• The Korean Journal of Nuclear Medicine Technology
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• v.18 no.2
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• pp.33-38
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• 2014

Purpose Auto exposure control (AEC) in SPECT/CT automatically controls the exposure dose (mA) according to patient's shape and size. The aim of this study was to evaluate the effect of AEC in SPECT/CT on exposure dose reduction and image quality. Materials and Methods The model of SPECT/CT used in this study was Discovery 670 (GE, USA), Smart mA for AEC; and $^{99m}Tc$ as a radioisotope. To compare SPECT and CT images by CT exposure dose variation, we used a standard technique set at 80, 100, 120, 140 kVp, 10, 30, 50, 100, 150, 200, 250 mA, and AEC at 80, 100, 120, 140 kVp, 10-250 mA. To evaluate resolution and contrast of SPECT images, triple line phantom and flangeless Esser PET phantom were used. For CT images, noise and uniformity were checked by anthropomrphic chest phantom. For dose evaluation to find DLP value, anthropomorphic chest phantom was used and the CT protocol of torso was applied by standard technique (120 kVp, 100 mA) and AEC (120 kVp, 10-250 mA). Results When standard and AEC were applied, the resolutions at SPECT images with attenuation correction (AC) were the same as FWHM by center 3.65 mm, left 3.48 mm, right 3.61 mm. Contrasts of standard and AEC showed no significant difference: standard 53.5, 29.8, 22.5, 15.8, 6.0, AEC 53.5, 29.6, 22.4, 15.7, 6.1 In CT images, noise values at standard and AEC were 15.4 and 18.5 respectively. The application of AEC increases noise but the value of coefficient variation were 33.8, 24.9 respectively, obtaining uniform noise image. The values of DLP at standard and AEC were 426.78 and 352.09 each, which shows that the application of AEC decreases exposure dose more than standard by approximately 18%. Conclusion The results of our study show that there was no difference of AC in SPECT images based on the CT exposure dose variation at SPECT/CT images. It was found that the increased CT exposure dose leads to the improvement of CT image quality but also increases the exposure dose. Thus, the use of AEC in SPECT/CT contributes to obtaining equal AC SPECT images, and uniform noise in CT images while reducing exposure dose.

• The Journal of the Korea Contents Association
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• v.19 no.8
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• pp.284-292
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• 2019

To evaluate the usefulness of pediatric chest CT scans by comparing the dose, examination time, and image quality by applying Helical mode, High-pitch mode, and Volume Axial mode to minimize the radiation exposure and obtain high diagnostic value. Revolution (GE Healthcare, Wisconsin USA) was used to divide PBU-70 phantom into Helical mode, High-pitch mode, and Volume Axial mode. After acquiring images, ROI is set for each image, heart, bone, lung, and back-ground air, and the average value is obtained by measuring CT number (HU) and noise (SD). SNR and CNR were measured and compared with DLP values provided directly by the equipment. Determining statistical significance Statistical analysis was performed using ONE-WAY-ANAOVA using SPSS 21.0. In this experiment, it was possible to inspect at a short time without deterioration of image quality with the lowest dose when using volume axial mode. Although the detector coverage of 16 cm is limited to all pediatric chest CT scans, it is recommended to be actively used in pediatric patients, and further study is needed to apply other test sites in volume axial mode.

• Journal of Electrical Engineering and Technology
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• v.10 no.5
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• pp.2197-2204
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• 2015

In recent years, medical image diagnosis has growing significant momentous in the medicinal field. Brain and lung image of patient are distorted with salt and pepper noise is caused by moving the head and chest during scanning process of patients. Reconstruction of these images is a most significant field of diagnostic evaluation and is produced clearly through techniques such as linear or non-linear filtering. However, restored images are produced with smaller amount of noise reduction in the presence of huge magnitude of salt and pepper noises. To eliminate the high density of salt and pepper noises from the reproduction of images, a new efficient fuzzy based median filtering algorithm with a moderate elapsed time is proposed in this paper. Reproduction image results show enhanced performance for the proposed algorithm over other available noise reduction filtering techniques in terms of peak signal -to -noise ratio (PSNR), mean square error (MSE), root mean square error (RMSE), mean absolute error (MAE), image enhancement factor (IMF) and structural similarity (SSIM) value when tested on different medical images like magnetic resonance imaging (MRI) and computer tomography (CT) scan brain image and CT scan lung image. The introduced algorithm is switching filter that recognize the noise pixels and then corrects them by using median filter with fuzzy two-sided π- membership function for extracting the local information.

