H. K. Lee

Analysis of low-dose radiation shield effectiveness of multi-gate polymeric sheets

Computed tomography (CT) uses a high dose of radiation to create images of the body. As patients are exposed to radiation during a CT scan, the use of shielding materials becomes essential in CT scanning. This study was focused on the radiation shielding materials used for patients during a CT scan. In this study, sheets were manufactured to shield the eyes and the thyroid, the most sensitive parts of the body, against radiation exposure during a CT scan. These sheets are manufactured using silicone polymers, barium sulfate (BaSO4) and tungsten, with the aim of making these sheets equally or more effective in radiation shielding and more cost-effective than lead sheets. The use of barium sulfate drew more attention than tungsten due to its higher cost-effectiveness. The barium sulfate sheets were coated to form a multigate structure by applying the maximum charge rate during the agitator and subsequent mixing processes and creating multilayered structures on the surface. To measure radiation shielding effectiveness, the radiation dose was measured around both eyes and the thyroid gland using sheets in three different thicknesses (1, 2 and 3 mm). Among the 1 and 2 mm sheets, the Pb sheets exhibited greater effectiveness in radiation shielding around both eyes, but the W sheets were more effective in radiation shielding around the thyroid gland. In the 3 mm sheets, the Pb sheet also attenuated a higher amount of radiation around both eyes while the W sheet was more effective around the thyroid gland. In conclusion, the sheets made from barium sulfate and tungsten proved highly effective in shielding against low-dose radiation in CT scans without causing ill-health effects, unlike lead.

Dose assessment according to changes in algorithm in cardiac CT

The principal objective of this study was to determine the effects of the application of the adaptive statistical iterative reconstruction (ASIR) technique in combination with another two factors (body mass index (BMI) and tube potential) on radiation dose in cardiac computed tomography (CT). For quantitative analysis, regions of interest were positioned on the central region of the great coronary artery, the right coronary artery, and the left anterior descending artery, after which the means and standard deviations of measured CT numbers were obtained. For qualitative analysis, images taken from the major coronary arteries (right coronary, left anterior descending, and left circumflex) were graded on a scale of 1–5, with 5 indicating the best image quality. Effective dose, which was calculated by multiplying the value of the dose length product by a standard conversion factor of 0.017 for the chest, was employed as a measure of radiation exposure dose. In cardiac CT in patients with BMI of less than 25 kg/m2, the use of 40% ASIR in combination with a low tube potential of 100 kVp resulted in a significant reduction in the radiation dose without compromising diagnostic quality. Additionally, the combination of the 120 kVp protocol and the application of 40% ASIR application for patients with BMI higher than 25 kg/m2 yielded similar results.

Factor analysis of the biochemical markers related to liver cirrhosis.

Objectives: The purpose of this study was to find the correlations between biochemical study and liver cirrhosis. Methods: The patients had liver biopsy to check the degree of their liver fibrosis, from August 2013 to August 2014 at the current medical center. In order to find the etiology of hepatitis, a research was done on gender, age, weight, and biochemical study through the investigation of subjects’ medical record and medical history. For biochemical study, we examined hemoglobin, platelets, albumin, aspartate aminotransferase (AST), alanine aminotransferase (ALT), total bilirubin, gamma-glutamyl transferase (GGT), prothrombin time (PT), and international normalised ratio (INR). We also analyzed the factors that are related to liver cirrhosis. Results: As a result, the patients at liver cirrhosis F≥2 stage showed 0.973, which is higher than the patients at FO stage with 0.943. F≥2 stage of hemoglobin was 0.544, which is lower than FO stage of hemoglobin with 0.817. Platelet count in F≥2 stage was 0.417, which is higher than FO stage with 0.074. For Albumin, F≥2 stage was 0.155 when F0 stage was 0.135. ATS’s F≥2 stage was 0.665, which is 6 times higher than FO stage with 0.100. Moreover, in the case of GGT, F≥2 stage was higher with 0.492 than FO stage with 0.078. Conclusions: In conclusion, it was confirmed that there is an increase in liver cirrhosis in the following general characteristics and biochemical factors: increase of age, increase of GGT, decrease of albumin, increase of the total bilirubin, and growth of INR (International Normalized Ratio).

