• Imaging Science in Dentistry
• /
• v.52 no.3
• /
• pp.283-288
• /
• 2022

Purpose: This study was conducted to measure the radiation exposure and image quality of various cone-beam computed tomography (CBCT) machines under common clinical conditions and to analyze the correlation between them. Materials and Methods: Seven CBCT machines used frequently in clinical practice were selected. Because each machine has various sizes of fields of view (FOVs), 1 large FOV and 1 small FOV were selected for each machine. Radiation exposure was measured using a dose-area product (DAP) meter. The quality of the CBCT images was analyzed using 8 image quality parameters obtained using a dental volume tomography phantom. For statistical analysis, regression analysis using a generalized linear model was used. Results: Polymethyl-methacrylate (PMMA) noise and modulation transfer function (MTF) 10% showed statistically significant correlations with DAP values, presenting positive and negative correlations, respectively (P<0.05). Image quality parameters other than PMMA noise and MTF 10% did not demonstrate statistically significant correlations with DAP values. Conclusion: As radiation exposure and image quality are not proportionally related in clinically used equipment, it is necessary to evaluate and monitor radiation exposure and image quality separately.

• The Journal of The Korea Institute of Intelligent Transport Systems
• /
• v.22 no.2
• /
• pp.54-63
• /
• 2023

Pedestrian traffic needs to be accurately quantified to predict effectively pedestrian traffic accidents, however, pedestrian traffic is more difficult to measure than vehicle traffic. In this study, we suggest the time-and cost-effective application of mobile closed-circuit television (CCTV) using a smartphone as an alternative that can collect and analyze real-time data with little. In the present investigation, the pedestrian-vehicle conflict that can develop into an accident was defined as the pedestrian accident exposure. After installing mobile CCTV in 40 sections of Dongseong-ro, Daegu, the pedestrian accident exposure was estimated through negative binomial regression analysis using the collected data. The results of the analysis showed statistically significant changes in the pedestrian accident exposure variables. Based on the present results, a pedestrian accident exposure estimation model was developed which can be used in sections where pedestrian accidents may occur.

• The Journal of Advanced Prosthodontics
• /
• v.15 no.5
• /
• pp.248-258
• /
• 2023

PURPOSE. This study aims to evaluate the effects of exposure energy on the lateral resolution and mechanical strength of dental zirconia manufactured using digital light processing (DLP). MATERIALS AND METHODS. A zirconia suspension and a custom top-down DLP printer were used for in-office manufacturing. The viscosity of the suspension and uniformity of the exposed light intensity were controlled. Based on the exposure energy dose delivered to each layer, the specimens were classified into three groups: low-energy (LE), medium-energy (ME), and high-energy (HE). For each energy group, a simplified molar cube was used to measure the widths of the outline (X_o and Y_o) and isthmus (X_i and Y_i), and a bar-shaped specimen of the sintered body was tested. A Kruskal-Wallis test for the lateral resolution and one-way analysis of variance for the mechanical strength were performed (α = .05). RESULTS. The zirconia green bodies of the ME group showed better lateral resolution than those of the LE and HE groups (both P < .001). Regarding the flexural strength of the sintered bodies, the ME group had the highest mean value, whereas the LE group had the lowest mean value (both P < .05). The ME group exhibited fewer agglomerates than the LE group, with no distinctive interlayer pores or surface defects. CONCLUSION. Based on these findings, the lateral resolution of the green body and flexural strength of the sintered body of dental zirconia could be affected by the exposure energy dose during DLP. The exposure energy should be optimized when fabricating DLP-based dental zirconia.

