Hi, I'm Dr. John Shim, an orthopedic spinal surgeon, and today I'd like to
discuss how to read a lumbar MRI. As many of you know, MRI is a specific study used
to closely examine various body parts. It has lots of applications and can give a
very detailed look. It's useful to identify findings to your lower back, or
the so-called lumbar spine. To understand how an MRI works, typically you're placed
into a cylinder. Magnetic beams are then fired from the cylinder into your body.
Magnetic beams start as parallel energy, but once it hits various parts, the
magnetic beams get scattered in very specific patterns. The scatter is
dependent on the nature of the tissue hit by the beam. To give you an example,
muscles will scatter in a certain direction. Other tissues such as nerves,
and ligaments will also scatter in another direction.
And firmer and harder tissue such as cartilages and bones will scatter in
another direction. Scientists have figured out how to measure the scatter,
and by measuring the scatter they can make a three-dimensional reconstruction,
MRI studies are excellent tools to reconstruct your body parts onto a
diagnostic study. Radiologists typically look at spine MRIs in several different
planes. The two main planes are, the axial plane,
and the sagittal plane. The axial plane is a cross-sectional view from the top
of the body. I like to call it the bologna slice view. If you've ever been
to the deli counter, the bologna loaf is placed onto the slicer. The
cross-sectional view is similar to the axial view. As you can see on the screen,
that is the axial view of the lumbar spine. Anteriorly on the front, is a
vertebral body. Posteriorly for the back is the posterior spinal
elements. In the middle is the round space called a spinal canal.
Within the spinal canal, we can see individual nerve roots floating within
the spinal sac, and the exiting hole for the nerve going down into the legs
called the foramen. The sagittal plane is also a cross-sectional view, but this is
from the side of the body. The best way to look at the axial view is to look at
the side view of the spine, and again takes thin slices from the side to the
middle of the body. In the sagittal view, we can see the vertebral body in the
front. We see the posterior spinous processes in the back, and in the center,
we see the space, which is a tube of water called a spinal sac, and within the
sac, we can see individual nerves that are exiting from the spinal cord. As we
go through various slices of the sagittal view, we can also see the
foramen. To fast-forward your understanding of
the relationship between the axial sagittal views, we will superimpose the
axial views on this sagittal view and reconstruct the spinal anatomy. By doing
this, we have accelerated your understanding of the relationship
between the axial and sagittal views and now you have a much better understanding
of the anatomy of the spine, as well as how the MRI can be used to identify
specific areas of the lumbar spine. Of course this is an oversimplification of how
we read the MRI. Radiologist's, and spinal specialists, spend years learning the
nuances of the MRI studies. There are different signaling sequence
parameters that better highlight water content, or fat content, or inflammatory
responses. The simple MRI reconstruction does fast forward most of your
understanding of how the MRI of the lumbar spine is read. Once we understand what is
considered normal, we can then see the difference between the normal and things
such as disc herniations, spinal stenosis, broken bones, degeneration, tumors, and
infections. This is Dr. John Shim, I hope this video has simplified how to look
and read a lumbar MRI. Thank You.