• Radiation Oncology Journal
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• v.24 no.4
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• pp.211-216
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• 2006

$\underline{Purpose}$: An analysis of the infrastructure for radiotherapy in Korea was performed to establish a baseline plan in 2006 for future development. $\underline{Materials\;and\;Methods}$: The data were obtained from 61 radiotherapy centers. The survey covered the number of radiotherapy centers, major equipment and personnel. Centers were classified into technical level groups according to the IAEA criteria. $\underline{Results}$: 28,789 new patients were treated with radiation therapy in 2004. There were 104 megavoltage devices in 61 institutions, which included 96 linear accelerators, two Cobalt 60 units, three Tomotherapy units, two Cyberknife units and one proton accelerator in 2006. Thirty-five high dose rate remote after-loading systems and 20 CT-simulators were surveyed. Personnel included 132 radiation oncologists, 50 radiation oncology residents, 64 medical physicists, 130 nurses and 369 radiation therapy technologists. All of the facilities employed treatment-planning computers and simulators, among these thirty-two percent (20 facilities) used a CT-simulator. Sixty-six percent (40 facilities) used a PET/CT scanner, and 35% (22 facilities) had the capacity to implement intensity modulated radiation therapy. Twenty-five facilities (41%) were included in technical level 3 group (having one of intensity modulated radiotherapy, stereotactic radiotherapy or intra-operative radiotherapy system). $\underline{Conclusion}$: Radiation oncology in Korea evolved greatly in both quality and quantity recently and demand for radiotherapy in Korea is increasing steadily. The information in this analysis represents important data to develop the future planning of equipment and human resources.

• Progress in Medical Physics
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• v.25 no.3
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• pp.185-192
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• 2014

The purpose of this study is to evaluate the results for the quality assurance through a statistical analysis on the output characteristics of linear accelerators belonging to Yeungnam University Medical Center by using the Shewhart-type chart, Exponentially weighted moving average chart (EWMA) chart, and process capability indices $C_p$ and $C_{pk}$. To achieve this, we used the output values measured using respective treatment devices (21EX, 21EX-S, and Novalis Tx) by medical physicists every month from September, 2012 to April, 2014. The output characteristics of treatment devices followed the IAEA TRS-398 guidelines, and the measurements included photon beams of 6 MV, 10 MV, and 15 MV and electron beams of 4 MeV, 6 MeV, 9 MeV, 12 MeV, 16MeV, and 20 MeV. The statistical analysis was done for the output characteristics measured, and was corrected every month. The width of control limit of weighting factors and measurement values were calculated as ${\lambda}=0.10$ and L=2.703, respectively; and the process capability indices $C_p$ and $C_{pk}$ were greater than or equal to 1 for all energies of the linear accelerators (21EX, 21EX-S, and Novalis Tx). Measured values of output doses with drastic and minor changes were found through the Shewhart-type chart and EWMA chart, respectively. The process capability indices $C_p$ and $C_{pk}$ of the treatment devices in our institution were, respectively, 2.384 and 2.136 for 21EX, 1.917 and 1.682 for 21EX-S, and 2.895 and 2.473 for Novalis Tx, proving that Novalis Tx has the most stable and accurate output characteristics.

• Journal of Korean Medical classics
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• v.17 no.4
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• pp.8-11
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• 2004

"황제내경(黃帝內經)"(간칭(簡稱)"내경(內經)")의 내용을 임상치료와 진단에서 사용하면서 얻은 체험을 종합해보면 다음과 같다. 1. "내경(內經)"에서는 병을 치료하는 방법과 기술에 있어서는 대부분 직접 어느 한 가지 질병에 어떠한 치료방법을 사용할 것과 그 치료방법의 구체적인 조작방법과 사용에 대하여 기록하고 있다. 이러한 기록은 저자가 진실로 보고 들은 것으로서 거짓됨이 없다. "내경(內經)"에는 치료 방법만으로도 침구(鍼灸), 약물요법(藥物療法)뿐만이 아니라 또한 방복수법(放腹水法)이 있으며, 물리강온법(物理降溫法), 단식요법(斷食療法), 수술절제법(手術切除法), 압추경동맥강온법(壓推頸動脈降溫法)(자절진사(刺節眞邪)), 견인(牽引), 자료(磁療) 및 "딸꾹질을 치료하는 세 가지 방법" 등 거의 30가지에 가까운 치료방법들이 기재되어 있다. 2. "내경('內經)"의 이론은 어느 한 사랑의 손에서 만들어진 것이 아니며 또한 어느 한 시기에 저술 된 것도 아니다. "각가학설(各家學說)"의 성격을 띠고 있다. 3. "내경('內經)"에서는 글귀가 간결하고 함축성이 아주 강하므로 한마디에 많은 뜻을 내포하고 있다. 그러므로 임상에서 사용할 때 그 뜻을 잘 이해하면서 사용해야 한다. 4. "내경(內經)"을 연구하는 사람들이 "내경(內經)"의 이론을 임상에서 사용할 때 가장 먼저 장중경선사(張仲景先師)를 본받아 여러 의학자들의 장점을 취해야 한다. "상한잡병론(傷寒雜病論)"에서는 곳곳에 내경(內經)"의 취지를 나타내고 있으며 내경(內經)" 에 나오는 방법을 치료의 원칙으로 삼고 있다. 치료원칙은 대부분 "음양응상대론(陰陽應象大論)의 기준으로 삼고 있다.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2003.09a
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• pp.42-42
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• 2003

