DOI: 10.1148/rg.26si065512
Multichannel CT: Evaluating the Spine in Postoperative Patients with Orthopedic Hardware1
Annette C. Douglas-Akinwande, MD,
Kenneth A. Buckwalter, MD,
Jonas Rydberg, MD,
James L. Rankin, RT and
Robert H. Choplin, MD
1 From the Department of Radiology, Indiana University Medical Center, University Hospital 0279, 550 N University Blvd, Indianapolis, IN 46202. Presented as an education exhibit at the 2005 RSNA Annual Meeting. Received April 3, 2006; revision requested June 23 and received July 14; accepted July 24. A.C.D.A., K.A.B., J.R., and R.H.C. supported by educational grants from Philips Medical Systems, Cleveland, Ohio; J.L.R. is a member of the Philips CT Medical Advisory Board, Cleveland, Ohio; and A.C.D.A. is a consultant with Bracco Diagnostics, Princeton, NJ.
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Figure 1a. Metal-related artifacts at conventional CT. (a) CT scan (soft-tissue windowing) shows severe artifacts that obscure anatomy and limit evaluation of the spine and hardware. (b) CT scan (bone windowing) shows reduction of the artifacts; however, the image remains nondiagnostic.
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Figure 1b. Metal-related artifacts at conventional CT. (a) CT scan (soft-tissue windowing) shows severe artifacts that obscure anatomy and limit evaluation of the spine and hardware. (b) CT scan (bone windowing) shows reduction of the artifacts; however, the image remains nondiagnostic.
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Figure 2a. Detector array configuration and collimation. (a) Schematic illustrates a 16-channel scanner operating in the 12-mm beam collimation mode. Note that the nominal and reconstructed section thicknesses are small. (b) Schematic illustrates the same scanner operating in the 24-mm beam collimation mode. Note how the smaller central detectors are paired to increase the nominal section thickness. The possible reconstructed sections from raw data are thicker than with the 12-mm beam collimation mode.
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Figure 2b. Detector array configuration and collimation. (a) Schematic illustrates a 16-channel scanner operating in the 12-mm beam collimation mode. Note that the nominal and reconstructed section thicknesses are small. (b) Schematic illustrates the same scanner operating in the 24-mm beam collimation mode. Note how the smaller central detectors are paired to increase the nominal section thickness. The possible reconstructed sections from raw data are thicker than with the 12-mm beam collimation mode.
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Figure 3. Drawings illustrate voxels acquired with single-channel scanners versus 4–64-channel scanners. Voxels acquired with single-channel scanners (left) are anisotropic, and reformatted images have lower resolution than the axial source images. However, 4–64-channel scanners yield isotropic voxels (right), which facilitate reformation with image resolution similar to that of the source images. X, Y, and Z represent the three dimensions of the voxel.
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Figure 4a. Appearance of artifacts with use of an edge-enhancement algorithm versus a smooth algorithm. (a) Sagittal MPR image acquired with an edge-enhancement algorithm from postmyelographic CT data obtained on a 64-channel scanner shows artifacts at L3–L4. (b) Sagittal MPR image acquired with a smooth algorithm minimizes the artifacts. (c) Curved coronal MPR image shows disk herniation, nerve root impingement, and spinal stenosis at L3–L4 (arrow). (d, e) Coronal multiplanar maximum intensity projection (d) and average intensity projection (AIP) (e) images clearly depict intact Harrington rods.
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Figure 4b. Appearance of artifacts with use of an edge-enhancement algorithm versus a smooth algorithm. (a) Sagittal MPR image acquired with an edge-enhancement algorithm from postmyelographic CT data obtained on a 64-channel scanner shows artifacts at L3–L4. (b) Sagittal MPR image acquired with a smooth algorithm minimizes the artifacts. (c) Curved coronal MPR image shows disk herniation, nerve root impingement, and spinal stenosis at L3–L4 (arrow). (d, e) Coronal multiplanar maximum intensity projection (d) and average intensity projection (AIP) (e) images clearly depict intact Harrington rods.
