J Korean Soc Magn Reson Med.  2011 Dec;15(3):200-207. 10.13104/jksmrm.2011.15.3.200.

Assessment of Therapeutic Response of Ablated Lesion after Radiofrequency Ablation in Patients with Unresectable Lung Malignancies by Multiphase Contrast-enhanced MRI

• Jin GY
• Han YM
• Chung GH
• Hwang SB
• Lee YC
• Kwon KS

• KMID: 2000048
• DOI: http://doi.org/10.13104/jksmrm.2011.15.3.200

Abstract

PURPOSE
We evaluated which phase was important to recognize local progression of an ablated zone after RFA on multiphase contrast-enhanced MRI (CE-MRI) in patients with unresectable lung malignancy.
MATERIALS AND METHODS
Twenty patients who had unresectable lung malignancy underwent multiphase CE-MRI examinations immediately after RFA. We evaluated the enhancement patterns of the ablated zone on multiphase CE-MRI: type I, no enhancement of the ablated zone; type II, enhancement of the ablated margin; type III, heterogeneous enhancement of the ablated zone. We evaluated the association enhancement type with local progression of the ablated zone on the follow up CT using Spearman's ranked test.
RESULTS
In complete ablation, the enhancement pattern was types I (11.1%) or II (88.9%). In unsuccessfully treated, type II (57.1%) or III (42.9%) pattern observed in the arterial phase. However, types II (21.4%) and III (78.6%) observed in the venous, and types II (7.1%) and III (92.9%) observed equilibrium phases. Local progression of the ablated zone was associated with the enhancement pattern in equilibrium phases (r=0.8, p < .05).
CONCLUSION
Equilibrium phases on multiphase CE-MRI might play a more important role in evaluating an ablated zone for predicting local recurrence after RFA.

Keyword

Lung neoplasms; Radiofrequency (RF) ablation; Magnetic resonance imaging (MRI)

MeSH Terms

Follow-Up Studies
Humans
Lung
Lung Neoplasms
Recurrence

Figure

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  Fig. 1 Diagrams of the enhancement patterns on the contrast-enhanced MRI performed immediately after RFA: The ablation zone was divided into the central region (central ablated zone except ablated margin) and the ablated margin (peripheral ablated zone within 10 mm of the outermost margin of the ablated zone). These enhancement patterns of ablated zone are classified into the following three types: Type I, absolutely no enhancement; Type II, only enhancement of the ablated margin; and Type III, heterogeneous enhancement of the ablated zone.

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  Fig. 2 46-year-old man with a complete response. He had undergone radiation therapy due to lung malignancy. (a) Chest CT scans (lung setting) before RFA shows a 1 cm, single metastatic nodule in the left lower lobe. (b) On the CE-MRI, the enhancement pattern of the ablated zone leads it to be categorized as type I in the arterial and venous phases. In the equilibrium phase, the enhancement pattern is type II. Enhancement of the hyperemic zone is observed on the equilibrium phases (arrow). (c) Eighteen months later, the previous single metastatic nodule had disappeared completely and a large uniloculated cavity is observed as a post-RFA complication on chest CT (lung setting).

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  Fig. 3 62-year-old man with progressive disease. (a) Contrast-enhance chest CT scans before RFA shows a 6 cm mass in the left lower lobe. (b) On CE-MRI, the enhancement pattern of the ablated zone leads it to be categorized as type II in the arterial and venous phase but the enhancement pattern in the equilibrium phase changes to type III. (c) Eight months later, the tumor size increase approximately 9 cm and completely obstructed the bronchus of the left lower lobe on contrast-enhanced CT.

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