Published online Nov 14, 2014. doi: 10.3748/wjg.v20.i42.15549
Revised: April 23, 2014
Accepted: May 19, 2014
Published online: November 14, 2014
Over the last decade, the development of stabilised microbubble contrast agents and improvements in available ultrasonic equipment, such as harmonic imaging, have enabled us to display microbubble enhancements on a greyscale with optimal contrast and spatial resolution. Recent technological advances made contrast harmonic technology available for endoscopic ultrasound (EUS) for the first time in 2008. Thus, the evaluation of microcirculation is now feasible with EUS, prompting the evolution of contrast-enhanced EUS from vascular imaging to images of the perfused tissue. Although the relevant experience is still preliminary, several reports have highlighted contrast-enhanced harmonic EUS (CH-EUS) as a promising noninvasive method to visualise and characterise lesions and to differentiate benign from malignant focal lesions. Even if histology remains the gold standard, the combination of CH-EUS and EUS fine needle aspiration (EUS-FNA) can not only render EUS more accurate but may also assist physicians in making decisions when EUS-FNA is inconclusive, increasing the yield of EUS-FNA by guiding the puncture with simultaneous imaging of the vascularity. The development of CH-EUS has also opened up exciting possibilities in other research areas, including monitoring responses to anticancer chemotherapy or to ethanol-induced pancreatic tissue ablation, anticancer therapies based on ultrasound-triggered drug and gene delivery, and therapeutic adjuvants by contrast ultrasound-induced apoptosis. Contrast harmonic imaging is gaining popularity because of its efficacy, simplicity and non-invasive nature, and many expectations are currently resting on this technique. If its potential is confirmed in the near future, contrast harmonic imaging will become a standard practice in EUS.
Core tip: The recent development of stabilised contrast agents and enhancements to the endoscopic ultrasound equipment have opened an avenue for the real-time imaging of parenchymal microvascularisation without Doppler-related artefacts. Preliminary experience suggests that contrast-enhanced harmonic endoscopic ultrasound (CH-EUS) is superior to other imaging techniques, such as EUS or computed tomography, in the differential diagnosis of pancreatic masses and other gastrointestinal diseases. In this paper, we describe the basic principles and technical aspects of performing this new technique and analyse the clinical value of CH-EUS and its potential applications in the near future.