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MRI scanners in medical settings generally operate at 1.5 T or 3 T.
Comparison with Earth’s Magnetic Field:
- Earth's magnetic field: ~0.00006 T.
- A 3 T MRI scanner is approximately 60,000 times stronger.

Cellular Magnetism:
- Each cell contains a positive and negative field in its DNA.
- The force of magnetic energy is crucial for cell division, promoting health and rejuvenation.
- The health of organs and systems in the body relies on adequate magnetic energy.
- The body operates as an electromagnetic system, integral for overall health.

Proton Behavior:
- Protons in hydrogen atoms have a positive charge and spin, creating tiny magnetic fields, akin to the Earth's rotation mechanics.
- This spinning is termed precession.

MRI utilizes magnets and radio waves to provide detailed internal body images without ionizing radiation.
The first MRI scanner was developed in 1977 in New York.

Human bodies consist of about 65% water, enhancing the signal captured during MRI scans.
Water molecules (H2O), composed of two hydrogen atoms and one oxygen atom, are critical due to their hydrogen atoms.

When placed within a strong magnetic field, hydrogen protons align similarly to compass needles in Earth's magnetic field.
The alignment involves:
- B0 Field: The Magnetic Field of MRI scanners.
- Protons align in either parallel (up) or anti-parallel (down) directions.

Tesla (T): Unit of measurement for magnetic strength.
- 1 T = 10,000 gauss.
- Typical hospital MR scanners operate within a range of 1.5 to 3.0 T.

Main components include:
- The magnet (generating B0 field).
- Gradient coils (for image localization).
- RF coils (for sending and receiving radiofrequency signals).

Gradient Coils:
- Introduce variations in the magnetic field for image slice localization.
- There are three sets for X, Y, Z orientations corresponding to axial, coronal, and sagittal planes.
Shim Coils:
- Adjust the homogeneity of the magnetic field by modifying the current flowing through them.
- Improve the clarity and quality of MRI images by compensating for magnetic field inhomogeneities.

Permanent Magnets
- Low power consumption, typically weights 18,000-200,000 lbs, lower field strength.
- Limitations include poor resolution and longer scan times.
Resistive Magnets
- Require constant electrical current, producing a magnetic field in the range of 0-0.6 T.
- High running costs due to cooling required for heat dissipation.
Superconductive Magnets
- Operate at near absolute zero, typically using niobium-titanium, generating field strengths between 0.35 T and 14 T.
- Advantages include exceptional field homogeneity and signal-to-noise ratio.
- Disadvantages include high construction costs and the requirement for cryogenics.

RF Pulses: Used to excite nuclei and can cause thermal heating in tissues.
Thermal Effects: Different organs have varying heat dissipation characteristics which affect safety limits.
Approval Levels for SAR (Specific Absorption Rate): Regulated under clinical norms:
- Normal mode: 2 W/kg.
- First-Level Controlled Mode: 4 W/kg.
- Second-Level Controlled Mode: 4 W/kg with IRB approval for research.

Titanium: Preferred for its nonmagnetic properties and strength; used for surgical implants.
Stainless Steel: Austenitic stainless steel is generally MRI compatible, while ferritic types are not.
Ferromagnetic Materials: Dangerous in MRI settings; must be limited to prevent patient and staff injuries.

Types of Magnetic Behavior:
1. Diamagnetic: Repelled by magnets, e.g., water, glass.
2. Paramagnetic: Attracted to magnets, e.g., oxygen, gadolinium.
3. Ferromagnetic: Strong attraction and permanent magnetization, e.g., iron, cobalt.