eISSN 2384-1109
Open Access, Peer-reviewed
    Investig Magn Reson Imaging. 2022 Dec;26(4):284-293. English.
    Published online Dec 31, 2022.
    https://doi.org/10.13104/imri.2022.26.4.284
    Copyright © 2022 Korean Society of Magnetic Resonance in Medicine (KSMRM)
    Original Article

    Comparison of 2D Thin Section Dixon, 3D Isotropic SPACE, and 2D T2-Weighted Sequences in Ankle MRI

    Tae Ran Ahn,1,* Yu Mi Jeong,1,* Ji Young Jeon,1 So Hyun Park,1 and Sheen-Woo Lee2
      • 1Department of Radiology, Gil Medical Center, College of Medicine, Gachon University, Incheon, Korea.
      • 2Department of Radiology, The Catholic University of Korea, Eunpyeong St. Mary’s Hospital, Seoul, Korea.
    • Correspondence: Sheen-Woo Lee, MD, PhD. Department of Radiology, The Catholic University of Korea, Eunpyeong St. Mary’s Hospital, 1021 Tongil-ro, Eunpyeong-gu, Seoul 03312, Korea. Email: leesw1@gmail.com

      *These authors contributed equally to this work.
    Received January 05, 2022; Revised April 07, 2022; Accepted April 13, 2022.

    This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

    Abstract

    Purpose

    This study aimed to conduct a comparison between 2D thin section intermediate-weighted Dixon turbo spin echo (TSE), 3D intermediate-weighted SPACE (sampling perfection with application-optimized contrasts using flip angle evolutions) TSE, and 2D fat-suppressed T2-weighted TSE in terms of their image quality and diagnostic performance for ankle ligament evaluation.

    Materials and Methods

    Thirty-eight ankle MRI studies were retrospectively analyzed. The signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of the multiplanar reformation images of the sequences were obtained. For each sequence, the subjective image quality and the diagnostic performance for ankle ligament tear were analyzed.

    Results

    The Dixon demonstrated the highest CNR both between ligament and fluid and between ligament and bone marrow. The 3D SPACE showed the highest SNR of the ligament. Regarding subjective image quality, it was significantly higher in the T2-weighted image than it was in the SPACE (p < 0.05), while there was no significant difference between the Dixon and the SPACE. The Dixon showed the highest sensitivity for anterior talofibular ligament (ATFL) tear (80.0%; 95% confidence interval [CI], 64.4–92.3) and deep deltoid ligament (DL) tear (86.4%; 95% CI, 65.1–97.1), and it showed the highest specificity for ATFL tear (70.2%; 95% CI, 59.3–79.7). The interobserver agreement was moderate to good (intraclass correlation coefficient [ICC], 0.50–0.93) in most cases except for the SNR of deep DL (ICC of 0.35–0.62).

    Conclusion

    For ankle ligament evaluation, the 2D thin section Dixon provides adequate image quality with high SNR and CNR and the highest sensitivity for detecting tears.

    Keywords
    Magnetic resonance imaging; Ankle; 3D; Dixon, Isotropic imaging

    INTRODUCTION

    The ankle joint has a complex anatomy with three articulations. Thus, injuries of the ankle ligament represent common musculoskeletal traumas [1]. In clinical practice, magnetic resonance imaging (MRI) examination of the ankle ligament is often the diagnostic tool of choice [2].

    High-resolution 3D isotropic MRI enables thin section and arbitrary multiplanar reformation (MPR) for the evaluation of complex joints. 3D MRI is also useful for detecting ligamentous or tendinous injuries and small cartilage defects of the ankle joint. There are certain cases in which 3D sequences can replace various 2D acquisition techniques to reduce the imaging time [3, 4]. Nevertheless, 3D isotropic MRI faces various limitations, with the most prominent including image blurring due to the long echo train length, difficult evaluation of bone marrow, and long acquisition time [4, 5, 6]. Ristow et al. [6] found that low-contrast targets such as bone marrow exhibit lower imaging quality on 3D sequences than on 2D turbo spin echo (TSE) sequences. This causes bone marrow to appear indistinct and noisy in 3D images, which hinders the visualization of related lesions. Further, the long acquisition time of a 3D sequence intensifies motion artifacts and radiofrequency power deposition (specific absorption rate) [5].