• Biomedical Science Letters
• /
• v.12 no.4
• /
• pp.375-383
• /
• 2006

The physiological responses following stress are different in individual or personality. We performed this study to clarify gender differences in influences of noise stress on physiological factors. 70 healthy subjects, which was divided man (n=30) and woman (n=40) groups, were exposed to 85 decibels of excavator noise for 15 minutes. Cardiac factors such as heart rate (HR), systolic and diastolic blood pressures (SBP and DBP, respectively), and heart rate-systolic pressure product (RPP) were determined. Transcranial Doppler ultrasound (TCD) was used to measure mean blood flow velocity (Vm), pulsatility index (PI), and resistance index (RI) in the middle, anterior and posterior cerebral arteries (MCA, ACA and PCA, respectively) before and during noise exposure. Cortisol level and hematological variables were also measured before (baseline) and immediately after the end of noise exposure. In the both groups HR, SBP, and RPP significantly decreased during noise exposure (P<0.05) but not significantly different between two groups (P>0.05). Vms of three cerebral arteries in man group decreased, whereas Vm of PCA in woman group fell during noise exposure (P<0.05). Vm, PI and RI in MCA and ACA during noise exposure were low in man group compared with woman group (P<0.05). Vm of PCA was low, whereas PI and RI of PCA were high in man group compared with woman group during noise exposure (P<0.05). Total leukocyte and red blood cell (RBC) counts slightly decreased during noise exposure but not significant (P>0.05). Levels in hematological variables decreased but not significant changed following noise exposure. Decreased rate of total leukocyte in man group was higher (P<0.05). Cortisol levels in the both groups decreased immediately after the end of noise exposure, while the decreased rate in man group was greater than that in woman group (p<0.05). These findings indicate that a transient exposure to experimental excavator noise may cause decreased changes in cardiac factors, cerebral hemodynamics and cortisol levels and the changes may be greater in men than in women.

• Journal of Korean Neurosurgical Society
• /
• v.64 no.6
• /
• pp.933-943
• /
• 2021

Objective : Percutaneous pedicle screw (PPS) fixation is a needle based procedure that requires fluoroscopic image guidance. Consequently, radiation exposure is inevitable for patients, surgeons, and operation room staff. We hypothesize that reducing the production of radiation emission will result in reduced radiation exposure for everyone in the operation room. Research was performed to evaluate reduction of radiation exposure by modifying imaging manner and mode of radiation source. Methods : A total of 170 patients (680 screws) who underwent fusion surgery with PPS fixation from September 2019 to March 2020 were analyzed in this study. Personal dosimeters (Polimaster Ltd.) were worn at the collar outside a lead apron to measure radiation exposure. Patients were assigned to four groups based on imaging manner of fluoroscopy and radiation modification (pulse mode with reduced dose) : continuous use without radiation modification (group 1, n=34), intermittent use without radiation modification (group 2, n=54), continuous use with radiation modification (group 3, n=26), and intermittent use with radiation modification (group 4, n=56). Post hoc Tukey Honest significant difference test was used for individual comparisons of radiation exposure/screw and fluoroscopic time/screw. Results : The average radiation exposure/screw was 71.45±45.75 µSv/screw for group 1, 18.77±11.51 µSv/screw for group 2, 19.58±7.00 µSv/screw for group 3, and 4.26±2.89 µSv/screw for group 4. By changing imaging manner from continuous multiple shot to intermittent single shot, 73.7% radiation reduction was achieved in the no radiation modification groups (groups 1, 2), and 78.2% radiation reduction was achieved in the radiation modification groups (groups 3, 4). Radiation source modification from continuous mode with standard dose to pulse mode with reduced dose resulted in 72.6% radiation reduction in continuous imaging groups (groups 1, 3) and 77.3% radiation reduction in intermittent imaging groups (groups 2, 4). The average radiation exposure/screw was reduced 94.1% by changing imaging manner and modifying radiation source from continuous imaging with standard fluoroscopy setting (group 1) to intermittent imaging with modified fluoroscopy setting (group 4). A total of 680 screws were reviewed postoperatively, and 99.3% (675) were evaluated as pedicle breach grade 0 (<2 mm). Conclusion : The average radiation exposure/screw for a spinal surgeon can be reduced 94.1% by changing imaging manner and modifying radiation source from real-time imaging with standard dose to intermittent imaging with modified dose. These modifications can be instantly applied to any procedure using fluoroscopic guidance and may reduce the overall radiation exposure of spine surgeons.

