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Orthopaedic Nursing November/December 2006 Volume 25 Number 6 415

Optimally, it is beneficial to have the patient empty thebladder and bowels prior to the examination. Overlying gasand fecal material may compromise radiographic clarity.A urine-filled bladder may cast a shadow on the sacrumand the distal end of the vertebral column (Ballinger &Frank, 2003).

Multiple structures are well demonstrated on the APlumbar spine image. Structures labeled in Figure 1 are the

vertebral body (A), the spinous process (B), intervertebraldisk space (C), examples of colonic gas (D), examples offecal material (E), and the left 12th rib (F).

The zygapophyseal or facet joint is not demonstrated inthe AP projection of the lumbar spine, but is seen in theoblique position. The articulation of the superior and infe-rior articular processes form the zygapophyseal joint. InFigure 2, the rectangle indicates the L2 vertebral body, A

is the superior articular process of L3, B is the inferiorarticular process of L2, C is the superior articularprocess of L4, D is the inferior articular process of L3,and E and F are the pedicles of L3 and L4, respectively.

A lateral lumbar radiographic image is seen in Figures 3and 4. Compression fractures of the vertebral body, bonedensity, and spinous processes are typically well seen onthis radiographic view. In Figure 3, A indicates onezygapophyseal joint, B points to pedicle screw place-ment, C depicts the L4 spinous process, and D theL3/L4 intervertebral disk space. The squares in both Fig-ures 3 and 4 indicate the vertebral body of L1. Note theloss of bone density (osteoporosis) in the vertebral bodyin Figure 4 as indicated by grayness of the body and thelack of differentiation from the surrounding abdominalsoft tissue. Compare this with the L1 vertebra in Figure 3,which is of normal bone density.

When patients present with symptoms associated with lumbar

spine pathology, often a series of diagnostic examinations of

escalating sophistication are utilized. To obtain a diagnosis,

the initial study is usually done on lumbar spine radiographs,

which demonstrate gross bony pathologies, spinal alignment,and bone density. Frequently, additional high-cost invasive or

noninvasive procedures may be required. Myelography is used

to examine the spinal cord, nerve root bundles, and possible

intrusion of the vertebral disk into the spinal canal. Computed

tomography is most useful for imaging small bony structures

and, when coupled with myelography, can demonstrate soft

tissue abnormalities in the spinal canal. Magnetic resonance

imaging is, however, the preferred modality for imaging

soft tissue.

Lumbar spine plain x-ray films (radiographs) are consid-ered for a general survey radiographic examination toevaluate disease processes and fractures. Patient symp-toms include persistent low back pain, a history of trauma,loss of feeling or tingling in the legs, weakness, and/orpainful ambulation. Routine radiography is less expensivethan computed tomography (CT) or magnetic resonanceimaging (MRI) procedures and is usually the first proce-dure in the diagnostic process for lumbar spine pathology.Lumbar spine radiographs are fast, noninvasive, and usu-ally pain-free. If the patient has discomfort in the recum-bent position, the patient may be examined in the erectposition (Ballinger & Frank, 2003).

Radiographs are two-dimensional (2D) images of three-dimensional (3D) structures, which result in superimposi-tion of anatomical structures. Consequently, it is usuallynecessary to obtain multiple images taken at differentangles. A term used in radiography to describe the pathof the radiation or x-ray beam is projection. Typically, thespine examination consists of an anterior-to-posterior (AP)projection, a lateral projection, two oblique projections,and occasionally a detailed image of the L5-S1 disk space

(Ballinger & Frank, 2003).

Elwin R. Tilson, EdD, RT(R)(QM)(M)(CT), FAERS, Professor ofRadiologic Sciences, Armstrong Atlantic State University, Savannah, GA.

Gloria Deal Strickland, EdD, RT(R)(QM)(M), Associate Professor ofRadiologic Sciences, Armstrong Atlantic State University, Savannah, GA.

Sharyn D. Gibson, EdD, RT(R), Professor and Department Head of

Radiologic Sciences, Armstrong Atlantic State University, Savannah, GA.

An Overview of Radiography,Computed Tomography, andMagnetic Resonance Imaging in theDiagnosis of Lumbar Spine Pathology

Elwin R. Tilson Gloria Deal Strickland Sharyn D. Gibson

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416 Orthopaedic Nursing November/December 2006 Volume 25 Number 6

One of the limitations of a routine lumbar radiographicexamination is that certain structures and pathologies arenot visible. For example, the spinal cord, the intervertebraldisks, nerve roots, and many soft tissue injuries are not

visible on plain radiographs. When these structures needto be assessed, other examinations such as myelography,

CT, and MRI are helpful.

