Pulmonary embolism (PE) occurs when a blood clot from a systemic vein dislodges and is swept by the blood (embolizes) into the pulmonary arteries, where it lodges and prevents blood flow to the lung beyond this point. This impairs the lungsâ€™ ability to adequately oxygenate blood and is a major cause of death in the industrialized world. To identify the source and impact of PE on lung function, imaging of the vascular anatomy and blood flow is required in combination with structural images to rule out alternative diagnoses. Traditionally, computed tomography angiography (CTA) has been used to assess the lung vasculature and structure, while scintigraphy has been used to evaluate lung perfusion and ventilation. However, CT is contraindicated in up to 22% of patients because of allergy to iodine-based contrast agents or renal insufficiency. Radiation exposure related to the use of CTA is also a concern, especially in young or pregnant patients.
Over the past decade, magnetic resonance imaging (MRI) has shown clinically viable imaging of lung structure, ventilation, and perfusion. The combination of these techniques offers the potential of a single comprehensive exam without the use of ionizing radiation.
In this study, we propose to conduct imaging experiments to develop an MRI technique for use in humans that would, in a single image session, be capable of assessing lung structure and function in the presence of pulmonary embolism. In this animal protocol, we will perform embolization of the pulmonary arteries via intravenous catheters to mimic PE. Results obtained with the new MRI technique will be validated using CTA and positron emission tomography as reference standards.