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

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)

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.

Literature Review

Literature Review

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