Robert Patrick Liddell MD, Presenter: Nothing to Disclose

Richard Leo Wahl MD, Abstract Co-Author: Nothing to Disclose

Stephen Yang, Abstract Co-Author: Nothing to Disclose

David Mason MD, Abstract Co-Author: Nothing to Disclose

Leo Patrick Lawler MD, Abstract Co-Author: Nothing to Disclose

Stephen Barnett Solomon MD, Abstract Co-Author: Nothing to Disclose

Radiofrequency thermal ablation (RFA) is an emerging technique in the treatment of primary and metastatic lung tumors. After RFA, anatomic changes related to thermal injury and inflammation make assessment for residual or recurrent disease difficult using anatomic imaging methods such as CT. Fluorodeoxyglucose (FDG) positron emission tomography (PET) can be used to detect metabolic activity, however, it lacks anatomic detail. Combined PET/CT scanners provide both the metabolic imaging of PET and the anatomic imaging of CT. The purpose of this investigation was to compare the appearance of lung tumors pre- (one-month) and post- (one- and six-months) RFA treatment obtained using combined FDG-PET/CT.

Eight patients with malignant lung tumors treated with RFA underwent pre- and post-treatment FDG-PET imaging. Twelve malignant lung tumors, 9 metastatic and 3 primary, mean diameter 2.8 cm, were identified with intense FDG uptake on pre-RFA PET/CT studies. All twelve tumors were imaged at one-month, while 3/12 were imaged at six-months post-RFA.

All twelve tumors were imaged using PET/CT at one-month post-RFA, while three tumors were again imaged at six-months post-RFA. Follow-up PET/CT performed one-month post-RFA demonstrated a central area of decreased FDG activity corresponding to the successfully treated lung tumor and a surrounding area of relatively increased FDG activity corresponding to post-RFA inflammation in 10/12 lesions. The two remaining lesions demonstrated focal nodular increased FDG uptake that was suspected of being residual tumor and were treated successfully with second RFA procedures. PET/CT imaging also demonstrated new metastatic lesions in two patients.

In this preliminary study, combined FDG-PET/CT performed one-month after RFA demonstrated a central area of decreased metabolic activity and a surrounding rim of increased metabolic activity in 10/12 lesions, corresponding to the treated lung tumor and surrounding RFA induced inflammation, respectively. The presence of focal nodular activity suggests residual or recurrent disease. Six-month imaging demonstrated continued lack of metabolic activity and resolution of inflammatory changes.

S.B.S.: Honoraria from Boston Scientific and Rita.

Liddell, R, Wahl, R, Yang, S, Mason, D, Lawler, L, Solomon, S, PET/CT Appearance of Lung Malignancies Following Radiofrequency Thermal Ablation.  Radiological Society of North America 2004 Scientific Assembly and Annual Meeting, November 28 - December 3, 2004 ,Chicago IL. http://archive.rsna.org/2004/4412389.html