목적 : 조사면 크기에 따른 금속쐐기와 가상쐐기에 의한 6 MV 와 15 MV 엑스선의 출력 및 상부와 하부 에 설치하는 금속쐐기의 출력을 비교하고자 한다. 대상 및 방법 : Varian Clinac21EX(미국)는 두부의 상부와 하부에 설치하는 각각의 금속쐐기와 제한기에 의한 가상쐐기 기능을 가지고 있다. 금속쐐기의 쐐기각은 네 가지 (15$^{\circ}$, 30$^{\circ}$, 45$^{\circ}$, 60$^{\circ}$)이며 투과력에 무관하게 한 쐐기각에 대한 쐐기는 사하부는 각 1 개이고, 가상쐐기는 일곱 가지 ($10^{\circ}$, 15$^{\circ}$, 20$^{\circ}$, 25$^{\circ}$, 30$^{\circ}$, 45$^{\circ}$, 60$^{\circ}$) 이다. 각 쐐기에 대하여 3$\times$3～20$\times$20 $\textrm{cm}^2$ 의 조사면 크기에서 6 및 15 MV 엑스선의 쐐기출력인수 (wedge field output factor)를 $d_{max}$와 10 $\textrm{cm}^2$ 깊이에서 측정하였다. 조사면크기와 측정깊이에 따른 쐐기출력인수의 변화추이를 관찰하였다. 쐐기출력인수 O $F_{Wdg}$는 다음과 같다. O $F_{Wdg}$(r)= $D_{Wdg}$(r)/ $D_{op}$ ( $r_{0}$) 여기서 $r_{0}$와 r은 각각 민조사면의 기준조사면크기, 쐐기조사면크기이다. 하부쐐기에 대한 상부쐐기의 출력인수의 상대적인 백분율 차이, %ROD=l00$\times$(O $F_{upWdg}$/O $F_{lowWdg}$ lowWdg/ - 1)를 구하였다. 조사면크기와 깊이에 따른 %ROD의 변화추이를 평가하였으며 쐐기 각각에 대하여 출력인수를 측정해야하는지 평가하였다. 결과 : 금속쐐기에 대한 쐐기출력인수는 방사선의 투과력과 깊이에 관계없이 조사면 크기가 커짐에 따라 증가하였으나 가상쐐기의 쐐기출력인수는 쐐기각이 작은 경우에는 조사면크기가 커짐에 따라 증가하다가 감소하였으며 최대값을 보이는 조사면크기는 쐐기각이 커짐에 반하여 감소하였으며 투과력에 관계없이 60。 쐐기에 대해서는 조사면 크기가 4 cm(A/P=1) 이상에서 조사면크기가 커짐에 따라 감소하였다. 6 MV 엑스선 에 대한 10 cm 깊이에서 15。 쐐기와 15 MV 엑스선에 대한 10 cm 깊이에서 45。 쐐기의 A/P 가 1.5보다 작은 조사면을 제외하고는 조사면의 크기가 커짐에 따라 %ROD는 감소하였다. $d_{max}$에서는 15。 쐐기와 30。 쐐기에 대해서는 %ROD가 음수였으며 절대값이 증가하였다. 이는 곧 조사면의 크기가 커짐에 따라 상부쐐기의 쐐기출력계수가 하부쐐기와 접근하고 드디어는 상부쐐기의 출력인수가 하부쐐기의 출력인수보다 작아질 수도 있다는 것을 의미하고 있다. 또한 %ROD 는 쐐기각이 클수록 변화가 컸으며, 조사면 크기가 커짐에 따라 10 cm 깊이에서보다 $d_{max}$에서 더 급하게 감소하였다. %ROD 는 6 MV 엑스선에 대해서는 -0.52～4.18 % 였고, 15 MV 엑스선에 대해서는 -0.44-4.18 % 였다. 결론 : 두 가지 투과력의 엑스선이 방출되는 선형가속기의 상하부 쐐기와 가상쐐기의 출력인수를 측정하여 비교하였다. 결과에서 얻어진 결론은 아래와 같다. 1. 조사면의 크기가 커짐에 따라 금속쐐기의 출력계수 는 증가하였으나 가상쐐기의 경우는 증가하다가 감소하거나 큰 쐐기각에 대해서는 감소만 하였다. 2. 상부쐐 기와 하부쐐기는 쐐기출력인수가 4% 이상 차이가 날 수 있으므로 독립적으로 측정하여 이용하여야 할 것이다.것이다.다.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2004.11a
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• pp.158-161
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• 2004