    The Dixon method is a fat-suppression technique that is based on chemical shift and has various advantages over similar techniques. These advantages include uniform and robust fat suppression, the possibility of combination with various types of sequences (e.g., gradient echo, spin echo, and steady-state free precession sequences) and diverse weighting (T1, T2, proton density, and intermediate weighting), and the availability of images with and without fat suppression from a single acquisition [7, 8]. In musculoskeletal MRI, as fat suppression is important for detecting pathologic lesions, the Dixon method is increasingly being used for uniform and robust fat suppression [9, 10].

    In our institution, the 3D SPACE (sampling perfection with application-optimized contrasts using flip angle evolutions) sequence is routinely used for ankle MRI examinations of joint derangement. However, the SPACE sequence often produces an image with a deteriorated image quality due to inhomogeneous fat suppression of soft tissue, including Kager fat pad and bone marrow.

    The hypothesis of our study is that 2D fluid-sensitive sequences—in particular, those with submillimeter thickness without interslice gap—may be arbitrarily reformatted to depict the anatomy of interest while achieving sufficient SNR, CNR, and diagnostic quality. To test this, we compared the image qualities of ankle MRI between the sequences of 2D thin section Dixon TSE, 3D SPACE TSE, and 2D fat-suppressed (FS) T2-weighted TSE in terms of the signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of the ligaments in the ankle joint. We additionally evaluated the subjective image quality and diagnostic performance of each sequence for ligament tear in the ankle.

    MATERIALS AND METHODS

    Patients

    This retrospective study was approved by the Institutional Review Board of Gil Medical Center (IRB file no. GCIRB2021-171), and the requirement for written consent was waived. The data in this study included imaging results from 41 consecutive patients who had undergone non-contrast ankle MRI using 2D thin section Dixon, 3D SPACE, and 2D FS T2-weighted TSE sequences from November 2017 to February 2018. Of these 41 patients, we excluded 2 due to a very thin measurable ligament or a lack thereof and 1 patient due to poor MRI quality. As a result, 38 patients and their corresponding MRI examinations were ultimately included for evaluation in this study. These 38 patients included 14 men and 24 women (age range, 12–72 years; mean age, 50.1 years).

    MRI Protocol

    All MRI examinations were performed on a 3-T scanner (Magnetom Skyra or Magnetom Vida; Siemens Healthcare, Erlangen, Germany) with a dedicated 16-channel receive-only foot and an ankle coil. Conventional 2D MRI was performed followed by 2D thin section Dixon sequence and 3D isotropic SPACE sequence; the MRI protocol is detailed in Table 1. MRI was performed with the patient in the supine and the foot in the neutral position for three orthogonal planes: axial, coronal, and sagittal. The axial images were acquired from approximately 3–4 cm above the tibiotalar joint to the plantar fascia; the coronal images were obtained parallel to the malleolar axis on the axial image; and the sagittal images were obtained perpendicular to the malleolar axis, including the medial and lateral malleoli. Meanwhile, the 2D Dixon images and 3D SPACE images were acquired on the sagittal plane. One radiologist reformatted the original sagittal Dixon and SPACE images into axial images using Syngo.via VB20 software (Siemens Healthcare).

    Table 1
    Comparison of Image Parameters of Three MRI Sequences

    MRI Analysis

    Three radiologists with 16, 11, and 3 years of experience in musculoskeletal imaging independently evaluated the reformatted axial images of the water-only image from the 2D thin section Dixon, 3D SPACE, and original axial 2D FS T2-weighted sequences. They evaluated one set of images (three sequences) per session. They were blinded to clinical information about the patients, including information about their physical examinations and surgical results. The image sets were analyzed using a picture archiving and communication system (PACS, INFINITT Healthcare, Seoul, Korea) and a multimodality workstation (Syngo.via VB20 software).

    SNR and CNR

    For the evaluation of SNR and CNR, we compared the 2D thin section Dixon and 3D SPACE sequences. The signal intensities from the anterior talofibular ligament (ATFL), deep deltoid ligament (DL), synovial fluid, bone marrow, and background noise were measured in all patients in the circular regions of interest in each of the representative central slice of ATFL, deep DL, subtalar joint, talus, and air region anterior to the tibiotalar joint. The diameter of each region of interest was at least 2 mm. We did not analyze the superficial DL group because it was too thin for the region of interest to be depicted. The SNR of the index structure was defined as the signal power for a given region of interest divided by the noise power, which was measured as the standard deviation of the background air region [11]. The CNR was defined as the difference between the signals for two types of tissues. The readers calculated the SNR of the ATFL and DL and the CNR between the ATFL and bone marrow, between the DL and bone marrow, between the ATFL and synovial fluid, and between the DL and synovial fluid.

