| The advances
in multidetector CT, have given the radiologist unique imaging capabilities
that provide the opportunity to revolutionize the evaluation of liver tumors.
The use of subsecond multidetector CT with ability to acquire multiple well-timed
sets of image data has increased the ability to detect hepatic tumors and
recurrences after treatment. A minimum of two phases of data acquisition
are needed: an arterial phase (25-30-second delay) and a (portal) venous
phase (60-second delay). CT examinations of the liver for suspected metastatic
or primary tumor are performed with a multidetector CT (Somatom Volume Zoom/
Siemens) 2.5-mm collimation and reconstruction thickness (mm)/interval (mm)
of 5/5 or 5/3. Computed tomography (CT) is used most frequently to determine
whether the ablation is complete and to screen for early recurrences that
may benefit from reablation. Complete ablation creates an area of necrosis
that, at CT, is of low attenuation compared with the surrounding liver tissue,
is often homogeneous, and has smooth margins. The disadvantages of CT are:
potential radiation dose, the need of contrast-agent injection with it's
usual inconvenient, timing of scanning is more critical as the increased
speed of multidetector CT narrows the "temporal window" for desirable phase
of enhancement. |
Successful
treatment of a small metastasis from colon cancer. Contrast-enhanced
CT scan obtained 10 days after RF ablation with insertion
of a single infused electrode shows a hypoattenuation without
contrast enhancement, suggestive of a complete response.