Nuclear magnetic resonance imaging

An imaging technique used in radiology to form pictures of the anatomy and the physiological processes of the body.

Template:Infobox medical imaging

Nuclear Magnetic Resonance Imaging (commonly known as MRI) is a medical imaging technique used in radiology to form pictures of the anatomy and the physiological processes of the body. MRI scanners use strong magnetic fields, magnetic field gradients, and radio waves to generate images of the organs in the body.

History

The development of MRI is based on the principles of nuclear magnetic resonance (NMR), a technique used to obtain microscopic chemical and physical information about molecules. The first MR image was published in 1973, and the first cross-sectional image of a living mouse was published in January 1974. The first studies performed on humans were published in 1977.

Principles of Operation

MRI is based on the principles of nuclear magnetic resonance. When placed in a magnetic field, certain nuclei resonate at a characteristic frequency. In MRI, hydrogen nuclei (protons) in water molecules in the body are used to generate a signal that is processed to form an image.

Magnetic Field

The main component of an MRI scanner is a large magnet. The strength of the magnet is measured in teslas (T), and clinical MRI scanners typically operate at 1.5 T or 3 T. The magnetic field aligns the nuclear magnetization of hydrogen atoms in the body.

Radiofrequency Pulses

Radiofrequency (RF) pulses are used to systematically alter the alignment of this magnetization, causing the hydrogen nuclei to produce a rotating magnetic field detectable by the scanner. This signal can be manipulated by additional magnetic fields to build up enough information to construct an image of the body.

Gradient Coils

Gradient coils are used to spatially encode the positions of the protons by varying the magnetic field linearly across the body. This allows for the creation of two-dimensional and three-dimensional images.

Applications

MRI is used to image every part of the body and is particularly useful for imaging the brain, muscles, heart, and cancers. It is the investigation of choice for neurological cancers, as it provides better contrast in soft tissues than CT scans.

Neurology

MRI is widely used in the field of neurology for the diagnosis of brain tumors, traumatic brain injury, developmental anomalies, multiple sclerosis, stroke, dementia, and infection.

Cardiology

In cardiology, MRI is used to assess the structure and function of the heart and surrounding blood vessels. It is particularly useful for evaluating congenital heart disease, cardiomyopathies, and cardiac tumors.

Oncology

MRI is used in oncology to detect and characterize tumors, assess the extent of disease, and evaluate the response to treatment.

Safety

MRI is generally considered safe, as it does not use ionizing radiation. However, the strong magnetic fields can pose risks, particularly to patients with implanted medical devices such as pacemakers. Screening for contraindications is essential before performing an MRI.

Also see

• Nuclear magnetic resonance
• Computed tomography
• Ultrasound imaging
• Radiology