• Korean Journal of Radiology
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• v.24 no.10
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• pp.1006-1016
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• 2023

Objective: Computed tomography (CT) is an established method for the diagnosis, staging, and treatment of multiple myeloma. Here, we investigated the potential of photon-counting detector computed tomography (PCD-CT) in terms of image quality, diagnostic confidence, and radiation dose compared with energy-integrating detector CT (EID-CT). Materials and Methods: In this prospective study, patients with known multiple myeloma underwent clinically indicated whole-body PCD-CT. The image quality of PCD-CT was assessed qualitatively by three independent radiologists for overall image quality, edge sharpness, image noise, lesion conspicuity, and diagnostic confidence using a 5-point Likert scale (5 = excellent), and quantitatively for signal homogeneity using the coefficient of variation (CV) of Hounsfield Units (HU) values and modulation transfer function (MTF) via the full width at half maximum (FWHM) in the frequency space. The results were compared with those of the current clinical standard EID-CT protocols as controls. Additionally, the radiation dose (CTDIvol) was determined. Results: We enrolled 35 patients with multiple myeloma (mean age 69.8 ± 9.1 years; 18 [51%] males). Qualitative image analysis revealed superior scores (median [interquartile range]) for PCD-CT regarding overall image quality (4.0 [4.0-5.0] vs. 4.0 [3.0-4.0]), edge sharpness (4.0 [4.0-5.0] vs. 4.0 [3.0-4.0]), image noise (4.0 [4.0-4.0] vs. 3.0 [3.0-4.0]), lesion conspicuity (4.0 [4.0-5.0] vs. 4.0 [3.0-4.0]), and diagnostic confidence (4.0 [4.0-5.0] vs. 4.0 [3.0-4.0]) compared with EID-CT (P ≤ 0.004). In quantitative image analyses, PCD-CT compared with EID-CT revealed a substantially lower FWHM (2.89 vs. 25.68 cy/pixel) and a significantly more homogeneous signal (mean CV ± standard deviation [SD], 0.99 ± 0.65 vs. 1.66 ± 0.5; P < 0.001) at a significantly lower radiation dose (mean CTDIvol ± SD, 3.33 ± 0.82 vs. 7.19 ± 3.57 mGy; P < 0.001). Conclusion: Whole-body PCD-CT provides significantly higher subjective and objective image quality at significantly reduced radiation doses than the current clinical standard EID-CT protocols, along with readily available multi-spectral data, facilitating the potential for further advanced post-processing.

• The Korean Journal of Nuclear Medicine
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• v.27 no.1
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• pp.81-87
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• 1993

Retrospective analysis of cholescintigraphy and ultrasonography was done in 76 patients with clinically suspected acute cholecystitis to assess the relative value of the two modalities. Excluding the Patients with obstructive jaundice, the overall results of cholescintigraphy(sensitivity 100%, specificity 95%, false positive rate 5%, false negative rate 0%, accuracy 97%) are nearly identical with or rather superior to those of the ultrasonography(sensitivity 94%, specificity 100%, false positive rate 0%, false negative rate 5%, accuracy 97%). We recommend the cholescintigraphy as the initial modality in patients with clinically suspected acute cholecystitis, and ultrasonography can be used in jaundiced patients to exclude the possibility of the false positive of cholescintigraphy.

• 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.2 no.1
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• pp.52-56
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• 2001

Extracranial carotid artery dissection may manifest as arterial stenosis or occlusion, or as dissecting aneurysm formation. Anticoagulation and/or antiplatelet therapy is the first-line treatment, but because it is effective and less invasive than other procedures, endovascular treatment of carotid artery dissection has recently attracted interest. We encountered two consecutive cases of trauma-related extracranial internal carotid artery dissection, one in the suprabulbar portion and one in the subpetrosal portion. We managed the patient with suprabulbar dissection using a self-expandable metallic stent and managed the patient with subpetrosal dissection using a balloon-expandable metallic stent. In both patients the dissecting aneurysm disappeared, and at follow-up improved luminal patency was observed.