    Subjective Image Quality

    For the evaluation of subjective image quality, we compared the 2D thin section Dixon, 3D SPACE, and 2D FS T2-weighted sequences. The image sets were assessed for subjective image quality in terms of the following 5-point scale: i) Excellent image quality (5): ligament fibers sharply delineated from joint fluid and adjacent bone marrow, minimal image blurring, and minimal artifacts; ii) Good image quality (4): one or two of the criteria for score 5 being below optimal; iii) Fair image quality (3): three of the criteria for score 5 being below optimal but not affecting the diagnostic quality of the image; iv) Below average image quality (2): mild limitation for ligament evaluation; and v) Poor image quality (1): severe limitation for ligament evaluation due to extensive image blurring or artifacts.

    Diagnostic Performance

    For the evaluation of diagnostic performance, we compared the 2D thin section Dixon, 3D SPACE, and 2D FS T2-weighted sequences. The radiologists analyzed the images and classified the ATFL and deep DL as being either not-torn or torn (complete, partial) for each sequence. The readers were blinded to clinical information (e.g., physical examination, surgical results) and radiologic reports. We defined ligament tear as the presence of any of the following conditions: fiber detachment, discontinuity, thickening, thinning, irregular contour, heterogeneous or increased signal intensity in ATFL, and loss of normal striation in deep DL [12, 13]; full thickness discontinuity of the ligament was classified as a complete tear. In the analysis of the 2D Dixon and 3D SPACE sequences, MPR was performed if necessary.

    Statistical Analysis

    The interobserver agreements of SNR and CNR in the ankle joint structures were calculated using the intraclass correlation coefficient (ICC), with values below 0.50 indicating poor agreement, values between 0.50 and 0.75 indicating moderate agreement, values between 0.75 and 0.90 indicating good agreement, and values above 0.90 indicating excellent agreement [14].

    The subjective image qualities between the two sequences were compared using one-way analysis of variance with post hoc Bonferroni correction for multiple comparisons.

    The diagnostic performance was evaluated in terms of pooled sensitivity and pooled specificity for diagnosing ATFL and deep DL tear using a 95% confidence interval (CI) per sequence. The interobserver agreements for detecting ATFL and deep DL tears were calculated using the ICC, with values below 0.50 indicating poor agreement, values between 0.50 and 0.75 indicating moderate agreement, values between 0.75 and 0.90 indicating good agreement, and values above 0.90 indicating excellent agreement [14].

    A p-value below 0.05 was considered to be statistically significant. The statistical procedures were conducted using the MedCalc software (version 15.8; MedCalc Software, Ostend, Belgium) or SPSS software (version 22.0; IBM, Armonk, NY, USA).

    RESULTS

    The highest CNR values between the ligament and fluid and between the ligament and bone marrow were achieved by the 2D thin section Dixon sequence, followed by the 3D SPACE sequence. Meanwhile, the 3D SPACE sequence showed superior SNR for the ligament than the 2D thin section Dixon sequences (Table 2 and Figs. 1, 2, 3). There was moderate to good agreement in the CNRs provided by the three readers between ligament and bone marrow (ICC, 0.587–878), between ligament and fluid (ICC, 0.705–0.926), and in the SNR of the ATFL (ICC, 0.635–0.760). By contrast, the SNR for the deep DL showed poor to moderate agreement (ICC, 0.349–0.620) between the readers.

    Fig. 1
    Average SNR (A) and CNR (B) of 2D thin section Dixon, 3D SPACE, and 2D FS T2-weighted sequences. SNR, signal-to-noise ratio; CNR, contrast-to-noise ratio; SPACE, sampling perfection with application-optimized contrasts using flip angle evolutions; FS, fat-suppressed; ATFL, anterior talofibular ligament; DL, deltoid ligament.

