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Intervertebral disc herniation is frequently encountered in radiological practice. Sequestered disc herniation occurs when the disc material undergoes degeneration and completely loses continuity with the parent nucleus pulposus. Sequestered discs can reside within and outside the spinal canal, exerting a mass effect on adjacent structures, compressing nerve pathways, and eliciting a range of clinical symptoms. In particular, sequestered discs within the dura cannot be identified without durotomy. Therefore, precise preoperative localization is crucial for surgical planning. On MRI, the signal intensity of the sequestered disc may vary due to independent degeneration processes. Additionally, most sequestered disc fragments show varying degrees of peripheral enhancement depending on the degree of angiogenesis and granulation around the isolated tissue. In this article, we review various imaging findings and the location of the sequestered disc to provide patients with an accurate diagnosis and appropriate treatment direction., Competing Interests: Conflicts of Interest: The authors have no potential conflicts of interest to disclose., (Copyrights © 2024 The Korean Society of Radiology.)

Metallic artifacts on MR imaging are typically induced by differences in magnetic susceptibility between the metallic implant and surrounding tissue. Conventional techniques for metal artifact reduction require MR machines with low field strength, shift in the frequency-encoding and phase-encoding directions according to the axis of metallic implant, increased receiver bandwidth and matrix, decreased slice thickness, and utilization of the short tau inversion recovery or Dixon method for fat-suppression. Slice-encoding for metal artifact correction and multi-acquisition variable-resonance image combination can dramatically reduce the number of metallic artifacts. However, these sequences have a considerably long acquisition time. Furthermore, the recently developed acceleration techniques including compressed sensing can solve this problem., Competing Interests: Conflicts of Interest: The authors have no potential conflicts of interest to disclose., (Copyrights © 2020 The Korean Society of Radiology.)