• The Korean Journal of Nuclear Medicine
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• v.32 no.5
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• pp.414-424
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• 1998

Purpose: Cross-modality coregistration of positron emission tomography (PET) and magnetic resonance imaging (MR) could enhance the clinical information. In this study we propose a refined technique to improve the robustness of registration, and to implement more realistic visualization of the coregistered images. Materials and Methods: Using the sinogram of PET emission scan, we extracted the robust head boundary and used boundary-enhanced PET to coregister PET with MR. The pixels having 10% of maximum pixel value were considered as the boundary of sinogram. Boundary pixel values were exchanged with maximum value of sinogram. One hundred eighty boundary points were extracted at intervals of about 2 degree using simple threshold method from each slice of MR images. Best affined transformation between the two point sets was performed using least square fitting which should minimize the sum of Euclidean distance between the point sets. We reduced calculation time using pre-defined distance map. Finally we developed an automatic coregistration program using this boundary detection and surface matching technique. We designed a new weighted normalization technique to display the coregistered PET and MR images simultaneously. Results: Using our newly developed method, robust extraction of head boundary was possible and spatial registration was successfully performed. Mean displacement error was less than 2.0 mm. In visualization of coregistered images using weighted normalization method, structures shown in MR image could be realistically represented. Conclusion: Our refined technique could practically enhance the performance of automated three dimensional coregistration.

• Journal of the Korean Society of Radiology
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• v.7 no.2
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• pp.157-163
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• 2013

This study was to analyze quantitatively movement of planning target volume (PTV) and change of PTV volume through movement of diaphragm according to breathing phase. The purpose of present study was to investigate optimized respiration phase for radiation therapy of lung cancer. Simulated breathing training was performed in order to minimize systematic errors which is caused non-specific or irregular breathing. We performed 4-dimensional computed tomography (4DCTi) in accordance with each respiratory phase in the normalized respiratory gated radiation therapy procedures, then not only defined PTVi in 0 ~ 90%, 30 ~ 70% and 40 ~ 60% in the reconstructed 4DCTi images but analyzed quantitatively movement and changes of volume in PTVi. As a results, average respiratory cycle was $3.4{\pm}0.5$ seconds by simulated breathing training. R2-value which is expressed as concordance between clinically induced expected value and actual measured value, was almost 1. There was a statistically significant. And also movement of PTVi according to each respiration phase 0 ~ 90%, 30 ~ 70% and 40 ~ 60% were $13.4{\pm}6.4mm$, $6.1{\pm}2.9mm$ and $4.0{\pm}2.1mm$ respectively. Change of volume in PTVi of respiration phase 30 ~ 70% was decreased by $32.6{\pm}8.7%$ and 40 ~ 60% was decreased by $41.6{\pm}6.2%$. In conclusion, PTVi movement and volume change was reduced, when we apply a short breathing phase (40 ~ 60%: 30% duty cycle) range. Furthermore, PTVi margin considered respiration was not only within 4mm but able to get uniformity of dose.

• Journal of Biomedical Engineering Research
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• v.25 no.4
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• pp.261-268
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• 2004

Osteoporosis is a clinical condition in which the amount of bone tissue is reduced and the likelihood of fracture is increased. It is known that the electrical property of the bone is related to its density, and, in particular, the electrical resistance of the bone decreases as the bone loss increases. This implies that the electrical property of bone may be an useful parameter to diagnose osteoporosis, provided that it can be readily measured. The study attempted to evaluate the electrical conductivity of bone using a technique of electrical impedance tomography (EIT). It nay not be easy in general to get an EIT for the bone due to the big difference (an order of 2) of electrical properties between the bone and the surrounding soft tissue. In the present study, we took an adaptive mesh regeneration technique originally developed for the detection of two phase boundaries and modified it to be able to reconstruct the electrical conductivity inside the boundary provided that the geometry of the boundary was given. Numerical simulation was carried out for a tibia phantom, circular cylindrical phantom (radius of 40 mm) inside of which there is an ellipsoidal homeogenous tibia bone (short and long radius are 17 mm and 15 mm, respectively) surrounded by the soft tissue. The bone was located in the 15 mm above from the center of the circular cross section of the phantom. The electrical conductivity of the soft tissue was set to be 4 mS/cm and varies from 0.01 to 1 ms/cm for the bone. The simulation considered measurement errors in order to look into its effects. The simulated results showed that, if the measurement error was maintained less than 5 %, the reconstructed electrical conductivity of the bone was within 10 % errors. The accuracy increased with the electrical conductivity of the bone, as expected. This indicates that the present technique provides more accurate information for osteoporotic bones. It should be noted that tile simulation is based on a simple two phase image for the bone and the surrounding soft tissue when its anatomical information is provided. Nevertheless, the study indicates the possibility that the EIT technique may be used as a new means to detect the bone loss leading to osteoporotic fractures.

