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Introduction
In recent years significant technical and clinical advances have resulted in the recognition of cardiovascular magnetic resonance (CMR) as a valuable tool for the comprehensive evaluation of diseases of the cardiovascular system in childhood. In contrast to echocardiography CMR is not limited by acoustic windows. It is non-invasive and avoids the use of ionising radiation and iodinated contrast when compared with invasive angiography. In current clinical practice, CMR is increasingly used in concert with other imaging modalities to provide high-resolution three-dimensional (3D) imaging of complex anatomy, accurate quantitative assessment of physiology and function and for tissue characterisation within the cardiovascular system. This review highlights the basic techniques and clinical applications of CMR in the evaluation of congenital and acquired diseases of the cardiovascular system in childhood.
CMR imaging techniques
Background
The primary source of the signal used to construct MR images is derived from hydrogen protons (1H). The highest concentration of 1H protons are in water and fat. Through the use of a strong static magnetic field, much weaker but time-varying magnetic field gradients and short pulses of radiofrequency (RF) energy, the 1H protons in selected regions of the body are stimulated to emit RF waves. These RF waves are then used to construct MR images. The strength of the static magnetic field in most clinical scanners used for CMR is 1.5 Tesla (T) (1 T =10 000 gauss (G); the strength of the earth's magnetic field at its surface is approximately 0.5 G). More recently MRI scanners with static field strength of 3 T have become available. An in-depth knowledge of underlying MRI physics enhances the quality of interpretation of the imaging data and is necessary for understandings its pitfalls and limitations. A detailed discussion of MRI physics is beyond the scope of this review and can be found in …
Footnotes
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Competing interests None.
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Provenance and peer review Commissioned; externally peer reviewed.