Late arterial phase

Last revised by Andrew Murphy on 23 Mar 2023

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

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

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

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