• Journal of Radiation Protection and Research
• /
• v.34 no.1
• /
• pp.31-36
• /
• 2009

The purpose of this study is to measure the tube voltage, the tube current/volume, exposure time and exposure dose of diagnostic X-ray unit in each doctor offices, hospitals and general hospitals for evaluating the performance of such device, to learn the method and technology of its measurement and to suggest its importance. Research subjects were total 30 X-ray units and divided into groups of 10 X-ray units each. The tube voltage, the tube current/volume, exposure time and exposure dose were measured using percentage average error, and then reproducibility of exposure dose was measured through calculating coefficient of variation. The results are like followings; The tube voltage correctness examination showed that incongruent devices among total 30 X-ray units were 5 devices (16.7%). The tube current correctness examination showed that incongruent X-ray units were 3 devices (10.0%). The tube current volume correctness examination showed that incongruent X-ray units were 4 devices (13.3%). Finally, according to exposure time correctness examination, incongruent X-ray units were 5 devices (16.7%) and according to reproducibility examination of exposure dose, incongruent X-ray units were 7 devices (23.3%). Above results showed serious problem in performance management based on management regulation of diagnostic X-ray unit; it means that regular checkout and safety management are required, and as doing so, patients will be able to receive good quality of medical service by the reduction of radiation exposure time, image quality administration, unnecessary retake and etc. Therefore, this study suggests that the performance of diagnostic X-ray units should be checked regularly.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
• /
• v.27 no.1
• /
• pp.55-71
• /
• 1997

Digora/sup (R)/ an intraoral digital radiography system utilizing image plate (IP) - has a dynamic range of exposure time which allows it to decrease the patient's exposure time and to increase diagnostic ability through image processing, transmission and storage. The purpose of this study was to evaluate the Digora/sup (R)/ system by assessing the effects of various exposure times on the detectability on the tip of the endodontic file. Examining the root canals of 45 extracted sound premolars, K -files No. 10, 15, and 20 were placed at slightly varying distances from the apex. The teeth were glued onto resin-plaster blocks. Five exposure times varying between 0.01 seconds and 0.25 seconds were used. Four observers were asked to measure the distance between the tip of the file and a reduction of crown portion, and obtained mean errors (subtracting true file length from the measured file length), comparing Digora/sup (R)/ monitors with E-plus films, which were both obtained under the same geometrical positions. The results were as follows : 1. Comparing E-plus film with Digora/sup (R)/ at 0.01 seconds, the mean errors in E-plus film showed -4.453 nun, -4.497 nun, and -3.857 nun, while the mean errors in Digora/sup (R)/ showed 0.065 nun, 0.607 nun, and 0.719 mm according to the file groups. Therefore there was a significant difference between E-plus film and Digora/sup (R)/(p<0.05). 2. By comparison of mean errors according to the various exposure times in the Digora/sup (R)/ system, the mean error at 0.01 seconds was significantly lower than that at 0.12 and 0.25 seconds in the No. 10 file group(p<0.05). And the standard deviation was the highest at 0.01 seconds. 3. Comparing E-plus film at 0.25 seconds with the Digora/sup (R)/ system, the mean errors showed a significant difference between E-plus film at 0.25 seconds and the Digora/sup (R)/ system at 0.25 seconds in No. 10 and 20 file groups(p<0.05). 4. Comparing E -plus film at 0.25 seconds with other exposure times, the mean errors showed a significant difference between E-plus film at 0.25 seconds and E-plus film at 0 .. 01 and 0.03 seconds in 10 file group(p<0.05). In the No. 15 and 20 file groups, there was a significant difference between E-plus film at 0.25 seconds and E-plus film at 0.01 seconds(p<0.05). In conclusion, Digora/sup (R)/ was better than E-plus film in detectability on the tip of the file at the exposure time of 0.01 seconds in all file groups. And we concluded that Digora/sup (R)/ can shorten exposure times up to 4％ of 0.25 seconds (0.01 sec), which is adequate exposure time for premolar in E-plus film using No. 15 and 20 files.

