MRI (RF) system Benefits • Non-invasive and

MRI (Magnetic resonance imaging)

-anatomical image will be produced by magnetic fields and radio frequency pulses

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Applications: (neurology, angiography, gastroenterology)

(examine concentrations of different substances in tissue to identify disease)

• Examining the abnormalities of the brain and spinal cord.

• Examining the tumours (by lipid concentration), cysts, and other abnormalities in various parts of the body.

• Examining the injuries or abnormalities of the joints.

• Examining the diseases of the liver and other abdominal organs.

• Knowing causes of pelvic pain in women.

• Finding the unhealthy tissue in the body.

• Planning the surgery.

• Providing a global view of collateral veins.

• Providing a global view of intra and extra cranial.

• Functional tomography (detecting or measuring changes in metabolism, blood flow, regional chemical composition, and absorption)

• MR angiography (evaluate blood vessels and help identify abnormalities or diagnose atherosclerotic (plaque) disease)

 

Diagnosis: Brain tumours, Abdomen organs, Osteoporosis.

 

Components of MRI machine

-main magnet• 1.5T or 3T superconducting magnet

-magnetic field gradient system

-Radio Frequency (RF) system

Benefits

• Non-invasive and painless.

• Without ionizing radiation.

• High spatial resolution. (very good image quality)

• Operator independent.

• Easy to blind and ability to measure flow and velocity with advanced technique.

• Can be performed without contrast (pregnancy allergy).

• Good soft tissue contrast (effective for soft tissues).

• Functional tomography (detecting or measuring changes in metabolism, blood flow, regional chemical composition, and absorption)

 

Risks

• Relatively low sensitivity.

• Long scan and post processing time.

H. Kasban et. al. / International Journal of Information Science and Intelligent System (2015) 43

• Mass quantity of the probe may be needed.

• No real time information.

• Cannot detect intra-luminal abnormalities.

• Can make some people feel claustrophobic.

• Sedation may be required for young children who can’t remain still.

• Relatively expensive. (a) MR scanner drawing (b) MRI machine

 

 

Working Mechanism of MRI

1.      Magnetic field is generated by the spinning single proton in a hydrogen atom, each hydrogen atom acts like a tiny magnet. When external magnetic field is absent, Hydrogen nuclei magnetic moments are randomly oriented and the net magnetization of zero. If external magnetic field is present, hydrogen protons align in two directions, parallel or anti-parallel to net magnetic field, hence a net magnetic field is produced.

1.      A patient is placed within a strong magnet.

2.      Within the strong external field, the hydrogen atom in the patient’s body will align in a direction of parallel or antiparallel to the field.

3.      The net vector of the alignment will be the net magnetic vector which is known as longitudinal magnetization.

4.      Another magnetic field (radiofrequency pulse) will be applied to the normal of the original field. Hydrogen atoms turn towards the transverse plane when RF pulse is applied.

5.      An electrical current (MR signal) is induced by the net magnetization vector.

6.      An image will be produced.

Results

The image formed is affected by strength of signal

high signal- white or light grey areas

low signal- dark grey or black areas

High: Fat, bone marrow, contrast agents

Intermediate: Soft Tissues

Low: Water (urine, CSF)