• The Journal of the Korea Contents Association
• /
• v.12 no.10
• /
• pp.340-348
• /
• 2012

To evaluate the usefulness of tomosynthesis in the chest area, simple radiograph, low-dose CT, and tomosynthesis examinations were performed, and their absorbed doses were compared, and finally the images were evaluated. The absorbed dose recorded with the simple Radiograph examination was $0.33{\pm}0.27$ mGy, that of low-dose CT $1.26{\pm}0.56$ mGy, and that of tomosynthesis $0.55{\pm}0.02$ mGy, which indicate significance differences in absorbed doses among the examinations(p<0.001). Based on the evaluations of the images, The simple radiograph scores were $1.66{\pm}0.72$, $1.61{\pm}0.63$, and $1.57{\pm}0.73$, respectively; low-dose CT scores were $2.92{\pm}0.26$, $2.91{\pm}0.29$, and $2.88{\pm}0.32$, respectively; and tomosynthesis scores were $2.69{\pm}0.51$, $2.76{\pm}0.43$, and $2.66{\pm}0.61$, respectively. That is, there were statistically significant differences among the examinations(p<0.001), although there was no significant difference between low-dose CT and tomosynthesis examinations. Therefore, tomosynthesis is judged to be a useful examination that can minimize radiation doses to patients during chest examinations and enhance diagnostic efficacy.

• Progress in Medical Physics
• /
• v.26 no.1
• /
• pp.28-35
• /
• 2015

In this study, we investigated the effects of an iterative reconstruction algorithm and an automatic exposure control (AEC) technique on image quality and radiation dose through phantom experiments with coronary computed tomography (CT) angiography protocols. We scanned the AAPM CT performance phantom using 320 multi-detector-row CT. At the tube voltages of 80, 100, and 120 kVp, the scanning was repeated with two settings of the AEC technique, i.e., with the target standard deviations (SD) values of 33 (the higher tube current) and 44 (the lower tube current). The scanned projection data were reconstructed also in two ways, with the filtered back projection (FBP) and with the iterative reconstruction technique (AIDR-3D). The image quality was evaluated quantitatively with the noise standard deviation, modulation transfer function, and the contrast to noise ratio (CNR). More specifically, we analyzed the influences of selection of a tube voltage and a reconstruction algorithm on tube current modulation and consequently on radiation dose. Reduction of image noise by the iterative reconstruction algorithm compared with the FBP was revealed eminently, especially with the lower tube current protocols, i.e., it was decreased by 46% and 38%, when the AEC was established with the lower dose (the target SD=44) and the higher dose (the target SD=33), respectively. As a side effect of iterative reconstruction, the spatial resolution was decreased by a degree that could not mar the remarkable gains in terms of noise reduction. Consequently, if coronary CT angiogprahy is scanned and reconstructed using both the automatic exposure control and iterative reconstruction techniques, it is anticipated that, in comparison with a conventional acquisition method, image noise can be reduced significantly with slight decrease in spatial resolution, implying clinical advantages of radiation dose reduction, still being faithful to the ALARA principle.

• Journal of the Korean Society of Radiology
• /
• v.83 no.3
• /
• pp.669-679
• /
• 2022

Purpose To evaluate the feasibility of pediatric low-dose facial CT reconstructed with filtered back projection (FBP) using adequate kernels. Materials and Methods We retrospectively reviewed the clinical and imaging data of children aged < 10 years who underwent facial CT at our emergency department. The patients were divided into two groups: low-dose CT (LDCT; Group A, n = 73) with a fixed 80-kVp tube potential and automatic tube current modulation (ATCM) and standard-dose CT (SDCT; Group B, n = 40) with a fixed 120-kVp tube potential and ATCM. All images were reconstructed with FBP using bone and soft tissue kernels in Group A and only bone kernel in Group B. The groups were compared in terms of image noise, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR). Two radiologists subjectively scored the overall image quality of bony and soft tissue structures. The CT dose index volume and dose-length product were recorded. Results Image noise was higher in Group A than in Group B in bone kernel images (p < 0.001). Group A using a soft tissue kernel showed the highest SNR and CNR for all soft tissue structures (all p < 0.001). In the qualitative analysis of bony structures, Group A scores were found to be similar to or higher than Group B scores on comparing bone kernel images. In the qualitative analysis of soft tissue structures, there was no significant difference between Group A using a soft tissue kernel and Group B using a bone kernel with a soft tissue window setting (p > 0.05). Group A showed a 76.9% reduction in radiation dose compared to Group B (3.2 ± 0.2 mGy vs. 13.9 ± 1.5 mGy; p < 0.001). Conclusion The addition of a soft tissue kernel image to conventional CT reconstructed with FBP enables the use of pediatric low-dose facial CT protocol while maintaining image quality.

