Purpose. The purpose of this study was to evaluate the feasibility of detecting pulmonary emboli utilizing noncontrast magnetic resonance imaging techniques in patients with known pulmonary embolism. Materials and Methods. Eleven patients were enrolled in a study to evaluate right ventricular function by cardiac MRI in patients diagnosed with acute pulmonary embolism on CT pulmonary angiogram. Cardiac MRI was performed as soon as possible following pulmonary embolism detection. Two independent observers reviewed the precontrast portion of each MRI, scoring right, left, and lobar arteries as positive or negative for PE. The CTs were reviewed and interpreted in the same manner. Results. MRI was obtained on average of 40 hours after the CT. Forty-eight vessels were affected by PE on CT, 69% of which were identified on MRI. All eight pulmonary emboli located in the right or left pulmonary arteries were detected on MRI. Of the 15 pulmonary emboli that were not detected on MRI, 7 were subsegmental, 6 were segmental, and 2 were located in a branch not included in the MRI field of view. Conclusions. Most pulmonary emboli detected on CT were identified on noncontrast MRI, even though our MRI protocol was not optimized for pulmonary artery visualization. 1. Introduction Pulmonary embolism (PE) is a serious condition responsible for significant morbidity and mortality. PE is currently the third leading cause of cardiovascular death in the United States [1]. PE requires prompt diagnosis and treatment to prevent potentially deadly consequences. Currently, CT pulmonary angiography (CTPA) is considered the gold standard in the making of the diagnosis [2, 3]. However, CTPA requires the use of iodinated contrast media with its risk of renal failure and ionizing radiation with its risk of cancer induction [4, 5]. Many patients with suspected PE, such as pregnant women and patients with impaired renal function, have at least a relative contraindication to contrast media or radiation. MRI offers a potential alternative to CTPA in the evaluation of the pulmonary vasculature and the diagnosis of PE [6–8]. To date, however, the majority of studies evaluating the use of MRI in the diagnosis of PE have used gadolinium-based intravenous contrast media, which is contraindicated in pregnant patients and in those with renal failure [9]. The purpose of this study was to evaluate the feasibility of detecting pulmonary emboli using noncontrast bright blood and dark blood MR imaging techniques. 2. Materials and Methods 2.1. Subjects This HIPAA-compliant study was approved by our
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