[Correlation of signal intensity of blood flow in the pulmonary artery on MR images and clinical features of two cases of primary pulmonary hypertension].

ECG-gated spin-echo MR images of the chest were obtained in two patients with primary pulmonary hypertension (PPH). In transverse section at the level of the right main pulmonary artery (rPA), flow signals in the rPA were quantitatively evaluated, and the correlations with MR signal intensity of intravascular flow and data of routine clinical examinations and the severity of clinical manifestations were studied. In one case, the signal intensity of flowing blood markedly increased with exacerbation of hypoxemia and other clinical manifestations. However, in the other case with a stable course, the signal intensity of intravascular flow did not change significantly. Increase of flow signal in the rPA can reflect decrease of flow velocity that may be cause by a state of high pulmonary vascular resistance or low cardiac output. Therefore, it is suggested that MRI is a useful modality to evaluate the severity of disturbance of the pulmonary circulation in PPH.