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Discussion of MRI & Links to other Sites |
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This atlas contains five different views of the heart: sagittal, coronal, axial (sometimes called transverse or transaxial), long axis and shortaxis. The views are presented according to the standard radiological convention of being viewed from below rather than the anatomical convention of being viewed from above. Of these five views the sagittal, coronal and axial views are classical cross-sectional views applied to all regions of the,body while the short and long axis views are standard cardiac views.
Each image is planned from a scout view that is perpendicular to the view of interest. Thus the axial view is planned from a coronal scout, the coronal from an axial, the sagittal from a coronal, the short axis from a long, and the long axis from a short axis scout. The long axis image plane is determined by the line that runs from the apex of the heart to a midpoint at the base of the heart, often taken to be midway between the mitral valve leaflets. The short axis is perpendicular to it.
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(Figure C: short axis) |
While MRI early on demonstrated its utility for imaging bone and tissue it is only within the last 10 years that MRI has been used for cardiac imaging. Previously the problems of cardiac and respiratory motion and the need to view the heart temporally throughout the cardiac cycle limited the application of MRI.
Three main techniques have been developed to overcome these problems. A breath hold technique was employed to reduce the influence of respiratory motion. The related problems of cardiac motion and the need to view the heart temporally were solved with the development of cine MRI techniques. Cine MRI relies on an ECG signal triggering the scanner to image. Data for the plane being imaged is obtained over a series of consecutive heartbeats (this number varies in size though for this study it was 15 heartbeats). The data collected by the scanner is reassembled by computers which reconstruct the images in time. Thus it is possible to obtain a set of consecutive images throughout the cycle. The images are not obtained sequentially however. Rather, parts of each image are obtained during each heartbeat. The final image therefore is a composite of this data.
The images contained in the atlas was were obtained using a sequence similar to breath hold cine sequences though in the interests of higher resolution only the end-diastolic image was obtained. Each image remains however a composite accumulated over 15 heartbeats.
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MRI
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Graham Wright PhD, An Introduction to MRI, University of Toronto.
Compilation of Educational NMR Software
William J Weadock MD, Qian Dong MD, Frank Londy, Martin Prince MD PhD, Renal MR Angiography, University of Michigan.
SCMR Society for Cardiovascular Magnetic Resonance
ISMRM International Society of Magnetic Resonance in Medicine
William J Weadock MD, Haraldur Bjarnson MD, Stephen H Hite MD, David
W Hunter MD, Kurt Amplatz MD,
Congenital Heart Disease on the World Wide Web, University of Minnesota.
Educational Anatomy on the Internet
The Visible Human Project
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