    Fig. 2
    Normal ATFL of left ankle in 68-year-old man. Images from axial reformatted 2D thin section Dixon (A), axial reformatted 3D SPACE (B), and original axial 2D FS T2-weighted (C) sequences. The average SNR values of ATFL were 10.9 for the Dixon, 46.9 for the SPACE, and 7.4 for the FS T2-weighted sequences. The average CNR values of ATFL to bone marrow were 107.4 for the Dixon, 79.62 for the SPACE, and 33.4 for the FS T2-weighted sequences. The CNR values of ATFL to synovial fluid were 1683 for the Dixon, 341 for the SPACE, and 756.2 for the FS T2-weighted sequences. The average subjective image quality of each sequence was 4.7, 4, and 5, respectively. ATFL, anterior talofibular ligament; SPACE, sampling perfection with application-optimized contrasts using flip angle evolutions; FS, fat-suppressed; SNR, signal-to-noise ratio; CNR, contrast-to-noise ratio.

    Fig. 3
    Normal deep DL of left ankle in 68-year-old man. Images from axial reformatted 2D thin section Dixon (A), axial reformatted 3D SPACE (showing inhomogeneous fat suppression in anterior subcutaneous fat tissue) (B), and original axial 2D FS T2-weighted (C) sequences. The average SNR values of the deep DL were 26.2 for the Dixon, 86.5 for the SPACE, and 11.5 for the FS T2-weighted sequences. The average CNR values of the deep DL to bone marrow were 488.7 for the Dixon, 166.5 for the SPACE, and 101.9 for the FS T2-weighted sequences. The average CNR values of the deep DL to synovial fluid were 1250.1 for the Dixon, 254.1 for the SPACE, and 687.7 for the FS T2-weighted sequences. The average subjective image quality of each sequence was 5, 4.3, and 5, respectively. DL, deltoid ligament; SPACE, sampling perfection with application-optimized contrasts using flip angle evolutions; FS, fat-suppressed; SNR, signal-to-noise ratio; CNR, contrast-to-noise ratio.

    Table 2
    Average SNR and CNR of Dixon and SPACE Sequences

    The three readers scored the subjective image quality of the ligaments in all cases as 3–5 (fair to excellent); there were no grades of poor or below average image quality (scores of 1 or 2) for the ankle ligament on the three MRI sequences. The 2D FS T2-weighted sequence provided the highest subjective image quality for the ATFLs and deep DLs according to the three readers (p < 0.05). There was no significant difference between the 2D thin section Dixon and 3D SPACE sequences in terms of the subjective image quality for the ATFL (p > 0.5) (Table 3).

    Table 3
    Subjective Image Quality of Ankle Ligament on Each MRI Sequence by Three Readers

    Among the 38 cases considered, there were 10 ATFL tears and 9 deep DL tears (Figs. 4 and 5). Of these, two ATFL tears and two deep DL tears were confirmed surgically whereas the remaining tears were confirmed clinically and/or by using another image modality, such as stress test by X-ray or ultrasound (Table 4). Ankle stress X-ray was performed with the aid of the stress-testing device Telos (Telos, Griesheim, Germany). The diagnostic criteria of ATFL tear on stress X-ray was a side-by-side difference of 3 mm or greater of the anterior translation of talus on lateral X-ray, while the diagnostic criteria of deep DL tear was a side-by-side difference of greater than 2° valgus talar tilt on anteroposterior X-ray. Meanwhile, the diagnostic criteria of the ligament (ATFL, deep DL) tear on ultrasound were: 1) discontinuity of ligament and 2) hypoechoic lesion within the ligament. The 2D thin section Dixon sequence showed the highest sensitivity in evaluating the ATFL (80.0%; 95% CI, 64.4–92.3) and deep DL (86.4%; 95% CI, 65.1–97.1), the highest specificity in evaluating ATFL tear (70.2%; 95% CI, 59.3–79.7), and moderate specificity in evaluating deep DL tear (74.7%; 95% CI, 64.5–83.3) (Table 5). For the detection of ligament tear, interobserver agreements were moderate for all cases, except for the SPACE sequence for deep DL evaluation (Table 6).

    Fig. 4
    Partial tear in ATFL of right ankle in 25-year-old woman. Images from axial reformatted 2D thin section Dixon (A), axial reformatted 3D SPACE (B), and original axial 2D FS T2-weighted (C) sequences showing focal full thickness disruption with intervening fluid gap in central portion of ATFL (white arrow). All readers diagnosed this lesion correctly. The average subjective image quality of each sequence was 4.7, 4.7, and 5, respectively. This patient underwent the Broström operation. ATFL, anterior talofibular ligament; SPACE, sampling perfection with application-optimized contrasts using flip angle evolutions; FS, fat-suppressed.

