• Journal of the Korean Society of Radiology
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• v.13 no.7
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• pp.933-939
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• 2019

The purpose of this study is to provide basic clinical data by evaluating images, measuring absorbed dose and effective dose by using high resolution CT and low dose CT by using anthropomorphic chest phantom and glass dosimeter. Tissue dose was measured by inserting a glass dosimeter into the anthropomorphic chest phantom. A 64-slice CT system (SOMATOM Sensation 64, Siemens AG, Forchheim, Germany) and CARE Dose 4D were used, and the parameters of the high resolution CT were 120 kVp, Eff. Scan parameters of mAs 104, scan time 7.93 s, slice 1.0 mm (Acq. 64 × 0.6 mm), convolution kernel (B60f sharp) were used, and low dose CT was 120 kVp, Eff. mAs 15, scan time 7.41 s, slice 3.0 mm (Acq. 64 × 0.6 mm), scan of convolution kernel B50f medium sharp. CTDIvol was measured at 8.01 mGy for high resolution CT and 1.18 mGy for low dose CT. Low dose CT scans showed 85.49% less absorbed dose than high resolution CT scans.

• Nuclear Medicine and Molecular Imaging
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• v.43 no.1
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• pp.26-34
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• 2009

Purpose: The purpose of this study was to find out what clinicopathologic or immunohistochemical parameter that may affect FDG uptake of primary tumor in PET/CT scan of the gastric carcinoma patient. Materials and Methods: Eighty-nine patients with stomach cancer who underwent pre-operative FDG PET/CT scans were included. In cases with perceptible FDG uptake in primary tumor, the maximum standardized uptake value (SUVmax) was calculated. The clinicopathologic results such as depth of invasion (T stage), tumor size, lymph node metastasis, tumor differentiation and Lauren's classification and immunohistochemical markers such as Ki-67 index, expression of p53, EGFR, Cathepsin D, c-erb-B2 and COX-2 were reviewed. Results: Nineteen out of 89 gastric carcinomas showed imperceptible FDG uptake on PET/CT images. In cases with perceptible FDG uptake in primary tumor, SUVmax was significantly higher in T2, T3 and T4 tumors than T1 tumors ($5.8{\pm}3.1$ vs. $3.7{\pm}2.1$, p=0.002). SUVmax of large tumors (above or equal to 3 cm) was also significantly higher than SUVmax of small ones (less than 3 cm) ($5.7{\pm}3.2$ vs. $3.7{\pm}2.0$, p=0.002). The intestinal types of gastric carcinomas according to Lauren showed higher FDG uptake compared to the non-intestinal types ($5.4{\pm}2.8$ vs. $3.7{\pm}1.3$, p=0.003). SUVmax between p53 positive group and negative group was significantly different ($6.0{\pm}2.8$ vs. $4.4{\pm}3.0$, p=0.035). No significant difference was found in presence of LN metastasis, tumor differentiation, Ki-67 index, and expression of EGFR, Cathepsin D, c-erb-B2 and COX-2. Conclusion: T stage of gastric carcinoma influenced the detectability of gastric cancer on FDG PET PET/CT scan. When gastric carcinoma was perceptible on PET/CT scan, T stage, size of primary tumor, Lauren's classification and p53 expression were related to degree of FDG uptake in primary tumor.

• Journal of the Korea Convergence Society
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• v.9 no.1
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• pp.433-440
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• 2018

Recently, MTV(metabolic tumor volume) has been used as indices of the whole tumor FDG uptake on FDG PET image but it is influenced by image reconstruction. The purpose of this study was to evaluate the correlation between actual volume and metabolic tumor volume applying different SUVmax threshold for different reconstruction algorithm on phantom study. Measurement were performed on a Siemens Biograph mCT40 using a NEMA IEC body phantom containing different size six spheres filled with F18-FDG applying four SBRs (4:1, 8:1, 10:1, 20:1). Images reconstructed four algorithms (OSEM3D, OSEM3D+PSF, OSEM3D +TOF, OSEM3D+TOF+PSF) and MTV were measured with different SUVmax threshold. Overall, the use of increasing thresholds result in decreasing MTV. and increasing the signal to background ratio decreased MTV by applying same SUVmax threshold. The 40% SUVmax threshold gave the best concordance between measured and actual volume in PSF and PSF+TOF reconstruction image. and the 45% threshold had the best correlation between the volume measured and actual volume in OSEM3D and TOF reconstruction image. we believe that this study will be used when the measurement of MTV applying various reconstruction image.

