• Korean Journal of Radiology
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• v.23 no.4
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• pp.402-412
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• 2022

Objective: To evaluate the image quality and lesion detectability of lower-dose CT (LDCT) of the abdomen and pelvis obtained using a deep learning image reconstruction (DLIR) algorithm compared with those of standard-dose CT (SDCT) images. Materials and Methods: This retrospective study included 123 patients (mean age ± standard deviation, 63 ± 11 years; male:female, 70:53) who underwent contrast-enhanced abdominopelvic LDCT between May and August 2020 and had prior SDCT obtained using the same CT scanner within a year. LDCT images were reconstructed with hybrid iterative reconstruction (h-IR) and DLIR at medium and high strengths (DLIR-M and DLIR-H), while SDCT images were reconstructed with h-IR. For quantitative image quality analysis, image noise, signal-to-noise ratio, and contrast-to-noise ratio were measured in the liver, muscle, and aorta. Among the three different LDCT reconstruction algorithms, the one showing the smallest difference in quantitative parameters from those of SDCT images was selected for qualitative image quality analysis and lesion detectability evaluation. For qualitative analysis, overall image quality, image noise, image sharpness, image texture, and lesion conspicuity were graded using a 5-point scale by two radiologists. Observer performance in focal liver lesion detection was evaluated by comparing the jackknife free-response receiver operating characteristic figures-of-merit (FOM). Results: LDCT (35.1% dose reduction compared with SDCT) images obtained using DLIR-M showed similar quantitative measures to those of SDCT with h-IR images. All qualitative parameters of LDCT with DLIR-M images but image texture were similar to or significantly better than those of SDCT with h-IR images. The lesion detectability on LDCT with DLIR-M images was not significantly different from that of SDCT with h-IR images (reader-averaged FOM, 0.887 vs. 0.874, respectively; p = 0.581). Conclusion: Overall image quality and detectability of focal liver lesions is preserved in contrast-enhanced abdominopelvic LDCT obtained with DLIR-M relative to those in SDCT with h-IR.

• The Journal of the Korean dental association
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• v.58 no.9
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• pp.556-562
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• 2020

Neurofibroma is a benign, heterogenous peripheral nerve sheath tumor arising from the connective tissue of peripheral nerve sheaths, especially the endoneurium. Its intraoral occurrence is uncommon and its occurrence within mandible is extremely rare. A case of solitary intraosseous neurofibroma of the mandible involving masticator space in a 8-year-old male is reported. He was referred from a private local clinic with a chief complaint of limitation in opening of the mouth. Panoramic and cone-beam computed tomographic images showed unilocular radiolucent lesion with scalloped border at the right mandibular ramus, connected posteriorly to the enlarged mandibular foramen and anteriorly to the mandibular canal. T1-weighted magnetic resonance images showed soft tissue mass of isointensity compared with muscles. Contrast-enhanced T1-weighted images showed peripheral enhancement and T2-weighted images showed the heterogeneous hyperintense mass with extension between lateral and medial pterygoid muscles. The tumor was surgically removed under general anesthesia and diagnosed to be neurofibroma at the biopsy.

• Imaging Science in Dentistry
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• v.43 no.1
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• pp.55-58
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• 2013

A ranula is a bluish, transparent, and thin-walled swelling in the floor of the mouth. They originate from the extravasation and subsequent accumulation of saliva from the sublingual gland. Ranulas are usually limited to the sublingual space but they sometimes extend to the submandibular space and parapharyngeal space, which is defined as a plunging ranula. A 21-year-old woman presented with a complaint of a large swelling in the left submandibular region. On contrast-enhanced CT images, it dissected across the midline, and extended to the parapharyngeal space posteriorly and to the submandibular space inferiorly. Several septa and a fluid-fluid level within the lesion were also demonstrated. We diagnosed this lesion as a ranula rather than cystic hygroma due to the location of its center and its sublingual tail sign. As plunging ranula and cystic hygroma are managed with different surgical approaches, it is important to differentiate them radiologically.