    Fig. 5
    Complete tear in deep DL of right ankle in 16-year-old man with trimalleolar fracture. Images from axial reformatted 2D thin section Dixon (A), axial reformatted 3D SPACE (B), and original axial 2D FS T2-weighted (C) sequences showing complete disruption of deep DL (posterior tibiotalar) and irregular contour of visible fibers (white arrow), which are retracted. Superficial DL disruption (thin white arrow) is also noted. All readers diagnosed this lesion correctly. The average subjective image quality of each sequence was 4.3, 4, and 4.7, respectively. This patient underwent internal fixation for trimalleolar fracture and conservative treatment for deep DL tear. DL, deltoid ligament; SPACE, sampling perfection with application-optimized contrasts using flip angle evolutions; FS, fat-suppressed.

    Table 4
    Clinical Diagnosis of ATFL and Deep DL

    Table 5
    Diagnostic Performance of Ankle Ligament Injury on Each MRI Sequence

    Table 6
    Interobserver Agreement (ICC) of Ligament Tear

    DISCUSSION

    This study compared the image quality and diagnostic performance between 2D thin section Dixon, 2D FS T2-weighted, and 3D SPACE sequences in ankle ligaments. The 2D thin section Dixon demonstrated the highest CNR. The 2D FS T2-weighted sequence provided a higher subjective image quality than the 2D thin section Dixon or 3D SPACE. The 2D thin section Dixon showed the best sensitivity of ankle ligament tear detection. The specificity of ligament tear detection varied according to the type of sequence and ligament (ATFL or deep DL). The 3D SPACE sequence only showed the best performance in the SNR.

    The ATFL is the most injured ligament in the ankle joint, and DL injuries are often associated with injury to other ligaments or malleolar fractures. ATFL is the primary restraint to inversion in plantar flexion, and the deep DL is the primary medial stabilizer against valgus forces and anterior/lateral talar excursion [15]. In MRI, a normal ATFL appears as a homogeneously low signal intensity on T1-weighted, T2-weighted, and proton-density-weighted sequences, and it is typically seen on a single axial image [16]. Meanwhile, the deep DL has a striated appearance on T1-weighted and intermediated-weighted sequences due to interspersed fat; this appearance is less conspicuous on the T2-weighted sequence, especially on the FS sequence [17, 18, 19]. On MRI, an injured ligament may exhibit fiber detachment, discontinuity, thickening, thinning, irregular contour, heterogeneous or increased signal intensity, a bright rim sign for the ATFL [20], loss of normal striation for deep DL [17], or an associated bony avulsion [12, 13].

    The treatment of ankle ligament tear depends on the severity of the injury, functional instability, and clinical symptoms such as persistent pain or swelling. Ankle ligament injuries are generally treated conservatively [21, 22, 23]. In our study population, out of the 10 patients with ATFL tear, 2 underwent surgical treatment whereas the remaining 8 underwent conservative treatment. All 9 patients with deep DL tear were treated conservatively.

    Several clinical studies have compared image quality and diagnostic performance between 3D and 2D sequences in musculoskeletal imaging, with the 3D sequence often showing superior or comparable indicators to the 2D sequence for detecting small structures (e.g., triangular fibrocartilage complex, Lisfranc ligament, neural foramen, cuboid groove of peroneus tendon) [24, 25, 26, 27]. However, the 2D sequence has shown higher performance than the 3D sequence in low-contrast structures (e.g., bone marrow, menisci) [6]. For ankle ligaments, Notohamiprodjo et al. [28] reported a lower SNR in the 3D sequence using SPACE than in the 2D TSE sequence for ATFL evaluation.

