• Korean Journal of Radiology
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• v.22 no.7
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• pp.1034-1043
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• 2021

Objective: The purpose of this meta-analysis was to investigate the pooled agreements of the coronary artery calcium (CAC) severities assessed by electrocardiogram (ECG)-gated and non-ECG-gated CT and evaluate the impact of the scan parameters. Materials and Methods: PubMed, EMBASE, and the Cochrane library were systematically searched. A modified Quality Assessment of Diagnostic Accuracy Studies-2 tool was used to evaluate the quality of the studies. Meta-analytic methods were utilized to determine the pooled weighted bias, limits of agreement (LOA), and the correlation coefficient of the CAC scores or the weighted kappa for the categorization of the CAC severities detected by the two modalities. The heterogeneity among the studies was also assessed. Subgroup analyses were performed based on factors that could affect the measurement of the CAC score and severity: slice thickness, reconstruction kernel, and radiation dose for non-ECG-gated CT. Results: A total of 4000 patients from 16 studies were included. The pooled bias was 62.60, 95% LOA were -36.19 to 161.40, and the pooled correlation coefficient was 0.94 (95% confidence interval [CI] = 0.89-0.97) for the CAC score. The pooled weighted kappa of the CAC severity was 0.85 (95% CI = 0.79-0.91). Heterogeneity was observed in the studies (I² > 50%, p < 0.1). In the subgroup analysis, the agreement between the CAC categorizations was better when the two CT examinations had reconstructions based on the same slice thickness and kernel. Conclusion: The pooled agreement of the CAC severities assessed by the ECG-gated and non-ECG-gated CT was excellent; however, it was significantly affected by scan parameters, such as slice thickness and the reconstruction kernel.

• Journal of Veterinary Clinics
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• v.26 no.5
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• pp.490-494
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• 2009

A 2-year-old Maltese and a 5-month-old Yorkshire terrier were presented with ataxia. Tetraparesis was observed in a 9-year -old Yorkshire terrier. The localizations of the lesions suggested brain or cervical spinal cord by the neurological examination, and the following images was achieved: radiography, axial images of computed tomography (CT), reconstruction image of CT such as multi-planar reformation(MPR) and 3-dimensional(3D) reconstruction and magnetic resonance imaging (MRI). On radiography, the misalignment between atlas (C1) and axis (C2), absent dens of axis, and increased space between the dorsal arch of C1 and spinous process of C2 were found. The discontinuation between dens and body of C2 was identified through axial CT images, and the fragmentation of dens separated from axis was observed through MPR and 3D image in all case. The hyperintense lesions and the spinal cord compression on T2-weighted MR images were represented in a dog with tetraparesis, the others represented only spinal cord compression. Three dogs were diagnosed as atlantoaxial instability (AAI) by dens fracture of C2. The dog with tetraparesis was euthanized due to guarded prognosis. The others were recovered completely. It is difficult to differentiate dens fracture of C2 from abnormal dens such as agenesis and hypoplasia. We thought that CT is very useful to evaluate the dens of C2 and differentiate the causes of AAI, and the reconstruction images of CT such as MPR and 3D make the translation of the fragmented dens or axis of AAI more precisely evaluate.

• The Korean Journal of Nuclear Medicine Technology
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• v.18 no.1
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• pp.115-121
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• 2014