• Proceedings of the Korean Society of Computer Information Conference
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• 2019.01a
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• pp.465-467
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• 2019

본 논문에서는 영상생성이 가능한 딥러닝 네트워크를 이용하여 조영증강 CT 영상을 획득하는 연구를 수행하였다. CT는 고해상도 영상을 바탕으로 환자의 질병 및 암 세포 진단에 사용되는 의료영상 기법 중 하나이다. 특히, 조영제를 투여한 다음 CT 영상을 획득되는 영상을 조영증강 CT 영상이라 한다. 조영증강된 CT 영상은 물질의 구성 성분의 영상대비를 강조하여 임상의로 하여금 진단 및 치료반응 평가의 정확성을 향상시켜준다. 하지많은 수의 환자들이 조영제 부작용을 갖기 때문에 이에 해당되는 환자의 경우 조영증강 CT 영상 획득이 불가능해진다. 따라서 본 연구에서는 조영증강 영상을 얻지 못하는 환자 및 일반 환자의 불필요한 방사선의 노출을 최소화 하기 위하여 영상생성 딥러닝 기법을 이용하여 CT 영상에서 조영증강 CT 영상을 생성하는 연구를 진행하였다. 영상생성 딥러닝 네트워크는 generative adversarial network (GAN) 모델을 사용하였다. 연구결과 아무런 전처리도 거치지 않은 CT 영상을 이용하여 영상을 생성하는 것 보다 히스토그램 균일화 과정을 거친 영상이 더 좋은 결과를 나타냈으며 생성영상이 기존의 실제 영상과 영상의 구조적 유사도가 높음을 확인할 수 있다. 본 연구결과 딥러닝 영상생성 모델을 이용하여 조영증강 CT 영상을 생성할 수 있었으며, 이를 통하여 환자의 불필요한 방사선 피폭을 최소하며, 생성된 조영증강 CT 영상을 바탕으로 정확한 진단 및 치료반응 평가에 기여할 수 있을거라 기대된다.

• Journal of Trauma and Injury
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• v.34 no.4
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• pp.294-298
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• 2021

Extrahepatic biliary tract and gallbladder injuries following blunt abdominal trauma are uncommon. Traumatic cystic duct transection is even rarer, which has frequently caused missed diagnosis and delayed treatment. An 18-year-old female patient with no past medical history was transferred to the Trauma Center of Kyungpook National University Hospital after falling from a height of approximately 20 meters. She became hemodynamically stable after initial resuscitation, and initial contrast-enhanced abdominal computed tomography (CT) showed right kidney traumatic infarction and multiple intrahepatic contusions with minimal fluid collection but no extravasation of the contrast. She was admitted to the intensive care unit. On the second day of hospitalization, her abdomen became distended, with follow-up CT showing a large collection of intra-abdominal fluid. Laparoscopic exploration was then performed, which revealed devascularization of the gallbladder with complete transection of the cystic duct and artery. Laparoscopic cholecystectomy was performed, as well as primary closure of the cystic duct orifice on the common bile duct using a 4-0 Prolene suture. After surgery, no clinical evidence of biliary leakage or common bile duct stricture was observed.

• Investigative Magnetic Resonance Imaging
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• v.13 no.2
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• pp.152-160
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• 2009

Purpose : To intra-individually compare diagnostic accuracy of high-resolution contrast-enhanced magnetic resonance angiography (CE-MRA) with computed tomography angiography (CTA) and digital subtraction angiography (DSA) for the assessment of supraaortic steno-occlusive disease. Materials and Methods : Twenty-eight patients (20 men, 8 women, 53-79 years of age) underwent supraaortic CE-MRA, CTA and DSA. CE-MRA was performed on two 1.5T MR scanners (voxel dimension: $0.66{\times}0.66{\times}1.1$ or $1.2\;mm^3$), and CTA on 64-slice CT scanners (voxel dimension: $0.42{\times}0.42{\times}0.63\;mm^3$). All the three examinations were completed within 40 days (median 19 days; range 1-40 days). Retrospective evaluation and measurement of diameter of 6 extracranial and 9 intracranial arterial segments was done by 2 experienced radiologists. Results: A total of 420 arterial segments were examined by CE-MRA, CTA and DSA. On DSA, 34 stenoocclusive lesions were noted at extracranial (n= 19) and intracranial (n = 15) vessels. For extracranial stenosis greater than 70%, sensitivity, specificity, positive predictive value (PPV) and negative predictive values (NPV) were 94.7%, 98.7%, 90.0% and 99.3% on CE-MRA, and 94.7%, 99.3%, 94.7% and 99.3% on CTA. For intracranial stenosis greater than 50%, sensitivity; specificity, PPV and NPV were 93.3%, 98.3%, 77.8%and 99.6% on CE-MRA, and 86.7%, 97.9%, 72.2% and 99.1 % on CTA, with DSA as the standard of reference. Conclusion : Supraaortic CE-MRA is as reliable as CTA in depicting the arterial stenosis, and is effective in screening of significant stenosis of both extracranial and intracranial arterial stenosis.

