The study of lung perfusion in normal and diseased subjects is of great interest to physiologists and physicians. In this work we demonstrate the application of a liquid-phase hyperpolarized (HP) carbon-13 ( 13 C) tracer to magnetic resonance imaging (MRI) of the pulmonary vasculature and pulmonary perfusion in a porcine model. Our results show that high spatial and temporal resolution images of pulmonary perfusion can be obtained with this contrast technique. The primary function of the lung is to supply oxygen to the body and eliminate carbon dioxide to meet its metabolic needs. In order to accomplish this, the lungs must bring sufficient quantities of air and blood into close enough proximity to allow for adequate exchange of gases. Efficient operation of the respiratory system requires a large gas-exchange surface area and a constant supply of both fresh air and blood to the exchange membrane. The study of pulmonary ventilation, perfusion, and gas-exchange characteristics is therefore of great interest to physiologists and physicians alike.Because of their ability to supply both spatial and temporal information, radiographic methods are well suited for studying the pulmonary vasculature and lung perfusion. Effective radiographic techniques for performing these tasks have been well received by the medical community and rapidly assimilated into clinical practice. For example, pulmonary angiography, computed tomographic angiography (CTA), and nuclear medicine ventilation/perfusion studies are routinely used by physicians to diagnose and manage diseases that affect pulmonary perfusion, such as pulmonary emboli, chronic obstructive pulmonary disease, pulmonary tumors, and pulmonary hypertension. However, the development of non-radiographic techniques could aid in longitudinal studies for drug development (to show disease modification), as well as in disease management. Such techniques would also benefit the subpopulation of patients who have a suspected pulmonary embolism and for whom a standard CT scan is either disallowed or inadvisable, such as pregnant women and patients with iodine allergies or renal insufficiency. The first group should not be exposed to radiation, and patients with the other two conditions may not be able to tolerate large volumes of iodinated contrast agents. This is not a trivial subpopulation. In Perrier et al.'s (1) recent prospective management trial regarding the role of multidetector CT in detecting pulmonary embolism, more than 5% of the patients had to be excluded from the trial for one of these reasons.MRI methods for measuring pulmonary perfusion and visualizing the pulmonary vasculature are available and can produce clinically acceptable results. However, these techniques have not found widespread clinical acceptance due to practical difficulties with the scan time and ease of interpretation. The limitations of current MRI techniques might be overcome by the development of a water-soluble, nonextravasating contrast agent with a particularly high signal-to-noise ratio (SNR) perf...
