History - fundamental - development of MRI system

MRI HistoryDamadian created the world's first magnetic resonance imaging machine in 1972 Damadian, along with Larry Minkoff and Michael Goldsmith, performed the first MRI body scan of

DR NGUYEN XUAN THUC

MRI History

Damadian created the world's first magnetic

resonance imaging machine in 1972

Damadian, along with Larry Minkoff and

Michael Goldsmith, performed the first MRI

body scan of a human being on July 3, 1977

Paul Christian Lauterbur shared the Nobel Prize in

Physiology in 2003 with Peter Mansfield for his work which made the development of magnetic resonance imaging (MRI) possible (researched from 1963 until 1985)

The magnet ss the most important component of the MRI scanner

The magnet currently used are in the 0.2 to 3.0-tesla

range (2,000 to 30,000-gauss)

Higher values are used for research

Earth magnetic field : 0,5-gauss

There are three types of magnets used in MRI systems:

- Resistive magnets : no more used

- Permanent magnets: 0.2 to 1.0-tesla

- Super conducting magnets: 1.0 to 3.0-tesla

Magnetic field

The lower field strengths can be achieved with

permanent magnets, which are often used in "open" MRI scanners

Higher field strengths can be achieved only with

superconducting magnets

The atom that MRI uses is the hydrogen atom

Fundamentals

The patient is placed in the magnet bore, radio waves are passed through the body in

particular sequences The body tissues

respond by emitting the pulses, which are then recorded by a detector then sent to computer

Fundamentals

Various body tissues emit characteristic MR signals, which determine whether they will appear white, grey or black on the images.

In general: Water is black on T1-WI, white on T2-WI Most tumors and inflammatory masses appear white on T2-WI Compact bone appears black in all sequences

-T1WI - BOLD images

- Perfusion images - STIR

T1W T2W

Fluid signal ↓ Fluid signal ↑ Signal of Lipid ↑ Signal of Lipid ↑ T1W (+-FS) + CE T2W – FS (STIR)

T1W T2W

T1W

T1W + CE T2W

T2W T2W-FS

- Greater differentiation of soft tissue structures

- Can be acquired in any planes

- Can provide vascular study without use of IV contrast

Disadvantages

- Longer time of scanning

- Motion artifacts from respiration, cardiac pulsation

Generally, MRI is very safe and adverse reactions to contrast agent (gadolinium) are extremely rare.

Absolute contraindications:

Cardiac pacemakers, implanted cardiac defibrilations, otic/inner ear/ cochlear implantsm metal fragments in the eye.

Others:

- Heart valve, aneurysm clip (depending on the models), passive implants (depending on its ferromagnetic status)

- Pregnancy : No known risks, how ever

MRI ACCIDENTS

MRI ACCIDENTS

Patterns of Contrast Enhancement

.Bacterial, fungal, parasitic abscess

.Empyema (epidural, subdural, orintraventricular)

Cyst with enhancing mural nodule

Low-grade diffuse astrocytoma

(WHO grade II)

This 44-year-old woman presented with an epileptic seizure