In order for better management of a medical linear accelerator, the records of the operational failures of Varian CL2100C over ten years were analyzed. The failures were classified according to the involved functional subunits and each class was rated into three levels depending on operational conditions. The relationship between the failure rate and working ratio was investigated. Among the recorded failures ( total 587 failures), the most frequent failure, which was 20% of the total. was observed in the parts related to the collimation system including monitor chamber. Regrading to the operational conditions, the 2nd level of failures, that temporally interrupted treatments, was the most frequent. The 3rd level of failures, that interrupted treatment for more than several hours, was mostly caused by the accelerating subunit. The average life-time of a Klystron and Thyratron became shorter as the working ratio increased, which was 42 and 83% of the expected values, respectively. Recording equipment problems and failures in detail over a long period of time can provide a good knowledge of equipment function as well as the capability to forecast future failure. More rigorous equipment maintenance is required for old medical linear accelerator to avoid the serious failure in advance, and improve the patient treatment quality.

• Progress in Medical Physics
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• v.14 no.2
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• pp.108-123
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• 2003

The purpose of this study is to evaluate the contribution of $^{18}$ F-FDG brain PET in the differentiating Idiopathic parkinson's diesease (IPD), progressive supranuclear palsy (PSP), and multiple system atrophy (MSA). We studied 24 patients with parkinsonism : 8 patients (mean age 67.9$\pm$10.7 y: M/F : 3/5) with IPD, 9 patients (57.9$\pm$9.2 y : M/F : 4/5) with MSA and 7 patients (67.6$\pm$4.8 y : M/F 3/4) with PSP. All patients with parkinsonism and 22 age-matched normal controls underwent $^{18}$ F FDG PET in 3D mode after the injection of 370 MBq $^{118}$ F FDG. The patients with IPD, MSh and PSP were compared with a normal control group by a two-sided t-test of SPM99 (uncorrected P<0.001, extent threshold>100 voxel). All three parkinsonism groups, showed significant hypometabolism in the cerebral neocortex compared to the normal control group. However, the three groups displayed different metabolism in the subcortical structure, brain stem, and cerebellum. In IPD, there was no significant hypometabolism in the putamen, brain stem and cerebellum. However, MSA patients showed significant hypometabolism in the striatum, pons, and cerebellum compared to the normal controls and IPD patients. In addition, PSP showed significant hypometabolism in the caudate nuclei, the thalamus, midbrain, and the cingulate gyrus compared to the normal controls, the IPD, and MSA groups (IPD vs Normal sensitivity/specificity : 75%/l00%, MSA vs Normal sensitivity/specificity :100%/87%, PSP vs Normal sensitivity/specificity : 86%/94%). Our results show that the regional metabolism of IPD, MSA, and PSP is different mainly in the striatum, thalamus, brain stem and cerebellum. An assessment of the $^{18}$ F-FDG PET scan images using SPM may be a useful adjunct to a clinical examination in making a differential diagnosis of Parkinsonism.

• Progress in Medical Physics
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• v.26 no.3
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• pp.160-167
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• 2015

Radiation exposure from medical diagnostic imaging procedures to patients is one of the most significant interests in diagnostic x-ray system. A miniature x-ray intraoral tube was developed for the first time in the world which can be inserted into the mouth for imaging. Dose evaluation should be carried out in order to utilize such an imaging device for clinical use. In this study, dose evaluation of the new x-ray unit was performed by 1) using a custom made in vivo Pig phantom, 2) determining exposure condition for the clinical use, and 3) measuring patient dose of the new system. On the basis of DRLs (Diagnostic Reference Level) recommended by KDFA (Korea Food & Drug Administration), the ESD (Entrance Skin Dose) and DAP (Dose Area Product) measurements for the new x-ray imaging device were designed and measured. The maximum voltage and current of the x-ray tubes used in this study were 55 kVp, and 300 mA. The active area of the detector was $72{\times}72mm$ with pixel size of $48{\mu}m$. To obtain the operating condition of the new system, pig jaw phantom images showing major tooth-associated tissues, such as clown, pulp cavity were acquired at 1 frame/sec. Changing the beam currents 20 to $80{\mu}A$, x-ray images of 50 frames were obtained for one beam current with optimum x-ray exposure setting. Pig jaw phantom images were acquired from two commercial x-ray imaging units and compared to the new x-ray device: CS 2100, Carestream Dental LLC and EXARO, HIOSSEN, Inc. Their exposure conditions were 60 kV, 7 mA, and 60 kV, 2 mA, respectively. Comparing the new x-ray device and conventional x-ray imaging units, images of the new x-ray device around teeth and their neighboring tissues turn out to be better in spite of its small x-ray field size. ESD of the new x-ray device was measured 1.369 mGy on the beam condition for the best image quality, 0.051 mAs, which is much less than DRLs recommended by IAEA (International Atomic Energy Agency) and KDFA, both. Its dose distribution in the x-ray field size was observed to be uniform with standard deviation of 5~10 %. DAP of the new x-ray device was $82.4mGy*cm^2$ less than DRL established by KDFA even though its x-ray field size was small. This study shows that the new x-ray imaging device offers better in image quality and lower radiation dose compared to the conventional intraoral units. In additions, methods and know-how for studies in x-ray features could be accumulated from this work.

