Sungjun Kim

Yonsei University Hospital, Sŏul, Seoul, South Korea

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Publications (56)134.38 Total impact

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    ABSTRACT: To optimize the dose of contrast agent and the level of energy for dual-energy computed tomography (DECT) arthrography of the shoulder joint and to evaluate the benefits of the optimized imaging protocol. Dual-energy scans with monochromatic spectral imaging mode and conventional single energy scans were performed on a shoulder phantom with 10 concentrations from 0 to 210 mg/mL of iodinated contrast medium at intervals of 15 or 30 mg/mL. Image noise, tissue contrast, and beam hardening artifacts were assessed to determine the optimum dose of contrast agent and the level of monochromatic energy for DECT shoulder arthrography in terms of the lowest image noise and the least beam hardening artifacts while good tissue contrast was maintained. Material decomposition (MD) imaging for bone-iodine differentiation was qualitatively assessed. The optimized protocol was applied and evaluated in 23 patients. The optimal contrast dose and energy level were determined by the phantom study at 60 mg/mL and 72 keV, respectively. This optimized protocol for human study reduced the image noise and the beam-hardening artifacts by 35.9% and 44.5%, respectively. Bone-iodine differentiation by MD imaging was not affected by the iodine concentration or level of energy. Dual-energy scan with monochromatic spectral imaging mode results in reduced image noise and beam hardening artifacts.
    Korean journal of radiology: official journal of the Korean Radiological Society 11/2014; 15(6):746-56. · 1.32 Impact Factor
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    ABSTRACT: To assess the feasibility of T2(*)-corrected fat-signal fraction (FF) map by using the three-echo volume interpolated breath-hold gradient echo (VIBE) Dixon sequence to differentiate between malignant marrow-replacing lesions and benign red marrow deposition of vertebrae. We assessed 32 lesions from 32 patients who underwent magnetic resonance imaging after being referred for assessment of a known or possible vertebral marrow abnormality. The lesions were divided into 21 malignant marrow-replacing lesions and 11 benign red marrow depositions. Three sequences for the parameter measurements were obtained by using a 1.5-T MR imaging scanner as follows: three-echo VIBE Dixon sequence for FF; conventional T1-weighted imaging for the lesion-disc ratio (LDR); pre- and post-gadolinium enhanced fat-suppressed T1-weighted images for the contrast-enhancement ratio (CER). A region of interest was drawn for each lesion for parameter measurements. The areas under the curve (AUC) of the parameters and their sensitivities and specificities at the most ideal cutoff values from receiver operating characteristic curve analysis were obtained. AUC, sensitivity, and specificity were respectively compared between FF and CER. The AUCs of FF, LDR, and CER were 0.96, 0.80, and 0.72, respectively. In the comparison of diagnostic performance between the FF and CER, the FF showed a significantly larger AUC as compared to the CER (p = 0.030), although the difference of sensitivity (p = 0.157) and specificity (p = 0.157) were not significant. Fat-signal fraction measurement using T2(*)-corrected three-echo VIBE Dixon sequence is feasible and has a more accurate diagnostic performance, than the CER, in distinguishing benign red marrow deposition from malignant bone marrow-replacing lesions.
    Korean journal of radiology: official journal of the Korean Radiological Society 11/2014; 15(6):781-91. · 1.32 Impact Factor
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    ABSTRACT: Dual-energy computed tomography (DECT) images may be underutilized for the evaluation of skeletal metastasis. Spectral parametric segmentation of DECT can produce bone-iodine separated images, which have the potential to detect bone metastases. To evaluate the potential of bone-iodine separation in the detection of bone metastasis with spectral parametric segmentation of DECT images which are acquired at clinical follow-up for patients with prior malignancy. The institutional review board approved the protocol of this retrospective review. Chest DECT scans using fast kV-switching between 80 and 140 kVp were included in this study. Bone-iodine separated reformatted images were produced by spectral parametric segmentation of synthesized monochromatic images. All chest CT images of 702 metastatic lesions from 54 patients were retrospectively evaluated in terms of visualization of metastatic lesions compared with (99m)Tc-MDP (methylene diphosphonate) whole-body bone scintigraphy (WBBS) as reference standard of diagnosis. Spectral parametric segmentation images of DECT visualized metastatic lesions in 92.3% (n = 648/702). Osteoblastic metastases were delineated as subtle enhancing lesions on DECT in comparison to WBBS. Spectral parametric segmentation of iodine from cortical and medullary bone allowed visualization of bone metastasis. DECT might be utilized for the screening or detection of bone metastases.