• Proceedings of the Korean Society of Broadcast Engineers Conference
• /
• 2013.06a
• /
• pp.274-277
• /
• 2013

CT(Computed Tomography)영상에서 선량과 화질은 중요한 요소이다. 선량은 환자에게 직접적으로 악영향을 끼치는 요소이며, 화질은 환자의 병변을 판단하는데 매우 중요하게 작용한다. 반복적 재구성 알고리즘을 이용하면 저선량 영상에서도 고화질의 영상을 얻을 수 있는지 FBP와 정량적, 정성적으로 비교하였다. 촬영 프로토콜은 관전압 80, 100, 120kVp에서 관전류를 동일하게 200mA로 촬영하여 획득하였으며, 정량적 평가를 위해 SD(Standard Deviation), SNR(Signal to Noise Ratio), MTF(Modulation Transfer Function)를 측정하여 분석하였다. 선량은 80kVp일 때 가장 낮았으며, 120kVp일 때 가장 높았다. 80kVp의 영상을 Toshiba 사(社)의 AIDR 3D(Adaptive Iterative Reduction integrated into $^{SURE}Exposure$)로 재구성하고, 120kVp의 영상에 FBP로 재구성한 다음 정량적 비교를 한 결과 AIDR 3D를 적용한 영상의 SD가 낮게 나왔으며, SNR이 높게 나타났고, MTF 곡선은 유사하게 나타났다. 그리고 FWHM(Full Width at Half Maximum) 값의 오차가 거의 없었다. 결론적으로 AIDR 3D는 저선량에서도 높은 화질을 나타냄을 확인하였다.

• Proceedings of the Korea Information Processing Society Conference
• /
• 2015.04a
• /
• pp.1041-1043
• /
• 2015

본 논문은 저선량 흉부 CT 영상을 활용하여 패결절을 자동으로 검출하는 알고리즘에 관한 연구내용을 담고 있다. 폐 결절 자동 검출을 위해 폐 CT 영상 내에 폐결절의 가지고 있는 특징들 중, 이동성 및 기하학적 특징을 가지고 폐혈관과 폐결절을 구분하였다. 실험한 영상은 폐결절이 없는 정상환자군을 가지고 실시 하였으며, 그 결과 4.4False Positive / Scan이 발생하였다.

• Journal of the Korean Society of Radiology
• /
• v.15 no.3
• /
• pp.301-306
• /
• 2021

The use of tin filters as a way to reduce the medical radiation in computed tomography (CT). However, due to the changed X-ray spectrum with the use of tin filters, disease diagnosis could be affected because it appears as images of different impressions from previous images. Therefore, this study evaluates the changes in images when using tin filter and high pitch in chest low-dose CT. In this study, images were acquired in groups of three for comparison. Group 1 did not apply to tin filter, and used the existing pitch 0.8. Group 2 used a tin filter, pitch 0.8, Group 3 used a tin filter, and pitch 2.5. To compare the image quality, the natural image quality evaluator (NIQE) and the blind/referenceless image quality evaluator (BRISQUE) were used among the blind quality evaluation factors depended on a no-reference basis. As a result, the NIQE values were low in the order of Group 1, Group 3, and Group 2. BRISQUE values were low in the order of Group 3, Group 2 and Group 1. This study confirms the superiority of images of tin filter and high pitch techniques in chest low-dose CT, which is considered to be a fundamental study for acquiring accurate images of patients with difficult breathing control.

• Journal of the Korean Society of Radiology
• /
• v.17 no.3
• /
• pp.343-350
• /
• 2023

Based on Lung CT Screening Reporting and Data System (Lung-RADS), which has been used to standardize reading for lung cancer screening since November 2016, the types and frequency of "S" modifier findings other than lung cancer were analyzed. As a result of this study, 360 cases (35.19%) of "S" modifier were found in 1,023 subjects, and the most frequent diseases were coronary calcification and emphysema, 145 (14.17%) of coronary calcification and 138 (13.49%) of emphysema, indicating that the discovery rate was very high compared to other findings. In addition, it was found to be highly associated with the duration of smoking, and in the case of coronary calcification, 9 cases (5.73%) were found in the non-smokers group A, 23 cases (11.44%) within 10 years of smoking, 39 cases (13.68%) in the C group within 20 years of smoking, and 31% of the E group over 30 years of smoking. In addition to coronary calcification and emphysema, abnormal findings of pneumonia, lung epilepsy, and mediastinal disease were also found to be p<0.05 as a result of the analysis of the association with the smoking period, indicating that the smoking period was affected.