Analyzing radiation absorption difference of dental substance by using Dual CT

The purpose of this study was to evaluate the changes of noise and computer tomography (CT) number in each dental substance, by using the metal artefact reduction algorithm; we used dual CT for this study. For the study, we produced resin, titanium, gypsum, and wax that are widely used by dentists. In addition, we made nickel to increase the artefact. While making the study materials, we made sure that there is no difficulty when inserting the substances inside phantom. In order to study, we scanned before and after using the metal artefact reduction algorithm. We conducted an average analysis of CT number and noise, before and after using the metal artefact reduction algorithm. As a result, there was no difference in CT number and noise before and after using the metal artefact reduction algorithm. However, when it comes to the noise value in each substance, waxs noise value was the lowest whereas titaniums noise value was the highest, after applying the metal artefact reduction algorithm. In nickel, CT number and noise value from artefact area showed a decreased noise value when applying the metal artefact reduction algorithm. In conclusion, we assumed that we could increase the effectiveness of CT examination by applying dual energys metal artefact reduction algorithm.

Analyzing correlation between epicardial fat area and metabolic syndrome risk factor by using low-dose Lung CT.

Objectives: To study about the blood count of a risk factor related to physical measurement and metabolic syndrome, and the area of epicardial fat for medical checkup patients. Methods: From April 1st to November 15th in 2014, we measured the area of epicardial fat in the adult out patients under 60 years of age, who are in good health; and the patients took the blood test and low-dose lung CT. In order to identify the relationship between the area of epicardial fat and the risk factor of metabolic syndrome, we conducted correlation analysis. Then, we performed multiple regression analysis to evaluate an independent correlation of epicardial area. In addition, we computed the cut-off value of epicardial fat area by using ROC (Receiver Operating Characteristic) curve to foresee a metabolic syndrome factor that has the most proper sensitivity and specificity. Results: Waist circumference, fasting blood sugar, triglyceride, high-density lipoprotein (HDL) cholesterol, systolic blood pressure, and diastolic blood pressure were shown to be the factors that affect the area of epicardial fat. Therefore, if waist circumference, fasting blood sugar, triglyceride, systolic blood pressure, and diastolic blood pressure were increased, the area of epicardial fat would be significantly increased (P<0.05); and if high-density lipoprotein cholesterol was increased, the area of epicardial fat would be significantly decreased (P<0.05). Out of metabolic syndrome factors, waist circumference’s ROC curve area was 0.79 (Confidence Interval 0.73-0.84, P<0.05), which was the highest. The sensitivity was 83.7% when specificity was 70.1%, which proves that they are important factors for the diagnosis. In brief, metabolic syndrome is a disease that mostly appears in obesity patients, so we should try to monitor and cure the disease. Conclusion: The risk factors of metabolic syndrome can be managed through health care, and if we try to decrease the risk factors, we will be able to shrink epicardial fat area and decrease metabolic syndrome at the same time.

Physical analysis of breast cancer using dual-source computed tomography

This study was aimed to analyze various physical characteristics of breast cancer using dual-source computed tomography (CT). A phantom study and a clinical trial were performed in order and a 64-multidetector CT device was used for the examinations. In the phantom study, single-source (SS) CT was set up with a conventional scanning condition that is usually applied for breast CT examination and implementation was done at tube voltage of 120 kVp. Dual-source CT acquired images by irradiating X-ray sources with fast switching between two kilovoltage settings (80 and 140 kVp). After scanning, Hounsfield Unit (HU) values and radiation doses in a region of interest were measured and analyzed. In the clinical trial, the HU values were measured and analyzed after single-source computed tomography (SSCT) and dual-source CT in patients diagnosed with breast cancer. Also, the tumor size measured by dual-source CT was compared with the actual tumor size. The phantom study determined that the tumor region was especially measured by dual-source CT, while nylon fiber and specks region were especially measured by SSCT. The radiation dose was high with dual-source CT. The clinical trial showed a higher HU value of cancerous regions when scanned by dual-source CT compared with SSCT.

Analysis of Images According to the Fluid Velocity in Time-of-Flight Magnetic Resonance Angiography, and Contrast Enhancement Angiography

In this study we evaluated that flow rate changes affect the (time of flight) TOF image and contrast-enhanced (CE) in a three-dimensional TOF angiography. We used a 3.0T MR System, a nonpulsatile flow rate model. Saline was used as a fluid injected at a flow rate of 11.4 cm/sec by auto injector. The fluid signal strength, phantom body signal strength and background signal strength were measured at 1, 5, 10, 15, 20 and 25-th cross-section in the experienced images and then they were used to determine signal-to-noise ratio and contrastto- noise ratio. The inlet, middle and outlet length were measured using coronal images obtained through the maximum intensity projection method. As a result, the length of inner cavity was 2.66 mm with no difference among the inlet, middle and outlet length. We also could know that the magnification rate is 49-55.6% in inlet part, 49-59% in middle part and 49-59% in outlet part, and so the image is generally larger than in the actual measurement. Signal-to-noise ratio and contrast-to-noise ratio were negatively correlated with the fluid velocity and so we could see that signal-to-noise ratio and contrast-to-noise ratio are reduced by faster fluid velocity. Signal-to-noise ratio was 42.2-52.5 in 5-25th section and contrast-to-noise ratio was from 34.0-46.1 also not different, but there was a difference in the 1st section. The smallest 3D TOF MRA measure was 2.51 ± 0.12 mm with a flow velocity of 40 cm/s. Consequently, 3D TOF MRA tests show that the faster fluid velocity decreases the signal-to-noise ratio and contrast-to-noise ratio, and basically it can be determined that 3D TOF MRA and 3D CE MRA are displayed larger than in the actual measurement.