• Journal of Biomedical Engineering Research
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• v.19 no.5
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• pp.455-468
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• 1998

For the objective interpretation of cerebral metabolic patterns in epilepsy patients, we developed computer-aided classifier using artificial neural network. We studied interictal brain FDG PET scans of 257 epilepsy patients who were diagnosed as normal(n=64), L TLE (n=112), or R TLE (n=81) by visual interpretation. Automatically segmented volume of interest (VOI) was used to reliably extract the features representing patterns of cerebral metabolism. All images were spatially normalized to MNI standard PET template and smoothed with 16mm FWHM Gaussian kernel using SPM96. Mean count in cerebral region was normalized. The VOls for 34 cerebral regions were previously defined on the standard template and 17 different counts of mirrored regions to hemispheric midline were extracted from spatially normalized images. A three-layer feed-forward error back-propagation neural network classifier with 7 input nodes and 3 output nodes was used. The network was trained to interpret metabolic patterns and produce identical diagnoses with those of expert viewers. The performance of the neural network was optimized by testing with 5~40 nodes in hidden layer. Randomly selected 40 images from each group were used to train the network and the remainders were used to test the learned network. The optimized neural network gave a maximum agreement rate of 80.3% with expert viewers. It used 20 hidden nodes and was trained for 1508 epochs. Also, neural network gave agreement rates of 75~80% with 10 or 30 nodes in hidden layer. We conclude that artificial neural network performed as well as human experts and could be potentially useful as clinical decision support tool for the localization of epileptogenic zones.

• Journal of dental hygiene science
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• v.14 no.2
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• pp.158-166
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• 2014

This study is trying to grasp the stress of the male high school students and the correlation between the stress according to the oral health important cognitive and self-rated oral health status and number of brushing, emphasizing the need for the education of oral health important, providing the basic data in order to accomplish correctly until the enhance of oral health-related quality of the oral health correct behavior. From May to July 2013, a self administered survey was conducted by the selected by convenience sampling from subjects of two high school located in Chungcheongnam-do 1, 2 grade. The SPSS PASW Statistics 18.0 and Amos 5.0 program had been used for the statistical data analysis. The study results were as follow: 1) Among five areas of stress, the stress of school life was the highest as 2.11 points and the stress of home problem was the lowest as 1.51 points; 2) The significance analysis results between the five areas of stress according to the stress of latent variable and the oral health-related quality of life all showed the significant difference (p<0.001). 3) Oral health-related quality of life was higher as oral health important and self-rated oral health status positive. Furthermore oral health-related quality of life was higher as number of brushing increased; 4) Fit Measures test result of stress, academic level, and family economic level model all showed more than 0.9 in goodness of fit index (GFI), adjusted GFI, normed fit index and root mean square residual and root mean square error of approximation values is all estimated less than 0.1, so it showed good model. From this study, it can be concluded that there is the correlation between stress and oral health-related quality of life.

• Journal of the Korean Society of Radiology
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• v.11 no.7
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• pp.547-553
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• 2017

In the current medical field, lead is widely used as a radiation shield. However, the lead weight is very heavy, so wearing protective clothing such as apron is difficult to wear for long periods of time and there is a problem with the danger of lethal toxicity in humans. Recently, many studies have been conducted to develop substitute materials of lead to resolve these problems. As a substitute materials for lead, barium(Ba) and iodine(I) have excellent shielding ability. But, It has characteristics emitting characteristic X-rays from the energy area near 30 keV. For patients or radiation workers, shielding materials is often made into contact with the human body. Therefore, the characteristic X-rays generated by the shielding material are directly exposured in the human body, which increases the risk of increasing radiation absorbed dose. In this study, we have developed the FLUKA transport code, one of the most suitable elements of radiation transport codes, to remove the characteristic X-rays generated by barium or iodine. We have verified the reliability of the shielding fraction of the structure of the structure shielding by comparing with the MCPDX simulations conducted as a prior study. Using the MCNPX and FLUKA, the double layer shielding structures with the various thickness combination consisting of barium sulphate ($BaSO_4$) and bismuth oxide($Bi_2O_3$) are designed. The accuracy of the type shown in IEC 61331-1 was geometrically identical to the simulation. In addition, the transmission spectrum and absorbed dose of the shielding material for the successive x-rays of 120 kVp spectra were compared with lead. In results, $0.3mm-BaSO_4/0.3mm-Bi_2O_3$ and $0.1mm-BaSO_4/0.5mm-Bi_2O_3$ structures have been absorbed in both 33 keV and 37 keV characteristic X-rays. In addition, for high-energy X-rays greater than 90 keV, the shielding efficiency was shown close to lead. Also, the transport code of the FLUKA's photon transport code was showed cut-off on low-energy X-rays(below 33keV) and is limited to computerized X-rays of the low-energy X-rays. But, In high-energy areas above 40 keV, the relative error with MCNPX was found to be highly reliable within 6 %.