• Journal of Ubiquitous Convergence Technology
• /
• v.2 no.1
• /
• pp.27-39
• /
• 2008

In this paper we present a simple, efficient method for detecting the blurry photographs. Recently many digital cameras are equipped with various auto-focusing functions to help users take well-focused pictures as easily as possible. In addition, motion compensation devices are able to compensate motion causing blurriness in the images. However, digital pictures can be degraded by limited contrast, inappropriate exposure, imperfection of auto-focusing or motion compensating devices, unskillfulness of the photographers, and so on. In order to decide whether to process the images or not, or whether to delete them or not, reliable measure of image degradation to detect blurry images from sharp ones is needed. This paper presents a blurriness/sharpness measure, and demonstrates its feasibility by using extensive experiments. This method is fast, easy to implement and accurate. Regardless of the detection accuracy, the proposed measure in this paper is not demanding in computation time. Needless to say, this measure can be used for various imaging applications including auto-focusing and astigmatism correction.

• Journal of Korean Society of Occupational and Environmental Hygiene
• /
• v.25 no.1
• /
• pp.27-35
• /
• 2015

Objectives: To investigate safety and health management, conditions in factories or facilities handling radiation-generating devices and radioactive isotopes were reviewed in terms of regulations of radiation safety control in Korea. Radiation exposure levels generated at those facilities were directly measured and evaluated for establishing an effective safety and health management plan. Methods: Government organizations with laws and systems of radiation safety and health were investigated and compared. There are three laws governing radiation-related employment such as occupational safety and health acts, nuclear safety acts, and medical service acts. We inspected 12 workplaces as research objects:four workplaces that manufacture and assemble semiconductor devices, three non-destructive inspection workplaces that perform inspections on radiation penetration, and five workplaces in textile and tire manufacturing. Monitoring of radiation exposure was performed through two methods. Spatial and surface monitoring using real-time radiation instruments was performed on each site handling radiation generating devices and radioactive isotopes in order to identify radiation leakage. Results: According to the occupational safety and health act, there is no legal obligation to measure ionizing radiation and set dose limits. This can cause confusion in the application of the laws, because the scopes and contents are different from each other. Surface dose rates in radiation generating devices such as implanters, thickness gages and accelerators, which were registered according to nuclear safety acts, using surveymeters, and seven of 36 facilities(19.4%) exceeded the international standards for surface radiation dose of $10{\mu}Sv/hr$. Conclusions: The results showed that occupational health and safety acts require a separate provision for measuring and assessing the radiation exposure of workers performing radiation work. Like noise, ionizing radiation will also periodically be controlled by including it in the object factors of work-environment measurement.

• Journal of Korean Society of Occupational and Environmental Hygiene
• /
• v.3 no.2
• /
• pp.227-239
• /
• 1993

The author selected 77 dust emissing processes from 71 types of industries which placed in Sasang Industrial Complex in Pusan. The level of total dust was measured as areal concentration and personal exposure concentration by low volume air sampler and personal air sampler, respectively. Collected samples were classified into 5 groups (chemicals and rubber product, metal product, sawmills and wood, foundries and others). Respirable particulate and total dust of areal and personal exposure were analyzed. The results were as follows; 1. All of the respirable dust concentration and total dust of areal and personal concentration were log-normally distributed. 2. Geometric mean of respirable particulate of personal exposure concentration measured $0.55mg/m^3$ in the first group, $0.86mg/m^3$ in the second group, $0.39mg/m^3$ in the third group, $0.81mg/m^3$ in the forth group and $0.52mg/m^3$ in the fifith group. The exceed rates over TLV (thehold limit values) of total dust were 31.3% in the first group, 31.3% in the second group, 70% in the third group, 80% in the forth group and 13.3% in the fifth group. 3. There were singnificant difference between areal and personal exposure concentration and personal exposure concentration was higher than that of area. 4. In the case of high ratio of respirable particulate to total dust, pneumoconiosis incidence was high even though the workshop was opened and emissing dust concentration was low. These findings suggest that it is desirable to measure respirable particulate in environmental assessment of dust emissing workshops.