State-of-the-art imaging techniques in endoscopic ultrasound

Abstract

Endoscopic ultrasound (EUS) has recently evolved through technological improvement of equipment, with a major clinical impact in digestive and mediastinal diseases. State-of-the-art EUS equipment now includes real-time sono-elastography, which might be useful for a better characterization of lesions and increased accuracy of differential diagnosis (for e.g. lymph nodes or focal pancreatic lesions). Contrast-enhanced EUS imaging is also available, and is already being used for the differential diagnosis of focal pancreatic masses. The recent development of low mechanical index contrast harmonic EUS imaging offers hope for improved diagnosis, staging and monitoring of anti-angiogenic treatment. Tridimensional EUS (3D-EUS) techniques can be applied to enhance the spatial understanding of EUS anatomy, especially for improved staging of tumors, obtained through a better assessment of the relationship with major surrounding vessels. Despite the progress gained through all these imaging techniques, they cannot replace cytological or histological diagnosis. However, real-time optical histological diagnosis can be achieved through the use of single-fiber confocal laser endomicroscopy techniques placed under real-time EUS-guidance through a 22G needle. Last, but not least, EUS-assisted natural orifice transluminal endoscopic surgery (NOTES) procedures offer a whole new area of imaging applications, used either for combination of NOTES peritoneoscopy and intraperitoneal EUS, but also for access of retroperitoneal organs through posterior EUS guidance.

Keywords: Contrast-enhancement; Endoscopic ultrasound; Endoscopic ultrasound-guided fine needle aspiration; Hybrid imaging; Real-time sono-elastography; Tridimensional (3D).

Figure 1

Pancreatic carcinoma at the level of pancreatic head depicted by different endoscopic ultrasound imaging techniques. A: Real-time elastography showing an in-homogenous hard mass; B: Power Doppler endoscopic ultrasound (EUS) without contrast-enhancement; C: Power Doppler EUS after contrast-enhancement with Sono-Vue, showing a hypovascular mass; D: Pulsed Doppler (triplex mode) after contrast-enhancement, with high resistivity and pulsatility indexes of intratumoral arteries; E: Contrast-enhanced low-mechanical index EUS harmonic imaging, showing a hypovascular appearance in the late (venous) phase; F: Tridimensional EUS showing an enhanced image in the opacity mode; G: Transparency mode obtained after contrast-enhancement with Sono-Vue; H: Multiview tridimensional (3D)-EUS display of the pancreatic tumor.