What is the purpose of CT (Computed Tomography) liver triphasic?

Purpose of CT Liver Triphasic

CT liver triphasic imaging is primarily used for accurate detection and characterization of liver lesions, particularly for distinguishing between benign and malignant lesions, with different phases optimized to detect specific types of lesions based on their vascular characteristics. 1

Components of Triphasic CT Liver Protocol

• Non-contrast phase: Provides baseline density measurements and helps identify calcifications or hemorrhage, particularly important in patients who have received liver-directed therapy 2
• Arterial phase: Acquired 20-27 seconds after contrast injection, critical for detection of hypervascular lesions such as hepatocellular carcinoma and certain metastases 1, 2, 3
• Portal venous phase: Obtained 60-70 seconds after contrast injection, most sensitive for detecting hypovascular metastases with 85-91.5% sensitivity 1, 2, 4
• Delayed phase (sometimes included): Acquired 3-5 minutes after contrast injection, improves lesion characterization 2

Clinical Applications

Detection and Characterization of Liver Metastases

• Triphasic CT enables detection of both hypervascular and hypovascular metastases with high sensitivity 3, 4
• Portal venous phase is most sensitive for hypovascular metastases (common in colorectal, lung, and breast cancer), with detection rates of 85-91.5% 1
• Arterial phase is essential for hypervascular metastases (such as those from neuroendocrine tumors), which may be missed if only portal venous phase is performed 3, 4
• Combining all phases improves overall lesion characterization and detection 5

Preoperative Assessment for Liver Surgery

• Triphasic CT is widely used in preoperative assessment of liver metastases, particularly for colorectal cancer patients 1
• The goal is to determine the extent and segmental distribution of liver metastases and delineate hepatic vascular anatomy 1
• Complete negative-margin hepatic resection is associated with 5-year survival of up to 58% in colorectal cancer, making accurate imaging crucial 1

Hepatocellular Carcinoma (HCC) Evaluation

• Triphasic CT is essential for HCC diagnosis, which typically shows arterial hypervascularity and "washout" on portal venous phases 2, 6
• The arterial phase is particularly important for detecting small HCCs that may not be visible on other phases 3

Technical Considerations

• Optimal technique requires:
  • Injection rate of 4-5 mL/s for best arterial phase imaging 1, 2
  • Slice thickness of 2.5-5 mm (thinner slices improve lesion detection) 1, 2
  • kVp of 120-150 and mA of 80-300 2

Advantages and Limitations

Advantages

• Provides comprehensive evaluation of the liver and potential extrahepatic disease sites in one examination 1
• Enables differentiation between benign and malignant lesions based on enhancement patterns 5
• Widely available and relatively rapid imaging method 6

Limitations

• Exposure to ionizing radiation 1
• Limited sensitivity for detecting lesions in fatty liver 1
• May miss subcentimeter and subcapsular lesions 1
• MRI may be superior for lesion detection in certain scenarios, particularly in the setting of fatty liver or following neoadjuvant chemotherapy 1

When to Consider Alternative Imaging

• MRI should be considered when:

  • Patient has fatty liver (which limits CT detection of hypovascular metastases) 1
  • Patient has received neoadjuvant chemotherapy 1
  • Lesions are subcentimeter or subcapsular 1
  • Patient has renal insufficiency 2

• A combined approach incorporating both MDCT and MRI (particularly with hepatobiliary contrast agents) often yields the most accurate results for presurgical planning 1