• Imaging Science in Dentistry
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• v.52 no.4
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• pp.409-413
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• 2022

This report presents a rare case where a displaced temporomandibular joint (TMJ) disc was reduced to its normal position after orthognathic surgery, and long-term magnetic resonance imaging (MRI) follow-up visualized these postoperative changes. A 22-year-old male patient presented for facial asymmetry. He also complained of pain in the right TMJ area, and MRI showed disc displacements in both TMJs. After orthognathic surgery for facial asymmetry correction, the TMJ was re-evaluated. The symptom had resolved and the disc was positioned within the normal range during mouth opening. However, 6 and a half years after surgery, he complained of recurrent pain in the right joint, and MRI revealed medial disc displacement in the right TMJ. In conclusion, the influence of orthognathic surgery on the disc position might continue for a long time until the TMJ adapts to the new position. Careful and long-term follow-up is suggested to assess the TMJ complex.

• Korean Journal of Radiology
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• v.22 no.4
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• pp.547-558
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• 2021

The perihepatic space is frequently involved in a spectrum of diseases, including intrahepatic lesions extending to the liver capsule and disease conditions involving adjacent organs extending to the perihepatic space or spreading thanks to the communication from intraperitoneal or extraperitoneal sites through the hepatic ligaments. Lesions resulting from the dissemination of peritoneal processes may also affect the perihepatic space. Here we discuss how to assess the perihepatic origin of a lesion and describe the magnetic resonance imaging (MRI) features of normal structures and fluids that may be abnormally located in the perihepatic space. We then review and illustrate the MRI findings present in cases of perihepatic infectious, tumor-related, and miscellaneous conditions. Finally, we highlight the value of MRI over computed tomography.

• Korean Journal of Radiology
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• v.22 no.2
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• pp.198-212
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• 2021

Placenta accreta spectrum (PAS) is an abnormal placental adherence or invasion of the myometrium or extrauterine structures. As PAS is primarily staged and managed surgically, imaging can only guide and facilitate diagnosis. But, imaging can aid in preparations for surgical complexity in some cases of PAS. Ultrasound remains the imaging modality of choice; however, magnetic resonance imaging (MRI) is required for evaluation of areas difficult to visualize on ultrasound, and the assessment of the extent of placenta accreta. Numerous MRI features of PAS have been described, including dark intraplacental bands, placental bulge, and placental heterogeneity. Failure to diagnose PAS carries a risk of massive hemorrhage and surgical complications. This article describes a comprehensive, step-by-step approach to diagnostic imaging and its potential pitfalls.

• Korean Journal of Radiology
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• v.20 no.6
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• pp.894-908
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• 2019

Kidney transplantation is the treatment of choice for patients with end-stage renal disease, as it extends survival and increases quality of life in these patients. However, chronic allograft injury continues to be a major problem, and leads to eventual graft loss. Early detection of allograft injury is essential for guiding appropriate intervention to delay or prevent irreversible damage. Several advanced MRI techniques can offer some important information regarding functional changes such as perfusion, diffusion, structural complexity, as well as oxygenation and fibrosis. This review highlights the potential of multiparametric MRI for noninvasive and comprehensive assessment of renal allograft injury.

• Investigative Magnetic Resonance Imaging
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• v.16 no.1
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• pp.16-24
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• 2012

Purpose : The purpose of this study was to determine whether there is a significant correlation between vertebral marrow fat fraction measured using Dixon quantitative chemical shift MRI (QCSI) and BMD on dual-energy X-ray absorptiometry (DXA). Materials and Methods: This retrospective study included 68 healthy individuals [mean age, 50.7 years; range, 25-76; male/female (M/F) = 36/32] who underwent DXA of the L-spine and whole body MRI including QCSI of the L-spine and chemical shift MRI of the liver. The enrolled individuals were divided into subgroups according to sex and T-score [i.e., normal bone density (M/F=27/23) and osteopenia (M/F=9/9)]. Vertebral marrow (Dixon QCSI, TR/TE 10.2/4.8 ms) and hepatic fat fractions (chemical shift technique, TR/TE 110/4.9 and 2.2 ms) were calculated on MRI. We evaluated whether there were significant differences in age, body mass index (BMI), vertebral marrow fat fraction, or hepatic fat fraction among the subgroups. Whether or not the participant had reached menopause was also evaluated in females. The correlations among variables (i.e., age, BMI, vertebral marrow and hepatic fat fractions, BMD) were evaluated using Spearman's correlation method. Results: There were no significant differences in age, BMI, or vertebral marrow and hepatic fat fractions between the two male subgroups (normal bone density vs. osteopenia). In female subjects, mean age in the osteopenic subgroup was greater than that in the normal subgroup (p=0.01). Presence of menopause was more common in the osteopenic subgroup [77.8% (7/9)] than the normal subgroup [26.1% (6/23), p<0.05]. The other variables showed no significant difference between female subgroups. The only significant correlation with marrow fat fraction after partial correlation analysis was that with age in the female subjects (r=0.43, p<0.05). Conclusion: The vertebral marrow fat fraction calculated using the Dixon QCSI does not precisely reflect the mild decrease in BMD for either sex.

