Principles of CMR, clinical indications and research implications

Abstract

Overview • History • Principles of CMR • Safety of MRI • How CMR is performed • Clinical indications • Research implications. History (1) • Magnetic resonance imaging (MRI) was invented by Paul C. Lauterbur in 1971; he published the theory behind it in 1973 • However, factors leading to image contrast has been described 20 years earlier by Eric Odeblad • In the late 1970s, Peter Mansfield developed the echo-planar imaging (EPI). History (2) • In a 1971 Raymond Damadian reported that tumors and normal tissue can be distinguished in vivo by nuclear magnetic resonance (“NMR”) • R. Damadian with colleagues obtained an image of a tumor in the thorax of a mouse in 1976 • They also performed the first MRI body scan of a human being on 1977. Basic principles (1) • MRI is based on imaging of protons within the hydrogen atoms in the human body (free water and lipid molecules) • Magnetic spins precess at frequencies according to their locations and can be excited by specific radiofrequency (RF) pulses. Basic principles (2) • An RF pulse excites magnetic spins of interest to a higher energy state and leads to transition of the net magnetization vector from the z-axis onto the x-y plane • The magnitude of the vector onto the x-y plane will determine the amount of signal generated, which is received by a set of surface coils. Basic principles (3) • The absorbed electromagnetic energy is released by two coexisting mechanisms : - Longitudinal magnetization recovery - Transverse magnetization decay • All relevant information of the magnetic resonance signal is stored in a data matrix called the k-space, which will undergo two-dimensional inverse Fourier transformation to form an image. [...].