MRI Basics and Applications

MRI Basics

• MRI machines use powerful magnets to create a strong magnetic field (typically 1.5 to 3 Tesla).
• Inside the magnetic field, hydrogen nuclei (protons) in the body's water molecules align.
• Radiofrequency (RF) pulses temporarily disturb proton alignment.
• Protons return to their original alignment, releasing energy.
• This energy is detected by the MRI scanner, forming images.
• Differences in signals reflect varying tissue properties (e.g., fat, muscle, fluid).
• A computer processes the data to create cross-sectional images (slices), forming 3D representations.
• Contrast agents (often gadolinium-based) are injected to enhance visibility of structures, differentiating between healthy and diseased areas.

Why MRI?

• MRI provides detailed images of soft tissues, allowing for accurate diagnoses.
• Unlike CT scans, MRI does not use ionizing radiation, making it safer.
• MRI can image organs and tissues in multiple planes (e.g., sagittal, axial, coronal).

Understanding MRI Brain Planes

• Sagittal plane: Divides the body into left and right halves.
• Axial (or transverse) plane: Divides the body into upper and lower halves.
• Coronal plane: Divides the body into front and back halves.

History of MRI

• The phenomenon of nuclear induction (later termed NMR - Nuclear Magnetic Resonance) was first described by Bloch and Purcell in 1946.
• They won the Nobel Prize for Physics in 1952.
• In 1971, Damadian noted that tumors have elevated MR relaxation times, filed a patent for cancer detection using MRI.
• Human in vivo images were first published in 1977.
• Damadian performed the first full-body scan in 1977 to diagnose cancer.
• Damadian died in 2022 from cardiac arrest.

MRI Types

• Different types exist, such as "open" and "dynamic," allowing for different patient needs.

MRI Advantages

• Non-invasive, using no ionizing radiation.
• Presents detailed images of soft tissues, suitable for diagnoses.
• Provides functional imaging (such as fMRI) to show brain activity.

MRI Signal Detection

• The MRI equipment detects the radio frequency signals.
• The signals translate into images, allowing for diagnosis of various illnesses.
• Several factors influence the quality of the signals.

Other factors influencing MRI

• Different tissues in the body have different relaxation times, so the signal received from each will be different.
• The length of time of the pulses affects the signal collected, allowing for differentiation between types of tissues in the body.
• The equipment used influences the amount of detail seen, meaning that the newer equipment produces images with greater clarity and quality.
• Proton density, relaxation times influence the signal received from tissues, influencing the quality of the diagnostic images.

T1 and T2 Values-Tissue properties

• T1 and T2 are fundamental tissue properties relevant in MRI.
  • Different tissues have different relaxation times.
  • T1 and T2 values vary depending on the tissue type and the strength of the magnetic field.
  • These times provide further detail regarding the varying properties of the tissues.

Practical Applications of MRI

• Images in various planes provide crucial insights into the body.
• MRI allows for accurate diagnosis and monitoring of various illnesses.
• MRI images help determine the cause and treatment of various illnesses, and are critical in both diagnosis and treatment.