In this talk we will discuss the three major hardware components of the MRI system: magnet, gradients, and coils. Each of these topics can easily fill an entire lecture. Therefore, we will have to limit ourselves to the basics. For a more in-depth review of each of these topics, please see this (and previous) years weekend educational sessions on “MRI Systems Engineering”. Similarly, although the essential MR physics will be covered in passing, a more in-depth review of MR physics can be found in the weekend educational “physics for physicist” sessions.

To make this talk a little more fun we will discuss these topics in the form of a fictional story. Imagine it is 1972 and you just had a wonder full idea. Employing principles from NMR, it should be possible to “form images through local interactions” [1]. As you arrive in the lab you immediately start discussions with the local engineering team to build such a system for human imaging. We will use these imagined discussions to better understand the functional role and design constrains of the basic components found in modern day MRI systems. It should be noted that these imagined discussions don’t follow the chronological development of MRI and cover developments made over many decades thanks to the effort of an ever-growing community of scientists and clinicians.

The talk will roughly be divided into three equal parts, each about 10 minutes long. The first part will focus on magnet design [2,3]. In our discussion we will cover basic questions such as: “Why do we (mostly) use superconducting solenoids?” and “How does the quenching mechanisms work?”.

The second part will focus on the gradient system [2,3,4]. We will see how the ever-increasing demand for faster switching gradients (for example to do EPI), drive the development of more and more advanced gradient technology. Starting from a very minimalistic gradient, we will develop a sense for the voltages and currents needed to drive the gradients and see how this leads to other technical challenges such as heating, and eddy currents. In addition, we will use our discussion to answer basic questions such as: “Where does the sound produced during the MRI experiment come from?”.

The third part will focus on the coils used to excite and detect the MRI signal [5,6]. We will briefly review three basic coil designs: the loop, solenoid, and birdcage coil. We will see why clinical systems use a large birdcage transmit coil hidden behind the covers of the bore in combination with dedicated arrays of local loop coils to detect the signal. If time allows, we will also briefly talk about the “back end”. In particular, we will follow the receive chain starting at the coil, through the preamps all the way into the analogue to digital converter to discover how the complex NMR signal is obtained.

Acknowledgements

No acknowledgement found.