    Acta Radiologica 04/2014; · 1.33 Impact Factor
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    ABSTRACT: To assess the usefulness of T2*-corrected fat fraction (FF) map from volume-interpolated breathhold examination (VIBE) magnetic resonance (MR) sequence in patients with the rotator cuff pathology. The phantom study was performed to validate the FF maps. Eighty-nine shoulder MR arthrographies were analyzed: (1) divided into three groups namely tendinopathy/normal tendons, partial-thickness tears, and full-thickness tears, and (2) occupation ratio (OR) was measured for muscular atrophy. Uncorrected and T2*-corrected FF maps were reconstructed from the VIBE images. The Pearson correlation test was used to correlate the FFs with ORs. The FF and the OR were compared between groups using the Student t test. T2*-corrected FF maps could provide a higher correlation than uncorrected FF maps. There were significantly negative correlations between the ORs and the FFs (P < .01). In the normal and the partial-thickness tear group, the OR did not show a significant difference, although the FF maps showed a significant difference (P < .01). This quantitative assessment of the T2*-corrected FF in the rotator cuff muscles was found to be reliable and correlated well with the ORs. The T2*-corrected FF maps could be used for more sophisticated assessments of the fat even in the partial-thickness tear.
    Academic radiology 04/2014; · 2.09 Impact Factor
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    ABSTRACT: Background and Purpose Fluid-sensitive MR imaging in postoperative evaluation is important, however, metallic artifacts is inevitable. The purpose is to investigate the feasibility of fat-saturated slice encoding for metal artifact correction (SEMAC)-corrected T2-weighted magnetic resonance (MR) at 3 T in patients with spinal prostheses. Methods Following institutional review board approval, 27 SEMAC-encoded spinal MR between September 2012 and October 2013 in patients with spinal metallic prostheses were analyzed. The MR images were scanned on a 3 T MR system including SEMAC-corrected and uncorrected fast spin echo (FSE) T2-weighted MR images with fat-saturation. Two musculoskeletal radiologists compared the image sets and qualitatively analyzed the images using a five-point scale in terms of artifact reduction around the prosthesis, visualization of the prosthesis and pedicle, and intervertebral neural foramina. Quantitative assessments were performed by calculating of the ratio of signal intensity from the fixated vertebra and that from upper level vertebra. For statistical analyses, paired t-test was used. Results Fat-saturated SEMAC-corrected T2-weighted MR images enabled significantly improved metallic artifact reduction (P < 0.05). Quantitative evaluation of the signal intensity ratio of screw-fixated vertebra and upper level vertebra showed a significantly lower ratio on fat-saturated SEMAC images (P < 0.05), however, the high signal intensity of signal pile-up could be not completely corrected. Conclusion SEMAC correction in fat-suppressed T2-weighted MR images can overcome the signal loss of metallic artifacts and provide improved delineation of the pedicle screw and peri-prosthetic region. Signal pile-up, however, could not be corrected completely, therefore readers should be cautious in the evaluation of marrow around the prosthesis.
    Magnetic Resonance Imaging. 01/2014;
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    ABSTRACT: PURPOSE To determine the most optimal carpal bone level for measurement of median nerve cross-sectional area (CSA) using ultrasonography (US) in the diagnosis and surgical outcome measure of carpal tunnel syndrome (CTS). METHOD AND MATERIALS Between Mar. 2011 to Mar. 2013, US was done for 39 wrists from the 29 female patients with CTS and 27 wrists from 14 non-symptomatic control group. CSAs of median nerves were measured at four different levels with carpal bones adopted as the landmark: pronator quadratus (PQ); lunate; pisiform; and hamate. Six parameters were used for analysis. The 3 parameters were CSA values at lunate, pisiform, and hamate. Additional 3 parameters were CSA value differences between lunate and PQ (L-PQ), between pisiform and PQ (P-PQ), and between hamate and PQ (H-PQ). The 6 parameters were subjected to receiver operating characteristic (ROC) curve analysis to test diagnostic performances, and areas under curves (AUCs) of the parameters were compared to each other. The sensitivity and specificity for each parameter at the most ideal cut off values was obtained. Clinical symptom with/without electrodiagnostic test results was used as the reference standard. Additionally, for the 39 wrists for which carpal tunnel release was done, the parameters were validated whether they can be used as a predictor of surgical outcome by correlating their post-op decrease with the post-op percent decrease of Boston Carpal Tunnel Questionnaire (BCTQ) scores with the use of Spearman rho test. RESULTS AUCs of the six parameters were 0.872 for lunate, 0.783 for pisiform, 0.654 for hamate, 0.770 for L-PQ, 0.686 for P-PQ, 0.503 for H-PQ, where CSA at lunate level showed the highest diagnostic performance (AUC, 0.872; sensitivity, 79.5 %; specificity, 85.2 %). The cut off value for CSA at lunate level was 10.7㎟. L-PQ was the only parameter that showed statistically significant post-op decrease that correlated with BCTQ decrease (r=0.33, p=0.041). CONCLUSION The CSA of the median nerve at lunate level appears to be the parameter with the highest diagnostic performance. CSA difference between lunate and PQ was the only parameter that correlated with surgical outcome. CLINICAL RELEVANCE/APPLICATION CSA measurement for median nerve at the lunate level appears to be sufficient to diagnose CTS. To assess surgical outcome using US, CSA difference between lunate and PQ level appears to be optimal.
