Investig Magn Reson Imaging.  2018 Dec;22(4):209-217. 10.13104/imri.2018.22.4.209.

Susceptibility Weighted Imaging of the Cervical Spinal Cord with Compensation of Respiratory-Induced Artifact

• Lee H
• Nam Y
• Gho SM
• Han D
• Kim EY
• Lee SW
• Kim DH

• KMID: 2431105
• DOI: http://doi.org/10.13104/imri.2018.22.4.209

Abstract

PURPOSE
The objective of this study was to obtain improved susceptibility weighted images (SWI) of the cervical spinal cord using respiratory-induced artifact compensation.
MATERIALS AND METHODS
The artifact from B0 fluctuations by respiration could be compensated using a double navigator echo approach. The two navigators were inserted in an SWI sequence before and after the image readouts. The B0 fluctuation was measured by each navigator echoes, and the inverse of the fluctuation was applied to eliminate the artifact from fluctuation. The degree of compensation was quantified using a quality index (QI) term for compensated imaging using each navigator. Also, the effect of compensation was analyzed according to the position of the spinal cord using QI values.
RESULTS
Compensation using navigator echo gave the improved visualization of SWI in cervical spinal cord compared to non-compensated images. Before compensation, images were influenced by artificial noise from motion in both the superior (QI = 0.031) and inferior (QI = 0.043) regions. In most parts of the superior regions, the second navigator resulted in better quality (QI = 0.024, P < 0.01) compared to the first navigator, but in the inferior regions the first navigator showed better quality (QI = 0.033, P < 0.01) after correction.
CONCLUSION
Motion compensation using a double navigator method can increase the improvement of the SWI in the cervical spinal cord. The proposed method makes SWI a useful tool for the diagnosis of spinal cord injury by reducing respiratory-induced artifact.

Keyword

SWI; Cervical spinal cord; Motion compensation; Respiratory-induced artifact; Navigator echo

MeSH Terms

Artifacts*
Cervical Cord*
Compensation and Redress*
Diagnosis
Methods
Noise
Qi
Respiration
Spinal Cord
Spinal Cord Injuries

Figure

• 

  Fig. 1 Pulse sequence diagram including two navigator echoes and imaging echoes.

• 

  Fig. 2 GRE images and phase of the navigator signal from representative slices. The value shown in the image means QI. The 12th slice (top, C3 level) shows the good result when compensation using the second navigator echo data is used. The 10th slice (middle, C4 level) shows similar compensation between the first and second navigator, which is supported from the plot of the phase navigator signal (right). The 5th slice (bottom, C6 level) shows better compensation when the first navigator data is used for correction.

• 

  Fig. 3 Representative magnitude, phase, and SWI showing (a) before compensation and (b) after compensation of respiratory-induced artifact. The blue boxes indicate better corrected images when using the first navigator, and the red boxes indicate better corrected images when using the second navigator as determined by the QI factors.

• 

  Fig. 4 Comparison of the QI value for the (a) superior part (C1–C4) and (b) inferior part (C5–C7) of the cervical spinal cord from the 5 volunteers. Top and bottom of each box are the 25th and 75th percentiles of the samples, respectively. The line in the middle of each box represents the sample median, and the cross represents the mean value. The whisker line shows adjacent values. Asterisks indicate P < 0.005.

• 

  Fig. 5 GRE images (a, c) and SWI (b, d) of uncorrected and corrected images using the proposed respiratory noise compensation method. (a, b) Tumor patient and (c, d) hemorrhagic patient. The yellow arrows indicate microhemorrhage or vascular structures containing deoxyhemoglobin. The red arrows indicate hemorrhage lesion.

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