• Imaging Science in Dentistry
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• v.34 no.1
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• pp.13-18
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• 2004

Purpose : This study was to evaluate the influence of slice thickness of computed tomography (CT) and rapid protyping (RP) type on the accuracy of 3-dimensional medical model. Materials and Methods: Transaxial CT data of human dry skull were taken from multi-detector spiral CT. Slice thickness were 1, 2, 3 and 4 mm respectively. Three-dimensional image model reconstruction using 3-D visualization medical software (V-works /sup TM/ 3.0) and RP model fabrications were followed. 2-RP models were 3D printing (Z402, Z Corp., Burlington, USA) and Stereolithographic Apparatus model. Linear measurements of anatomical landmarks on dry skull, 3-D image model, and 2-RP models were done and compared according to slice thickness and RP model type. Results: There were relative error percentage in absolute value of 0.97, 1.98,3.83 between linear measurements of dry skull and image models of 1, 2, 3 mm slice thickness respectively. There was relative error percentage in absolute value of 0.79 between linear measurements of dry skull and SLA model. There was relative error difference in absolute value of 2.52 between linear measurements of dry skull and 3D printing model. Conclusion: These results indicated that 3-dimensional image model of thin slice thickness and stereolithographic RP model showed relative high accuracy.

• Archives of Craniofacial Surgery
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• v.10 no.2
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• pp.103-108
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• 2009

Purpose: Although there are many reports on the development of paranasal sinuses, few studies were performed with respect to the frontal sinus with 3D CT, especially in Korean children. In this study, we evaluated the normal development of frontal sinus in Korean children with 3D CT imaging. Methods: A total of 301 patients under the age of 20 were reviewed retrospectively. Maximal AP (anteroposterior) length, height and width were measured with the aid of computer device. The volume of frontal sinus was also evaluated. Results: At the age of more than 4, the pneumatization of frontal sinus was detected. Frontal sinus developed continuously and was observed in almost every children at the age of more than 17. The AP length, height, width and volume of frontal sinus were enlarged continuously until the age of 20. And the maximal growth of frontal sinus was observed at puberty. The width and volume of frontal sinus showed high correlation coefficient (r=0.8) relative to height or AP distance. Conclusion: The results of this study may be helpful in the comprehension of normal development of frontal sinus in Korean children.

• Progress in Medical Physics
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• v.33 no.4
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• pp.142-149
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• 2022

Purpose: This study seeks to compare the dosimetric parameters of the bulk electron density (ED) approach and synthetic computed tomography (CT) image in terms of position variation of the air cavity in magnetic resonance-guided radiotherapy (MRgRT) for patients with pancreatic cancer. Methods: This study included nine patients that previously received MRgRT and their simulation CT and magnetic resonance (MR) images were collected. Air cavities were manually delineated on simulation CT and MR images in the treatment planning system for each patient. The synthetic CT images were generated using the deep learning model trained in a prior study. Two more plans with identical beam parameters were recalculated with ED maps that were either manually overridden by the cavities or derived from the synthetic CT. Dose calculation accuracy was explored in terms of dose-volume histogram parameters and gamma analysis. Results: The D_95% averages were 48.80 Gy, 48.50 Gy, and 48.23 Gy for the original, manually assigned, and synthetic CT-based dose distributions, respectively. The greatest deviation was observed for one patient, whose D_95% to synthetic CT was 1.84 Gy higher than the original plan. Conclusions: The variation of the air cavity position in the gastrointestinal area affects the treatment dose calculation. Synthetic CT-based ED modification would be a significant option for shortening the time-consuming process and improving MRgRT treatment accuracy.