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Figure 4c. Appearance of artifacts with use of an edge-enhancement algorithm versus a smooth algorithm. (a) Sagittal MPR image acquired with an edge-enhancement algorithm from postmyelographic CT data obtained on a 64-channel scanner shows artifacts at L3–L4. (b) Sagittal MPR image acquired with a smooth algorithm minimizes the artifacts. (c) Curved coronal MPR image shows disk herniation, nerve root impingement, and spinal stenosis at L3–L4 (arrow). (d, e) Coronal multiplanar maximum intensity projection (d) and average intensity projection (AIP) (e) images clearly depict intact Harrington rods.
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Figure 4d. Appearance of artifacts with use of an edge-enhancement algorithm versus a smooth algorithm. (a) Sagittal MPR image acquired with an edge-enhancement algorithm from postmyelographic CT data obtained on a 64-channel scanner shows artifacts at L3–L4. (b) Sagittal MPR image acquired with a smooth algorithm minimizes the artifacts. (c) Curved coronal MPR image shows disk herniation, nerve root impingement, and spinal stenosis at L3–L4 (arrow). (d, e) Coronal multiplanar maximum intensity projection (d) and average intensity projection (AIP) (e) images clearly depict intact Harrington rods.
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Figure 4e. Appearance of artifacts with use of an edge-enhancement algorithm versus a smooth algorithm. (a) Sagittal MPR image acquired with an edge-enhancement algorithm from postmyelographic CT data obtained on a 64-channel scanner shows artifacts at L3–L4. (b) Sagittal MPR image acquired with a smooth algorithm minimizes the artifacts. (c) Curved coronal MPR image shows disk herniation, nerve root impingement, and spinal stenosis at L3–L4 (arrow). (d, e) Coronal multiplanar maximum intensity projection (d) and average intensity projection (AIP) (e) images clearly depict intact Harrington rods.
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Figure 5a. Reduction of metal-related artifacts and assessment of spinal alignment with postprocessing. (a–c) Axial CT scans obtained at L1 (a), L1–L2 (b), and L3 (c) show extensive bone destruction. Minimal artifact from the orthopedic hardware does not obscure the spinal canal or bone disease. (d) Coronal MPR image shows complete compression of the vertebral body. (e) Sagittal MPR image shows dislocation of the vertebral body. (f) Three-dimensional VR image shows further reduction of the artifacts and provides a general overview of the region of interest, which is helpful for surgical planning. Postprocessing with three-dimensional VR images and coronal and sagittal MPR images is essential for image interpretation.
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Figure 5b. Reduction of metal-related artifacts and assessment of spinal alignment with postprocessing. (a–c) Axial CT scans obtained at L1 (a), L1–L2 (b), and L3 (c) show extensive bone destruction. Minimal artifact from the orthopedic hardware does not obscure the spinal canal or bone disease. (d) Coronal MPR image shows complete compression of the vertebral body. (e) Sagittal MPR image shows dislocation of the vertebral body. (f) Three-dimensional VR image shows further reduction of the artifacts and provides a general overview of the region of interest, which is helpful for surgical planning. Postprocessing with three-dimensional VR images and coronal and sagittal MPR images is essential for image interpretation.
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Figure 5c. Reduction of metal-related artifacts and assessment of spinal alignment with postprocessing. (a–c) Axial CT scans obtained at L1 (a), L1–L2 (b), and L3 (c) show extensive bone destruction. Minimal artifact from the orthopedic hardware does not obscure the spinal canal or bone disease. (d) Coronal MPR image shows complete compression of the vertebral body. (e) Sagittal MPR image shows dislocation of the vertebral body. (f) Three-dimensional VR image shows further reduction of the artifacts and provides a general overview of the region of interest, which is helpful for surgical planning. Postprocessing with three-dimensional VR images and coronal and sagittal MPR images is essential for image interpretation.
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Figure 5d. Reduction of metal-related artifacts and assessment of spinal alignment with postprocessing. (a–c) Axial CT scans obtained at L1 (a), L1–L2 (b), and L3 (c) show extensive bone destruction. Minimal artifact from the orthopedic hardware does not obscure the spinal canal or bone disease. (d) Coronal MPR image shows complete compression of the vertebral body. (e) Sagittal MPR image shows dislocation of the vertebral body. (f) Three-dimensional VR image shows further reduction of the artifacts and provides a general overview of the region of interest, which is helpful for surgical planning. Postprocessing with three-dimensional VR images and coronal and sagittal MPR images is essential for image interpretation.
