What is the role of CT scanning in the postprocedural follow-up of radiofrequency ablation (RFA) of liver tumors?

Updated: Nov 25, 2019
  • Author: Badar Bin Bilal Shafi, MBBS, MRCP, FRCR, CCT, EBIR; Chief Editor: Kurt E Roberts, MD  more...
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Answer

After RFA, patient follow-up normally includes contrast-enhanced CT (CECT). At the authors’ center, a post-RFA CT study is followed by a additional study 3 months later. The usual protocol on a multidetector CT consists of precontrast and dual-phase postcontrast helical scanning. (See the images below.)

CT appearance of a liver lesion before radiofreque CT appearance of a liver lesion before radiofrequency ablation.
CT appearance of a liver lesion after radiofrequen CT appearance of a liver lesion after radiofrequency ablation.

Perihepatic collections and basal consolidation with pleural effusion are common, normal posttreatment changes. Intraperitoneal free fluid may also be seen; this normally resolves within a few days. [22] Iatrogenic arterioportal shunting and small intralesional air pockets are also seen frequently at immediate follow-up CT. [51] These usually settle within 1 month after the procedure.

A hypervascular area around the ablation, which represents increased arterial perfusion and possible inflammatory reaction after RFA, is the most common finding in the immediate postablation period. [52] In one study, this was noted in approximately 90% of patients in the first month and in more than 50% of cases between 1-3 months. [53]

A lesion with low attenuation and no enhancement after contrast with or without hyperattenuating rim shows a successful ablation. [52] In contrast, nodular and thick enhancement represents a tumor recurrence. [54] Another study indicated that lesion shape and nonenhanced CT attenuation are not significant parameters to differentiate between successfully and unsuccessfully treated lesions. [55] On the other hand, increase in lesion size and nodular enhancement pattern have significant relation to treatment failure.

Catalano et al described four different helical CT patterns of recurrence post RFA, as follows [56] :

  • Enhancing tissue within the edge of the ablated nodule (ingrowth)
  • Enhancing tissue around the treated nodule but continuously to its border (outgrowth)
  • Enhancing tissue within the same segment of the treated nodule on arterial phase images (spread)
  • Enhancing tissue within different segments from the treated nodule on arterial phase images (progression)

The postablation area is generally larger than the actual tumor size, for obvious reasons. An ablation area that is smaller than the tumor should be closely followed. [51] The ablated area gradually decreases in size but may also remain stable over the course of time.

Curvilinear calcification at the edge of the ablated area and fat between the ablated zone and normal parenchyma may also be seen occasionally. [22]


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