Magnetic resonance coronary angiography using navigator echo gated real-time slice following.
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abstract
Navigator echo gating allows for the elimination of breath-holding in MR imaging by providing a real-time monitor of respiratory position to gate image acquisition. In this study we examined the advantages and utility of real-time, navigator echo gated slice following technique in 2D magnetic resonance coronary angiography of patients with coronary artery disease. Thirteen patients with coronary artery disease were examined. MR images of the right coronary artery (RCA) were obtained parallel to the atrioventricular groove to image long sections of the RCA in a small number of slices. In-plane resolution was 0.7 x 0.9 mm and 2-6 signals were averaged to support this high spatial resolution. Targeted maximum intensity projection (MIP) images were generated from the slices to present the RCA in a single image. All patients had x-ray angiograms available for comparison with the MR images. Using the navigator echo gated real-time slice following technique, MRI successfully obtained images in 11 of 13 cases. The technique failed in two patients with irregular breathing patterns. The average length of the RCA seen in the 11 successful MR exams was 61 mm and the average length seen in the x-ray angiograms was 80 mm. Eight patients were determined to be without disease in the RCA by x-ray angiography, and all eight were correctly identified as normal on the MRI exam. In the three patients who had a successful MRI exam and were determined to have disease in the RCA by x-ray angiography, MRI identified the lesion in two cases. In the third case MRI indicated a discrete lesion and x-ray angiography indicated diffuse disease without a focal lesion. Navigator echo gating improves patient tolerance, provides aligned sections of coronaries over multiple slices, and allows for improved resolution through signal averaging. This preliminary patient study suggests that navigator echo gated magnetic resonance coronary angiography may play a role in evaluating coronary artery disease.
