PubMed · 9117612
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T Ikeda, T Ban. 1996. [Persistent fifth aortic arch].. https://pubmed.ncbi.nlm.nih.gov/9117612/
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We report on the MR appearance of acute myocardial infarction in a 61-year-old man with Ehlers-Danlos syndrome using motion-independent, T2-weighted echo train spin echo and immediate post-gadolinium three-dimensional gradient echo imaging performed as an MRI angiographic study of the aortic arch. The region of acute infarction was of high signal intensity on the T2-weighted images and demonstrated greatly diminished enhancement on the immediate post-gadolinium three-dimensional gradient echo images. MRI findings showed good correlation with autopsy specimens obtained within 24 hours of the MRI study.
A novel method is presented for measuring motion using individual magnetic resonance (MR) signals. This method uses a volume-localized excitation with reduced spatial encoding to measure displacement with a temporal resolution of several milliseconds. The trajectory of the excited volume is derived from the time-dependent frequency of the MR signal, which changes as the volume moves through a magnetic-field gradient. Phantom and in vivo experiments confirm that this method can monitor the trajectory of plug-like structures accurately, with T2* decay limiting the measurement period. The displacement of flowing blood in a human aorta has been measured for 65 msec from one MR signal, with a theoretical accuracy of 0.25 mm and an effective time resolution of 2 msec. The high temporal resolution of this method is useful for capturing rapid motions. An interesting property of this method is that it measures motion from the reference frame of the moving anatomy.
A cardiac motion compensation method using magnetic resonance signal-based triggering is presented. The method interlaces a triggering pulse sequence with an imaging sequence. The triggering sequence is designed to measure aortic blood velocity, from which cardiac phase can be inferred. The triggering sequence is executed repeatedly and the acquired data processed after each sequence iteration. When the desired phase of the cardiac cycle is detected, data are acquired using the imaging sequence. A signal-processing unit of a conventional scanner is used to process the triggering data in real time and issue triggering commands. Alternatively, a workstation, with a bus adaptor, can access data as they are acquired, process and display the data, and issue triggering commands. With a graphical user interface, the triggering pulse sequence and data-processing techniques can be modified instantaneously to optimize triggering. The technique is demonstrated with coronary artery imaging using both conventional two-dimensional Fourier transform scans and spiral trajectories.