Time-Resolved MR Angiography: A Primary Screening Examination of Patients with Suspected Pulmonary Embolism and Contraindications to Administration of Iodinated Contrast Material

Abstract

The purpose of this study was to evaluate the efficiency and reproducibility of a single-breath-hold time-resolved 3D MR angiographic technique in the diagnosis of pulmonary embolism. Twenty-seven consecutively registered patients with clinically suspected pulmonary embolism and contraindication to administration of iodinated contrast agents underwent imaging by time-resolved 3D MR angiography at 1.5 T. Bolus timing was not required. Two reviewers independently analyzed MR angiograms for overall image quality and evidence of pulmonary embolism. Additional imaging techniques, including pulmonary embolism CT angiography, ventilation-perfusion (V/Q) lung scanning, venous duplex sonography for deep venous thrombosis, and echocardiography for right ventricular strain, and 30-day and 3-month clinical follow-up were used to confirm the MR angiographic findings. Image quality was sufficient for diagnosis in the cases of 98% of lobar, 92-93% of segmental, and 94-95% of all vessel parts from the main pulmonary artery though the segmental branches with excellent interobserver agreement. Findings on MR angiography were concordant with the anatomic distribution of abnormalities for all pulmonary embolism CT angiographic examinations (n = 2) and four of seven V/Q lung scans. Screening with time-resolved 3D MR angiography allowed confident exclusion or inclusion of pulmonary embolism in 96% of patients. Time-resolved 3D MR angiography provides high temporal resolution (nine phases, one phase per 3.3 seconds) and consistently yields arterial phase only images. As found with clinical follow-up, confident diagnosis of pulmonary embolism from the main pulmonary artery through the segmental branches can be incorporated into a clinical service as a screening examination of patients with contraindications to the use of iodinated contrast material.