Imaging of pulmonary embolism and t-PA therapy effects using MDCT and liposomal iohexol blood pool agent: preliminary results in a rabbit model.

Authors

Stephen J Burke, Department of Radiology, University of Iowa, Iowa city, USA
Ananth Annapragada, School of Health Information Sciences, University of Texas Health Science Center, Houston, USA, Department of Chemical Engineering, University of Houston, Houston, USA
Eric A Hoffman, Department of Radiology, University of Iowa, Iowa city, USA, Iowa Comprehensive Lung Imaging Center, University of Iowa, Iowa city, USA, Department of Biomedical Engineering, University of Iowa, Iowa City, USA
Emmanuel Chen, School of Health Information Sciences, University of Texas Health Science Center, Houston, USA, Department of Chemical Engineering, University of Houston, Houston, USA
Ketan B Ghaghada, School of Health Information Sciences, University of Texas Health Science Center, Houston, USA, Department of Chemical Engineering, University of Houston, Houston, USA
Jered Sieren, Iowa Comprehensive Lung Imaging Center, University of Iowa, Iowa city, USA
Edwin J R van Beek, Department of Radiology, University of Iowa, Iowa city, USA, Iowa Comprehensive Lung Imaging Center, University of Iowa, Iowa city, USA

Publication Date

3-1-2007

Journal

Acad Radiol. 2007 March; 14(3): 355–362.

Abstract

RATIONALE AND OBJECTIVES: Polyethylene glycol-coated liposomal blood pool contrast agents maintain contrast enhancement over several hours. This study aimed to evaluate (long-term) imaging of pulmonary arteries, comparing conventional iodinated contrast with a liposomal blood pool contrast agent. Also, visualization of the (real-time) therapeutic effects of tissue plasminogen activator (t-PA) on pulmonary embolism (PE) was attempted. MATERIALS AND METHODS: Six rabbits (weight approximately 4 kg) had autologous blood clots injected through the superior vena cava. Imaging was performed using conventional contrast (iohexol, 350 mg I/ml; GE HealthCare, Princeton, NJ) at a dose of 1400 mg I per animal, and after wash-out, animals were imaged using an iodinated liposomal blood pool agent (88 mg I/mL, dose 900 mg I/animal). Subsequently, five animals were injected with 2 mg of t-PA and imaging continued for up to 4(1/2) hours. RESULTS: Both contrast agents identified PE in the pulmonary trunk and main pulmonary arteries in all rabbits. Liposomal blood pool agent yielded uniform enhancement, which remained relatively constant throughout the experiments. Conventional agents exhibited nonuniform opacification and rapid clearance postinjection. Three of six rabbits had mistimed bolus injections, requiring repeat injections. Following t-PA, pulmonary embolus volume (central to segmental) decreased in four of five treated rabbits (range 10-57%, mean 42%). One animal showed no response to t-PA. CONCLUSIONS: Liposomal blood pool agents effectively identified acute PE without need for reinjection. PE resolution following t-PA was quantifiable over several hours. Blood pool agents offer the potential for repeated imaging procedures without need for repeated (nephrotoxic) contrast injections.

Keywords

Animals, Blood, Contrast Media, Fibrinolytic Agents, Iohexol, Liposomes, Male, Pulmonary Artery, Pulmonary Embolism, Rabbits, Tissue Plasminogen Activator, Tomography, X-Ray Computed

Comments

PMCID: PMC2213908