Minako Marunaka, Presenter: Nothing to Disclose

Hideo Gobara MD, Abstract Co-Author: Nothing to Disclose

Jun Sakurai, Abstract Co-Author: Nothing to Disclose

Takao Hiraki MD, Abstract Co-Author: Nothing to Disclose

Hidefumi Mimura MD, Abstract Co-Author: Nothing to Disclose

Susumu Kanazawa MD, Abstract Co-Author: Nothing to Disclose

The purpose of this study was to evaluate the usefulness of contrast enhanced CT for the diagnosis of local progression of the lung tumors treated with radiofrequency (RF) ablation.

From Jun 2001 to May 2006, 582 lung tumors in 217 patients were treated with RF ablation. We reviewed CT images of the tumor that no local progression was confirmed more than 24 month-follow up after RF ablation (n=111) and that local progression was demonstrated after RF ablation (n=126). Among these tumors, the tumors that contrast enhanced CT images were not available were excluded. The attenuation of every tumor was measured by standardized region of interest (in Hounsfield unit; HU), and the nodule enhancement (NE) was defined as a difference of CT attenuation between pre and post contrast enhancement. We compared NE of before, at 6 months after RF ablation, and at the time of local progression was found. Statistical analyses was performed the Student t test, and cutoff value of the NE for evaluating local progression were estimated by using receiver operating characteristic (ROC) analysis.

A total of 23 tumors in 14 patients with no local progression (7 men, 7 women, mean age 51.9 years, mean tumor diameter 17.1 mm) and 33 tumors in 30 patients with local progression (19 men, 11 women, mean age 61.8 years, mean tumor diameter 23.9 mm) were included. The NE before RF ablation was 43.4±21.0 HU in no local progression group, and 31.0±18.9 HU in local progression group (P = 0.89), respectively. The NE 6 months after RF ablation was 1.56±10.1 HU in no local progression group,and was significantly lower than that before RF ablation. Whereas the NE was 30.2±23.6 HU at 6 months after RF ablation, and 35.4±19.8 HU at the time of local progression was found. These were significantly higher than the NE without in no local progression group (P < 0.0001, P < 0.0001, respectively). The cutoff value of the NE was 14.5 HU at 6 months after RF ablation, and showed 89.7% sensitivity and 94.7% specificity.

Nodule enhancement after RF ablation was significantly different between in no local progression group and in local progression group. Thus, nodule enhancement may be a useful and reliable predictor of local progression.

If contrast enhanced CT is available after RF ablation, local progression may be diagnosed earlier than with unenhanced CT.

Marunaka, M, Gobara, H, Sakurai, J, Hiraki, T, Mimura, H, Kanazawa, S, The Usefulness of Contrast-enhanced CT for Evaluating the Local Progression after Percutaneous Radiofrequency Ablation of Lung Tumors.  Radiological Society of North America 2008 Scientific Assembly and Annual Meeting, February 18 - February 20, 2008 ,Chicago IL. http://archive.rsna.org/2008/6016430.html