radiology

2. 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:

3. 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).

4.  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.

5. 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

6. 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.

7. 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).

8. 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)

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

10. 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.

11. Scan Method
 Delay Phase – 5 mm with 2.5 mm recon 3 minutes from
injection (top of liver to bottom of kidneys).

12. 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.