• Asian Pacific Journal of Cancer Prevention
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• v.15 no.11
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• pp.4705-4709
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• 2014

Objective: To determine the accuracy of magnetic resonance imaging (MRI) in detection of metastasis in pelvic and para-aortic lymph nodes from different gynecological malignancies. Materials and Methods: This retrospective cross sectional analytic study was conducted at the Department of Diagnostic Radiology, Aga Khan University Hospital Karachi Pakistan from January 2011 to December 2012. A sample of 48 women, age range between 20-79 years, fulfilling inclusion criteria were included. All patients had histopathologically proven gynecological malignancies in the cervix, endometrium or ovary and presented for a pretreatment MRI to our radiology department. Results: MRI was 100% sensitive and had a 100% positive predictive value to detect lymph node metastasis in lymph nodes with spiculated margins and 100% sensitive with a 75% positive predictive value to detect lymph node metastasis in a lymph node with lobulated margins. The sensitivity and positive predictive value of MRI to detect heterogeneous nodal enhancement were 100% and 75% respectively. Conclusions: Our study results reinforce that MRI should be used as a modality of choice in the pretreatment assessment of lymph nodes in proven gynaecological malignancies in order to determine the line of patientmanagement, distinguishing surgical from non-surgical cases.

• The Korean Journal of Nuclear Medicine
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• v.26 no.1
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• pp.58-64
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• 1992

We performed exercise radionuclide ventriculography to evaluate left ventricular (LV) function in 35 patients with pure mitral stenosis (MS). There were 6 males and 29 females ranging from 21 to 63 years of age (mean $37{\pm}10$ years). We also studied 8 healthy men as control group (mean age $27{\pm}5$ years). Each patients was evaluated at rest and during maximal exercise on an isokinetic bicycle ergometer. Peak filling rate (PFR), peak ejection rate (PER), ejection fracion (EF), end-diastolic volume (EDV), end-systolic volume (ESV), stroke volume (SV), and cardiac output (CO) were determined by the radionuclide technique. The results were summarized as follows: 1) LV systolic dysfunction and reduced PFR were noted in patients with MS. 2) EDV as well as SV decreased with exercise in patients with MS. 3) No significant increase in EF during exercise compared to rest value was observed because it was caused by reduced EDV and SV during exercise in patients with MS. 4) CO increased with exercise was significantly lower than normal in patients with MS. 5) Patients with MS were divided into two groups according to whether SF increased more than 5% druing exercise compared to resting state or decreased. Significant difference were found between these two groups. Patients with a fall in EF with exercise were older, had larger left atrial size, and had lesser decreased in ESV during exercise.

• Quality Improvement in Health Care
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• v.19 no.1
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• pp.64-72
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• 2013

Objective: To improve customer satisfaction through accurate information using computerized automation of the test reservation system and by performing all fasting tests on the same day with one fasting. Methods: Quality improvement activities of the test reservation system of Seoul National University Bundang Hospital improves internal and external customer satisfaction at the time of test scheduling by having the reservation system reflect test order and test time automatically and making the system to increase the same day test reservation rate. Results: Test process was smooth due to accurate test reservation and information based on test priority due to the introduction of the computerized test reservation system. Internal and external customer satisfaction improved due to the marked reduction in time required for making a reservation thanks to the improvement of work process. Conclusion: Building a computerized test reservation system was an effective measure to improve external and internal customer satisfaction.

