How Much Should I Record During a CEUS Examination? Practical Aspects of the “Real-Time” Feature of a Contrast Ultrasound Study

The application of microbubble contrast agents to the ultrasound examination over the last 20 years has revolutionised the assessment of focal liver lesions [1], has been applied to many other organs in the body [2, 3] and is now an established adult application, with the use in paediatric patients increasing [4]. The technique is safe and repeatable [5, 6]. A contrast-enhance ultrasound (CEUS) examination generates a substantial amount of data for storage with the use of continuous recording, so much so that in Departments of Radiology, where a Picture Archiving System (PACS) stores data for a considerable number of imaging examinations, rumblings of discontent from the PACS manager can be heard. The misconception that the “video-clips” from a CEUS occupy too much storage is a fallacy, as many whole body computed tomography (CT) examinations from a trauma patient, with reconstruction in thin slices and 3-D, can occupy a large amount of storage space. The perception is that the “new-boy on the block” will clog up the PACS with superfluous images; perhaps better to make room for other imaging modalities. There is no battle to be fought here; we can help ourselves. There is perhaps no real need to take long and extensive real time “video-clips” of the entire CEUS examination, but to record only the most informative sections. This is not a new concept, and it is worthwhile revisiting the background to extensive image storage as there are very good technical reasons not to perform a continuous recording, making the CEUS examination recording shorter and even more useful [7]. Characterisation of focal liver lesions with CEUS represents the single most important application of CEUS with numerous studies confirming the accuracy of this technique in comparison with CT, and near ability to match Magnetic Resonance (MR) imaging [8, 9]. The arterial phase and the late portal venous phase are crucial to the assessment for characterisation; the washout particularly important with hepatocellular carcinoma, which may be delayed as opposed to metastatic lesions where washout is relatively early [10]. With a focal liver lesion, the arterial pattern, particularly in the benign lesion is paramount to the interpretation, but this phase lasts only for 30 to 40 seconds at most, and is nearly always informative by 20 to 30 seconds [11]. The washout phase starts early for the metastatic lesion, often before 60 seconds and will continue to wash-out for the rest of the examination. A hepatocellular carcinoma will washout slowly and may not demonstrate this washout for 180 seconds or more, depending on the cell differentiation. A most unlikely scenario is that a lesion that washes out then reaccumulates contrast and enhances over time; in-filling of a benign haemangioma is an exception where the characteristic globular in-filling is diagnostic. The essence of this is twofold; it is unlikely that extending the “video-clip” beyond 60 seconds will capture any further relevant information, and recording of washout is a prolonged effort, not needing continuous image storage. More important is the potential for microbubble “destruction” with prolonged, intense scanning over one area, with near field lesions most vulnerable, resulting in “pseudo-washout” [12, 13]. In short, continuous scanning for the first 60 seconds and then intermittent scanning after Annamaria Deganello Maria E. Sellars Gibran T. Yusuf Paul S. Sidhu Editorial