Lumbar Spine MRI

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Anatomical Structures

Sagittal Scans

Sagittal MRI scans are typically taken across five standard planes. There may be further scans between these planes, or it may be slightly displaced to the left or right.

Sagittal MRI five standard planes and the intersecting structures
Plane Vertebral structures Vertebral canal structures Extra-vertebral structures
Median Vertebral bodies and intervertebral discs (AP and AF) anteriorly, and the spinous processes posteriorly Conus medullaris at upper segmental levels, and the cauda equina at lower levels. Aorta terminates opposite L4
Paramedian Vertebral bodies and intervertebral discs anteriorly (AP and AF), and the laminae posteriorly May miss the spinal cord, and only show the cauda equina. Right of midline: right side edge of the aorta, right common iliac artery in front of L5, and left common iliac vein.
Left of midline passes through the aorta.
Posteriorly there is multifidus.
Transpedicular Lateral sectors of the vertebral bodies, the lateral sectors of the intervertebral discs (AF +/- NP), the pedicles, and some portions of the facet joints. Slightly more medial intersects the inferiorly articular processes. Slightly more lateral intersects the superior articular processes Spinal nerves and their dural sleeves as they pass under the pedicles in the intervertebral foraminae Right of midline: IVC, right common iliac artery in front of L5
Left of midline: might intersect lateral aorta
Posteriorly multifidus.
Tangential Most lateral margins of the vertebral bodies and the AF at each segmental level, or the concavity of the vertebral body and their lumbar arteries and veins No intersection Left of midline: lateral to aorta or lateral segments
Right of midline: IVC, right common iliac artery in front of L5
Posteriorly the erector spinae at most levels and multifidus at lumbosacral levels.
Peripheral Transverse processes No intersection Psoas major, quadratus lumborum anteriorly. Erector spinae posteriorly.
  • Anteriorly different planes have various intersections with the crura of the diaphragm, the great vessels, psoas major, and quadratus lumborum.
  • Posteriorly there is intersection through multifidus, longissimus thoracic, or iliocostalis lumborum.
  • Across the vertebral body concavities there are the lumbar arteries and lumbar veins that are covered by psoas
  • Anterior to the vertebral bodies on the right there is the right crus and the IVC
  • Anterior to the vertebral bodies towards the centre and left there is the left crus and the aorta
  • Posterior to the laminae there is multifidus
  • Anterior to the transverse processes there is the psoas major and quadratus lumborum
  • Posterior the the transverse processes there is various components of the erector spinae.
T2 Sagittal scans to the right of midline
Sagittal Median
Sagittal Paramedian
Sagittal Transpedicular
Sagittal Tangential
Sagittal Peripheral

Axial scans

There are three main planes for axial MRI scans. With interpretation, the first step is determining whether the scan is transpedicular, subpedicular, or transarticular. The second step is estimating the segmental level by examining the external relations.

Axial MRI three standard planes and the internal relations
Plane Vertebral structures Vertebral canal structures
Transpedicular Pedicles project form the posterior surface of the vertebral body. Posteriorly various parts of the laminae and spinous process. Dural sac and nerve roots of the cauda equina. Nerve roots typically towards posterior surface of the sac due to the patient lying supine.
Subpedicular Vertebral body anteriorly, laminae posteriorly Dural sac with nerve roots of the cauda equina, and spinal nerves of the segment as they run through the intervertebral foramen. Spinal nerve lateral to the dural sac +/- dural sleeve with CSF.
Transarticular Intervertebral disc, facet joints Dural sac and cauda equina centrally. Spinal nerve or ventral ramus leaving the vertebral column at the posterolateral corner of the disc and entering the psoas major. The spinal nerve passes obliquely and caudally through the foramen and so it is located further laterally than in subpedicular scans and is dissociated from the dural sac.

The external relations can be used to identify the segment being used.

External Relations
Segment Anterior Lateral Posterior
L1 Left and right crus, IVC, Aorta, left renal vessels Broad flat quadratus lumborum, and a narrow psoas major Narrow multifidus plus longissimus thoracic, and iliocostalis lumborum.
L2 Crura are smaller, IVC, Aorta, right renal vessels Quadratus lumborum, larger psoas major Multifidus, longissimus thoracic, and iliocostalis lumborum
L3 No crura. IVC and Aorta Quadratus lumborum, large psoas major Multifidus expands laterally to the limits of the laminae. Plus longissimus thoracic and iliocostalis lumborum
L4 3 great vessels: IVC and common iliac arteries large psoas major, small quadratus lumborum Multifidus is wide, and erector spinae are small.
L5 4 great vessels: common iliac veins and arteries Huge psoas major, absent quadratus lumborum, iliolumbar ligament Multifidus is wide. No iliocostalis, and a small portion of longissimus.
T2 Axial scans
L1 Transpedicular
L1 Subpedicular
L1-L2 Transarticular
L2 Transpedicular
L2 Subpedicular
L2-L3 Transarticular
L3 Transpedicular
L3 Subpedicular
L3-L4 Transarticular
L4 Transpedicular
L4 Subpedicular
L4-L5 Transarticular
L5 Transpedicular
L5 Subpedicular
L5-S1 Transarticular