• Radiation Oncology Journal
• /
• v.14 no.2
• /
• pp.123-128
• /
• 1996

Purpose : This is a retrospective study to compare the Palliation rates, survival rates and complications of low dose rate and high dose rate endobronchial brachytherapy in the management of malignant airway obstruction. Materials and methods : Forty three consecutive patients with malignant airway compromise from primary or metastatic lung tumors were treated with low dose rate(LDR) endobronchial Iridium-192 insertion(21 patients) between October 1988 and June 1992, and high dose rate(HDR) endobronchial brachytherapy(22 patients) between August 1992 and April 1994 with palliative aim Flexible fiberoptic bronchoscopy under fluoroscopic control was utilized in all 91 procedures. Twenty seven LDR Procedures delivered a dose of 5-7.5 Gy to a 1.0 cm radius respectively. Results : Subjective and objective responses to treatments were evaluated on follow-up examinations by clinical examination, chest x-rays and CT scan of the chest on some patients. Fifteen of 21 LDR patients and 19 of 22 HDR Patients showed subjective improvement in terms of better breathing and less Productive cough as well as complete disappearance of hemoptysis. Objective improvement on chest x-rays and CT scan of the chest had been demonstrated on 8 LDR Patients and 10 HDR patients. Conclusion : The technique of LDR and HDR endobronchial brachytherapy is simple and well tolerated procedure with minimal morbidity It Provides excellent palliation by keeping airway Patent in these short life-spanned patients.

• Progress in Medical Physics
• /
• v.23 no.1
• /
• pp.54-61
• /
• 2012

A polymer gel dosimeter was fabricated. A 3-dimensional dosimetry experiment was performed in the small field of the photon of the cyberknife. The dosimeter was installed in a head and neck phantom. It was manufactured from the acrylic and it was used in dosimetry. By using the head and neck CT protocol of the CyberKnife system, CT images of the head and neck phantom were obtained and delivered to the treatment planning system. The irradiation to the dosimeter in the treatment planning was performed, and then, the image was obtained by using 3.0T magnetic resonance imaging (MRI) after 24 hours. The dose distribution of the phantom was analyzed by using MATLAB. The results of this measurement were compared to the results of calculation in the treatment planning. In the isodose curve on the axial direction, the dose distribution coincided with the high dose area, 0.76mm difference on 80%, rather than the low dose area, 1.29 mm difference on 40%. In this research, the fact that the polymer gel dosimeter and MRI can be applied for analyzing a small field in a 3 dimensional dosimetry was confirmed. Moreover, the feasibility of using these for the therapeutic radiation quality control was also confirmed.

• Journal of the Korean Society of Radiology
• /
• v.16 no.4
• /
• pp.411-417
• /
• 2022

This study aimed to learn and evaluate the effectiveness of VGGNet in the detection of pulmonary emphysema using low-dose chest computed tomography images. In total, 8000 images with normal findings and 3189 images showing pulmonary emphysema were used. Furthermore, 60%, 24%, and 16% of the normal and emphysema data were randomly assigned to training, validation, and test datasets, respectively, in model learning. VGG16 and VGG19 were used for learning, and the accuracy, loss, confusion matrix, precision, recall, specificity, and F1-score were evaluated. The accuracy and loss for pulmonary emphysema detection of the low-dose chest CT test dataset were 92.35% and 0.21% for VGG16 and 95.88% and 0.09% for VGG19, respectively. The precision, recall, and specificity were 91.60%, 98.36%, and 77.08% for VGG16 and 96.55%, 97.39%, and 92.72% for VGG19, respectively. The F1-scores were 94.86% and 96.97% for VGG16 and VGG19, respectively. Through the above evaluation index, VGG19 is judged to be more useful in detecting pulmonary emphysema. The findings of this study would be useful as basic data for the research on pulmonary emphysema detection models using VGGNet and artificial neural networks.