Figure 1.

Schematic evolution of the MRI system. (a) Scheme of a basic single channel transmit/receive system (Tx/Rx) used for MR spectroscopy. A corresponding proton spectrum is given which can be visualised via the user interface (UI) running on the host computer of the system. Please note, human-size systems of this kind existed only as prototypes. However, the technical roots of early MR imagers were in MR spectroscopy equipment used for chemical and structural analysis. (b) Scheme of an early MRI scanner with a three-dimensional gradient system added for spatial encoding (GA denotes the three gradient amplifiers). An early human head image added⁴. (c) Basic MRI extended with parallel reception (please see the multiple Rx channels) with a Turbo Spin Echo (TSE) image obtained with an eight-channel head coil. (d) Scheme of a modern high-field MRI additionally equipped with a parallel transmission system to mainly homogenise the transmit RF field. A dual-transmit channel RF-shimmed 3T body image added for illustration. Additionally, the reconstruction is schematically highly parallelised to keep track with the increased reconstruction demands of parallel imaging and compressed sensing. So, in general, a clear trend of parallelisation becomes visible, on the reception, the transmission and the reconstruction side. Please note that the triangles represent the amplifiers present in the corresponding chains. The small black triangles denote the MR signal pre-amplifiers, whereas the big ones mark the RF amplifiers present in the Tx chain. The large grey triangles mark the gradient amplifiers.