MI Techniques Research Articles

Contrast Enhanced Endoscopic Ultrasound With Low Mechanical Index, a New Technique-Preliminary Report

Introduction: Recent advances in technology have supported the development of new endoscopic systems making it possible to apply contrast enhanced low MI techniques with wide band harmonic imaging by endoscopic ultrasound at a preliminary stage. We report on the first use of real-time, contrast-enhanced, endoscopic ultrasound with low mechanical index technique in 6 patients. Methods: Endoscopic ultrasound was performed using an electronic echoendoscope HITACHI/Pentax EG-3830UT and adapted dynamic Contrast Harmonic Wideband Pulsed Inversion Software with low mechanical index (MI, 0.09–0.25) before and from up to 180 seconds after injection of BR1 4.8 mL. Results: Adequate visualization of the arterial and portal venous phase was sufficient in all patients. The pancreas and liver were studied thereafter. In contrast to the mentioned vessels enhancement of the liver was sufficient only in 4 patients. In the remaining 2 patients with liver cirrhosis the enhancement was less pronounced in contrast to the strong enhancement of the hepatic artery and portal vein. Discussion: Recent advances in technology have supported the development of new echoendoscopic systems making it possible to apply real-time, contrast-enhanced, low mechanical index techniques also by endoscopic ultrasound. We could preliminarily show that arterial, portal venous, and parenchymal contrast enhancement is possible.

Contrast‐enhanced power Doppler sonography of malignant ovarian tumors using harmonic flash‐echo imaging: preliminary experience

To investigate the potential usefulness of contrast-enhanced intermittent harmonic sonography in the diagnosis of ovarian cancer, we evaluated 4 patients with complex adnexal masses suspected of malignancy using intermittent harmonic sonography after injection of a contrast agent. Tumor and/or mural nodule tissue enhancement was detected in all cases of ovarian malignancy. Contrast-enhanced, intermittent harmonic sonography provides a satisfactory visualization of blood flow in the solid portion of the tumor tissue and may support a diagnosis of ovarian malignancy. Depiction of blood vessels using low MI techniques may be possible with other vascular ultrasonographic contrast agents.

Imaging techniques for ultrasound contrast agents

Contrast agents are used today to enhance and aid organ (myocardium, liver, brain, etc.) perfusion studies. From the early days of contrast imaging it was understood that microbubble specific imaging modalities would have to be invented to utilize the contrast effect. The two main characteristics of contrast microbubbles that have defined today’s ultrasound modalities are (1) microbubbles are nonlinear scatterers that generate harmonic signals and (2) they exhibit a transient response, i.e., they are destroyed by ultrasound. Harmonic Doppler and imaging techniques were introduced at first to help with the detection of microbubbles in small vessels and capillaries. The harmonic response of bubbles and their Doppler signals increase with increasing acoustic amplitudes (mechanical index, MI), which results in fast bubble destruction. Triggered (intermittent) imaging, insonifying every n cardiac cycles (where n=1,2,3,...), was established to minimize destruction. Triggered imaging is a cumbersome technique. Real-time imaging techniques are now available. They are made possible by low-amplitude (MI) scanning and by more sensitive low MI techniques like pulse inversion and amplitude modulation. Both triggered and real-time techniques will be discussed in this presentation and clinical examples will be presented.