• The Korean Journal of Nuclear Medicine Technology
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• v.16 no.2
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• pp.29-34
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• 2012

Purpose : Presently, hardwares and softwares for reducing radiation exposure are continually developed for PET/CT examination. Purpose of this study is to evaluate effectiveness of reducing radiation exposure dose of CT and SUV changes of PET when applied each kernel to ACCT (Attenuation Correction Computed Tomography) according to adopted IRIS (Iterative Reconstruction in Image Space) software. Materials and Methods : Biograph mCT (Siemens, Germany) was used as a PET/CT scanner. Using AAPM CT performance phantom, from standard (120 kVp, 100 mAs), 7 scans were conducted by reducing 15 mAs each. After image reconstruction by FBP (Filtered Back Projection) and IRIS, noise and spatial resolution were evaluated. The same method was applied to anthropomorphic chest phantom and acquired images were compared. NEMA IEC body phantom was used for SUV evaluation. Injected dose rate for hot sphere (hot) and background cylinder (BKG) were 1:8. CT dose condition (120 kVp, 50 mAs) was the same for each scan and PET scan durations were 1, 2, 3 and 4min. After scanning, each kernel of IRIS was applied to ACCT. And PET images were reconstructed by ACCT adopted IRIS for comparing SUV changes. Results : AAPM phantom test for noise evaluation, SD for FBP 100 mAs, IRIS 55 mAs were 8.8 and 8.9. FBP 85 mAs, IRIS 40 mAs were 9.5 and 9.7. FBP 70 mAs, IRIS 25 mAs were 11.9 and 11.1. Above mAs condition for FBP and IRIS, SD showed similar values. And for spatial resolution test, there was no significant difference. For chest phantom test, when applied the same mAs and kernel to both of FBP and IRIS, every applied kernels showed reduced noise. Lower mAs and higher kernel value showed higher noise reduction. There was no considerable difference only except for I70 very sharp kernel for SUV comparison using NEMA IEC body phantom. Conclusion : In this study, low mAs (55 mAs) applied IRIS and standard mAs (100 mAs) applied FBP showed similar noise. And only except for I70 kernel, there was no significant SUV changes. It is possible to reduce needless radiation exposure and acquire better image quality than FBP's through applying appropriate kernel of IRIS to PET/CT.

• Journal of Radiation Protection and Research
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• v.37 no.2
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• pp.84-89
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• 2012

The purpose of this study was to compare radiation dose and image quality between low-dose (LDP) and standard-dose protocol (SDP). LDP (120 kVp, 30 mAs, 2-mm thickness) and SDP (120 kVp, 180 mAs, 1.2-mm thickness) images obtained from 61 subjects were retrospectively evaluated at level of carina bifurcation, using multi-detector CT (Brilliance 16, Philips Medical Systems). Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated at ascending aorta and infraspinatus muscle, from CT number and back-ground noise. Radiation dose from two protocols measured at 5-point using acrylic-phantom, and CT number and noise measured at 4-point using water-phantom. All statistical analysis were performed using SPSS 19.0 program. LDP images showed significantly more noise and a significantly lower SNR and CNR than did SDP images at ascending aorta and infraspinatus muscle. Noise, SNR and CNR were significantly correlated with body mass index (p<0.001). Radiation dose, SNR and CNR from phantom were significant differences between two protocols. LDP showed a significant reduction of radiation dose with a significant change in SNR and CNR compared with SDP. Therefore, exposure dose on LDP in clinical applications needs resetting highly more considering image quality.

• The KIPS Transactions:PartB
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• v.10B no.5
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• pp.509-514
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• 2003

The virtual bronchoscopy was implemented using chest CT images to visualize inside of tracheo-bronchial wall. The optical endoscopy procedures are invasive, uncomfortable for patients and sedation or anesthesia may be required. Also, they have serious side effects such as perforation, infection and hemorrhage. In order to determine the navigation path, we segmented the tracheo-bronchial wall from the chest CT image. We used the coordinates as a navigation path for virtual camera that were calculated from medial axis transformation. We used the perspective projection and marching cube algorithm to render the surface from volumetric CT image data. The tracheobronchial disease was classified into tracheobronchial stenosis causing from inflammation or lung cancer, bronchiectasis and bronchial cancer. The virtual bronchoscopy is highly recommended as a diagnosis tool with which the specific place of tracheobronchial disease can be identified and the degree of tracheobronchial disease can be measured qualitatively, Also, the virtual bronchoscopy can be used as an education and training tool for endoscopist and radiologist.

