Detection of acute pulmonary embolism: feasibility of diagnostic accuracy of MRI using a stepwise protocol

Abstract

Multidetector computed tomography (MDCT) has become the imaging method of choice in patients suspected of having pulmonary embolism (PE) but has the inherent limitation of radiation dose and the side effects of contrast agents. The purpose of the study was to assess the feasibility of a stepwise MRI protocol in the clinical setting of acute PE. The stepwise approach should make it possible to diagnose acute PE in critically ill patients using fast MR sequences and included the option to add comprehensive sequences when patients were stable. Forty-five patients with acute PE (26 men, 19 women; 41 ± 16 years) were included in this prospective study. The diagnosis was initially confirmed by MDCT as gold standard. MRI at 1.5 T was subsequently performed without any delay in medical treatment. The MRI protocol proceeded stepwise from robust to detailed imaging techniques (i.e., from TrueFISP and single shot HASTE sequence to MR perfusion and 3D-MR angiography) if the patient was able to tolerate additional imaging time. Diagnostic accuracy was evaluated on the central (lobar) and peripheral (segmental) levels. The complete MR protocol was applied in 40 of the 45 patients (88 %). In the remaining five patients with severe dyspnea the diagnosis of acute PE was established by using fast TrueFISP sequences that were insensitive to respiratory movement. All five patients suffered from a major central PE. Highest sensitivity was achieved by MR perfusion (lobar, 98 %; segmental, 95 %). Real-time TrueFISP and MR angiography showed the highest specificity (lobar, 90-100 %; segmental, 95-97 %). The combination of all MR sequences matched closely the results of MDCT (lobar: sensitivity 98 %, specificity 100 %; segmental: sensitivity 95 %, specificity 97 %). MRI using a stepwise protocol is a promising approach for diagnosing acute PE. The protocol can be tailored for dyspneic patients with central PE using real-time MRI sequences. The diagnostic accuracy for peripheral PE can be improved by using combined MR techniques, achieving comparable results to MDCT.

Impact of Extracardiac Findings during Cardiac MR on Patient Management and Outcome

“…In our study, all pulmonary embolisms were diagnosed on contrast-enhanced T1-weighted VIBE images by detecting endoluminal hyposignals on at least 2 orthogonal sequences in order to exclude flow artifacts [ 18 ]. As no dedicated MR pulse sequences were used to detect pulmonary embolism and the T1-weighted VIBE images did not cover the entire lung parenchyma, this specificity is not surprising, but is rather low in comparison to previous findings [ 19 – 21 ]. Pulmonary nodules and other parenchymal lung lesions were detected in 5.8% of patients, but diagnoses were confirmed in only 2 of 13 patients (specificity of 15%).…”

Computer-Aided Detection, Pulmonary Embolism, Computerized Tomography Pulmonary Angiography: Current Status

“…Finally, several reports showed promising results for the assessment of PE with magnetic resonance imaging (MRI) [24,25]. This modality is promising because images can be generated without radiation, and because it allows a combination of morphological and functional imaging (e.g., perfusion).…”

Diagnosis of Deep Venous Thrombosis and Pulmonary Embolism

“…78 Additionally, stepwise protocols have been proposed and assessed that take advantage of the variety of MRI protocols available to improve the speed and accuracy of clot detection using MRI. 89 …”