A three phase CT scan usually of the liver, that requires an injection of contrast medium, this injection helps outline the vessels of your body by giving the x-rays something to be absorbed by besides blood which has a very low absorption rate. The phases are:

Arterial Phase Scan during injection: arterial phase, this will

highlight lesions in or around the artery leading into

the liver.

The arterial phase of scanning is performed

approximately 30 seconds after the contrast injection

is initiated and is most accurately determined by using

bolus tracking software (eg Smart Prep) to monitor

the level of contrast enhancement in the aorta and

automatically triggering the scan when it reaches a pre

determined level of enhancement (eg 120HU).

Hypervascular lesions enhance during the

arterial phase and appear hyperdense. Arterial

phase images are also used for pre operative

evaluation of the arterial vasculature through

the use of MIPs and 3D reconstructions.

Scan Method 5 mm – post contrast – top to bottom of liver for arterial

phase, 2.5 mm recon

Arterial phase – “SMART PREP” Aorta (170HU

baseline) (usual delay 30 sec) Ideally obtain

excellent hepatic arterial opacification with minimal

contrast in portal vein

CT of the abdomen. Arterial phase images of dynamic computed topography scan showed a highly necrotic tumor compressing the renal parenchyma without either invasion to surrounding tissues or local lymphadenopathy.

Portal Vein Phase Scan during injection or shortly after: portal vein phase,

this will show lesions in or around the portal vein.

The portal venous phase is performed 70-90 seconds post

contrast and hypovascular lesions appear hypodense and

hypervascular lesions appear isodense (same density as

surrounding liver).

Scan Method Portal venous phase – 5mm with 2.5 mm recon at 80 sec

delay. Scan the entire abdomen in this acquisition (top of

the liver to spleen)

Portal venous phase image of an axial CT cut showing a large heterogeneous cystic mass within the right lobe of the liver

Delayed Phase Delayed scan after injection: this will allow the soft tissue

to absorb the contrast and may highlight changes in tissue.

Delayed scans thru kidneys at 3 minutes

The delayed phase is performed 5-10 minutes post

contrast and is used to further characterise lesions.

Haemangiomas are slow to enhance and some HCC can

appear hypodense due to rapid washout and CCC can

appear hyperdense due to delayed washout.

Scan Method Delay Phase – 5 mm with 2.5 mm recon 3 minutes from

injection (top of liver to bottom of kidneys).

General Notes TRIPLE PHASE LIVER - HCC

(Non contrast, arterial, portal venous, equilibrium)

This scan is performed in cases of surveillance or follow up for hepatocellular carcinoma in patients with chronic liver disease/cirrhosis .

DUAL PHASE LIVER

(arterial, portal venous, delay)

This scan is performed for further characterization of a known or suspected liver lesion in a non-cirrhotic.