    Radiological Society of North America 2013 Scientific Assembly and Annual Meeting; 12/2013
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    ABSTRACT: PURPOSE To assess feasibility of T2*-corrected fat fraction map using three-point Dixon-VIBE sequence as a tool for differentiation between malignant marrow replacing lesion and benign red marrow deposition of vertebra. METHOD AND MATERIALS From Mar. 2012 to Feb. 2013, magnetic resonance imaging was performed for consecutive 33 patients who were referred for vertebral marrow abnormality assessment. Twenty two pathologically confirmed malignant marrow replacing lesions and 11 benign red marrow lesions from the patients were subjects of this study. Three sequences were applied using a 1.5-T MR imaging scanner like follows: three-point Dixon-volume interpolated breath-hold GRE sequence (VIBE) for fat fraction (FF) measurement; conventional T1 weighted imaging (T1WI); pre- and post-contrast enhanced fat-suppressed T1WI (CE). To measure fat fraction or signal intensity (SI), region of interest (ROI) was placed at the target lesions. Average measurements from consecutive three slices of the target lesions were used for data analysis. Three parameters from the measurements were obtained like follows for each lesion: FF from VIBE; LDR (lesion-disc ratio; [SI of marrow lesion / SI of disc]*100) for T1WI; CER (contrast enhancement ratio; [LDR of post-contrast T1WI-LDR of pre-contrast T1WI]*100 / LDR of pre-contrast T1WI) for CE. To evaluate diagnostic performance of the three parameters, receiver operating characteristic (ROC) curves were obtained and areas under curves (AUCs) of the parameters were compared to each other. The sensitivity and specificity at the most ideal cut off values for the parameters were obtained. RESULTS AUCs of FF, LDR, CER were 0.96, 0.83, 0.74. FF showed superior AUC than CER with statistical significance. The optimal cut-off value and the corresponding sensitivity/specificity in percentage were like follows: 16, 0.81/1 in FF; 116.2, 1/63.6 in LDR; 93.4, 0.68/0.81 in CER. CONCLUSION T2*-corrected fat fraction measurement using a three-point Dixon-VIBE sequence showed superior diagnostic performance than contrast enhanced T1WI, and it showed excellent specificity in differentiation between malignant marrow replacing lesion and benign red marrow deposition of vertebra. CLINICAL RELEVANCE/APPLICATION T2*-corrected fat fraction measurement using a three-point Dixon-VIBE sequence is expected to play an important role to differentiate benign red marrow from malignant marrow lesion.