    In our study, the 2D thin section Dixon sequence provided suitable image quality and diagnostic performance with the available MPR. The corresponding images were also obtained with a similar image acquisition time to those obtained using the 3D SPACE sequence. Musculoskeletal MRI protocols are typically composed of non-FS scans to evaluate the morphology and FS scans to increase the clarity of processes such as acute trauma and inflammation. As the Dixon sequence provides both non-FS and FS data from a single acquisition, it may conveniently replace various types of sequences, including 3D sequences. Additional studies on other body parts and structures are required for confirmation. In ankle MRI, fat suppression is often inhomogeneous under chemical-shift selective imaging; however, the Dixon sequence reliably provides uniform fat suppression in the heel, Kager’s fat pad, and tarsal bones. Therefore, the Dixon sequence has excellent diagnostic ability when applied to Kager’s fat pad pathology or stress fracture of tarsal bones. Nevertheless, the Dixon sequence has various limitations: It leads to artifacts in highly heterogeneous magnetic fields, such as cases involving the interference of metallic hardware. There is also fat-water swapping, which is a Dixon-specific artifact that is associated with insensitivity to B1 inhomogeneity and sensitivity to inhomogeneity in main magnetic field B0 due to phase-shift errors [8]. Regarding fat fraction, some sclerotic fat-containing marrow lesions—such as myelofibrosis, compacted bone in healing fracture, atypical hemangioma, and Paget’s disease—have exhibited insufficient signal decrease on Dixon opposed image, which could potentially cause false positives during diagnosis [10, 29]. Overall, a thorough understanding of the Dixon sequence is required for accurate diagnosis.

    The 3D SPACE sequence exhibited poor pooled sensitivity (45.5%; 95% CI, 24.4–67.8) in detecting deep DL tear in our study. Normally, the posterior tibiotalar ligament of the deep DL, which is the thickest medial ligament, shows striation on MRI due to the intervening fat separating the ligament fascicles. Therefore, loss of striation in the deep DL is indicative of ligament injury [16, 17, 18]. However, in an FS image, the normal striation may not be clearly visible, and a low-grade tear may be overlooked. Another possible explanation is the blurring effect, which is often seen in 3D sequences; as ankle ligaments are small, tear diagnosis may be particularly affected by blurring [30].

    This study has various limitations. First, we used parallel imaging to reduce the image acquisition time; since the noise is not spatially constant, this deteriorates the reproducibility according to location, and the accuracy of SNR might decrease as a result. Second, our study population excluded healthy people, focusing only on a small number of symptomatic patients. Third, the readers could not be blinded to the sequence type. Thus, reader bias may have influenced the image quality evaluation. Fourth, the study included a small number of surgically confirmed cases. Finally, the 2D Dixon sequence is not entirely isotropic, so the SNR of the MPR image may not be the same as that of the original image.

    The 2D thin section Dixon sequence provided the highest CNR in ankle ligament evaluation. Regarding the diagnostic performance of ankle ligament tear, the 2D Dixon sequence showed suitable sensitivity and specificity and comparable scan time to the 3D SPACE sequence. Therefore, when bone marrow evaluation and ligament evaluation are both required in ankle MRI, using MPR from the 2D thin section Dixon sequence appears to be more convenient than using the 3D SPACE sequence.

    Notes

    Conflicts of Interest:The authors have no potential conflicts of interest to disclose.

    Author Contributions:

    • Conceptualization: Sheen-Woo Lee.

    • Data curation: Sheen-Woo Lee, Tae Ran Ahn.

    • Formal analysis: Sheen-Woo Lee, Yu Mi Jeong, So Hyun Park, Tae Ran Ahn.

    • Investigation: Sheen-Woo Lee, Yu Mi Jeong, Tae Ran Ahn.

    • Methodology: Sheen-Woo Lee, Tae Ran Ahn.

    • Project administration: Sheen-Woo Lee, Yu Mi Jeong, Tae Ran Ahn.

    • Resources: Sheen-Woo Lee, Yu Mi Jeong, Ji Young Jeon, Tae Ran Ahn.

    • Software: Sheen-Woo Lee, Yu Mi Jeong, Tae Ran Ahn.

    • Supervision: Sheen-Woo Lee.

    • Validation: Sheen-Woo Lee.

    • Visualization: Tae Ran Ahn.

    • Writing—original draft: Sheen-Woo Lee, Yu Mi Jeong, Tae Ran Ahn.

    • Writing—review & editing: Sheen-Woo Lee, Yu Mi Jeong, Tae Ran Ahn.

    • Approval of final manuscript: all authors.

    Funding Statement:None

    Availability of Data and Material

    The datasets generated or analyzed during the study are not publicly available due the images containing information that could compromise the privacy of research participants, but are available from the corresponding author on reasonable request.

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    MeSH Terms
    Ankle*
    Bone Marrow
    Ligaments
    Magnetic Resonance Imaging*
    Retrospective Studies
    Sensitivity and Specificity
    Signal-To-Noise Ratio
    Tears
    Metrics
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