• Journal of Technologic Dentistry
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• v.24 no.1
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• pp.51-63
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• 2002

The purpose of this study was to be of use for getting rid of job stress from dental technicians, by examining how much they were stressed out at work place as one of the professional medical personnels. The subjects in this study were 255 selected dental technicians who were working in the region of Taegu. The one-on-one interview was conducted from March 1 to 30, 2001, with structured questionnaire. The questionnaire sued in this study included 19 question items about the general characteristics and 29 items regarding job stress. The job stress was categorized into seven subareas based on earlier studies and considering the job situations of dental technicians: heavy workload, job conflicts, improper treatment, role and job knowledge, human relations, physical environment and personal matters. The job stress extent was measured on five-point Likert scale that is widely used in social science: one point for no stress, two for little stress, three for so-so, four for a little stress, and five for severe stress. Therefore, a higher point means a severer job stress. The reliability of the questionnaire turned out very good with Cronbach a = 0.9272. The findings of this study were as follows: 1. The general characteristics of the dental technicians investigated could be described as below: (1) By gender, 80.4% of the dental technicians were male, and 50.2%, the largest percentage, were in their 20s, followed by those in their 30s, those in their 40s, and those in their 50s in the order named. (2) The most common work place was dental technician shop(92.5%), followed by dental technology room in dental hospital or clinic and in general hospital in the order named. The primary duties were coating materials work(30.6%), followed by sculpture, grinding, partial and full denture and orthodontics in the order named. 2. The most larges (1) The most largest motivation to be a dental technician was its being a professional(33.7%), followed by the advice from others, their own aptitude, and good economic treatment in the order named. 3. Their job stress could be explained as below: (1) Their collective job stress average was 3.96$^{\circ}{\ae}$0.50 on the basis of 5 point, which showed that they were exposed to a fairly severe job stress. (2) By area, they were most stressed out from heavy workload (4.12), and they also were severely stressed from role and job knowledge(4.02) and personal matters(4.00). (3) By situation, they were most stressed when the disagreement of prosthesis that results from a specific error is unconditionally attributed to them(4.43). And they were also stressed a lot when their workload increases due to the rework(4.38), when a dentist asks something difficult for them to resolve(4.20), when heavy workload makes their working hours irregular and it's impossible to lead a personal life or have leisure time(4.16), and when they are o work for an excessively short time(4.16). This fact indicated that most of the dental technicians were exposed to a lot of stress in conjunction with job performance. 4. The main duties they took charge of didn't make any significant difference to their job stress, but yielded a significant difference to the extent of job stress in individual areas and the order of the most stressful one. Those who were engaged in grinding were most stressed from their own matters, whereas heavy workload was most stressful for those who were engaged in the other types of works. 5. As a result of seeing if their personal characteristics yielded any differences to job stress, the personal characteristics that made their job stress vary significantly were working hours, motivation of being a dental technician, job satisfaction and willingness to continue doing dental technology works. There was a tendency that longer working hours led to severer job stress, and those who chose to be a dental technician according to their own aptitude were less stressed than the others who became a dental technician because of economic reason or advices from others. And the people who were satisfied with their job were exposed to less job stress than the others who weren't, and those who had an intention to keep that job as much as possible were less stressed, compared to the others who hadn't.

• The Journal of Korean Academy of Prosthodontics
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• v.47 no.3
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• pp.273-285
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• 2009