• Journal of the Institute of Convergence Signal Processing
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• v.4 no.2
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• pp.1-6
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• 2003

The study is to automatically or semi-automatically detect the accurate contour of tumors or lesions using active contour models (Snakes) in the MRI images of the brain. In the study we have improved the energy-minimization problem of snakes using dynamic programming and have utilized the values of the canny edge detector by the image force to make the snake less sensitive in noises. For the extracted boundary, the inside area, the perimeter and its center coordinates could be calculated. In addition, the multiple 2D slices with the contour of the lesion wore combined to visualized the shape of the lesion in 3D. We expect that the proposed method in this paper will be useful to make a treatment plan as well as to evaluate the treatments.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.11 no.6
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• pp.42-47
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• 2012

Followed by a paper on the Pig and Bone orthopedic prosthetic, this experiment using Phantom and Bone MRI imaging I, II of orthopedic prosthetic metal effect combines magnetic resonance imaging on metal signal-to-noise ratio(Signal to noise : SNR) and CNR(Contrast to noise: CNR), fat signal suppression(Fat-suppression) images was compared. Specimen trees to measure the reliability of the experimental reproducibility tests and statistical analysis using the SPSS statistical package was applied program SPSS(IBM SPSS Statistice 19) by * P = 0.000 < significance level $({\alpha})$ = 0.01 as a significant there was a correlation(** P < 0.01). SNR and CNR results did not directly proportional to the Titanium, Stainless, Clip CNR and fat signal suppression of the order of images of blood specimens was found to be close to the image. The impact of orthopedic prosthetic metals on magnetic resonance imaging in the diagnostic value of Titanium is relatively high and are meant more.

• Journal of Biomedical Engineering Research
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• v.22 no.5
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• pp.385-392
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• 2001

This study Proposes a quadrature-typed inside-out receiver coil to obtain magnetic resonance(MR) images of lumen wall. This means that the coil should receive the signals from out-side of receiver coil. This coil has wide and uniform sensitive region to compare with previous coils such as anti-solenoid coil, octal-pole coil and so on. These coils have the disadvantages that sensitive region is narrow and inhomogenous. The proposed coil is consist of two saddle coils of which directions are orthogonal to one another. The sensitivity maps of octal-Pole coil single-saddle coil and quadrature-typed inside-out coil were obtained by computer simulation. And phantom images for each coil were obtained to evaluate the performances of the coil using both 1.5T superconducting and 0.3 Permanent magnet MRI system. The uniformity of quadrature coil's sensitivity map was superior to that of octal-polel coil. Experimentally measured SNR of quadrature coil is also 36% higher than that of single-saddle coil This study shows the possibility of quadrature-typed inside-out receiver coil for the MR lumen wall images.

• Journal of the Korean Society of Radiology
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• v.10 no.4
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• pp.241-246
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• 2016

The purpose of this study was to investigate the problems of low signal-to-noise ratio(SNR) of single-shot turbo spin echo(SS-TSE) by quantifying numerically decreased signal to noise ratio. Thirty five patients without brain disease underwent diffusion MRI in 3T scanner from July to October in 2015. Single shot echo planar imaging(SS-EPI) which is conventionally used in MRI was taken to compared SS-TSE in SNR of medulla oblongata. As a result, SNR of SS-TSE diffusion(b0=$314.41{\pm}42.96$, b1000=$117.33{\pm}14.04$) is than SS-EPI diffusion(b0=$514.84{\pm}48.97$, b=$208.65{\pm}25.70$) lower in b=0 image(38.9%) and b=1,000 image(43.8%). Thus, diffusion MR using SS-EPI of MS-EPI should be taken for diagnosis of disease in brain stem due to decreased SNR of diffusion using SS-TSE.

• The Journal of the Korean bone and joint tumor society
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• v.9 no.2
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• pp.148-154
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• 2003

Purpose: To correlate the significant MRI findings and histologic features of the Schwannoma of the extremities and to review the clinical characteristic and the result of the surgical enucleation. Materials and Methods: 67 patients with pathologically proven Schwannoma of the extremities, who were surgically treated at our institutes between January 1996 and June 2002, were selected for this study. The clinical records, EMG, MRI and histologic findings were reviewed. Age of the patients ranged from 8 to 75 years with average of 44.7 years. Mean follow-up period was 9.7 months with raging from 3 months to 46 months. Results: On MRI, Schwannoma shows a well-demarcated fusiform mass with a low to intermediate signal intensity on T1-weighted images and high signal intensity on T2-weighted images, which is connected to parent nerve. A target pattern with peripheral hyperintensive rim and central low intensity on T2-weighted images was seen in 6 cases (15%), and fasciculation pattern with inhomogenous intensity in the hyperintensity on T2-weighted images was observed in 24 cases (62%). Various degree of cystic degeneration was discovered in 25 cases (64%). Postoperative complications include tingling sense or radiating pain in 5 patients, paresthesia in 2 patients, nerve palsy in 2 patients, but all of the complications were recovered during followup period. There were no local recurrence or malignant change. Conclusion: MRI demonstrates characteristic findings of Schwannoma, and very useful tool for preoperative diagnosis and planning of surgery. Exact preoperative diagnosis and meticulous enucleation are enough option of treatment.