These guidelines are based on the experience of 1000 - 1500 annual CEUS exams since 2002 at the Ultrasound section, Radiology department, Linköping University Hospital, Sweden. The fundamentals of our work include strict exam standardization, PACS storage and re-evaluation of exams at US dedicated workstations. The guidelines are based on Sonodynamics in combination with our experience with Sonovue™ and Siemens Acuson Sequoia™.
CEUS pitfalls, tips and tricks
Characterization of focal liver lesion (FLL)
The liver consists of 8 segments. The goal of the Sonoexam is to cover the entire liver and defining the segment where any metastasis may be located. The following Sonoexam protocol is used for detailed diagnostic workstation reading, and the entire protocol is performed twice both without and with UCA.
Expected duration of a detection Sonoexam is 3-5 minutes.In the hands of an experienced Sonodynamics examiner, patient cooperation usually has the greatest influence on the Sonoexam duration. If it is evident that the microbubbles will deteriorate significantly before the Sonoexam is competed, it is essential to reinject UCA and wait for 90 seconds before continuation. Usually it is practical to start over from point 6 following reinjection, since the large right liver lobe comes last in the protocol and suffers the most from microbubble degradation.
Make repeated Sonoscans with different MI in areas where one MI setting is not sufficient.Begin with an MI that penetrates as deeply as possible without destroying superficial microbubbles. In many cases the initial MI setting does not penetrate the deepest areas, typically in Sonoscans 6 and 7. If this happens, increase MI at ~0,07 MI increments (Sequoia). See the Technique section for more details.
Priority for diaphragm over caudal margin in all longitudinal Sonoscans except number 3.All scanning of transversal scan planes is performed craniocaudally, and longitudinal scans are scanned from left to right. In the transversal Sonoscans the entire liver should be covered up-down with some margin. Sonoscans 3, 4 and 6 will frequently consist of more than one Sonoloop depending on the size of the liver. Sonoscans 4 and 5 to a large extent overlap 1 and 2 on the one end and 6 and 7 on the other.
Perform twice:
First with baseline US, then
CEUS 90 seconds after the injection of 2,4 ml of UCA.
Sonoscan number:
1. Supine position, inspiration, transversal Sonoscan of segments 2 and 3.Liver protocol (baseline) and Liver
protocol (CEUS for metastasis detection), including Sonoscans 8 and 9. Last Sonoscan 6
is repeated with higher MI. No significant pathology.
Liver
protocol (baseline) and Liver protocol (CEUS for metastasis
detection), Sonoscans 1 to 7. Sonoscan 6 is repeated with higher MI. Liver in breast
cancer, status prior to chemotherapy.
Courtesy of Dr. Anna-Karin Siösteen-Tofte, Karolinska University Hospital, Stockholm,
Sweden
The first HCC detection Sonoscan differs from the standard Sonoexam approach of scanning in one direction only. It also begins in the "wrong" direction from right to left, in order not to arrive at the right liver lobe late just in case the patient does not hold his breath optimally. MI is increased to about 0.5 - 0.7 (on Sequoia), as opposed to normally about 0,12, in this Sonoscan to deliberately destroy a fraction of the microbubbles in the non-malignant liver parenchyma, since this makes the hypervascular HCC:s stand out against the rest of the liver. The entire liver is scanned in the longitudinal plane in a "reversed C" motion, from upper lateral right lobe > tip of left lobe > lateral lower right lobe in a motion that totals about 30-40 seconds. If the right lobe is very long, the Sonoscan can be prolonged into a "reversed G", continuing from the lower lateral aspect up into the medial lateral aspect and then into the centre of the liver. The late phase scanning takes place later that in detection for metastases, since most HCC:s have a late wash out.
Left decubitus position for the HCC arterial phase detection.
1. Perform a baseline US "reversed C" scan covering from upper right to left of liver along the diaphragmatic margin all the way from the thoracic wall to the left liver tip, then back from left to lower right along the lower edge of the liver to the thoracic wall, then back into the centre of the liver in about 30 - 40 seconds.TCA applies to this protocol.
The purpose of this protocol is to be an aid for "characterization beginners", as well as a proposition on how to document and store the exams. Each FLL has its own enhancement character and speed, as well as late phase behavior. With experience one learns how to "follow" the lesions throughout the exams, but this protocol hopefully serves as a starting point for further training. If a lesion is difficult to characterize by the Sonoexam below, some useful tips may be found here.