The physics of magnetic resonance imaging (MRI)

Physique de l'imagerie par résonance magnétique (IRM) - Physique de l'IRM

The physics of magnetic resonance imaging (MRI) concerns fundamental physical considerations of MRI techniques and technological aspects of MRI devices. MRI is a medical imaging technique mostly used in radiology and nuclear medicine in order to investigate the anatomy and physiology of the body, and to detect pathologies including tumors, inflammation, neurological conditions such as stroke, disorders of muscles and joints, and abnormalities in the heart and blood vessels among others. Contrast agents may be injected intravenously or into a joint to enhance the image and facilitate diagnosis. Unlike CT and X-ray, MRI uses no ionizing radiation and is therefore a safe procedure suitable for diagnosis in children and repeated runs. Patients with specific non-ferromagnetic metal implants, cochlear implants, and cardiac pacemakers nowadays may also have an MRI in spite of effects of the strong magnetic fields. This does not apply on older devices, details for medical professionals are provided by the device's manufacturer.

Certain atomic nuclei are able to absorb and emit radio frequency energy when placed in an external magnetic field. In clinical and research MRI, hydrogen atoms are most often used to generate a detectable radio-frequency signal that is received by antennas in close proximity to the anatomy being examined. Hydrogen atoms are naturally abundant in people and other biological organisms, particularly in water and fat. For this reason, most MRI scans essentially map the location of water and fat in the body. Pulses of radio waves excite the nuclear spin energy transition, and magnetic field gradients localize the signal in space. By varying the parameters of the pulse sequence, different contrasts may be generated between tissues based on the relaxation properties of the hydrogen atoms therein.

In this app you will find:

MRI Physics and Imaging Technology

A Little MRI History

Why Use MRI?

Opportunities in MRI

The Imaging Hardware

Magnetism

Physics

Pulse Sequences Overview

Diffusion weighted imaging

MR perfusion weighted imaging

CSF flow studies

Functional MRI (fMRI)

Susceptibility weighted imaging

MR angiography and Venography

MR spectroscopy (MRS)

MR fingerprinting

MR enterography and MR enteroclysis

Sequence Parameters

Signal Processing

MR image quality

MRI contrast agents

MRI contrast agent safety

MRI Artifacts

MRI safety

Acquisition Parameters

Tissue Relaxation Times

MRI Acronyms