Real-time MR with TrueFISP for the detection of acute pulmonary embolism:: initial clinical experience

The feasibility and diagnostic value of real-time magnetic resonance imaging (RT-MRI) for the diagnosis of acute pulmonary embolism (PE) was evaluated by comparing RT-MRI and magnetic resonance angiography (MRA). In 39 consecutive patients with suspected PE real-time true fast imaging with steady-state precession (TrueFisp) was prospectively compared with contrast-enhanced MRA on a 1.5-T MR scanner. The TrueFisp sequence used allowed acquisition of T2-weighted images at 0.4 s per image so that the pulmonary vasculature could be visualized in three orientations in <3 min without the need for breath holding or contrast media application. Results of additional scintigraphic pulmonary perfusion examinations were available from 17 patients. All 39 primary RT examinations (100%) and 30 of 39 MRA examinations (77%) were of diagnostic quality. The reasons underlying failure to achieve diagnostic quality for MRA were breathing artifacts among dyspneic patients in all 9 cases. Compared with MRA, the sensitivities and specificities of RT sequences for PE were 93 and 100% (per examination), 96 and 100% (lobar artery PE), and 97 and 100% (segmental artery PE), respectively. Compared with scintigraphy, the sensitivity and specificity of RT-MRI were 83 and 100%, respectively. The MRA reached 100% sensitivity and specificity in this subgroup. The RT-MRI proved to be very robust and undisturbed by respiratory movements and patient cooperation. Its image quality assured fast diagnostic examinations, and its sensitivity and specificity, compared with MRA and scintigraphy, were sufficient to allow the diagnosis of acute central, lobar, and segmental PE; therefore, the emergency diagnosis of PE using RT-MRI is feasible and reliable.