    Radiological Society of North America 2013 Scientific Assembly and Annual Meeting; 12/2013
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    ABSTRACT: PURPOSE The computer has transformed the radiologic reading workflow. The radiologic reading workflow has come to a new era of computer-based radiology. Along with the expectations for improvement of accuracy of interpretation, radiologists should be aware of the typographical errors in radiologic reports as the number of radiologic examinations increase. Typographical errors of the right and left sides of the extremities are not infrequent during the interpretation of radiographs. With the introduction of PACS, more radiologists have started to typewrite their radiologic interpretations. Among a list of right/left or both sides of studies, radiologists should select the correct exam and typewrite. However, a radiologist could make errors in the laterality of right and left sides in the radiologic report. This tends to occur more frequently in busy radiology departments, especially with a huge amount of radiologic burden. We think this possible error could be minimized with additional software for Picture Archiving and Communicating System (PACS) and Electronic Medical Record (EMR). With dedicated software, the discrepancy of the examination name and error could be detected, and this additional software would be useful for the next generation PACS. In this article, we introduce the development of an automated detection and correction software algorithm by using Macro program, and illustrate its practical usages in the radiology reading work flow. From a viewpoint of long term investment, the next generation of PACS or EMR might be expected to include this additional or further advanced function for a better radiologic reading environment. METHODS 1. Hardware and software The PACS software was Centricity® Radiology RA1000 (GE Healthcare, Barrington, IL). The EMR software was designed in authors’ institution. Macro program AutoHotkey was used to design error detection and correction. This development tool is downloadable from the official webpage (http://www.autohotkey.com). 2. Flowchart The software was performed according to the flowchart illustrated in Fig. 1. The first step is real-time automatic discrepancy detection of the laterality between radiologic examination name and radiologic report. In our software, one cycle per 0.5 second was used, and this time can be reduced or increased by the PACS workstation performance. The second step is conditioned discrepancy correction. This second conditioned step is done if Yes button is pressed. If there is no laterality or discrepancy, nothing is done, and the radiologic reading workflow is based on the conventional flow. For studies of both laterality (e.g. Knee AP Lt/Rt ), we added an additional code for bypass. 3. Accuracy evaluation The accuracy of detection was evaluated from 300 consequently listed radiologic examinations on one day. Randomly sorted intended discrepancies and concordance of lateralities were input in the radiologic reporting system, and the detection and correction were counted in the radiologic reporting system. The confidence intervals of accuracies were calculated. RESULTS AutoHotkey-scripted macro program ran well in the radiologic reading workstation, and successfully acted as additional software for the PACS software and EMR. There was no interference between this macro program and the hospital software including PACS viewer and EMR. The automatic laterality detection can be performed in real-time. And the conditioned correction was successfully done. The accuracy of detection was 99.67% (95% CI; 99.01―%) in the consequent 300 radiologic examinations of the radiologic reading session. One failure was observed which resulted from a temporary lag of hospital computer network. This failure was not produced after second trial. CONCLUSION Automated detection and correction software was designed and ran well by using open-source Macro software. This method can be easily adapted for any PACS and EMR, and is expected to be included in the next generation PACS or EMR for a better radiologic reading environment.
    Radiological Society of North America 2013 Scientific Assembly and Annual Meeting; 12/2013
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    ABSTRACT: PURPOSE To evaluate MR arthrographic (MRA) findings and to compare the MR findings with arthroscopic findings of characteristics, anatomical distribution and extent of PASTA (partial articular-sided supraspinatus tendon avulsion) in arthroscopically confirmed patients. METHOD AND MATERIALS Sep 2009 to Feb 2013, 62 patients arthroscopically confirmed as PASTA. We excluded one lesion mixed with arthroscopically full-thickness tear. Total 61 patients were enrolled, and all patients underwent MRA with using 3-T MR. Mean interval time between MRA and arthroscopy was 77.3 days. Two musculoskeletal radiologists retrospectively reviewed the MRA by consensus blind to arthroscopic findings. PASTA was defined as undersurface tendon discontinuity at the footprint with articular side contrast. Anatomical locations were divided by four: anterior, posterior, transition zone, inferior half of the middle facet of the greater tuberosity. Vertical extension divided into 3 grade: grade 1; involving 1-2mm of tendon insertion, grade 2; involving ≤50%, grade 3; involving >50%. Arthroscopies were done by one experienced orthopedic surgeon. Pearson correlation test was used to correlate the vertical grade and surgical percentage of the PASTA. RESULTS Of the 61 patients, 51 patients were diagnosed as PASTA (83.6%): anterior in 36 (70.6%), posterior in 10 (19.6%), and transitional zone in 5 (9.8%). There was no involvement inferior half of the middle facet. Grade 1 vertical extension were 12 (23.5%), grade 2 in 18 (35.3%), and grade 3 in 21 (41.2%). The Pearson correlation test between MR vertical extension grade and surgical percentage was 0.69 (p<0.001). In remained 10 patients, PASTA could not be diagnosed on MR: 5 patients with contrast leakage on MRA showing more than 70% extension; and 5 patients diagnosed as partial-thickness tear. CONCLUSION PASTA lesion is well visualized on MRA as showing contrast filling at the partial articular-sided footprint avulsion at the greater tuberosity. The vertical extension grade was good correlation with surgical grade. In patients with extra-articular contrast leakage, the PASTA lesion could be misdiagnosed on MRA. CLINICAL RELEVANCE/APPLICATION PASTA lesion is well diagnosed on MRA and its extent was good correlation with surgical grade.