MyelographyOne cause of low back pain may be associated with neuro-logical impairment due to pressure on the spinal cord(Magee, 1997). This pressure may be associated with de-generative changes in the bony structure of the vertebra,traumatic fracture fragments, or intervertebral disk herni-ation. Myelography may show the relationship of bony toneural elements (Eisenberg & Johnson, 2003). This proce-dure involves lumbar puncture in which a small amount of

cerebral spinal fluid is removed and replaced by an iodine-

based, water-soluble contrast media. Contrast media out-lines the spinal cord, the nerve root bundles, and the edgesof the intervertebral disks. Images are taken using bothfluoroscopy and radiography and can be coupled to a CTexamination as indicated below.

Figure 5 is a positive image in which bone is darkgray and soft tissue is white. The contrast media is thedark column overlying the vertebral bodies and filling thespinal column. The two black arrows indicate strandingaround the nerve root bundles. Figure 6 is a traditionalnegative image of the same examination. In this image,bone and contrast media appear white. The white arrowson this image indicate nerve root bundles. The white col-umn overlying the vertebral bodies is the contrast media-filled spinal canal.

In a myelogram study, two of the areas that are evalu-

ated are the intervertebral spaces and potential intrusion

FIGURE 1. Annotated AP lumbar spine radiograph. (A) Vertebralbody, (B) spinous process, (C) intervertebral space, (D) exampleof colonic gas, (E) example of fecal material, and (F) left 12th rib.

FIGURE 2. Right posterior oblique radiograph of the lumbarspine. The body of L2 is outlined by the rectangle. (A) Superiorarticular process of L3, (B) inferior articular process of L2, (C) su-perior articular process of L4, (D) inferior articular process of L3,and (E) pedicles of L3 and L4.



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of the disk into the spinal canal. In Figure 7, a lateralmyelogram image, the black arrows indicate the inter-

vertebral space and the white arrows indicate the inter-section of the disk and the spinal canal. Note the U-shaped bulge pushing into the spinal canal at the point ofthe intersection. This is typical of intervertebral disk intru-sion into the spinal canal.

Computed TomographyComputed tomography is a technology using x-ray radia-tion and an array of radiation detectors that surround thepart being examined. On the basis of the amount of radia-tion absorbed by different body parts from multiple an-gles, it is possible to reconstruct a 2D or 3D image of theanatomy. In the 2D reconstruction, the computer producesslices through the part of interest. In the 3D reconstruc-tions, the computer produces an image that can be rotatedand viewed from any angle either as a solid or semitrans-parent structure. Computed tomography has good con-trast resolution, which means objects of slightly different

physiological densities are easily distinguishable. Although

CT is often used to examine soft tissue in the chest and ab-domen, it is not as useful for examining the soft tissues as-sociated with the lumbar spine. Computed tomography,however, is extremely useful in examining the spinal bonystructures such as degenerative facet changes and pathol-ogy associated with trauma. These pathologies are espe-cially important as they may or may not infringe upon the

spinal canal (Seeram, 2000).A representative example of a 2D CT slice of a lumbar vertebra is shown in Figure 8. This is a cross-sectionalslice through the vertebra, where A is the body of the

vertebra, B is the spinal canal, C is the transverse pro-cesses, D is the spinous process, E is the pedicle, andF is the lamina.

When combined with a myelogram, the CT scan demon-strates important information about soft tissue structuressuch as the spinal cord nerve roots. The white arrows inFigure 9 indicate the spinal cord with contrast media high-lighting the soft tissue in the spinal canal. Note the multiple

dark nerve root bundles inside the spinal cord. Compare

FIGURE 3. Lateral lumbar spine radiograph. The body of L1 isoutlined by the rectangle. (A) Zygapophyseal joint, (B) screwplacement, (C) spinous process, and (D) intervertebral joint space.

FIGURE 4. Lateral lumbar spine radiograph demonstratingosteoporosis as indicated by the loss of bone density (com-

pared to the surrounding soft tissue) in the L1 vertebral bodyoutlined by the rectangle.


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FIGURE 6. Negative image of a lumbar myelogram with arrows

indicating nerve root bundles.

FIGURE 7. Lateral projection of lumbar myelogram with darkarrows indicating intervertebral disk space and white arrows in-dicating intervertebral disk bulging into spinal cord.

FIGURE 8. Axial CT image of lumbar vertebra using bone win-dow settings. (A) Body of the vertebra, (B) spinal canal, (C) trans-

verse process, (D) spinous process, (E) pedicle, and (F) lamina.

FIGURE 5. Positive image of a lumbar myelogram with arrowsindicating nerve root bundles.


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FIGURE 9. Axial CT image of lumbar vertebra and spinal cord(arrows) during CT-augmented myelogram.

this contrast image with area B in Figure 8 where thespinal cord is not depicted.

