Pitfalls and Artefacts using Contrast Enhanced Ultrasound

Abstract

Ultrasound is the method of choice in the detection and characterization of diffuse and focal organic diseases. For B-mode and colour (power) Doppler ultrasound, besides manual skills, (hands-on) a technical knowledge about ultrasound images is of the upmost importance for the investigator. Contrast enhanced ultrasound (CEUS) has become an important diagnostic tool for hepatic, renal, pancreatic indications and several others due to: (a) an increasing rate of studies resulting in sufficient evidence especially in hepatic indications, (b) a rate of adverse events close to zero (1:10,000 in comparison to iodinated contrast agents from 1-12:100) enabling the application of CEUS in patients with severe renal insufficiency or thyroid gland autonomy, and (c) a reasonable price (depends on the country and influence of the health-care system [reimbursement]) and the dosage used. Mini-doses from 0.1 to 0.4 mL are used depending on the contrast agent and applied indication. Therefore a well founded knowledge concerning the technical aspects of CEUS is important for the investigator to avoid misinterpretation especially when artefacts specific for CEUS occur. Special literature is rare. In the presented article we present pitfalls concerning CEUS. The following aspects are considered and illustrated by images: (i) acoustic power (mechanical index) and other aspects resulting in micro bubble destruction, (ii) the possibility of false positive contrast signals in non-vascularized areas, (iii) attenuation caused by too high contrast agent dose, (iv) influence of the frame rate on the spatial resolution, (v) dealing with deep located lesions, (vi) differences in focus positioning in detection and characterization studies, (vii) advantages and disadvantages of replenishment studies, (viii) reliability of contrast enhanced spectral Doppler measurements.

Detection and characterization of small superficially located focal liver lesions by contrast-enhanced ultrasound with high frequency transducers

“…grey scale ultrasound or color flow Doppler techniques do not have the sensitivity to identify many of the vascular differences in FLLs. This technique fails to reliably differentiate between malignant and benign lesions [13,[25][26][27][28][29][30]. Some FLLs are particularly difficult to diagnose even by biopsy because of their small size (<10 mm) or superficial location (close to liver capsule) [12,15,26].…”

Dynamic Tissue Perfusion Measurement – Basics and Applications

“…liver tumours or renal transplant cortical perfusion [11][12][13]. External influences are relevant concerning the reproducible influx of the contrast enhancer from the injection site to the ROI [14,15]. The perfusion in CEUS is calculated as the velocity of contrast saturation.…”

Untitled

“…The characteristic features of a TIC analysis are shown in ▶ Fig. 3 [11,41]. This model for quantification of tumor vascularization was applied in multicentric studies validating the AUC as predictive marker [42,43].…”

“…The CEUS "circle of disaster" is characterized by the following criteria: Microbubble destruction → increase in contrast agent dose →attenuation (shadowing) → higher mechanical index → additional microbubble destruction [40,41,58].…”

“…Most often, the default settings on the machine provide an excellent starting point for beginning CEUS studies of the liver. For more details on CEUS artefacts we refer to the current literature [40,[55][56][57][58][59].…”