Purpose: In addition to improving the quality of the PET image, through much research, the development of various programs are performed. Astonish TF reconstruction techniques by Philips can confirm the improved contrast of the lesion. Also, It's image reconstruction of 2 mm is possible with rapid reconstruction rate than conventional. In this study, we compared and evaluated Standardized Uptake Value (SUV) in accordance with the 2 mm reconstruction techniques and traditional 4 mm from the $^{18}F-FDG$ PET whole body image. Materials and Methods: In the phantom experiment, NEMA IEC body phantom (sphere: 10, 13, 17, 22, 28, 37 mm) was used to obtain images by using GEMINI TF 64 PET/CT (Philips, Cleveland, USA). Also, In the clinical images, we performed $^{18}F-FDG$ PET/CT examination to 30 women (age: $55.1{\pm}11.3$, BMI: $24.1{\pm}2.9$) with a diagnosis of breast cancer. After that, we reconstructed images in 2 mm and 4 mm respectively. The region of interest was drawn to acquired images. Since then, we measured SUV and statistically analyzed with SPSS ver.18 by using EBW (Extended Brilliance Workstation) NM ver.1.0. Results: After analyzing the result of the phantom study, there was a tendency that the bigger hot sphere size, the higher SUV. If you compared the 2 mm reconstruction techniques to 4 mm, it increased 95.78% in 10 mm, 50.60% in 13 mm, 25.00% in 17 mm, 30.04% in 22 mm, 31.81% in 28 mm, and 27.84% in 37 mm. Through the result of the analysis of the 2 mm reconstruction techniques and 4 mm in clinical images, it appeared that SUV of 2 mm was higher than that of 4 mm. Also the smaller the volume was, the more the change rate increased. Conclusion: After analyzing the result of the clinical picture and phantom experiments applied by Astonish TF reconstruction techniques, as the size of the volume was small, the change rate of the SUV increased. Therefore, it was necessary to further research about the SUV correction for accurate and active utilization of 2 mm reconstruction techniques which had excellent lesion discrimination ability and contrast in clinic.

• The Journal of Advanced Prosthodontics
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• v.9 no.6
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• pp.470-475
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• 2017

PURPOSE. The purpose of this study was to identify the complex course of the mandibular canal using 3D reconstruction of microCT images and to provide the diagram for clinicians to help them understand at the interforaminal region in Korean. MATERIALS AND METHODS. Twenty-six hemimandibles obtained from cadavers were examined using microCT, and the images were reconstructed. At both the midpoint of mental foramen and the tip of anterior loop, the bucco-lingual position, the height from the mandibular inferior border, the horizontal distance between two points, and position relative to tooth site on the mandibular canal were measured. The angle that the mental canal diverges from the mandibular canal was measured in posterior-superior and lateral-superior direction. RESULTS. The buccal distance from the mandibular canal was significantly much shorter than lingual distance at both the mental foramen and the tip of anterior loop. The mandibular canal at the tip of anterior loop was significantly located closer to buccal side and higher than at the mental foramen. And the mental canal most commonly diverged from the mandibular canal below the first premolar by approximately $50^{\circ}$ posterior-superior and $41^{\circ}$ lateral-superior direction, which had with a mean length of 5.19 mm in front of the mental foramen, and exited to the mental foramen below the second premolar. CONCLUSION. These results suggest that it could form a hazardous tetrahedron space at the interforaminal region, thus, the clinician need to pay attention to the width of a premolar tooth from the mental foramen during dental implant placement.

• Journal of Korean Neurosurgical Society
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• v.46 no.4
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• pp.312-316
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• 2009

Objective : The purpose of this study was to evaluate the efficacy of a transforaminal suprapedicular approach, semi-rigid flexible curved probe, and 3-dimensional reconstruction computed tomography (3D-CT) with discogram in the endoscopic treatment of non-contained lumbar disc herniations. Methods : The subjects were 153 patients with difficult, non-contained lumbar disc herniations undergoing endoscopic treatment. The types of herniation were as follows : extraforaminal, 17 patients; foraminal, 21 patients; high grade migration, 59 patients; and high canal compromise, 56 patients. To overcome the difficulties in endoscopic treatment, the anatomic structures were analyzed by 3D reconstruction CT and the high grade disc was extracted using a semi-rigid flexible curved probe and a transforaminal suprapedicular approach. Results : The mean follow-up was 18.3 months. The mean visual analogue scale (VAS) of the patients prior to surgery was 9.48, and the mean postoperative VAS was 1.63. According to Macnab's criteria, 145 patients had excellent and good results, and thus satisfactory results were obtained in 94.77% cases. Conclusion : In a posterolateral endoscopic lumbar discectomy, the difficult, non-contained disc is considered to be the most important factor impeding the success of surgery. By applying a semi-rigid flexible curved probe and using a transforaminal suprapedicular approach, good surgical results can be obtained, even in high grade, non-contained disc herniations.

