J Korean Soc Radiol.  2019 Jan;80(1):105-116. 10.3348/jksr.2019.80.1.105.

Dual-Layer Spectral Detector CT Discography of the Lumbar Spine: A Preliminary Study

• Chae HD
• Hong SH
• Choi JY
• Yoo HJ
• Moon SJ
• Chang MY

• KMID: 2442469
• DOI: http://doi.org/10.3348/jksr.2019.80.1.105

Abstract

PURPOSE
To assess the feasibility of spectral detector CT (SDCT) with axial maximum-intensity projection (MIP) reconstruction for the evaluation of lumbar CT discography.
MATERIALS AND METHODS
We retrospectively evaluated 44 disc levels from 18 patients who underwent CT discography on a dual-layer SDCT between May 2016 and July 2017. We compared the distribution of contrast material between conventional CT and SDCT-based iodine maps using the Jaccard index (JI) and Dice similarity coefficient (DSC). Qualitative analysis of the post-discogram features was done according to the Dallas discogram description, and changes in reading time and diagnostic confidence were analyzed.
RESULTS
The intermethod variability between conventional CT and SDCT was good, with a mean DSC of 0.93 and a mean JI of 0.87. The mean sensitivity and positive predictive value of the SDCT-based method were 90% and 96%, respectively. The addition of SDCT-based axial MIP iodine maps increased the diagnostic confidence (p = 0.025) and reduced the reading time in both reviewers (p < 0.001).
CONCLUSION
SDCT discography demonstrates the distribution of contrast medium within the disc similarly to conventional CT. Additionally, axial MIP iodine maps using SDCT allow for the fast evaluation of disc pathology with reduced reading time and can increase diagnostic confidence.

MeSH Terms

Contrast Media
Humans
Intervertebral Disc Degeneration
Iodine
Methods
Pathology
Retrospective Studies
Spine*
Tomography, X-Ray Computed
Contrast Media
Iodine

Figure

• 

  Fig. 1. Screenshot showing a vendor-provided spectral view-er. The slab thickness was prop-erly chosen to include all disc regions with contrast media on the sagittal plane. Subsequently, color-coded axial maximum-intensity projection images were created using the spectral-based iodine density maps.

• 

  Fig. 2. Axial MIP iodine map images obtained from convention-al CT and SDCT discography. A, B. An axial MIP image and corresponding ROI obtained from conventional CT discography. The ROI was selected to include the area with contrast material by properly adjusting the window width and level. C, D. An axial MIP image and ROI of the same disc level obtained from SDCT are similar to those obtained from conventional CT discography. The Jaccard index between the two ROIs is 0.91 and the Dice similarity coefficient is 0.95. MIP = maximum-intensity projection, ROI = region of interest, SDCT = spectral detector CT

• 

  Fig. 3. CT discography images of the L4–5 disc in a 44-year-old female patient. A. An axial CT discography image showing annular disruption at the 6 o'clock position (arrow). This disc was evaluated to have localized annular degeneration (grade 1) and annular disruption extending to the outer annulus (grade 2). B. Corresponding spectral CT-based axial maximum-intensity projection iodine map also demonstrates a fairly similar shape of the annular disruption (arrow). There are several artifacts due to incomplete iodine-bone separation around the posterior element of the spine (arrowhead).

• 

  Fig. 4. CT discography images of the L5-S1 disc in a 54-year-old female patient. A. An axial conventional CT image showing a curvilinear, highly attenuated lesion (arrow) suspected to be a concentric annular disruption on the left posterolateral side of the L3–4 disc. B. In the corresponding spectral CT-based axial maximum-intensity projection iodine map, there is no iodine in the curvilinear area seen on conventional CT. The lesion was confirmed to be a ring apophysis and the disc was evaluated to have annular disruption extending to the inner annulus (grade 1).

Reference

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