Localized-Low Attenuation of the Lung on Thin-Section CT in Experimentally Induced Pulmonary Arterial Occlusion with Balloon Catheter in Pigs

Department of Radiology and the Institute of Radiation Medicine, SNUMRC, Seoul National University College of Medicine Department of Radiology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Korea. “This work was supported by the Korea Research Foundation Grant funded by the Korean Government (MOEHRD)” (KRF-2005-E00294) Received November 8, 2007 ; Accepted January 17, 2008 Address reprint requests to : Hyun Ju Lee, M.D., Department of Radiology, Seoul National University Hospital, 28 Yeongeon-dong, Jongno-gu, Seoul 110-744, Korea. Tel. 82-2-2072-2584 Fax. 82-2-743-6385 E-mail: [email protected] Purpose: To determine whether a localized low-attenuation (LLA) is induced on a thinsection CT (TSCT) during an acute pulmonary arterial occlusion in pigs. Materials and Methods: In eight pigs, 14 sites of the descending pulmonary artery were obstructed using balloon catheters. The lung TSCTs were obtained immediately after pulmonary artery obstruction (n=13), 10 min (n=10), 30 min (n=14) and 60 min (n=14) after pulmonary artery obstruction at the end of expiration. The TSCTs were also obtained after balloon-deflation at the end of expiration (n=11) and with the balloon-reinflation at inspiration (n=6). Results: Of the 14 sites of pulmonary artery obstruction, 11 (79%) showed LLA. However, LLA progressively became fainter or disappeared on a follow-up CT in seven sites. When the balloon was deflated, 10 of the 11 sites measured showed no change in lung attenuation. After full inspiration, LLA disappeared in three of the six sites. The corresponding areas of LLA on the CT showed a statistically significant increase compared to the baseline CT immediately after inflation (p = 0.021) and 30 minutes after inflation (p =0.041), and after balloon deflation (p =0.036). Conclusion: LLA was induced by acute pulmonary artery obstruction. However, LLA, gradually faded over the 60 minutes following obstruction. LLAs were maintained despite the restoration of pulmonary arterial flow, but disappeared as a result of a full inspiration. Thus, LLA might be caused by air trapping.