Update in Contrast-Enhanced Ultrasound

Abstract

Background: The aim of modern medicine is to safely classify diseases for successful therapy without invasive measures. Sonography, computed tomography (CT), and magnetic resonance imaging (MRI) are potent imaging techniques. However, without contrast medium, the informative value of the 3 native methods is limited. The advantages of sonography are: no radiation exposure or previously known physically harmful interactions with tissue, proportionate disappearance of a contrast agent risk, no (probably irreversible) contrast agent deposits, and no risk of renal insufficiency. But, is that enough to compete with of even exceed CT and MRI?

Summary: In this review, the state of the art of contrast-enhanced ultrasound (CEUS) in the abdominal cavity is presented. The remarkable diagnostic possibilities can unfortunately only be demonstrated here in a small number of impressive, typical case studies underpinned by the literature, so that, from one's own perspective, the full spectrum of CEUS can be used by oneself or initiated. Within the limits of physics, the real-time dynamics of CEUS enable conclusions to be drawn, so that with the current technology, sonography, including expansion by contrast, can be considered superior to other imaging methods. It is not uncommon for CEUS to have the value of a control and reference method.

Key messages: Sonography very often enables reliable diagnostics. The introduction of a contrast agent in sonography has led to a quantum leap similar to that of other imaging techniques. Already natively, the real-time representation of dynamic events leads to a certain superiority, i.e., complete observation of the inflow and outflow phases of the contrast medium and the resulting diagnostic; tissue-specific differentiation options provide a unique selling point. Further advantages of the first-choice imaging diagnostic method are: a lack of radiation exposure, repeatability of the examination at any time, local independence, a negligible allergy rate compared to the contrast agents of other methods, and a lack of kidney and thyroid exposure or excluded deposits.

Keywords: Abdomen; Echo contrast sonography; Imaging; Ultrasonography; Ultrasound.

Fig. 1

High mechanical index (>1) in power Doppler mode leads to disruption of the microbubbles, indicating highly vascularized tissue (currently known as replenishment or flash mode). Not-highlighted areas represent a low vascularity.

Fig. 2

Left: a metastasis of uveal melanoma looks similar to the angioma. Middle: the large angioma and the HCC cannot be distinguished in a gray scale image. Right: type 3 angioma and the metastasis of adenocarcinoma of the pancreas are indistinguishable without CEUS.

Fig. 3

FNH type 1a. Upper left: the middle hepatic vein seems dilated. The liver parenchyma left of the vein is inhomogeneous. Upper right: 13 s after the administration of contrast agent the dilated hepatic vein is filled with microbubbles. The right hepatic vein and the parenchyma show no bubbles. Lower left: feeding vessel (artery). Lower right: FNH with the typical scar.

Fig. 4

Top: cystic lesion on the head of the pancreas, spreading to the duct of Wirsung. Noduli and septa are shown. CEUS shows contrast-enhanced nodules and septa. Bottom: cystic lesion at the tail of the pancreas (probably nonvital). CEUS shows thin septa and nodules rising from the wall of the cystic lesion. The resected tissue shows the intraductal papillary mucinous neoplasm in the head and tail of the pancreas.

Fig. 5

Follow-up after therapy of uveal carcinoma. On a gray scale image the liver mass could be mistaken for an angioma. CEUS shows a high inflow of microbubbles into the tumor. The vascular pattern does not match the presumed angioarchitecture. About 60 s after administration of the contrast agent the bubble concentration of the tumor decreases. Metastases of melanomas are typically highly vascularized, as seen here. Lesion was not detected in CT und misinterpreted in MRI.

Fig. 6

Two metastases directly in the hepatic vein star. Intraoperative CEUS for determination of the thermoablative active zone in the tissue beyond the immediate, necrotized zone: wide arrows indicate vaporized necrosis, while narrow arrows indicate a destroyed, no longer perfused tissue margin (i.e., a sufficient safety margin, experience has shown that this void-free zone widens further within 24 h).