Statement of problem: The aim of dental research is to advance scientific knowledge and leads to improvement in the treatment and prevention of dental disease. Utilizing an effective research design and adequate statistical methods are essential procedures ensuring that the results of researches are based on evidences. A research should utilize proper statistical methods without statistical errors; Otherwise, it could adversely affect clinical practice and future research. Purpose: This study was made to investigate the statistical methods used in the Journal of Korean Academy of Prosthodontics (JKAP) and then to assess them for the statistical errors. Material and methods: Among the total of 399 articles in the JKAP published from 2000 to 2006, 292 articles using statistics were reviewed. The validity of the statistical methods used in them were assessed using a checklist based on the guideline for statistical reporting in the uniform requirements for manuscripts submitted to biomedical journals by International Committee of Medical Journal Editors. The checklist consisted of three categories of statistical errors: 1) Unspecified computer statistical packages, 2) Inadequate description of statistical methods, 3) Misuse of statistical terms. Then, the results were compared between the Korean version and the English version in the JKAP. Results: Among the 212 articles using statistics in the Korean version, 115 articles (54%) and among the 80 articles using statistics in the English version, 47 articles (59%) were shown to have unspecified computer statistical packages without statistically significant difference (P = .66). Likewise, 101 articles (48%) in the Korean version and 25 articles (31%) in the English version were shown to have the inadequate description of statistical methods without statistically significant difference (P = .09). However, 114 articles (54%) in the Korean version and 19 articles (24%) in the English version were shown to have the misuse of statistical terms with statistically significant difference (P = .01). Conclusion: Some of the articles in the JKAP had inadequate statistical validity, given the statistical errors identified in this assessment. Hence, dental researchers should be more careful when it comes to describing and applying statistical methods.

• Journal of Korean Ophthalmic Optics Society
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• v.19 no.4
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• pp.519-525
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• 2014

Purpose: On this study, we investigated the relationship between the kinetic visual acuity (KVA) and the dynamic stereoacuity and the effects of anisometropia with measuring KVA and the dynamic stereoacuity. Methods: For 63 adults (male 30, female 33), KVA and the dynamic stereoacuity were measured by using the kinetic visual acuity tester (KOWA AS-4A) and the Howard-Dolman test (H-D test) at distance 2.5 m after conducted full correction of subjects' refractive error respectly. Results: The means of KVA were $0.49{\pm}0.25$ for total subjects, $0.58{\pm}0.26$ for male, $0.40{\pm}0.22$ for female, and LogMAD (Log minimum angle of displacement) dynamic stereoacuities were $1.27{\pm}0.44$($28.44{\pm}25.03sec$ of arc) for total subjects, $1.28{\pm}0.44$($28.23{\pm}23.34sec$ of arc) for male, $1.27{\pm}0.45$($28.63{\pm}26.83sec$ of arc) for female. KVA showed a statistically significant difference between male and female (p=0.00), but dynamic stereoacuity was no significant difference (p=0.97). No significant correlation was present between KVA and dynamic stereoacuity (r=0.03). Also there were no significant differences in the dynamic stereoacuity of the three group which were classified according to the low, middle, high range of KVA (p=0.99). The anisometropia were less than 1 D and over 1 D when divided into two groups, KVA and dynamic stereoacuity showed no significant difference between each (p=0.11, p=0.99). There was no significant correlation between anisometropia and KVA (r=0.33), dynamic stereoacuity (r=0.18) but the correlation between KVA and anisometropia revealed more higer than between dynamic stereoacuity and anisometropia. Conculsions: The KVA for adults showed a significant difference between male and female and male was higher than female for KVA. The dynamic stereoacuity due to the KVA, the KVA and dynamic stereoacuity due to anisometropia were not significant differences between each and also were not great correlations.

• The Journal of Korean Academy of Prosthodontics
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• v.50 no.4
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• pp.258-270
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• 2012

Purpose: Use of inappropriate statistical methods may lead to incorrect conclusions and a waste of valuable resources. The goal of this study was to assess the frequency and the types of several common statistical errors in the published articles of the Journal of the Korean Academy of Prosthodontics (JKAP) for a 5-year period. Materials and methods: Of 336 articles in the JKAP published from 2006 to 2010, 255 articles using statistics were reviewed and classified by statistical method and year. The frequency and types of the statistical methods were examined, and the statistical errors were evaluated by the appropriateness of the experimental design, assumption check, independent outcomes, proper sample size and suitable use of statistical method. Statistical guidelines were completed based on the appropriateness. Results: Of the 255 articles using statistics, 193 articles (75.9%) used inferential statistics and 153 articles used SPSS statistical software (60.0%). Of the articles using inferential statistics, the three most frequently used statistical methods were ANOVA (41.5%), t-test (20.0%), and the nonparametric method (16.9%). The average rate of statistical errors was 61.2 percent, similar to the rate reported by several studies completed for the medical journal. Conclusion: After the whole analysis of the difference among the groups, post-hoc tests for the pairwise comparisons are required. The optimal sample size calculation is an essential part of this study protocol. To minimize the occurrence of statistical errors, statistical guidelines were developed according to each statistical test procedure and will contribute to the academic improvement in the JKAP.