    Radiological Society of North America 2013 Scientific Assembly and Annual Meeting; 12/2013
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    ABSTRACT: Purpose:To retrospectively assess how often and how early hip dual-energy x-ray absorptiometry (DXA) images show prefracture lesions in patients with atypical subtrochanteric fracture (ASF) and determine whether DXA images with assessment of prodromal symptoms could be used for early ASF prediction.Materials and Methods:The retrospective research protocol complied with HIPAA and was institutional review board approved, with waiver of informed consent. Among 62 women with ASF, nine without hip DXA images and seven without clear documentation of prodromal symptoms were excluded. Serial DXA images of 52 hips in 46 patients were included. Among them, 33 hips were assessed with ipsilateral DXA. For this ipsilateral group, each hip was assessed for prodromal symptoms and focal cortical changes in the lateral subtrochanteric femur cortex at DXA. Overall and cumulative detection rates for prodromal symptoms, DXA, and DXA with prodromal symptoms were measured and compared with a general linear model for overall detection rate and Cox proportional hazard models for cumulative detection rate. Thirty-three representative ipsilateral images and 199 images from subjects without fractures were reviewed in random order for prefracture lesions by three musculoskeletal radiologists independently, and the performance of DXA in ASF prediction was assessed.Results:Overall detection rates for DXA, prodromal symptoms, and DXA with prodromal symptoms were 61% (20 of 33), 42% (14 of 33), and 73% (24 of 33), respectively, in the ipsilateral group. Overall detection rate comparisons showed that DXA with prodromal symptoms was superior to prodromal symptoms alone (P = .0377). The cumulative detection rate curve for DXA with prodromal symptoms was also superior to that of prodromal symptoms alone (P = .0018). Sensitivity and specificity of DXA in ASF prediction ranged from 52% (17 of 33) to 58% (19 of 33) and 99% (197 of 199) to 100% (199 of 199), respectively.Conclusion:Assessment of hip DXA images combined with conventional assessment of prodromal symptoms enables detection of more ASFs earlier than assessment based on prodromal symptoms alone.© RSNA, 2013Supplemental material: http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.13122691/-/DC1.
    Radiology 10/2013; · 6.34 Impact Factor
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    ABSTRACT: This paper proposes a measurement method to quantify the abnormal characteristics of the broken parts of ribs using local texture and shape features in chest radiographs. OUR MEASUREMENT METHOD COMPRISES TWO STEPS: a measurement area assignment and sampling step using a spline curve and sampling lines orthogonal to the spline curve, and a fracture-ness measurement step with three measures, asymmetry and gray-level co-occurrence matrix based measures (contrast and homogeneity). They were designed to quantify the regional shape and texture features of ribs along the centerline. The discriminating ability of our method was evaluated through region of interest (ROI) analysis and rib fracture classification test using support vector machine. The statistically significant difference was found between the measured values from fracture and normal ROIs; asymmetry (p < 0.0001), contrast (p < 0.001), and homogeneity (p = 0.022). The rib fracture classifier, trained with the measured values in ROI analysis, detected every rib fracture from chest radiographs used for ROI analysis, but it also classified some unbroken parts of ribs as abnormal parts (8 to 17 line sets; length of each line set, 2.998 ± 2.652 mm; length of centerlines, 131.067 ± 29.460 mm). Our measurement method, which includes a flexible measurement technique for the curved shape of ribs and the proposed shape and texture measures, could discriminate the suspicious regions of ribs for possible rib fractures in chest radiographs.
    Healthcare informatics research. 09/2013; 19(3):196-204.
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    ABSTRACT: To assess the diagnostic value of fat-suppressed (FS) three-dimensional (3D) volume isotropic turbo spin echo acquisition (VISTA) imaging in detecting radial and root tears of the meniscus, including the reader-defined reformatted axial (RDA) plane. Twenty-three patients with arthroscopically confirmed radial or root tears of the meniscus underwent magnetic resonance imaging (MRI) with 2D and FS 3D VISTA sequences. MRIs were reviewed independently by two musculoskeletal radiologists blinded to the arthroscopic findings. Sensitivity, specificity, accuracy, and interobserver agreement were calculated for radial and root tears. Both radiologists reported confidence scale for the presence of meniscal tears in 2D axial imaging, 3D axial imaging, and RDA imaging, based on a five-point scale. Wilcoxon's signed rank test was used to compare confidence scale. The sensitivity, specificity, and accuracy of FS 3D VISTA MR imaging versus 2D MR imaging were as follows: 96%, 96%, and 96% versus 91%, 91%, and 91%, respectively in reader 1, and 96%, 96%, and 96% versus 83%, 91%, and 87%, respectively, in reader 2. Interobserver agreement for detecting meniscal tears was excellent (κ=1) with FS 3D VISTA. The confidence scale was significantly higher for 3D axial images than 2D imaging (p=0.03) and significantly higher in RDA images than 3D axial image in detecting radial and root tears. FS 3D VISTA had a better diagnostic performance in evaluating radial and root tears of the meniscus. The reader-defined reformatted axial plane obtained from FS 3D VISTA MR imaging is useful in detecting radial and root tears of the meniscus.