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Figure 5e. Reduction of metal-related artifacts and assessment of spinal alignment with postprocessing. (a–c) Axial CT scans obtained at L1 (a), L1–L2 (b), and L3 (c) show extensive bone destruction. Minimal artifact from the orthopedic hardware does not obscure the spinal canal or bone disease. (d) Coronal MPR image shows complete compression of the vertebral body. (e) Sagittal MPR image shows dislocation of the vertebral body. (f) Three-dimensional VR image shows further reduction of the artifacts and provides a general overview of the region of interest, which is helpful for surgical planning. Postprocessing with three-dimensional VR images and coronal and sagittal MPR images is essential for image interpretation.
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Figure 5f. Reduction of metal-related artifacts and assessment of spinal alignment with postprocessing. (a–c) Axial CT scans obtained at L1 (a), L1–L2 (b), and L3 (c) show extensive bone destruction. Minimal artifact from the orthopedic hardware does not obscure the spinal canal or bone disease. (d) Coronal MPR image shows complete compression of the vertebral body. (e) Sagittal MPR image shows dislocation of the vertebral body. (f) Three-dimensional VR image shows further reduction of the artifacts and provides a general overview of the region of interest, which is helpful for surgical planning. Postprocessing with three-dimensional VR images and coronal and sagittal MPR images is essential for image interpretation.
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Figure 6a. Assessment of hardware integrity. (a, b) Axial wide-window (a) and sagittal MPR (b) images of the lumbar spine show fixation hardware at L4–L5, but it is difficult to assess whether the metal is intact. (c–e) Axial (c), sagittal (d), and coronal (e) multiplanar AIP images more clearly show the absence of fracture in the hardware. Assessment of hardware integrity is easily achieved with multiplanar AIP.
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Figure 6b. Assessment of hardware integrity. (a, b) Axial wide-window (a) and sagittal MPR (b) images of the lumbar spine show fixation hardware at L4–L5, but it is difficult to assess whether the metal is intact. (c–e) Axial (c), sagittal (d), and coronal (e) multiplanar AIP images more clearly show the absence of fracture in the hardware. Assessment of hardware integrity is easily achieved with multiplanar AIP.
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Figure 6c. Assessment of hardware integrity. (a, b) Axial wide-window (a) and sagittal MPR (b) images of the lumbar spine show fixation hardware at L4–L5, but it is difficult to assess whether the metal is intact. (c–e) Axial (c), sagittal (d), and coronal (e) multiplanar AIP images more clearly show the absence of fracture in the hardware. Assessment of hardware integrity is easily achieved with multiplanar AIP.
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Figure 6d. Assessment of hardware integrity. (a, b) Axial wide-window (a) and sagittal MPR (b) images of the lumbar spine show fixation hardware at L4–L5, but it is difficult to assess whether the metal is intact. (c–e) Axial (c), sagittal (d), and coronal (e) multiplanar AIP images more clearly show the absence of fracture in the hardware. Assessment of hardware integrity is easily achieved with multiplanar AIP.
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Figure 6e. Assessment of hardware integrity. (a, b) Axial wide-window (a) and sagittal MPR (b) images of the lumbar spine show fixation hardware at L4–L5, but it is difficult to assess whether the metal is intact. (c–e) Axial (c), sagittal (d), and coronal (e) multiplanar AIP images more clearly show the absence of fracture in the hardware. Assessment of hardware integrity is easily achieved with multiplanar AIP.
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Figure 7a. CT of the cervical spine in a thin patient. Imaging was performed at 120 kVp on a 16-channel scanner. The cross-sectional areas of both the patient and the hardware are small, and the thinnest part of the hardware is perpendicular to the incident x-ray beam. (a, b) Axial (a) and sagittal (b) MPR images (narrow windowing) show prominent metal-related artifacts (arrow in a). (c, d) Axial (c) and sagittal (d) MPR images (wide windowing) minimize the artifacts and are of diagnostic quality. There is a manufactured opening (straight white arrow) in the anterior orthopedic plate and a bone fragment (arrowhead) at C4. An osteophyte at C4–C5 (black arrow) results in spinal canal stenosis (curved white arrow).
