Dynamic abdominal computed tomography: "top-down" compared with "bottom-up" imaging

Area of Science:

• Radiology
• Medical Imaging
• Hepatobiliary Imaging

Background:

• Standard top-down dynamic contrast-enhanced computed tomography (CT) of the liver often results in suboptimal opacification of superior liver segments.
• This uneven enhancement can potentially limit the diagnostic accuracy of CT in evaluating liver parenchyma and vasculature.

Purpose of the Study:

• To investigate whether reversing the scanning direction to a bottom-up approach improves liver parenchyma and hepatic vein enhancement in dynamic contrast-enhanced CT.
• To compare the degree of opacification between bottom-up and top-down scanning protocols.

Main Methods:

• Thirty-two patients were prospectively assigned to either a top-down or a bottom-up dynamic contrast-enhanced CT liver protocol.
• All patients received identical contrast agent administration (135 mL iohexol via power injector) with scanning initiated 30 seconds post-injection.
• Attenuation measurements were taken in specified liver regions and hepatic/portal veins to quantify enhancement.

Main Results:

• The upper liver portion demonstrated significantly greater enhancement with the bottom-up sequence (123%) compared to the top-down sequence (22%) (p < 0.01).
• Excellent overall liver enhancement was observed in the bottom-up group.
• Hepatic veins showed significantly improved conspicuity in the bottom-up scanning method (p < 0.01).

Conclusions:

• The dynamic bottom-up scanning technique provides superior hepatic parenchyma enhancement and vascular opacification compared to the conventional top-down method.
• This improved enhancement suggests the bottom-up approach is a more effective protocol for dynamic contrast-enhanced CT of the liver.