• Progress in Medical Physics
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• v.16 no.1
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• pp.47-51
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• 2005

We report a case of an accidental extravasation of contrast material. A large-volume extravasation occurred in an adult during spiral contrast-enhanced CT. The amount of contrast material extravasated was 47 ml. The patient had a swelling of the dorsum right hand. The extravasation injury site was determined by CT scanning. The extavasation case was examined using five separate display techniques: axial, multi planar reformation (MPR), maximum intensity projection (MIP), volume rendering, and shaded-surfaced display (SSD). This paper introduces extravasation with the CT and the three-dimensional appearance.

• Journal of Chest Surgery
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• v.53 no.5
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• pp.321-323
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• 2020

We describe the occurrence of acute type A aortic dissection in a patient with situs inversus totalis. A 37-year-old man presented to the emergency department with acute chest pain. Initial chest X-ray findings showed a right-sided heart and a left-sided liver. Contrast-enhanced computed tomography revealed a Stanford type A acute aortic dissection, aortic root dilatation, and situs inversus totalis. All of the thoracic structures were mirror-image reversed and an abnormal coronary artery was observed. The Bentall operation was performed. This report demonstrates that computed tomography and echocardiography were useful for understanding the anatomy and the presence or absence of concurrent anomalies in a patient with situs inversus totalis. The patient's postoperative course was uneventful.

• Progress in Medical Physics
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• v.29 no.4
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• pp.150-156
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• 2018

This study aims to develop an improved Feldkamp-Davis-Kress (FDK) reconstruction algorithm using anisotropic total variation (ATV) minimization to enhance the image quality of low-dose cone-beam computed tomography (CBCT). The algorithm first applies a filter that integrates the Shepp-Logan filter into a cosine window function on all projections for impulse noise removal. A total variation objective function with anisotropic penalty is then minimized to enhance the difference between the real structure and noise using the steepest gradient descent optimization with adaptive step sizes. The preserving parameter to adjust the separation between the noise-free and noisy areas is determined by calculating the cumulative distribution function of the gradient magnitude of the filtered image obtained by the application of the filtering operation on each projection. With these minimized ATV projections, voxel-driven backprojection is finally performed to generate the reconstructed images. The performance of the proposed algorithm was evaluated with the catphan503 phantom dataset acquired with the use of a low-dose protocol. Qualitative and quantitative analyses showed that the proposed ATV minimization provides enhanced CBCT reconstruction images compared with those generated by the conventional FDK algorithm, with a higher contrast-to-noise ratio (CNR), lower root-mean-square-error, and higher correlation. The proposed algorithm not only leads to a potential imaging dose reduction in repeated CBCT scans via lower mA levels, but also elicits high CNR values by removing noisy corrupted areas and by avoiding the heavy penalization of striking features.

• Journal of the Korean Society of Radiology
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• v.82 no.2
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• pp.487-492
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• 2021

Immunoglobulin G4 (IgG4)-related disease is a systemic disease characterized by dense lymphoplasmacytic infiltrates with abundant IgG4-positive plasma cells and fibroblast proliferation. The retroperitoneal involvement of IgG4-related disease usually appears as a soft-tissue mass covering the abdominal aorta or entrapping the ureters, resulting in hydronephrosis. Here, we present a case of IgG4-related disease with retroperitoneal involvement in a 75-yearold woman with an unusual manifestation. A preoperative computed tomography (CT) scan revealed an irregular infiltrative retroperitoneal mass invading the normal anatomic barriers, raising the suspicion of malignancy or inflammation. Contrast-enhanced CT revealed a homogeneous progressive enhancement of the mass.