• Korean Journal of Radiology
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• v.21 no.1
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• pp.108-116
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• 2020

Objective: To investigate the concordance of three international guidelines: the Korean Thyroid Association/Korean Society of Thyroid Radiology, American Thyroid Association, and American College of Radiology for thyroid nodules classified by ultrasonography (US) and the diagnostic performance of simulated size criteria for malignant biopsies. Materials and Methods: A total of 2586 thyroid nodules (≥ 1 cm) were collected from two multicenter study datasets. The classifications of the thyroid nodules were based on three different guidelines according to US categories for malignancy risk, and the concordance rate between the different guidelines was calculated for the classified nodules. In addition, the diagnostic performance of criteria related to four different simulated biopsy sizes was evaluated. Results: The concordance rate of nodules classified as high- or intermediate-suspicion was high (84.1-100%), but low-suspicion or mildly-suspicious nodules exhibited relatively low concordance (63.8-83.8%) between the three guidelines. The differences in sensitivity, specificity, and accuracy between the guidelines were 0.7-19.8%, 0-40.9%, and 0.1-30.5%, respectively, when the original biopsy criteria were applied. The differences decreased to 0-5.9%, 0-10.9%, and 0.1-8.2%, respectively, when simulated, similar biopsy size criteria were applied. The unnecessary biopsy rate calculated with the original criteria (0-33.8%), decreased with the simulated biopsy size criteria (0-8.7%). Conclusion: We found a high concordance between the three guidelines for high- or intermediate-suspicion nodules, and the diagnostic performance of the biopsy criteria was approximately equivalent for each simulated size criterion. The difference in diagnostic performance between the three guidelines is mostly influenced by the various size thresholds for biopsies.

• Korean Journal of Radiology
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• v.22 no.7
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• pp.1213-1224
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• 2021

Objective: To develop a machine learning (ML) pipeline based on radiomics to predict Coronavirus Disease 2019 (COVID-19) severity and the future deterioration to critical illness using CT and clinical variables. Materials and Methods: Clinical data were collected from 981 patients from a multi-institutional international cohort with real-time polymerase chain reaction-confirmed COVID-19. Radiomics features were extracted from chest CT of the patients. The data of the cohort were randomly divided into training, validation, and test sets using a 7:1:2 ratio. A ML pipeline consisting of a model to predict severity and time-to-event model to predict progression to critical illness were trained on radiomics features and clinical variables. The receiver operating characteristic area under the curve (ROC-AUC), concordance index (C-index), and time-dependent ROC-AUC were calculated to determine model performance, which was compared with consensus CT severity scores obtained by visual interpretation by radiologists. Results: Among 981 patients with confirmed COVID-19, 274 patients developed critical illness. Radiomics features and clinical variables resulted in the best performance for the prediction of disease severity with a highest test ROC-AUC of 0.76 compared with 0.70 (0.76 vs. 0.70, p = 0.023) for visual CT severity score and clinical variables. The progression prediction model achieved a test C-index of 0.868 when it was based on the combination of CT radiomics and clinical variables compared with 0.767 when based on CT radiomics features alone (p < 0.001), 0.847 when based on clinical variables alone (p = 0.110), and 0.860 when based on the combination of visual CT severity scores and clinical variables (p = 0.549). Furthermore, the model based on the combination of CT radiomics and clinical variables achieved time-dependent ROC-AUCs of 0.897, 0.933, and 0.927 for the prediction of progression risks at 3, 5 and 7 days, respectively. Conclusion: CT radiomics features combined with clinical variables were predictive of COVID-19 severity and progression to critical illness with fairly high accuracy.

• Journal of the Korean Society of Radiology
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• v.15 no.2
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• pp.159-164
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• 2021

The examination using diagnostic x-ray equipment is one of the most useful diagnostic equipment for identifying information in the human body in diagnostic radiology. For this reason, the number of examinations has recently increased a lot. Increasing the number of examinations will accelerate the aging of the device. In addition, this makes them aware of the importance of quality control for the diagnostic x-ray device. Particularly, in a diagnostic x-ray device, quality control refers to an act of always maintaining a certain level of image quality by identifying and correcting all problems that may lead to reduction of the diagnosis area in advance. Therefore, this study summarizes and reports general information about quality control in examinations using diagnostic x-ray equipment.