee the best possible treatment for such patients, avoiding under- and over-staging, which both inevitably leads to a suboptimal or wrong patient treatment.
Beside the importance of the tumor penetration depth, EUS also offers the option to collect tissue samples in a minimally invasive way at areas which can under normal conditions only be reached via invasive surgery. Endoscopic Ultrasound (EUS) guided Fine Needle Aspiration (FNA) is already proven to be a valuable tool to collect such tissue samples for the pathologist or cyto-pathologist who can then differentiate the specimen between normal, malignant and benign tissue.
The modern EUS technology differentiates between "radial" and "linear" scanning.
360° radial scanning technology
The 360° scanning range of the radial echoendoscope offers the advantage of a full panoramic view, a doppler functionality to display blood flow dynamics inside the blood vessels and imaging modalities like Contrast Harmonic – Endoscopic Ultrasound (CH-EUS) which can even visualize microvasculature structures down to capillary perfusions, adding valuable information to the examination, simplifying the orientation within the gastrointestinal tract and therefore speeding up the examination time.
Radial scanning technology
Radial scan of the gallbladder, pancreas, liver and vena cava from the duodenal bulb
Miniprobes – 360° radial scanning via the working channel of a standard endoscope
In addition to the described echoendoscope we also offer ultrasound miniprobes. Due to the very small diameter they can be pushed through the working channel of standard endoscopes, eliminating the need of a scope exchange during the examination and the small size allows the progress of the miniprobes to areas which can not be reached via any echoendoscopes (e.g. wirsung duct, bile duct). Miniprobes also allow the creation of 3D-ultrasound scans with functionalities like surface rendering, multi plane reconstructions or the calculation of the tumor volume.
180° linear scanning technology
The linear scanning technology comes along with a scanning range of 180° and differs additionally in the direction of the ultrasound scanning plane. The linear scanning technology is designed to continuously visualize the progression of the needle insertion into the tissue when performing a EUS-FNA procedure or other therapeutic procedures like pseudocyst drainage, celiac plexus neurolysis or when placing stents.
Linear scanning technology
linear scan showing the insertion of a needle during a EUS-FNA procedure
Beside the EUS usage in the Gastroenterology field, the technology also found its way into the pulmonology working field, offering EUS equipment for the diagnosis and staging of lung cancer. Endoscopic Bronchial Ultrasound (EBUS) guided Fine Needle Aspiration (FNA) was developed to acquire tissue samples in the bronchial tree and the mediastinum, similar to the previously described EUS-FNA.