Seok-Hwan Bae

Shielding Effect according to the Direction of Control Room Door Opening during Radiography

It is recommended that the door of control room is closed during radiography to protect a radiologic technologist. However, for those patients such as of emergency or pediatrics, the door must be kept open unavoidably to apply immediate medical administration and treatment on the potential case of emergency which could be happened through the course of radiography. In addition, it could be efficient by reducing patients waiting time when the door is open for a general case. This study was conducted to evaluate practical exposure rate to a radiologic technologist when the door is open during the radiography, and to find out the ways to minimize radiation exposure and to increase the efficiency simultaneously. Measuring practical exposure rate was fulfilled with glass dosimeter, and it was 2.02 mGy/week at the location of radiologic technologist under the condition that the door is open during the radiography, which was about 2.3 times higher than the 100 mR/week. It means that the considerable amount of scattered rays through the door opening, and increase exposure rate at the radiologic technologist. Hence we confirmed that a radiologic technologist probably overexposed if the door is open during the radiography. It was also confirmed by the Monte Carlo simulation that the exposure rate could be reduced up to approximately 1/100 by change only the door opening direction. In conclusion, since the proper door opening direction provides same shielding effect whether it is open or close, the door opening direction need to be considered when it is installed at radiography facilities.

Analysis of setup error at rectal cancer radiotherapy technique

Radiotherapy of rectal cancer requires a stabilized image but the movement of patients is almost unavoidable in radiotherapy. In this study, the setup error using the radiation treatment technique was compared according to the loading time and BMI(Body Mass Index) for 14 patients with rectal cancer. In addition, the variation of the dose by the average setup error was compared. Therefore, the technique of a selective standard was established. As a result, 3DCRT(3-Dimensional Radiation Therapy) and VMAT(Volumetric Modulated Arc Therapy) showed a similar time and error. In comparison, IMRT(Intensity Modulated Radiation Therapy) increased the time two fold and the error four fold. In BMI, a more pyknic patient showed a larger error for all techniques. Regarding the dose, IMRT and VMAT increased much more than 3DCRT in the average error at the small bowel. Therefore, 3DCRT of the short time will be applied to pyknic rectal cancer. Moreover, VMAT selects than IMRT in the overexposure of the small bowel.

Effect of Gamma Energy of Positron Emission Radionuclide on X-Ray CT Image

This study is aimed to assess the effect of the gamma ray of 511keV energy which is emitted from phantom where the positron emission radionuclide was injected on X-ray CT image. As a scanning method, the CT number and pixel value of the reference image where water was injected(0 mCi), and those acquired by changing the capacity of 18F(Fluorine), positron emission radionuclide, into 1 mCi, 2 mCi, 5 mCi, and 10 mCi were measured. As a result of measuring the CT number(HU) of the phantom image where the positron emission radionuclide() was injected, there were reference water ( HU), 1 mCi( HU), 2 mCi( HU), 5 mCi( HU), and 10 mCi( HU). Compared with the image where it was filled with water, there was a reduction of 5.89 Hu in 10 mCi, 3.73 in 5 mCi, 2.69 HU in 2 mCi, and 2 HU in 1 mCi. As for the pixel value of the phantom image, there were reference water (), 1 mCi(), 2 mCi(), 5 mCi(), and 10 mCi(). Compared with the reference image, there was a reduction of 5.50 in 10 mCi, 3.40 in 5 mCi, 3.10 in 2 mCi, and 2.02 in 1 mCi. Through this experiment, it was indicated that, with the increase in the dose of the positron emission radionuclide(), the CT number and the pixel value of the image reduced proportionally, and the width of reduction showed a similar value, too. Accordingly, according to the degree of change in X-ray CT image due to the positron emission radionuclide in the quality control item of PET/CT, the proper standard should be established and it should be periodically managed.

Evaluation of the reduced scalp dose at Volumetric Modulated Arc Therapy(VMAT)

The use of WBRT(whole brain radiation therapy) has increased due to the increase in the incidence of metastatic brain tumors. The development of radiation therapy techniques is expected to improve the quality of life. The VMAT (Volumetric Modulated Arc Therapy) is an excellent treatment technique that can distinguish the dose in each volume. Therefore, this study compared conventional WBRT and VMAT for hair loss according to the scalp dose using a head phantom. The CI (Conformity Index), HI (Homogeneity Index) and QOC (Quality of Coverage) were measured brain tissue. A 20 percent and 50 percent dose was measured at the scalp, eyeball, lens, and c-spine. Conventional WBRT is excellent at 10 percent of brain tissue. VMAT is far superior at 1000 percent at the other organs. VMAT at the prescribed dose can be used as radiation therapy of metastatic brain tumors with less hair loss.

Evaluation of Usefulness of an m-DIXON Technique during an Abdomen MRI Examination : A Comparison with an e-THRIVE Technique

Abstract This research is conducted to identify whether an m-DIXON technique which is useful for an abdomen MRI examination compared with an existing e-THRIVE technique is a clinically useful or not. There was evaluated quantitative and qualitative to 84 subjects who had abdomen MRI exam due to their liver disease were conducted during a period from September in 2013 to February in 2014. First of all the quantitative evaluation, the m-DIXON techniques SNR was 90.42±16.90 and the e-THRIVE technique was 60.42±11.54 and the m-DIXON techniques CNR was 52.38±22.58 and the e-THRIVE technique was 46.31±20.25. Secondly in the qualitative evaluation, the m-DIXON techniques image quality was 4.06±0.34, a artifact was 3.64±0.22, and fat suppression was 4.16±0.15, the e-THRIVE techniques image quality was 3.14±0.35, a artifact was 3.06±0.38, fat suppression was 3.14±0.30. In conclusion, m-DIXON technique for abdomen MRI examination showed superiority over both SNR as a quantitative anaylsis, CNR and a qualitative analysis.

Study on the Usefulness of respiration compensation PET/CT

When taking PET/CT, the distortion of the image happens due to the movement of a lesion with respiration. In this study, the experiment was conducted to see if the change in SUV value and distortion of the image could be somewhat corrected by comparing the image which was not compensated with that of the region of lung nodule, compensated with respiration compensation Plumonary Toolkit possessed by this hospital. The records of 17 patients with Lung cancer between May and August 2008. As the result of the experiment, Max SUV value increased by from 4.08% minimum to 43.10% maximum, and the average Max SUV value of lung nodule increased from 6.07 to 7.00(12.16%). In the case of respiration compensation PET/CT, the distortion of the image improved. As there was no significance in the comparison of SCC and Adenocarcinom respectively, though there was a statistically significant level(P