    European journal of radiology 08/2013; · 2.65 Impact Factor
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    ABSTRACT: Ultrashort echo time (UTE) image to directly visualize short T2 tissues requires postprocessing for the suppression of the surrounding long T2 tissues in a clinical magnetic resonance imaging (MRI) scanner. Weighted subtraction of UTE images with an optimal weighting factor could provide high positive contrast with adequate suppression. To demonstrate in-vivo UTE MRI with weighted subtractions of dual echo UTE imaging using a 3 T clinical MRI and to determine the optimal weighting factors through the analyses of signal-to-noise ratios (SNRs) and contrast-to-noise ratios (CNRs). Forty-seven consecutive knee MR including dual echo 3D UTE sequence (TE of 70 µs and 3.82 ms) were reviewed. Seven patients with normal findings in the knee MR were included in the current study. For variably weighted subtraction images, the initial UTE image was rescaled relative to that of the second echo image with weighting factors from 0.1 to 4.0. Thirty-five pairs of the ROI measurements of the UTE image and second long echo images were repeated after 2 weeks. For quantitative assessment, SNR and CNR were measured from the ROIs on the patellar tendon, cartilage, cortical bone, meniscus, and infrapatellar fat pad. Intra-observer agreement was assessed by using both Cohen's Kappa and Bland-Altman approach. The short T2 tissue could be visualized with adequate suppression on the subtraction images. Considering the CNRs and SNRs, the optimal ranges of the weighting factors could be suggested: 0.3 for the tendon, 0.4 for the cortical bone, and 1.0 for the meniscus. The 35 paired measurements showed excellent agreement with statistical significance (P < 0.05). The 3D UTE MRI provides imaging of short T2 tissues which cannot be visualized by conventional MRI. Using weighted subtractions with optimal weighting values, each tissue can be optimally depicted by overcoming the reduced T2 contrast.
    Acta Radiologica 08/2013; · 1.33 Impact Factor
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    ABSTRACT: Purpose: To validate the feasibility of real time kinematography with four-dimensional (4D) dynamic functional wrist joint imaging using dual source CT. Materials and Methods: Two healthy volunteers performed radioulnar deviation and pronation- supination wrist motions for 10 s and 4 s per cycle in a dual source CT scanner. Scan and reconstruction protocols were set to optimize temporal resolution. Cine images of the reconstructed carpal bone of the moving wrist were recorded. The quality of the images and radiation dosage were evaluated. Results: The 4D cine images obtained during 4 s and 10 s of radioulnar motion showed a smooth stream of movement with good quality and little noise or artifact. Images from the pronation-supination motion showed noise with a masked surface contour. The temporal resolution was optimized at 0.28 s. Conclusion: Using dual source CT, 4D cine images of in vivo kinematics of wrist joint movement were obtained and found to have a shorter scan time, improved temporal resolution and lower radiation dosages compared with those previously reported.
    Yonsei medical journal 07/2013; 54(4):1026-1032. · 0.77 Impact Factor
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    Kyu Hyun Yang, Sungjun Kim, Ji Do Jeong
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    ABSTRACT: Femoral neck fractures are associated with femoral shaft fractures in 1% to 9% of cases. Undisplaced neck fractures are susceptible to displacement during shaft nailing. We report the case of a 57-year-old male patient in whom we performed standard intramedullary nailing for a femoral shaft fracture. In doing so, we identified a vertical radiolucent line at the femoral neck, which was thought to be further displacement of a hidden silent fracture or an iatrogenic fracture that developed during nail insertion. Consequently, we decided to switch to reconstructive femoral nailing. Postoperative hip imaging failed to show the femoral neck fracture that we saw in the operating room. Here, we discuss the aforementioned case and review the literature concerning this artifact.
