Nassim Parvizi MBBS, BSC, Presenter: Nothing to Disclose

Daniel Yiu Fai Chung MBBS, FRCR, Abstract Co-Author: Nothing to Disclose

Mark William Little MBBS, MSc, Abstract Co-Author: Nothing to Disclose

Fergus Vincent Gleeson MBBS, Abstract Co-Author: Alliance Medical Ltd Consultant

Ewan Mark Anderson MBBCh, Abstract Co-Author: Nothing to Disclose

1. To assess changes in perfusion CT (pCT) parameters following microwave ablation (MWA) of lung tumors. 2. To determine the utility of direct visualization of perfusion maps and pCT parameters to confirm adequate treatment and predict local tumor progression (LTP).

Patients with primary and metastatic lung tumors who underwent pCT studies immediately pre and post MWA were included. LTP was defined as nodular, enhancing tissue in continuity within the ablation zone at 6 months post MWA. Perfusion maps of the tumors were constructed using Advantage Windows Workstation and CT perfusion 3 software (GE, Milwaukee, US). Regions of interest were drawn on sequential axial sections to extract the pCT parameters blood flow (BF), blood volume (BV) and mean transit time (MTT), from the entire tumor volume. Direct visualization of perfusion maps pre and post MWA was performed by two experienced observers blinded to outcome. Data was analyzed using the Student’s t-test.

32 patients with a mean age of 73.5 (48-90) years, with 34 lung tumors (11 primary and 21 metastatic) underwent pCT scans immediately pre and post MWA. The median tumor diameter was 20mm (10-52mm). 4 patients developed LTP, with a larger mean size at baseline compared to adequately treated tumors (28mm vs 20mm, p=0.006). pCT outcome parameters for all patients pre and post MWA were BF 97 vs 62 ml/min/100g, BV 4.1 vs 2.5 ml/100mg (p=0.02) and MTT 5.3 vs 5.2 s respectively. BV was significantly reduced for patients with no recurrence pre and post MWA 4.0 vs 2.4 ml/100mg (p=0.02), respectively. Direct visualization of pCT maps gave information on treatment adequacy and potential LTP. There was moderate agreement for direct visualization between the two observers (kappa coefficient 0.5). Adequate treatment was correctly determined in 26/34 lesions, with a sensitivity of 87% (CI 69-96%), specificity 75% (20-96%), PPV 96% (81-99%) and NPV 43% (10-81%).

BV is the most reliable quantitative pCT parameter for determining adequate treatment with MWA and in predicting LTP. Direct visualization of the perfusion maps may allow identification of areas requiring further treatment at the time of the procedure.

Lack of ground glass opacification at the time of procedure hampers assessment of adequacy of microwave ablation in the lung. pCT may be a useful assessment tool immediately following MWA of lung tumors.

Parvizi, N, Chung, D, Little, M, Gleeson, F, Anderson, E, Does Perfusion CT Play a Role in the Evaluation of Percutaneous Microwave Ablated Lung Tumors?.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14007868.html