What is the best approach for a CT (Computed Tomography) abdomen scan for liver evaluation?

From the Guidelines

The best approach for a CT abdomen scan for liver evaluation is a multiphasic contrast-enhanced CT protocol, as recommended by the American College of Radiology in their 2020 guidelines 1. This protocol typically includes a non-contrast phase followed by arterial, portal venous, and delayed phases.

• The arterial phase should be performed 25-30 seconds after contrast injection,
• the portal venous phase 60-70 seconds after contrast injection,
• and the delayed phase 3-5 minutes after contrast injection. Intravenous contrast should be administered at a rate of 3-5 mL/second,
• with a total dose of 100-150 mL of iodinated contrast (concentration 300-370 mg I/mL) based on patient weight. Patients should fast for 4-6 hours before the scan but may take small sips of water with medications.
• Oral contrast is generally not necessary for liver evaluation. The scan should be performed during breath-hold to minimize motion artifacts.
• Thin-slice acquisition (1-2.5 mm) allows for optimal multiplanar reconstructions. This multiphasic approach is essential because different liver lesions enhance differently during various phases -
• hepatocellular carcinoma typically shows arterial enhancement with washout on portal venous phase,
• while metastases are usually hypovascular and best seen during the portal venous phase.
• Hemangiomas show peripheral nodular enhancement with progressive fill-in on delayed images. For patients with renal insufficiency or contrast allergies, alternative approaches include MRI with hepatobiliary contrast agents or non-contrast CT with limited diagnostic value, as discussed in the 2017 guidelines 1.

From the FDA Drug Label

The combination of non-contrasted and EOVIST-contrasted MR images had improved sensitivity for the detection and characterization of liver lesions, compared to pre-contrasted MR images Liver lesion detection and characterization results were similar between CT and the combination of pre-contrasted and EOVIST-contrasted MR images

The best approach for a CT abdomen scan for liver evaluation is not explicitly stated in the provided drug label. However, it can be inferred that a combination of non-contrasted and contrasted MR images may have improved sensitivity for liver lesion detection and characterization.

• CT scans may be used for liver evaluation, but the label does not provide specific guidance on the best approach for CT scans.
• The label primarily discusses the use of EOVIST-contrasted MR images for liver lesion detection and characterization. 2

From the Research

CT Abd for Liver Evaluation

• The best approach for a CT abdomen scan for liver evaluation involves the use of contrast material to enhance the visibility of the liver and its structures 3, 4, 5, 6.
• Studies have shown that the use of a smaller volume of a more concentrated nonionic contrast agent can provide equivalent enhancement to a larger volume of a less concentrated agent 3.
• The choice of contrast agent and its concentration can affect the degree of liver enhancement, with some agents providing better enhancement than others 4, 5.
• The volume and concentration of the contrast agent, as well as the delay time between injection and scanning, can impact the quality of the images obtained 6.
• A delay time of 60 sec has been shown to provide greater hepatic enhancement than a 45-sec delay for spiral CT scans 6.
• The use of gadoxetate disodium-enhanced MR imaging has been shown to be more effective than multiphasic multidetector CT in detecting hypervascular hepatocellular carcinoma 7.

Key Considerations

• The concentration and volume of the contrast agent used can impact the cost and effectiveness of the scan 3, 5.
• The delay time between injection and scanning can affect the quality of the images obtained 6.
• The choice of imaging modality, such as CT or MR, can impact the detection and diagnosis of liver lesions 7.

Contrast Agents

• Ioversol and iopamidol have been shown to provide similar enhancement of the liver parenchyma 3.
• Iohexol has been shown to provide good enhancement of the liver, with a concentration of 300 mg/ml providing better enhancement than a concentration of 240 mg/ml 5.
• Gadoxetate disodium is a liver-specific MR imaging contrast agent that has been shown to be effective in detecting hypervascular hepatocellular carcinoma 7.