| Radio-frequency
ablation is performed percutaneously. Inaccurate targeting is probably the
major reason that tumors are under treated, as opposed to inadequate energy
deposition or thermal convection. The radio-frequency needle may be placed
with US, CT, or MR imaging guidance. The guidance system is chosen largely
on the basis of operator preference and local experience. Although acoustic
shadowing due to nitrogen bubbles and obscuration of the US image by the
radio-frequency current are major disadvantages. We are using routinely
for liver and bone tumors ablations the CT guidance. The most important
difference between surgical resection and radio-frequency ablation of hepatic
tumors is the surgeon's insistence on a 1-cm-wide tumor-free zone along
the resection margin, which for all but the smallest of lesions can be difficult
to achieve with a single radio-frequency application. Failure to adhere
to the surgical principle of obtaining at least a 1-cm-wide tumor-free margin
will result in an unacceptably high rate of local tumor recurrence. Another
important factor that affects the success of radio-frequency thermal ablation
is the ability to ablate all viable tumor tissue and an adequate tumor-free
margin. To achieve rates of local tumor recurrence with radio-frequency
ablation that are comparable to those obtained with hepatic resection, physicians
must produce a 360°, 1-cm-thick tumor-free margin around each tumor. This
cuff is necessary to assure that all microscopic invasions around the periphery
of a tumor have been eradicated. |
Procedure
performed under CT-guidance