Another use of CT examination of the lumbar spine isthat 2D slices can be produced in axial, sagittal, or coronalorientations. Traditional CT slices are in the axial orien-tation. Standard image reconstructions performed with alumbar spine CT examination are in the sagittal orienta-tion. Figure 10 is a sagittal CT reconstruction. Note that

the image looks similar to the traditional lateral lumbarradiograph in Figure 3. The white box in Figure 10 sur-rounds a fractured vertebra as demonstrated by the lackof a smooth superior surface and the fracture line fromthe superior aspect to the inferior aspect of the body.

Magnetic Resonance ImagingUnlike CT, MRI is very useful in demonstrating soft tissueswithout the addition of the contrast media and therefore isnot an invasive procedure. Magnetic resonance imagingrequires a strong external magnetic field, a source of radiowaves, a radio wave receiver, and an abundance of mobilehydrogen protons. Hydrogen is abundant in human tissuemaking up approximately two thirds of atoms within thebody (Woodward & Freimarck, 1995). When the patient is

placed in a strong external magnetic field, the hydrogenprotons align with the magnetic field. Because there is onlyone proton in the hydrogen nucleus, it spins like a spinningtop (Westbrook & Kaut, 1998). Envision the proton as spin-ning like a top that begins to lose energy. Owing to the lossof energy, the top starts to wobble and begins moving out-wardly from the center. This wobble or precession in atomsoccurs at a particular frequency and can be measured andused to create cross-sectional images in any plane.

Images are created due to the pulsing of radio frequencywaves that manipulate and move the magnetic fields asso-ciated with the spinning hydrogen protons. When the radiofrequency pulse is terminated, the protons magnetic field

FIGURE 10. Sagittal CT reconstruction image of lumbar verte-bra demonstrating a fracture of the vertebral body as indicated

by the rectangle.

FIGURE 11. Sagittal MRI image of the lumbar spine regiondemonstrating normal anatomy. (A) Intervertebral disk, (B) cauda

equina, (C) spinal cord, and (D) cerebral spinal fluid.


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FIGURE 12. Sagittal MRI image demonstrates a herniated diskat two levels as indicated by the bulging (white arrows) into the

spinal canal.

FIGURE 13. Sagittal MRI image showing a fracture of the ver-tebral body with displacement of the fracture (black arrows)and infringement of the spinal cord (white arrow).

When a patient presents with possible lumbar spinepathology, there are a wide range of radiologic examina-tions that may be used for diagnosis. These examinationscan be used individually or in combination to provide theclinician with comprehensive imaging data for diagnosisof subtle lumbar spine pathologies.

REFERENCES

Ballinger, P., & Frank, E. (2003). Merrills atlas of radiogra-phic positions and radiologic procedures (Vol. 1, 10th ed.).St. Louis, MO: Mosby.

Eisenberg, R., & Johnson, N. (2003). Comprehensive radio-graphic pathology (3rd ed.). St. Louis, MO: Mosby.

Magee, D. J. (1997). Orthopedic physical assessment (2nd ed.).Philadelphia: W. B. Saunders.

Seeram, E. (2000). Computed tomography: Physical principles, clinical applications, and quality control. Philadelphia:Saunders.

Westbrook, C., & Kaut, C. (1998). MRI in practice. Malden,MA: Blackwell Science.

Woodward, P., & Freimarck, R. (1995). MRI for technologists.

New York: McGraw-Hill.

will return to its original position. In doing so, the protonsgive off excess energy in the form of radio waves. The radiowaves from individual atoms are analyzed by a computerto form images (Woodward & Freimarck, 1995).

The MRI parameters known as T1 and T2 representdifferent methods of tissue relaxation of the hydrogenprotons, following manipulation of their magnetic fields(Westbrook & Kaut, 1998). Tissues within the human bodyconsist of various chemical structures containing differingamounts of hydrogen. Because these tissues are chemi-cally different, they relax or return to their original statesat different rates. These differing relaxation rates are re-ferred to as T1 and T2 relaxations. T1-weighted images arefrequently used for the visualization of anatomy, and T2-weighted images are usually the best for visualization ofpathology. Magnetic resonance imaging demonstrates spi-

nal alignment, disk height and hydration, vertebral bodyconfiguration, intervertebral disk abnormalities, spinalcanal size, nerves, and postsurgical changes. Figure 11 is asagittal MRI image showing normal anatomy. A commonabnormality demonstrated by MRI in the lumbar spine re-gion is herniated intervertebral disk (dark bulges as indi-cated by white arrows in Figure 12). A fracture of an osteo-penic L3 vertebral body with the displacement of bone intothe spinal canal is shown in Figure 13. The white arrow in-dicates the canal impingement and the black arrows pointto the fracture line of the body.

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