Reduction in radiation dose with reconstruction technique in the brain perfusion CT

The principal objective of this study was to verify the utility of the reconstruction imaging technique in the brain perfusion computed tomography (PCT) scan by assessing reductions in the radiation dose and analyzing the generated images. The setting used for image acquisition had a detector coverage of 40 mm, a helical thickness of 0.625 mm, a helical shuttle mode scan type and a rotation time of 0.5 s as the image parameters used for the brain PCT scan. Additionally, a phantom experiment and an animal experiment were carried out. In the phantom and animal experiments, noise was measured in the scanning with the tube voltage fixed at 80 kVp (kilovolt peak) and the level of the adaptive statistical iterative reconstruction (ASIR) was changed from 0% to 100% at 10% intervals. The standard deviation of the CT coefficient was measured three times to calculate the mean value. In the phantom and animal experiments, the absorbed dose was measured 10 times under the same conditions as the ones for noise measurement before the mean value was calculated. In the animal experiment, pencil-type and CT-dedicated ionization chambers were inserted into the central portion of pig heads for measurement. In the phantom study, as the level of the ASIR changed from 0% to 100% under identical scanning conditions, the noise value and dose were proportionally reduced. In our animal experiment, the noise value was lowest when the ASIR level was 50%, unlike in the phantom study. The dose was reduced as in the phantom study.

Development of a new nanocrystalline alloy for X-ray shielding

ABSTRACT The purpose of this study was to develop a new nanocrystalline alloy material, which can replace lead for the purposes of radiation shielding as it is not hazardous to the human body and it is light in weight, to use the developed alloy in a fiber, and to evaluate its performance. This study used tungsten carbide and cobalt as the base metals and developed a new nanocrystalline alloy material. Then, radiation-shielding fibers 0.2 and 0.4 mm thick were created from the prepared tungsten carbide and cobalt powder. Equivalent dose was measured and shielding rate was obtained by the lead-equivalent test method for X-ray protection of goods suggested in the Korean Standard. According to our results, the shielding rate of the 0.2-mm-thick WC–Co alloy was 96.52% at a tube voltage of 50 kVp, 94.86% at a tube voltage of 80 kVp, and 94.10% at a tube voltage of 100 kVp. The shielding rate of the 0.4-mm-thick WC–Co alloy was 97.47% at a tube voltage of 50 kVp, 96.57% at a tube voltage of 80 kVp, and 95.63% at a tube voltage of 100 kVp. It is believed that the nanocrystalline WC–Co alloy developed for radiation shielding in this study will contribute to a decrease in primary X-ray exposure as well as exposure to low-dose secondary X-rays, such as scattered rays. Furthermore, the use of a nanocrystalline WC–Co alloy oxide rather than lead will allow for the development of shielding wear that is lighter and contribute to the development of various radiation-shielding products made of environmentally friendly materials.

Measuring and analyzing the radioactivity released from construction floor materials

ABSTRACT This study measures the radioactivity contained in samples of floor materials used in construction. We would like to use the study as a basic document for the nation’s health and environment. Among construction floor materials, we chose pantheon, red pearl, royal pearl, and tan brown as samples and put them on a detector of high-purity germanium (HPGe) analysis by using a multichannel analyzer (MCA). In order to measure the concentrations of radionuclides, we set the measurement times at 1000 seconds, 4000 seconds, 7000 seconds, and 10,000 seconds, analyzed the concentrations of gamma radionuclides. As a result, Bi-214, Pb-214, Ra-226, and K-40 were detected in pantheon when the measurement time was 10,000 seconds, and Bi-214 was the highest, with a 0.08 Bq/g concentration. For red pearl, we detected Rn-222, K-40, Th-234, Bi-214, Pb-214, and Ra-226. Here, Rn-222 was the highest with a 4.8 Bq/g concentration. For royal pearl, we detected Rn-222, K-40, Th-234, Bi-214, Pb-214, and Ra-226, and Rn-222 was the highest, with a 7.0 Bq/g concentration. Finally, for tan brown, we detected Rn-222, K-40, Bi-214, and Pb-214. Rn-222 was the highest with a 3.8 Bq/g concentration. Though we have detected only low-level radionuclides, we still need to monitor the concentration of radionuclides from time to time.