You have seen that the receiver coil receives the energy released by the hydrogen nuclei that are moving from the high energy state to a low energy state. There are various types of receiver coils. It is often best to use a receiver coil that can be kept as near as possible to the area being imaged. For an example, for imaging structures in the head, one can use a “head coil”. In 1974, Paul C. Lauterbur, a professor of chemistry and radiology at New York University, and Peter Mansfield from the Department of Physics at the University of Nottingham in England, made groundbreaking advancements in the field of magnetic resonance. Independently of each other, they described the utilization of magnetic field gradients to spatially localize NMR signals. Their remarkable discoveries formed the foundation for the revolutionary technology known as Magnetic Resonance Imaging (MRI).

Comparing fat sensitive images (e.g. T1) vs water-sensitive images (e.g. T2 or STIR) can help differentiate pathologies such as ischaemia and inflammation. On the day of your MRI scan, you should be able to eat, drink and take any medication as usual, unless you're advised otherwise.

What happens during an MRI scan?

Figure 1. Normal brain MR shows differences between T1 and T2 images 3 Additional features of T1/T2 weighted images As the MRI machine scans different areas of the body, it changes the gradients as necessary. The changes of the gradients are made by rapidly changing the magnetic fields produced in the gradient coils. The gradient coils have a tough job to do. It is quite “difficult” for them to create their modifying magnetic fields in the presence of the extremely strong main magnetic field. When the gradient coils produce magnetic fields to alter the main magnetic field, due to the huge magnetic forces involved, they move slightly. This book has been published in good faith that the contents provided by the author contained herein In addition to enabling the use of thinner wires, super conductivity has another very interesting benefit. Normally, an electromagnet needs a constant current applied to it to generate a magnetic field.

Gadolinium enhances vasculature (i.e. arteries) or pathologically-vascular tissues (e.g. intracranial metastases, meningiomas). This process involves injecting 5-15ml of contrast intravenously, with images taken shortly thereafter. Gadolinium appears bright in signal, allowing for detection of detailed abnormalities (e.g. intracranial pathologies). Typical intracranial abscesses have a “ring-enhancement” pattern, while metastases enhance homogeneously. Meningiomas will have a homogenous enhancement after the contrast, but will also have a “dural tail,” meaning the lesion appears continuous with the dura (Figure 2). 4 Figure 2. Meningioma is shown more clearly by gadolinium contrast with a dural tail 5 The MRI machine can not see oxygen atoms of the water molecules, so let us ignore them. What you have left are the hydrogen atoms shown in red below. In the example shown below, as we go from the patients head towards his feet, the main magnetic field becomes weaker. We would now say that there is a ‘magnetic gradient” along the patient. The coils that modify the main magnetic field are called “gradient coils”. How these magnetic field gradients are created is fascinating but I will explain that later. You may wonder why scientists use a word like ‘spin’ to describe something that doesn’t actually spin. The answer to that I do not know. However, I can tell you that quantum scientists like to use strange names to describe things. For an example , there are particles in nature called ‘Quarks’ . There are six known types of Quarks, and here are their official names ( I am not joking): Gadolinium is a paramagnetic substance that appears bright on T1. Gadolinium-based contrast agents distribute in the vascular and interstitial spaces, particularly in areas with increased vascularity secondary to inflammation, angiogenesis, or altered homeostasis. Lesions that take up gadolinium contrast become T1 hyperintense, i.e., appear enhanced on post-contrast T1 and serves as a means of characterizing a lesion’s vascularity.[ 8]The understanding of the phenomena involved in obtaining an MRI image is fundamentally important in many areas of medicine: