Magnetic Resonance Imaging (MRI) of the Spine and Brain

By Sara Foster

(MRI Scan of the Spine, MRI Scan of the Brain)

Procedure overview

What is magnetic resonance imaging (MRI)?

Magnetic resonance imaging (MRI) is a diagnostic procedure that uses a combination of a large magnet, radiofrequencies, and a computer to produce detailed images of organs and structures within the body.

How does an MRI scan work?

The MRI machine is a large, cylindrical (tube-shaped) machine that creates a strong magnetic field around the patient. This magnetic field, along with a radiofrequency, alters the hydrogen atoms' natural alignment in the body. Computers are then used to form two-dimensional (2D) images of a body structure or organ based on the activity of the hydrogen atoms. Cross-sectional views can be obtained to reveal further details. MRI does not use ionizing radiation, as do X-rays or computed tomography (CT scans).

A magnetic field is created and pulses of radio waves are sent from a scanner. The magnetic field aligns the hydrogen protons in your body along the same vector. The radio waves then knock the particles out of this aligned  position. As the nuclei realign back into proper position, the nuclei send out radio signals. These signals are received by a computer that analyzes and converts them into an image of the part of the body being examined. This image appears on a viewing monitor. Some MRI machines look like narrow tunnels, while others are more open.

Magnetic resonance (MRI) may be used instead of computed tomography (CT) in situations where organs or soft tissue are being studied, because with MRI scanning bones do not obscure the images of organs and soft tissues, as does CT scanning.

New uses and indications for MRI have contributed to the development of additional magnetic resonance technology. Magnetic resonance angiography (MRA) is a new procedure used to evaluate blood flow through arteries in a noninvasive (the skin is not pierced) manner. MRA can also be used to detect intracranial (within the brain) aneurysms and vascular malformations (abnormalities of blood vessels within the brain, spinal cord, or other parts of the body).

Magnetic resonance spectroscopy (MRS) is another noninvasive procedure used to assess chemical abnormalities in body tissues, such as the brain. MRS may be used to assess disorders such as HIV infection of the brain, stroke, head injury, coma, Alzheimer's disease, tumors, and multiple sclerosis.

Functional magnetic resonance imaging of the brain (fMRI) is used to determine the specific location of the brain where a certain function, such as speech or memory, occurs. The general areas of the brain in which such functions occur are known, but the exact location may vary from person to person. During functional resonance imaging of the brain, you will be asked to perform a specific task, such as recite the Pledge of Allegiance, while the scan is being done. By pinpointing the exact location of the functional center in the brain, doctors can plan surgery or other treatments for a particular disorder of the brain.

Anatomy of the spine

The spinal column, also called the vertebral or spinal canal, is made up of 33 vertebrae that are separated by spongy disks and classified into distinct areas.

  • The cervical area consists of seven vertebrae in the neck.

  • The thoracic area consists of 12 vertebrae in the chest area.

  • The lumbar area consists of five vertebrae in the lower back area.

  • The sacrum has five, small fused vertebrae.

  • The four coccygeal vertebrae fuse to form one bone, called the coccyx or tailbone.

The spinal cord, a major part of the central nervous system, is located in the vertebral canal and reaches from the base of the skull to the upper part of the lower back. The spinal cord is surrounded by the bones of the spine and a sac containing cerebrospinal fluid. The spinal cord carries sense and movements signals to and from the brain, and controls many reflexes.

Anatomy of the brain

The central nervous system (CNS) consists of the brain and spinal cord. The brain is an important organ that controls thought, memory, emotion, touch, motor skills, vision, respirations, temperature, hunger, and every other process that regulates our body.