• Korean Journal of Radiology
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• v.24 no.4
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• pp.294-304
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• 2023

Objective: We aimed to investigate whether image standardization using deep learning-based computed tomography (CT) image conversion would improve the performance of deep learning-based automated hepatic segmentation across various reconstruction methods. Materials and Methods: We collected contrast-enhanced dual-energy CT of the abdomen that was obtained using various reconstruction methods, including filtered back projection, iterative reconstruction, optimum contrast, and monoenergetic images with 40, 60, and 80 keV. A deep learning based image conversion algorithm was developed to standardize the CT images using 142 CT examinations (128 for training and 14 for tuning). A separate set of 43 CT examinations from 42 patients (mean age, 10.1 years) was used as the test data. A commercial software program (MEDIP PRO v2.0.0.0, MEDICALIP Co. Ltd.) based on 2D U-NET was used to create liver segmentation masks with liver volume. The original 80 keV images were used as the ground truth. We used the paired t-test to compare the segmentation performance in the Dice similarity coefficient (DSC) and difference ratio of the liver volume relative to the ground truth volume before and after image standardization. The concordance correlation coefficient (CCC) was used to assess the agreement between the segmented liver volume and ground-truth volume. Results: The original CT images showed variable and poor segmentation performances. The standardized images achieved significantly higher DSCs for liver segmentation than the original images (DSC [original, 5.40%-91.27%] vs. [standardized, 93.16%-96.74%], all P < 0.001). The difference ratio of liver volume also decreased significantly after image conversion (original, 9.84%-91.37% vs. standardized, 1.99%-4.41%). In all protocols, CCCs improved after image conversion (original, -0.006-0.964 vs. standardized, 0.990-0.998). Conclusion: Deep learning-based CT image standardization can improve the performance of automated hepatic segmentation using CT images reconstructed using various methods. Deep learning-based CT image conversion may have the potential to improve the generalizability of the segmentation network.

• Progress in Medical Physics
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• v.23 no.1
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• pp.1-7
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• 2012

The purpose of this study was to develop the respiratory training system using individual characteristic guiding waveform to reduce the impact of respiratory motion that causes artifact in radiotherapy. In order to evaluate the improvement of respiratory regularity, 5 volunteers were included and their respiratory signals were acquired using the in-house developed belt-type sensor. Respiratory training system needs 10 free breathing cycles of each volunteer to make individual characteristic guiding waveform based on Fourier series and it guides patient's next breathing. For each volunteer, free breathing and guided breathing which uses individual characteristic guiding waveform were performed to acquire the respiratory cycles for 3 min. The root mean square error (RMSE) was computed to analyze improvement of respiratory regularity in period and displacement. It was found that respiratory regularity was improved by using respiratory training system. RMSE of guided breathing decreased up to 40% in displacement and 76% in period compared with free breathing. In conclusion, since the guiding waveform was easy to follow for the volunteers, the respiratory regularity was significantly improved by using in-house developed respiratory training system. So it would be helpful to improve accuracy and efficiency during 4D-RT, 4D-CT.

• Journal of the Korean Society of Radiology
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• v.84 no.4
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• pp.891-899
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• 2023

Purpose To survey perceptions of certified physicians on the protocol of chest CT in patients with coronavirus (COVID-19) using a negative pressure isolation stretcher (NPIS). Materials and Methods This study collected questionnaire responses from a total of 27 certified physicians who had previously performed chest CT with NPIS in COVID-19 isolation hospitals. Results The nine surveyed hospitals performed an average of 116 chest CT examinations with NPIS each year. Of these, an average of 24 cases (21%) were contrast chest CT. Of the 9 pulmonologists we surveyed, 5 (56%) agreed that patients who showed abnormalities in serum D-dimer required contrast chest CT. All 9 surveyed radiologists agreed that the image quality of the chest CT with NPIS was sufficient for CT image interpretation regarding pneumonia or pulmonary embolism. Furthermore, in our 9 surveyed infectionologists, 5 (56%) agreed that a risk of secondary infection in the CT room after temporary opening of NPIS could be prevented through a process of disinfection. Conclusion Experienced physicians considered that the effects of NIPS on chest CT image quality was minimal in patients with COVID-19, and the risk of CT room contamination was easily controlled.

• Nuclear Medicine and Molecular Imaging
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• v.42 no.1
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• pp.81-81
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• 2008

A 69-year old male with cholangiocellular carcinoma (CCC) was assigned to our department for whole body PET/CT scan. $^{18}F$-FDG PET/CT images showed an intense hypermetabolic lobulating mass(SUVmax = 8.7 / size : 11.4 mm) in the right hepatic lobe with multiple metastatic lung nodules. We made three dimensional volume rendering fusion images by using advantage workstation 4.3 (GE health care) which provide quick anatomic overview and improve the planning process significantly.