• Korean Journal of Radiology
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• v.19 no.6
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• pp.1031-1041
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• 2018

Objective: To compare image quality and radiation dose of high-pitch dual-source spiral cardiothoracic computed tomography (CT) between non-electrocardiography (ECG)-synchronized and prospectively ECG-triggered data acquisitions in young children with congenital heart disease. Materials and Methods: Eighty-six children (${\leq}3$ years) with congenital heart disease who underwent high-pitch dual-source spiral cardiothoracic CT were included in this retrospective study. They were divided into two groups (n = 43 for each; group 1 with non-ECG-synchronization and group 2 with prospective ECG triggering). Patient-related parameters, radiation dose, and image quality were compared between the two groups. Results: There were no significant differences in patient-related parameters including age, cross-sectional area, body density, and water-equivalent area between the two groups (p > 0.05). Regarding radiation dose parameters, only volume CT dose index values were significantly different between group 1 ($1.13{\pm}0.09mGy$) and group 2 ($1.07{\pm}0.12mGy$, p < 0.02). Among image quality parameters, significantly higher image noise ($3.8{\pm}0.7$ Hounsfield units [HU] vs. $3.3{\pm}0.6HU$, p < 0.001), significantly lower signal-to-noise ratio ($105.0{\pm}28.9$ vs. $134.1{\pm}44.4$, p = 0.001) and contrast-to-noise ratio ($84.5{\pm}27.2$ vs. $110.1{\pm}43.2$, p = 0.002), and significantly less diaphragm motion artifacts ($3.8{\pm}0.5$ vs. $3.7{\pm}0.4$, p < 0.04) were found in group 1 compared with group 2. Image quality grades of cardiac structures, coronary arteries, ascending aorta, pulmonary trunk, lung markings, and chest wall showed no significant difference between groups (p > 0.05). Conclusion: In high-pitch dual-source spiral pediatric cardiothoracic CT, additional ECG triggering does not substantially reduce motion artifacts in young children with congenital heart disease.

• Journal of Radiation Protection and Research
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• v.39 no.4
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• pp.206-212
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• 2014

We report here on the results of evaluating the radiation doses using chest computed tomography (CT) for patients with pneumoconiosis complication. For the first time, we visited the 17 MIPs to evaluate the dose-length product (DLP, $mGy{\cdot}cm$), CT unit, and protocols of scanning and image reconstruction those is routinely used for treating patients with pneumoconiosis who have complication. All statistical analysis was performed using the Statistical Program for Social Sciences (SPSS ver. 19.0, Chicago, IL, USA). Mean of total DLP was $727.7mGy{\cdot}cm$, ranging from 272.0 to $1228.7mGy{\cdot}cm$. DLP from obtaining parenchymal lung images was significantly reduced than that from obtaining total lung images (555.9 vs. 707.2, p<0.001). Third quartile of total and pre-scanning DLP was 1036.1 and $504.1mGy{\cdot}cm$, respectively. Chest CT radiation doses for patients with pneumoconiosis complication are similar with korean diagnostic reference level as well as international guidelines.

• The Journal of the Korea Contents Association
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• v.11 no.10
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• pp.333-341
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• 2011

To compare between calcium scoring CT (CSCT) and Low-dose CT (LDCT) image finding for coronary artery calcification (CAC) in screening of lung disease by MDCT. A total of 61 subjects who retired-workers exposed to inorganic dust were performed LDCT and CSCT by using a MDCT scanner on the same day, after be approved by the institutional review board, and obtaining the written informed consent from all subjects. LDCT images were read for detecting lung diseases as well as CAC by a experienced chest radiologist, then the subjects were divided either the positive group with CAC or the negative group without it. The CSCT was used to quantify and detect the presence of calcification in the coronary artery, and score of CAC calculated by using a Rapidia software (ver 2.8). In all coronary arteries, calcium score of positive group was higher better than that in negative group, especially in the total calcium (13.7 vs. 582.9, p=0.008) and the left anterior descending artery (3.2 vs. 249.0, p=0.006). CAC findings between CSCT and LDCT image were showed excellent agreement in cut-off point 100(K-value=0.80, 95% CI=0.69-0.91) from total calcium score. CAC findings on LDCT images showed the higher relation with CSCT. Therefore, the obstructive coronary artery disease could be predicted by CAC on LDCT images for screening of lung diseases.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2009.01a
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• pp.794-798
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• 2009

We introduce an implementation of plug-ins on PLUTO. These plug-ins discriminate inflammatory nodules from other types of nodules in chest X-ray CT images. The PLUTO is a common platform for computer-aided diagnosis systems on Microsoft Windows series and it is easy to add new functions as plug-ins. We coded two plug-ins. One of the them calculates features based on medical knowledge. The other plug-in calculates parameters to classify the type of nodules, and it also classifies nodules into inflammatory nodules and others using SVM. These plug-ins are coded using MIST library which is produced at Nagoya University, Japan. In our previous study, the MIST library was parallelized, so that we can utilize a number of CPUs to calculate features and SVM learning/classifying depending on the amount of computation. Using these plug-ins, it became easy to extract features to discriminate inflammatory nodules from other types of nodules and to change parameters for feature extraction and SVM learning/classifying with GUI interface. The accuracy of the classifying result is 100% with 78 solid nodules which contains 43 inflammatory nodules and 35 other type of nodules.