Sonodynamics in liver CEUS

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™.

Dark blue text in these guidelines define the actual Sonoexam scanning protocols.

Red links in the guidelines lead to live video samples of protocols and some typical findings. These videos are large, since they are tuned for diagnostic quality. In some cases there is also a low resolution alternative.

Good to know prior to performing CEUS Sonoexams:

CEUS technique

CEUS pitfalls, tips and tricks

Sonoexam protocols:

Detection of metastases with video

Detection of hepatocellular carcinoma (HCC) in cirrhosis with video

Characterization of focal liver lesion (FLL)

Detection of metastases:

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.

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.

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.

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.

Metastasis detection Sonoexam:

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.
2. Supine position, inspiration, longitudinal Sonoscan of segments 2 and 3.
3. Left decubitus position, inspiration, longitudinal Sonoscan of the caudal part of the entire liver.
   The depth should reach a few centimetres deeper than to the first branching of the portal vein.
4. Left decubitus position, inspiration, transversal Sonoscan with the inferior v cava positioned in the deep centre of the field of view.
   This Sonoscan includes segments 4, 1 and medial parts of segments 7 and 8.
5. Left decubitus position, inspiration, longitudinal Sonoscan.
   Includes segments 4, 1, medial parts of 7 and 8, passing the inferior v cava halfway through the Sonoscan.
6. Left decubitus position, inspiration, transversal Sonoscan below the right costal arch.
   Includes the lateral parts of segments 7 and 8 and the entire segments 5-6.
7. Left decubitus position, inspiration, longitudinal Sonoscan below the right costal arch.
   Includes the lateral parts of segments 8, 7, 6 and 5 respectively. Priority of the diaphragm over caudal parts.
   

8. Supine position. The right liver lobe is scanned with the transducer plane along the intercostal spaces, one 10 second Sonoscan jumping interstitium by interstitium craniocaudally. Depth setting just passed the portal vein.
9. Supine position, transversal scan with the transducer positioned subcostally in the right lateral flank for access to the caudal margin of the right liver lobe. The depth is set to cover the medial surface of the accessible liver, but not deeper.

US Sonoexam (low res) and CEUS Sonoexam (low res), including Sonoscans 8 and 9. Last Sonoscan 6 is repeated with higher MI. No significant pathology.
US Sonoexam (low res) and CEUS Sonoexam (low res), Sonoscans 1 to 7. Sonoscan 6 is repeated with higher MI. Liver in breast cancer, status prior to chemotherapy.

Detection of hepatocellular carcinoma (HCC) in cirrhosis:

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.

HCC detection Sonoexam:

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.
   This scan is to prepare for the first CEUS scan.
2. If the liver is very long craniocaudally, continue the scan as a "reversed G" scan.
3. Set MI to 0.5 - 0.7 (CPS on Sequoia), and set gain so that image noise is barely seen (at this MI level.
4. At the first visible arrival of contrast into the liver, perform a scan according to 1 or 2, lasting for about 30 - 40 seconds altogether.
5. During the following 20 seconds replenishment studies may be beneficial in equivocal areas.
6. Reduce MI to a normal CEUS level.
7. Perform a regular liver CEUS Sonoexam after 2,5 minutes for detection of lesions that show washout.

CEUS Sonoexam Arterial phase "reversed G" scan. Small hypervascular lesion adjacent to the gallbladder.

Courtesy of Dr. Anna-Karin Siösteen-Tofte, Karolinska University Hospital, Stockholm, Sweden.

CEUS Sonoexam High MI "reversed C" scan. Three suspicious areas.

Courtesy of Dr. Anna-Karin Siösteen-Tofte, Karolinska University Hospital, Stockholm, Sweden.

Characterization of focal liver lesion (FLL):

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 behaviour. 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.

FLL characterization Sonoexam:

1. Look for any evident feeding artery to the periphery of the lesion with colour Doppler.
2. Try to find a transducer position closer than 10 cm from the lesion.
3. Make a conventional US baseline scan.
4. Turn to contrast setting and adjust the MI to an appropriately low level.
5. Press Tissue Equalization (TEQ on Sequoia), and adjust the gain of the fundamental contrast signal (CPS on Sequoia) so that the image noise can barely be seen.
6. Position the transducer so that the centre (or other more interesting structure) of the lesion is seen, along with any obvious feeding artery at the periphery.
7. Start timer, and inject 1,2-2,4 ml UCA iv, volume depending on patient and lesion appearance.
8. Start first CEUS Sonoscan at TCA.
9. Depending on lesions initial contrast filling pattern and speed, hold the transducer still for roughly 1-5 seconds.
10. Scan upward or to the left, then fan back and forth covering the lesion according to the Technique section.
11. Continue "fanning" for about 15 seconds from TCA while adjusting gain manually or automatically.
12. Again, check that the MI is appropriate and adjust image noise with the gain control.
13. Try to scan once in one direction (up-down or left-right) at roughly 20, 35, 60 and 90 seconds from TCA.
14. Continue scanning once in one direction every 30 seconds.

Scanning more than 6 minutes rarely gives more reliable information for haemangiomas, or beyond 4 minutes for other lesions.

Try to scan only moving through the lesion from side to side capturing Sonoscans, not standing still with the scan plane, to preserve microbubbles as long as possible.