GE Healthcare (Waukesha, Wisconsin) provided research support for the implantation and application of the MAVRIC SL. This study was prospectively designed and approved by the Institutional Review Board of Inha University Hospital in accordance with the Declaration of Helsinki. Informed consent was obtained from all participating volunteers.
Volunteer enrollment and MRI scan
Eight volunteers (5 men, 3 women, mean age 50.88) who underwent ADR using Prodisc C (DePuy Sythes, Raynham, MA, USA) and had no recurrent cervical and radicular pain at our institution. ) would like to participate in the study. Written informed consent was obtained for all volunteers in accordance with the Institutional Review Board. Table 3 shows volunteer demographic data. Two volunteers underwent anterior interbody fusion before ADR because of cervical spondylotic myelopathy (Table 3). All volunteers underwent her MRI scans using her T2WI and MAVRIC SL T2 sequences in axial and sagittal directions. A 3 T MR system (Architect, General Electric, Waukesha, WI, USA) was used with head and neck coils. Scans covered the entire cervical bone structure in the sagittal plane and the surgical level in the axial plane. A calibration scan of the MAVRIC SL T2 was performed to determine the number of different spectral bins for each volunteer (between 16 and 24 in our study). The imaging parameters for the calibration scan are: Repetition time (TR)/echo time (TE), 2433.2/10. Receive Bandwidth (RBW), ± 125 kHz. Field of view (FOV), 40 cm. Acquisition matrix, 128×32. Section thickness (ST), 6 mm. echo train length (ETL), 16; Scan time, approximately 1 minute 57 seconds. Parallel imaging (data-driven parallel imaging reconstruction known as ARC, or auto-calibrated reconstruction for Cartesian imaging) was only applied to MAVRIC SL. A detailed MRI protocol is shown in Table 4.
After the MRI scan, the axial and sagittal image datasets for each sequence were relabeled to remove the original sequence name and randomized. Of the 8 volunteers, axial images of T2 and MAVRIC SL T2 of 1 volunteer (V5) were excluded from image analysis due to image quality.
Musculoskeletal radiologists used the Maroview PACS system (Maroview 5.4, Infinite, Seoul, Korea) for quantitative analysis of the area of the signal void in all axial and sagittal sequences. I measured the area of signal loss. ROIs were drawn around artifacts containing signal voids (including implants) for each image in all axial and sagittal T2WI and MAVRIC SL T2, and the areas of signal voids were summed.
Three musculoskeletal radiologists (one with 3 years experience, the other with 13 years experience) were trained to analyze image dataset geometric distortion, signal pileup, anatomical visualization, and Individually assessed for clinical utility.
A four-point scoring system was used to assess geometric distortion and signal pileup (Table 5).FourDistortion was defined as a change or disturbance in anatomical placement around the prosthesisFourSignal pile-up was defined as a peripheral rim of high signal intensity around the prosthesisFour.
A 5-point scoring system was used to assess anatomical visualization of the following structures: Appose the superior and inferior vertebral bodies at the surgical site in the sagittal plane (Table 5)Four.
Clinical utility was scored by the amount of information each sequence provided in determining common clinical questions regarding postoperative neck pain (Table 5). The clinical question was whether this sequence could provide sufficient information about the presence or absence of spinal cord and nerve root compression at the surgical level, disc herniation or bulge at the adjacent level, and spinal cord signal changes. All clinical questions were evaluated both axially and sagittal, except for disc herniation or bulging at the adjacent level, which was evaluated in the sagittal plane.
After 3 weeks of independent analysis, these 3 radiologists performed a second review of all image sets and rescored all qualitative variables in consensus for statistical analysis.
The total area of the signal void for each sequence in the axial and sagittal planes was tested using the Wilcoxon log-rank test. Weighted Cohen’s kappa statistics (k-value) was calculated to determine interobserver agreement. The strength of agreement, quantified by the kappa statistic, was graded as follows: 0.01 to 0.20, slight. 0.21–0.40, normal. 0.41 to 0.60, moderate. 0.61–0.80, substantial.and 0.81–1, near perfect12,13For comparisons between sequences, the Wilcoxon log-rank test was used to compare mean scores from consensus reads for qualitative analysis.
All statistical analyzes were performed using statistical software (MedCalc, version 10.4.0.0, MedCalc, Ostend, Belgium, SPSS 20, IBM, Armonk, NY).Statistical significance is p< 0.05 for all tests except weighted Cohen's kappa statistic.