Late arterial phase

The late arterial phase, also known as the corticomedullary phase or early venous portal phase, is a contrast-enhanced CT or MRI series, in which there is an optimal enhancement of structures that get their blood supply directly from the arterial system.

The standard characteristics for this phase are:

• peak aortic attenuation: 290 - 360 HU ^4,5,8
• minimal liver enhancement from unenhanced baseline: 20-30 HU ^4,6
• avid portal vein: density of 145 ± 20 HU ^5,8

Technique

The acquisition time depends on the intravenous device (central or peripheral), the concentration of the contrast medium, and the injection rate.

• time from injection through an upper extremity vein: 30-40 seconds ¹
  • ​30 seconds at an injection rate of 4 ml/s ⁷
• time from bolus tracking: 15-20 seconds

Clinical use

The late arterial phase offers optimal enhancement of the pancreas, spleen, and kidney outer cortex. It allows the detection of:

• pancreatic lesions
  • adenocarcinoma
  • hypervascular pancreatic lesions
• liver lesions
  • hypervascular liver lesions
• splenic lesions
  • hypervascular splenic lesions

See also

• early arterial phase
• portal venous phase
• nephrogenic phase
• excretory phase