Magnetic Resonance Imaging in the Diagnosis of Pulmonary lnfarction*

D ifferential diagnosis between pulmonary infarction and pneumonia is a frequent problem in general practice. Pulmonary infarction occurs in about 15 percent of pulmonary emboli. Its definition is radiologic or ‘ In clinical situations, only the radiologic definition is helpful: a parenchymal opacity lies in the territory of the thromboembolism and is characterized by its grossly triangular shape with a pleural base and an apex pointing to the hilum. Such shadows are segmental rather than lobar in distributioii. Pleural effusion is common. Anatomically, these radiologic findings are associated with alveolar hemorrhage, with or vithout parenchymal necrosis. The presence of alveolar hemorrhage in cases of pulmonary infarction prompted us to test the diagnostic value of MRI in this pathologic abnormality. Acute 01’ evolving pulmonary hemorrhage produces different views on MR!.2 Isointense Ti weighted images with hyperintense T2 weighted images represent early or acute hemorrhage. High Ti signals are caused by aging hemorrhage, because of methemoglobin formation.3 We hypothesized that the presence of alveolar hemorrhage in cases of pulmonary infarction could produce such a hyperintense Ti weighted signal. We report herein the results of MRI in seven patients with clinically suspected pulmonary thromboembolism.