    Yonsei medical journal 05/2013; 54(3):803-5. · 0.77 Impact Factor
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    ABSTRACT: PURPOSE: The purpose of the study was to assess the usefulness of slice encoding for metal artifact correction (SEMAC) in 3.0-T magnetic resonance (MR) in minimizing metallic artifacts in patients with spinal prostheses. MATERIALS AND METHODS: Institutional review board approval and informed consent were obtained for this study. Twenty-seven spine MR scans were performed with metal artifact reduction SEMAC between May 2011 and July 2012 in patients with metallic devices. The MR scans were performed on a 3-T MR system (Achieva; Philips Healthcare, Best, the Netherlands) including SEMAC-corrected T2-weighted axial/sagittal images and two-dimensional fast spin echo (FSE) axial/sagittal images. The SEMAC-corrected images were compared to conventional T2-weighted FSE images. Two musculoskeletal radiologists qualitatively analyzed the images in terms of visualization of the pedicle, vertebral body, dural sac, intervertebral disc, intervertebral neural foramina, screws and metallic artifacts. The paired images were rated using a 5-point scale. P values less than .05 were considered to indicate statistically significant differences. RESULTS: The SEMAC-corrected MR images significantly reduced the metal-related artifacts. The T2-weighted images with SEMAC sequences enabled significantly improved periprosthetic visualizations of the pedicle, vertebral body, dural sac and neural foramina, with the exception of the intervertebral disc (P<.05). In addition, there was significant improvement in prosthesis visualization (P<.05). CONCLUSION: MR images with SEMAC can reduce metal-related artifacts, providing improved delineation of the prosthesis and periprosthetic region. However, for the evaluation of the intervertebral disc, the SEMAC-corrected MR images showed no significant benefits.
    Magnetic Resonance Imaging 01/2013; · 2.06 Impact Factor
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    ABSTRACT: To investigate the validity of the 100 kVp setting in CT venography (CTV) in the diagnosis of deep vein thrombosis (DVT), and to evaluate the feasibility of reducing the amount of administered iodine in this setting. After receiving the contrast medium (CM) of 2.0 mL/kg, 88 patients underwent CTV of the pelvis and lower extremities by using one of four protocols: Group A, 120 kVp setting and 370 mgI/mL CM; group B, 120 kVp and 300 mgI/mL; group C, 100 kVp and 370 mgI/mL; group D, 100 kVp and 300 mgI/mL. The groups were evaluated for venous attenuation, vein-to-muscle contrast-to-noise ratio (CNRVEIN), DVT-to-vein contrast-to-noise ratio (CNRDVT), and subjective degree of venous enhancement and image quality. Venous attenuation and CNRVEIN were significantly higher in group C (144.3 Hounsfield unit [HU] and 11.9), but there was no significant difference between group A (118.0 HU and 8.2) and D (122.4 HU and 7.9). The attenuation value of DVT was not significantly different among the four groups, and group C had a higher absolute CNRDVT than the other groups. The overall diagnostic image quality and venous enhancement were significantly higher in group C, but there was no difference between groups A and D. The 100 kVp setting in CTV substantially help improve venous enhancement and CNRVEIN. Furthermore, it enables to reduce the amount of administered iodine while maintaining venous attenuation, as compared with the 120 kVp setting.
    Korean journal of radiology: official journal of the Korean Radiological Society 01/2013; 14(2):183-193. · 1.32 Impact Factor
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    ABSTRACT: PURPOSE To preliminarily assess the use of dual-energy X-ray absorptiometry (DXA) hip images for predicting atypical subtrochanteric fracture (ASF) METHOD AND MATERIALS Serial pre-fracture DXA images of 52 hips from 46 female patients who sustained ASF were reviewed retrospectively. The 52 hips were divided into two groups: ipsilateral DXA group I (n=33) and contralateral DXA group C (n=19). The lateral cortical changes in DXA were categorized as focal cortical change (FC), diffuse cortical thickening (DT), or negative. Cumulative detection rates (CDR) for DXA images and for PS were compared using Cox’s proportional hazard model. To assess the enhanced screening performance, CDRs for DXA and PS were compared to PS alone. RESULTS Among the 33 hips in group I, 20 hips (60.6%) demonstrated FC, 10 hips (30.3%) demonstrated DT, and 3 hips (9.1%) demonstrated negative results. Fourteen hips (42.4%) of group I showed PS. Among the 19 hips in group C, 2 hips (10.5%) demonstrated FC, 9 hips (47.4%) demonstrated DT, and 8 hips (42.1%) demonstrated negative results. CDR of DXA for group I was higher than that of PS. CDR from the combination of DXA and PS were statistically superior to PS alone (p<0.002) for predicting ASF. CDR of group I was superior to group C (p=0.0034). CONCLUSION Vigilance for lateral cortical changes at the subtrochanteric area on DXA images could serve as an adjunct to PS and help predict ASF. CLINICAL RELEVANCE/APPLICATION DXA can be used not only for the measurement of bone mineral density but for the prediction of atypical subtrochanteric fracture.