Check List for Interpretation

Before doing anything, first verify patient identification and the date of scan

Basic Pulse Sequences for MRI[1]
Image Type TR TE Fat Signal Intensity Water Signal Intensity Advantages Disadvantages
T1 Short Short Bright Dark Best anatomic detail, rapid acquisition Poor visualisation of pathology/oedema
T2 Long Long Intermediate Bright Moderate sensitivity for pathology/oedema Poor spatial resolution, time consuming
Fat-suppressed T2 Long Short Very dark Very bright Most sensitive for pathology/oedema Susceptible to artifacts related to magnetic resonance inhomogeneity
Gradient Echo Short Short Intermediate Intermediate/high Excellent for articular cartilage, PVNS, and blood Very susceptible to metallic artifacts
Proton Density Long Short Intermediate/high Intermediate Excellent for meniscal pathology


Survey View

Count vertebra, and assess for transitional anatomy

Fat Suppressed Coronal

Assess facet joints for effusions, size, cartilage thickness, oedema. Look for extra spinal pathology. Scroll through the sacroiliac joints looking for osteoarthritis, oedema, effusions.

T1 Sagittals

In T1, spinal fluid is dark and fat is bright. Determine the left-right orientation. On the left, the gives off branches at ~L1. On the right, the renal artery runs posterior to IVC. The Aorta is wider than IVC.

Working from caudal to rostral observe:

  • Neural foramina and nerve roots: nerve contact and compression.
  • Intervertebral discs: width, protrusions/ herniations.
  • Spinal column: alignment (spondylolisthesis), vertebral body shape (compression fractures, Schmorls’ nodes), posterior bony elements (spondylolysis), degenerative end plate changes (changes in fat content), hemangiomas.
  • Retroperitoneal space: adenopathy, masses, great vessel aneurysm, etc

T2 Sagittals

In T2, spinal fluid is bright.

Working from caudal to rostral observe:

  • Dural sac—cord and rootlets: width, compression, irregularities
  • Intervertebral discs: width, protrusions/ herniations, hydration, high intensity zones
  • Spinal column: alignment (spondylolisthesis), vertebral body shape (compression fractures, Schmorls’ nodes), posterior bony elements (spondylolysis), degenerative end plate changes (changes in fat content), hemangiomas.
  • Posterior bony elements: breakage, listhesis, pseudo-articulations, etc.

T1 Axials

The CSF appears gray and fat appears bright. Proceed caudal to cranial.

Orientation – neural foramina lie at level of discs.

  • Content of the spinal canal and neural foramina: Trace course of nerve roots through neural foramina
  • Intervertebral discs— continuity, bulges, etc.
  • Bone – Vertebral bodies; spondylolisthesis, posterior bony elements (spondylolysis, breakage)
  • Ligamentam flavum: thickened appearance, impingement
  • Retroperitoneal space: adenopathy, masses, muscle, fat infiltration of multifidus (see image)[2]

T2 Axials

Spinal fluid appears bright. Proceed caudal to cranial.

  • Content of the spinal canal and neural foramina: Trace course of nerve roots through neural foramina
  • Intervertebral discs— continuity, bulges, etc.
  • Bone – Vertebral bodies; spondylolisthesis, posterior bony elements (spondylolysis, breakage)
  • Ligamentam flavum: thickened appearance, impingement
  • Retroperitoneal space: adenopathy, masses, muscle, etc.

Assessment

Ensure you have covered all structures. Assess need for other studies

Bibliography

  • Bogduk, Nikolai. Clinical and radiological anatomy of the lumbar spine. Chapter 19. Edinburgh: Elsevier/Churchill Livingstone, 2012.

References

  1. Khanna et al.. Magnetic resonance imaging of the knee. Current techniques and spectrum of disease. The Journal of bone and joint surgery. American volume 2001. 83-A Suppl 2 Pt 2:128-41. PMID: 11712834. DOI.
  2. Kjaer et al.. Are MRI-defined fat infiltrations in the multifidus muscles associated with low back pain?. BMC medicine 2007. 5:2. PMID: 17254322. DOI. Full Text.

Literature Review