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Figure 7b. CT of the cervical spine in a thin patient. Imaging was performed at 120 kVp on a 16-channel scanner. The cross-sectional areas of both the patient and the hardware are small, and the thinnest part of the hardware is perpendicular to the incident x-ray beam. (a, b) Axial (a) and sagittal (b) MPR images (narrow windowing) show prominent metal-related artifacts (arrow in a). (c, d) Axial (c) and sagittal (d) MPR images (wide windowing) minimize the artifacts and are of diagnostic quality. There is a manufactured opening (straight white arrow) in the anterior orthopedic plate and a bone fragment (arrowhead) at C4. An osteophyte at C4–C5 (black arrow) results in spinal canal stenosis (curved white arrow).
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Figure 7c. CT of the cervical spine in a thin patient. Imaging was performed at 120 kVp on a 16-channel scanner. The cross-sectional areas of both the patient and the hardware are small, and the thinnest part of the hardware is perpendicular to the incident x-ray beam. (a, b) Axial (a) and sagittal (b) MPR images (narrow windowing) show prominent metal-related artifacts (arrow in a). (c, d) Axial (c) and sagittal (d) MPR images (wide windowing) minimize the artifacts and are of diagnostic quality. There is a manufactured opening (straight white arrow) in the anterior orthopedic plate and a bone fragment (arrowhead) at C4. An osteophyte at C4–C5 (black arrow) results in spinal canal stenosis (curved white arrow).
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Figure 7d. CT of the cervical spine in a thin patient. Imaging was performed at 120 kVp on a 16-channel scanner. The cross-sectional areas of both the patient and the hardware are small, and the thinnest part of the hardware is perpendicular to the incident x-ray beam. (a, b) Axial (a) and sagittal (b) MPR images (narrow windowing) show prominent metal-related artifacts (arrow in a). (c, d) Axial (c) and sagittal (d) MPR images (wide windowing) minimize the artifacts and are of diagnostic quality. There is a manufactured opening (straight white arrow) in the anterior orthopedic plate and a bone fragment (arrowhead) at C4. An osteophyte at C4–C5 (black arrow) results in spinal canal stenosis (curved white arrow).
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Figure 8. Photograph shows a patient positioned in the CT scanner for cervical spine imaging. The chin is hyperextended, and a shoulder traction device (arrows) is attached to the wrist and wrapped under the soles of the feet. Extension of the knees lowers the shoulders with slow steady traction, helping to minimize beam-hardening artifacts from the shoulders.
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Figure 9a. Multilevel fusion of the cervical spine. (a, b) CT scans obtained with soft-tissue (a) and bone (b) windowing on a 64-channel scanner at the level of screws within a vertebral body allow excellent visualization of the spinal canal without superimposed artifact. (c–e) Coronal MPR image (c) and sagittal MPR images obtained with soft-tissue (d) and bone (e) windowing show posterior subluxation of C3 on C4 (arrow in d and e), osteopenic bones, odontoid erosions, and compressed vertebral bodies. Multiple manufactured openings are seen in the anterior plate (arrowheads in e).
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Figure 9b. Multilevel fusion of the cervical spine. (a, b) CT scans obtained with soft-tissue (a) and bone (b) windowing on a 64-channel scanner at the level of screws within a vertebral body allow excellent visualization of the spinal canal without superimposed artifact. (c–e) Coronal MPR image (c) and sagittal MPR images obtained with soft-tissue (d) and bone (e) windowing show posterior subluxation of C3 on C4 (arrow in d and e), osteopenic bones, odontoid erosions, and compressed vertebral bodies. Multiple manufactured openings are seen in the anterior plate (arrowheads in e).