    Radiological Society of North America 2012 Scientific Assembly and Annual Meeting; 11/2012
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    ABSTRACT: PURPOSE The purpose of our study was to assess the diagnostic value of iso–volumetric 3D fat suppressed VISTA sequence in detecting the radial tear and root tear of the meniscus, especially in reformatted axial plane. METHOD AND MATERIALS Fifteen patients with arthroscopically confirmed radial tear or root tear of meniscus underwent MRI with conventional 2D sequences and iso–volumetric 3D fat suppressed VISTA sequence. The MR images were retrospectively reviewed for identification of meniscal tears by two musculoskeletal radiologists blinded to arthroscopic findings independently. Sensitivity, specificity, and interobserver agreement were calculated for all meniscal tears. Two radiologists reported a confidence level for the presence or absence of meniscal tear in axial plane of 2D sequence and reformatted axial plane made from iso–volumetric 3D fat suppressed VISTA sequence based on a 5-point scale: 1, completely uncertain of tear; 2, small likelihood of tear; 3, equivocal for tear; 4, probable tear, and 5, very certain of tear. Wilcoxon’s signed rank test was used to compare confidence levels. RESULTS Sensitivities and specificities on iso–volumetric 3D fat suppressed VISTA versus 2D sequence were as follows: 100% and 93% versus 100% and 100% in reader 1, 100% and 87% versus 100% and 100% in reader 2. Interobserver agreement for detecting meniscal tear was excellent (κ = 1) in iso–volumetric 3D fat suppressed VISTA sequence. The mean confidence level was significantly higher in reformatted axial plane made from iso–volumetric 3D fat suppressed VISTA than conventional 2D sequence; 4.06 versus 2.86 (P = 0.03) in detecting meniscal root tears and radial tears. CONCLUSION Compared to conventional 2D sequence, iso–volumetric 3D fat suppressed VISTA has more valuable diagnostic sequence in evaluating radial and root meniscal tear. User-reformatted axial plane made from iso–volumetric 3D fat suppressed VISTA is more valuable in detecting radial and root tear of meniscus. CLINICAL RELEVANCE/APPLICATION Accurate assessemnt of locaion, extent of tear lesion of meniscus can help in making treatment plan in meniscal root and radial tear patients.
    Radiological Society of North America 2012 Scientific Assembly and Annual Meeting; 11/2012
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    ABSTRACT: PURPOSE To propose a method to quantify the local texture and shape changes of ribs caused by rib fracture in chest radiographs. METHOD AND MATERIALS Our measurement method consists of two steps: (1) measurement area assignment and sampling step using a spline curve and sampling lines orthogonal to the spline curve, and (2) fracture-ness measurement step with three measures, asymmetry and Gray-level Co-occurrence Matrix based measures (contrast and homogeneity). They were designed to quantify the symmetric characteristics of ribs along the centerline. The discriminating ability of our method was evaluated through region of interest (ROI) analysis and rib fracture classification test using support vector machine. RESULTS The statistically significant difference was found between the measured values from fracture ROIs and normal ROIs; asymmetry (P < 0.0001), contrast (P < 0.001) and homogeneity (P = 0.022). The rib fracture classifier, trained with the measured values in ROI analysis, detected every rib fracture from chest radiographs used for ROI analysis, but it also classified some unbroken parts of ribs as abnormal parts (8 ~ 17 line sets, Length of each line set: 2.998±2.652 mm, Length of centerlines: 131.067±29.460 mm). CONCLUSION Our measurement method, which includes the flexible measurement technique for the curved shape of ribs and the proposed shape and texture measures, could discriminate the suspicious region of ribs for possible rib fractures in chest radiographs. CLINICAL RELEVANCE/APPLICATION With the use of the proposed method, routine screening of rib fracture on digital chest radiographs would become more feasible.
    Radiological Society of North America 2012 Scientific Assembly and Annual Meeting; 11/2012

Publication Stats

2k Citations
134.38 Total Impact Points

Institutions

  • 2007–2014
    • Yonsei University Hospital
      • Department of Internal Medicine
      Sŏul, Seoul, South Korea
  • 2005–2010
    • Yonsei University
      • • Department of Radiology
      • • Department of Chemistry
      Sŏul, Seoul, South Korea
  • 2009
    • Seoul National University Hospital
      • Department of Radiology
      Seoul, Seoul, South Korea