Korean J Radiol.  2019 Mar;20(3):469-478. 10.3348/kjr.2018.0517.

Cervical Spine CT Using Spectral Shaping: Can It Be a Solution to Overcome Artifacts in the Lower Cervical Spinal Region?

• Lee SM
• Choo HJ
• Lee SJ
• Kim SK
• Lee IS
• Kim DW
• Baek JW
• Heo YJ

• KMID: 2438277
• DOI: http://doi.org/10.3348/kjr.2018.0517

Abstract

OBJECTIVE
To investigate the image quality, radiation dose, and intermodality agreement of cervical spine CT using spectral shaping at 140 kVp by a tin filter (Sn140-kVp) in comparison with those of conventional CT at 120 kVp.
MATERIALS AND METHODS
Patients who had undergone cervical spine CT with Sn140-kVp (n = 58) and conventional 120 kVp (n = 49) were included. Qualitative image quality was analyzed using a 5-point Likert scale. Quantitative image quality was assessed by measuring the noise and attenuation within the central spinal canals at C3/4, C6/7, and C7/T1 levels. Radiation doses received by patients were estimated. The intermodality agreement for disc morphology between CT and MRI was assessed at C3/4, C5/6, C6/7, and C7/T1 levels in 75 patients who had undergone cervical spine MRI as well as CT.
RESULTS
Qualitative image quality was significantly superior in Sn140-kVp scans than in the conventional scans (p < 0.001). At C7/T1 level, the noise was significantly lower and the decrease in attenuation was significantly less in Sn140-kVp scans, than in the conventional scans (p < 0.001). Radiation doses were significantly reduced in Sn140-kVp scans by 50% (effective dose: 1.0 ± 0.1 mSv vs. 2.0 ± 0.4 mSv; p < 0.001). Intermodality agreement in the lower cervical spine region tended to be better in Sn140-kVp acquisitions than in the conventional acquisitions.
CONCLUSION
Cervical spine CT using Sn140-kVp improves image quality of the lower cervical region without increasing the radiation dose. Thus, this protocol can be helpful to overcome the artifacts in the lower cervical spine CT images.

Keyword

Cervical spine; Multidetector computed tomography; Spectral; Metal artifact

MeSH Terms

Artifacts*
Humans
Magnetic Resonance Imaging
Multidetector Computed Tomography
Noise
Spinal Canal
Spine*
Tin
Tin

Figure

• 

  Fig. 1 Grading system for analysis of qualitative image quality.Qualitative image quality was scored on sagittal image plane by using 5-point Likert scale (1, non-diagnostic; 2, limited diagnostic value with substantial image noise and artifacts; 3, diagnostic, sufficient image quality; 4, diagnostic, good image quality with mild image noise and artifacts; 5, diagnostic, excellent image quality with absent or subtle noise and artifacts) focusing on inside of central spinal canal in lower cervical spinal region including cervicothoracic junction.

• 

  Fig. 2 Measurement for analysis of quantitative image quality.About 30-mm2 circular region of interest was placing in center of central spinal canal on axial CT image of intervertebral disc level. To minimize bias, measurements were performed at three sequential slices and averaged. SD = standard deviation

• 

  Fig. 3 Column chart for analysis of qualitative image quality.Three readers determined qualitative image quality by using 5-point Likert scale (1, non-diagnostic; 2, limited diagnostic value with substantial image noise and artifacts; 3, diagnostic, sufficient image quality; 4, diagnostic, good image quality; 5, diagnostic, excellent image quality). Grading scores are statistically significant higher in cervical spinal CT with Sn140-kVp than 120-kVp by all three readers. Sn140-kVp = cervical spine CT using spectral shaping at 140 kVp by a tin filter, 120-kVp = cervical spine CT at 120 kVp

• 

  Fig. 4 Comparison of CT images obtained with Sn140-kVp or 120-kVp.A–C. Cervical spine CT with Sn140-kVp of 49-year-old woman with posterior neck pain (shoulder level, C7; shoulder width, 375 mm; neck diameter, 111 mm). D–F. Cervical spine CT with conventional CT with 120-kVp of 43-year-old woman with posterior neck pain (shoulder level, C7; shoulder diameter, 358 mm; neck diameter, 103 mm). B, C, E, and F are two consecutive axial images in level of C7/T1. In spite of similar body habitus of shoulder and neck between two patients, artifacts in lower cervical spinal levels are more severe in conventional scan than Sn140-kVp scan. Congenital blocked vertebrae of C5 and C6 is identified in D.

• 

  Fig. 5 Box-and-whiskers plots for noise inside central spinal canal.Noise is gradually increased from C3/4 to C7/T1 in both cervical spine CT scans with Sn140-kVp and 120-kVp. At level of C7/T1, noise in Sn140-kVp scans is significantly less than in conventional 120-kVp scans. Boxes represent medians and interquartile ranges and whiskers extend to 1.5 interquartile ranges. HU = Hounsfield units

• 

  Fig. 6 Box-and-whiskers plots for attenuation values inside central spinal canal.Attenuation gradually decreases from C3/4 to C7/T1 in both cervical spine CT scans with Sn140-kVp and 120-kVp. At level of C7/T1, attenuation in Sn140-kVp scans significantly less decreases than in 120-kVp scans.

• 

  Fig. 7 Box-and-whiskers plots for radiation dose.CTDIvol (A), DLP (B), and effective dose (C) are significantly reduced in cervical spine CT with Sn140-kVp. CTDIvol = volume CT dose index, DLP = dose length product

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