Magnetic Resonance Imaging (MRI): Principles and Applications

Magnetic Resonance Imaging (MRI)

Overview

Magnetic Resonance Imaging (MRI) is a non-invasive medical imaging test that provides detailed visualizations of the body's internal structures, including organs, bones, muscles, and blood vessels. Unlike other imaging technologies, such as Computed Tomography (CT) scans, MRI does not use ionizing radiation. Instead, it uses a strong magnetic field and radio waves to generate images.

How MRI Works

Magnetic Field

The MRI scanner utilizes a large, cylindrical magnet that creates a strong magnetic field around the patient. This field aligns the hydrogen atoms (protons) in the body, which behave like small bar magnets. The protons' axes align with the magnetic field's direction, creating a magnetic vector.

Radio Waves

When additional energy (in the form of radio waves) is added to the magnetic field, the magnetic vector is deflected. The radio wave frequency that causes the hydrogen nuclei to resonate depends on the element sought and the strength of the magnetic field. Different tissues, such as fat and water, have different relaxation times, allowing them to be distinguished.

Image Production

As the radiofrequency source is switched off, the magnetic vector returns to its resting state, emitting a signal. Receiver coils are used to enhance the detection of the emitted signal. The intensity of the received signal is then plotted on a grey scale, forming cross-sectional images.

Fat Suppression

By employing a "fat suppression" pulse sequence, the fat signal can be eliminated, leaving only the signal from any abnormalities within it.

Uses of MRI

MRI is used to identify various conditions, such as brain and spinal cord abnormalities, tumors, cysts, joint injuries, certain heart problems, liver and other abdominal organ diseases, and pelvic pain. It is particularly effective in detecting diseases that involve an increase in water content. fMRI further complements standard MRI scans by measuring brain activity, providing insights into the function of neurons.

Preparation and Contraindications

Patients are instructed to avoid eating before some specialized MRI exams. They are advised to remove all clothing, including undergarments, and securely store personal items outside the strong magnetic environment of the scanner. Individuals with pacemakers, metal clips, or valves should inform their healthcare provider before undergoing an MRI, as these metallic components can pose safety concerns within the device's magnetic field.

Explore the principles behind Magnetic Resonance Imaging (MRI) and its wide range of medical applications. Learn about how MRI works, its uses in identifying various conditions, as well as the preparation needed before undergoing an MRI scan.