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Figure 9c. Multilevel fusion of the cervical spine. (a, b) CT scans obtained with soft-tissue (a) and bone (b) windowing on a 64-channel scanner at the level of screws within a vertebral body allow excellent visualization of the spinal canal without superimposed artifact. (c–e) Coronal MPR image (c) and sagittal MPR images obtained with soft-tissue (d) and bone (e) windowing show posterior subluxation of C3 on C4 (arrow in d and e), osteopenic bones, odontoid erosions, and compressed vertebral bodies. Multiple manufactured openings are seen in the anterior plate (arrowheads in e).
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Figure 9d. Multilevel fusion of the cervical spine. (a, b) CT scans obtained with soft-tissue (a) and bone (b) windowing on a 64-channel scanner at the level of screws within a vertebral body allow excellent visualization of the spinal canal without superimposed artifact. (c–e) Coronal MPR image (c) and sagittal MPR images obtained with soft-tissue (d) and bone (e) windowing show posterior subluxation of C3 on C4 (arrow in d and e), osteopenic bones, odontoid erosions, and compressed vertebral bodies. Multiple manufactured openings are seen in the anterior plate (arrowheads in e).
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Figure 9e. Multilevel fusion of the cervical spine. (a, b) CT scans obtained with soft-tissue (a) and bone (b) windowing on a 64-channel scanner at the level of screws within a vertebral body allow excellent visualization of the spinal canal without superimposed artifact. (c–e) Coronal MPR image (c) and sagittal MPR images obtained with soft-tissue (d) and bone (e) windowing show posterior subluxation of C3 on C4 (arrow in d and e), osteopenic bones, odontoid erosions, and compressed vertebral bodies. Multiple manufactured openings are seen in the anterior plate (arrowheads in e).
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Figure 10a. Fibrosis. (a, b) Postmyelographic CT scans obtained with bone (a) and soft-tissue (b) windowing on a four-channel scanner show beam-hardening artifacts from orthopedic hardware. However, the spinal canal and neural foramina are well visualized. (c–e) Sagittal MPR images obtained with soft-tissue (c, d) and bone (e) windowing show a ventrolateral epidural defect at L5-S1 (arrows in c and d), a finding that may represent disk herniation or, as in this case, fibrosis.
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Figure 10b. Fibrosis. (a, b) Postmyelographic CT scans obtained with bone (a) and soft-tissue (b) windowing on a four-channel scanner show beam-hardening artifacts from orthopedic hardware. However, the spinal canal and neural foramina are well visualized. (c–e) Sagittal MPR images obtained with soft-tissue (c, d) and bone (e) windowing show a ventrolateral epidural defect at L5-S1 (arrows in c and d), a finding that may represent disk herniation or, as in this case, fibrosis.
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Figure 10c. Fibrosis. (a, b) Postmyelographic CT scans obtained with bone (a) and soft-tissue (b) windowing on a four-channel scanner show beam-hardening artifacts from orthopedic hardware. However, the spinal canal and neural foramina are well visualized. (c–e) Sagittal MPR images obtained with soft-tissue (c, d) and bone (e) windowing show a ventrolateral epidural defect at L5-S1 (arrows in c and d), a finding that may represent disk herniation or, as in this case, fibrosis.
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Figure 10d. Fibrosis. (a, b) Postmyelographic CT scans obtained with bone (a) and soft-tissue (b) windowing on a four-channel scanner show beam-hardening artifacts from orthopedic hardware. However, the spinal canal and neural foramina are well visualized. (c–e) Sagittal MPR images obtained with soft-tissue (c, d) and bone (e) windowing show a ventrolateral epidural defect at L5-S1 (arrows in c and d), a finding that may represent disk herniation or, as in this case, fibrosis.
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Figure 10e. Fibrosis. (a, b) Postmyelographic CT scans obtained with bone (a) and soft-tissue (b) windowing on a four-channel scanner show beam-hardening artifacts from orthopedic hardware. However, the spinal canal and neural foramina are well visualized. (c–e) Sagittal MPR images obtained with soft-tissue (c, d) and bone (e) windowing show a ventrolateral epidural defect at L5-S1 (arrows in c and d), a finding that may represent disk herniation or, as in this case, fibrosis.
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Copyright © 2006 by the Radiological Society of North America.