• Archives of Plastic Surgery
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• v.37 no.4
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• pp.380-384
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• 2010

Purpose: Distinguishing different types of implants and assessing the position and size of implants by radiologic exam after orbital wall reconstruction is important in determining the surgery outcome and forecasting prognosis. We observed time-dependent density changes in three types of implants (porous polyethylene, resorbing plate and titanium mesh plate) by performing facial bone CT after orbital wall reconstructions. Methods: A total of 32 patients, who had underwent orbital wall fracture surgery from October 2006 to March 2009 and received facial bone CT as outpatients at 1 postoperative year were included in the study. Follow-up facial bone CT was performed on the patients pre- operatively, 1 month post-operatively, and 1 year post-operatively to observe the status of the orbital implants. Medpor $^{(R)}$ (Porex Surgical, Inc., Newnan, Ga.) was used as porous polyethylene and followed-up in 14 cases; for resorbing plate, Synthes mesh plate (Synthes, Oberdorf, Switzerland) was used in the reconstruction, and followed-up in 11 cases; and titanium mesh plate usage was followed-up in 7 cases. Computed tomographic scan (CT) and water's view were done for radiography, and hounsfield unit (HU) was used to compare density of those facial bone CT. Wilcoxon signed rank test was applied to statistically verify measurement difference in each group of hounsfield units. Results: Facial bone CT examination performed in 1 month post-operative showed that the density of porous polyethylene, resorbing plate and titanium mesh plate were -42.07, 105.67 and 539.48 on average, respectively. Among the three types of implants, titanium mesh plate showed the highest density due to its radiopaque feature. Following up the density of three types of implants in CT during 1 year after the orbital wall fracture surgery, the density of porous polyethylene increased in 10.52 House Field Units and the resorbing plate was decreased in 26.87 HouseField Units. There were no significant differences between densities in 1 month post-operatively and 1 year post-operatively in each group ($p{\geq}0.05$). Conclusion: We performed facial bone CT on patients with orbital fractures during follow-up period, distinguishing the types of implants by the different concentration of implant density, and the densities showed little change even at 1 year post-operative. To observe how implant densities change in facial bone CT, further studies with longer follow-up periods should be carried out.

• Korean Journal of Radiology
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• v.21 no.10
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• pp.1165-1177
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• 2020

Objective: To assess the feasibility of applying a deep learning-based denoising technique to coronary CT angiography (CCTA) along with iterative reconstruction for additional noise reduction. Materials and Methods: We retrospectively enrolled 82 consecutive patients (male:female = 60:22; mean age, 67.0 ± 10.8 years) who had undergone both CCTA and invasive coronary artery angiography from March 2017 to June 2018. All included patients underwent CCTA with iterative reconstruction (ADMIRE level 3, Siemens Healthineers). We developed a deep learning based denoising technique (ClariCT.AI, ClariPI), which was based on a modified U-net type convolutional neural net model designed to predict the possible occurrence of low-dose noise in the originals. Denoised images were obtained by subtracting the predicted noise from the originals. Image noise, CT attenuation, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) were objectively calculated. The edge rise distance (ERD) was measured as an indicator of image sharpness. Two blinded readers subjectively graded the image quality using a 5-point scale. Diagnostic performance of the CCTA was evaluated based on the presence or absence of significant stenosis (≥ 50% lumen reduction). Results: Objective image qualities (original vs. denoised: image noise, 67.22 ± 25.74 vs. 52.64 ± 27.40; SNR [left main], 21.91 ± 6.38 vs. 30.35 ± 10.46; CNR [left main], 23.24 ± 6.52 vs. 31.93 ± 10.72; all p < 0.001) and subjective image quality (2.45 ± 0.62 vs. 3.65 ± 0.60, p < 0.001) improved significantly in the denoised images. The average ERDs of the denoised images were significantly smaller than those of originals (0.98 ± 0.08 vs. 0.09 ± 0.08, p < 0.001). With regard to diagnostic accuracy, no significant differences were observed among paired comparisons. Conclusion: Application of the deep learning technique along with iterative reconstruction can enhance the noise reduction performance with a significant improvement in objective and subjective image qualities of CCTA images.

