Is a CT triple phase (Computed Tomography triple phase) the same as a CT abdomen with and without contrast for a patient concerning for hepatocellular carcinoma (HCC)?

CT Triple Phase vs CT Abdomen With and Without Contrast for HCC Detection

A CT triple phase scan is the same as a CT abdomen with and without contrast for patients concerning for hepatocellular carcinoma (HCC), as both refer to a multiphasic CT protocol that includes non-contrast, arterial, and portal venous/delayed phases.

Understanding Multiphasic CT for HCC Detection

Definition and Components

• A triple-phase CT scan for HCC typically includes:
  • Non-contrast phase
  • Late hepatic arterial phase (approximately 30-45 seconds after contrast injection)
  • Portal venous phase (approximately 60-75 seconds after injection)
  • Delayed phase (approximately 180 seconds after injection) 1

Clinical Rationale

• The diagnosis of HCC relies on specific enhancement patterns that can only be observed across multiple contrast phases:
  • Arterial phase hyperenhancement (APHE)
  • "Washout" appearance in portal venous or delayed phases 1
  • Capsule appearance (best seen in delayed phase) 1

Evidence Supporting Multiphasic Imaging

Diagnostic Accuracy

• Multiphasic CT has a sensitivity of 43-63% for HCC detection across all sizes 1
• For HCCs greater than 2 cm, sensitivity increases to 98% 1
• The addition of a delayed phase significantly improves diagnostic accuracy:
  • Triple-phase CT (with delayed phase): Area under curve = 0.973
  • Dual-phase CT (without delayed phase): Area under curve = 0.954 2

Guidelines Recommendations

• The 2022 KLCA-NCC guidelines explicitly state that "single phase CT or MRI may not be used as a diagnostic tool" for HCC 1
• The ACR Appropriateness Criteria recommends "multiphasic contrast-enhanced CT" as a first-line imaging study for HCC detection in high-risk patients 1

Clinical Application

When to Use Triple Phase CT

• First-line imaging for liver nodules ≥1 cm detected during surveillance in high-risk patients 1
• For patients with chronic liver disease where US is limited by:
  • Obesity
  • Nonalcoholic fatty liver disease (NAFLD)
  • Nodular cirrhotic liver 1
  • Very high risk of HCC 1

Technical Considerations

• The non-contrast phase may be unnecessary in patients who have not received previous liver treatment 1
• However, the non-contrast phase is strongly recommended for patients who have received liver-directed therapy 1
• Dual-energy CT can create virtual unenhanced images that may replace separately acquired non-contrast images, reducing radiation exposure 1

Limitations and Alternatives

Limitations of CT

• Repeated radiation exposure with multiple scans 1
• Risk of contrast nephropathy in patients with renal insufficiency 1
• Lower soft-tissue contrast compared to MRI 1

MRI as an Alternative

• Higher sensitivity (59-95%) compared to CT (43-63%) 1
• Better soft-tissue contrast and lesion characterization 1
• Particularly valuable for HCCs less than 2 cm in size 1

Conclusion

When evaluating patients with suspected HCC, a CT triple phase scan and CT abdomen with and without contrast refer to the same imaging protocol that includes multiple phases of contrast enhancement. This approach is essential for accurate HCC diagnosis according to current guidelines, as the characteristic enhancement pattern of HCC can only be observed by comparing different phases of contrast enhancement.