Three-dimensional (3D) perfusion imaging allows the assessment of pulmonary blood flow in parenchyma and main pulmonary arteries simultaneously. MRI using laser-polarized 3 He gas clearly shows the ventilation distribution with high signal-tonoise ratio (SNR). In this report, the feasibility of combined lung MR angiography, perfusion, and ventilation imaging is demonstrated in a porcine model. Ultrafast gradient-echo sequences have been used for 3D perfusion and angiographic imaging, in conjunction with the use of contrast agent injections. 2D multiple-section 3 He imaging was performed subsequently by inhalation of 450 ml of hyperpolarized 3 He gas. The MR techniques were examined in a series of porcine models with externally delivered pulmonary emboli and/or airway occlusions. The development of high-speed gradient systems and fast imaging methods has permitted ultrafast contrast-enhanced lung perfusion imaging with subsecond temporal resolution and millimeter spatial resolution (1-8). Imaging of the lung parenchyma suffers from low proton density, physiological motion (cardiac and respiratory motion adjacent to the lung), and short T* 2 from local magnetic field inhomogeneity due to multiple interfaces of air and soft tissues (3,9 -12); significantly reduced times TR and TE in the gradient-echo sequence allow dramatically improved SNR. Recently, bolus injection of gadolinium contrast agent in conjunction with an ultrafast 3D gradient-echo sequence has demonstrated volumetric lung parenchymal perfusion images with 2-3 sec temporal resolution (7). This technique allows simultaneous evaluation of lung perfusion and flow in the major pulmonary vasculature. On the other hand, submillimeter high-spatial-resolution pulmonary angiography has been achieved with bolus administration of gadolinium contrast agent and first-pass MR data acquisition during the arterial phase of the contrast agent (13-15). This contrast-enhanced pulmonary angiography shows high SNR and can depict pulmonary arteries beyond the subsegmental branches. Integration of perfusion and angiography may allow better evaluation of parenchymal blood flow states and vasculature involvement; this is particularly interesting when pulmonary emboli are studied (10,16).The ability of MR to image the lung air space is important for the diagnosis of a variety of pulmonary ventilation abnormalities. Recently, assessment of regional lung ventilation using hyperpolarized noble gas has emerged as an imaging technique for evaluating patients with lung disease, such as tumor, emphysema, bronchiectasis, cystic fibrosis, and asthma (17-24). Compared to O 2 -enhanced lung MRI (25,26), which has the advantage of needing no special equipment, 3 He MRI provides high SNR and contrast-to-noise ratio (CNR), with image intensity directly proportional to the local concentration of inhaled 3 He. It has long been recognized that both pulmonary perfusion and ventilation images are needed to identify and distinguish certain lung diseases. For example, mismatched and matched perfusi...