• Journal of the Korean Society of Radiology
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• v.11 no.7
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• pp.679-685
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• 2017

Computed tomography has widely been used to diagnose patient disease, and patient dose also increase rapidly. To reduce the patient dose by CT, various techniques have been applied. The iterative reconstruction is used in view of image reconstruction. Image quality of the reconstructed section image through algebraic reconstruction technique, one of iterative reconstruction methods, was examined by the normalized root mean square error. The computer program was written with the Visual C++ under the parallel beam geometry, Shepp-Logan head phantom of $512{\times}512$ size, projections of 360, and detector-pixels of 1,024. The forward and backward projection was realized by Joseph method. The minimum NRMS of 0.108 was obtained after 10 iterations in the regularization parameter of 0.09-0.12, and the optimum image was obtained after 8 and 6 iterations for 0.1% and 0.2% noise. Variation of optimum value of the regularization parameter was observed according to the phantom used. If the ART was used in the reconstruction, the optimal value of the regularization parameter should be found in the case-by-case. By finding the optimal regularization parameter in the algebraic reconstruction technique, the reconstruction time can be reduced.

• Proceedings of the Korean Information Science Society Conference
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• 2007.10c
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• pp.480-484
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• 2007

일반적으로 x선 CT는 물체 투과율이 짧기 때문에 대형 산업공정 내부의 영상진단 시 대상체는 금속으로 구성되어 있으며 내부는 액체, 고체, 기체 등 고밀도 물질이 포함되어 있어 계측이 어렵다. 따라서 본 논문에서는 물체 투과율이 x선에 비해 긴 감마선을 사용하였다. 대형 산업공정 내부의 단면영상을 재구성하기 위하여 반복적인 영상재구성 방법의 가중치 함수를 비교하였다. 실험 결과를 통하여 감마 CT 영상에서 빔 통과 여부에 따른 가중치 함수보다 빔 길이나 면적에 의한 가중치 함수로 복원할 경우, 원 영상과 유사함을 확인하였다.

• Proceedings of the KIEE Conference
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• 1999.07g
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• pp.3153-3155
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• 1999

최근 수년간 의료영상분야는 국내외적으로 급격한 발전을 거듭하고 있다. 특히 자기공명영상장치 (Magnetic Resonance Imaging), X-ray CT(Computed Tomography)와 단층촬영장치는 인체내부를 비침습적(non-invasive)으로 영상화함으로써 해부학적인 질병진단에 많은 장점을 가지고 있다. 이와같은 단층영상 재구성에는 역매트릭스법(matrix inversion). 반복재구성법(interative method), 역투영 법(back-projection), 2차원 Fourier 변환법(2D FFT), 중첩재구성법(Filtered back-projection) 등의 다양한 알고리즘을 사용하고 있다. 본 연구에서는 X-ray CT에서의 단층영상재구성 기법 중 널리 사용되고 있는 Filtered Back Projection 기법의 연산순서도와 연산량을 분석하고 이를 시뮬레이션을 통하여 확인하고 실시간 영상재구성을 위하여 범용 Digital Signal Processor의 병렬처리시스템 구성에 기반된 최적 Architecture를 선정하고자 한다.