• Progress in Medical Physics
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• v.22 no.4
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• pp.216-223
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• 2011

Recently PTW developed a MicroLion liquid ionization chamber which is water_equivalent and has a small sensitive volume of $0.002cm^3$. The aim of this work is to investigate such dosimetric characteristics as dose linearity, dose rate dependency, spatial resolution, and output factors of the chamber for the external radiotherapy photon beam. The results were compared to those of Semiflex chamber, Pinpoint chamber and Diode chamber with the sensitive volumes of $0.125cm^3$, $0.03cm^3$ and $0.0025cm^3$, respectively and evaluated to be suitable for small fields. This study was performed in the 6MV photon energy from a Varian 2300 C/D linac accelerator and the MP3 water phantom (PTW, Freiburg) was used. Penumbras in the varios field sizes ranged from $0.5{\times}0.5cm^2$ to $10{\times}10cm^2$ were used to evaluate the spatial resolution. Output factors were measured in the field sizes of $0.5{\times}0.5$ to $40{\times}40cm^2$. Readings of the chamber was linearly proportional to dose. Dose rate dependency was measured from 100 MU/min to 600 MU/min, showed a maximum difference of 5.0%, and outputs decreased with dose rates. The spatial resolutions determined with comparing profiles for the field sizes of $0.5{\times}0.5cm^2$ to $10{\times}10cm^2$ agreed between every detector except the Semiflex chamber to within 2%. Outputs of detectors were compared to that of Semiflex chamber and showed good agreements within 2% for every chamber. This study shows that MicroLion chamber characterized by a high signal-to-noise ratio and water equivalence could be suitable for the small field dosimetry.

• Progress in Medical Physics
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• v.20 no.4
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• pp.308-316
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• 2009

To achieve the accurate evaluation of given absorbed dose from output dose of linear accelerator photon beam through investigate the characteristics of LiF:Mg,Cu,P TLD powder. This experimental TL phosphor is performed with a commercial LiF:Mg,Cu,P powder (Supplied by PTW) and TL reader (LTM, France). The TLD was exposed to 6 MV X rays of linear accelerator photon beam with range 15 to 800 cGy in blind dose at two hospitals. The dose evaluation of TLD was through the experimental algorithms which were dose dependency, dose rate dependency, fading and powder weight dependency. The glow curve has shown the three peaks which are 110, 183 and 232 degrees of heating temperature and the main dosimetric peak showed highest TL response at 232 high temperature. In this experiments, the LiF:Mg,Cu,P phosphor has shown the 2.5 eV of electron trap energy with a second order. This experiments guided the dose evaluation accuracy is within 1% +2.58% of discrepancy. The TLD powder of LiF:Mg,Cu,P was analyzed to dosimetric characterists of electron captured energy and order by glow shape, and dose-TL response curve guided the accuracy within 1.0+2.58% of output dose discrepancy.

• Progress in Medical Physics
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• v.11 no.1
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• pp.59-71
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• 2000

It is possible to obtain a fast CT scan during breath holding with spiral technique. But the risk of radiation is increased due to detailed and repeated scans. However, the limitation of X-ray doses is not fully specified on CT, yet. Therefore, the purpose of the present study is to define the limitation of X-ray doses on CT The CT unit was somatom plus 4. Alderson Rando phantom, Solenoid water phantom, TLD, and reader were used. For determining adequate position and size of organs, the measurement of distance(${\pm}$2mm) from the midline of vertebral body was performed in 40 women(20~40 years). On the brain scan for 8:8(8mm slice thickness, 8mm/sec movement velocity of the table) and 10:10(10mm slice thickness, 10mm/sec movement velocity of the table) methods, the absorption doses of exposed area of the 10:10 were slightly higher than those of 8:8. The doses of unexposed uterus were negligible on the brain scan for both 8:8 and 10:10. On the chest scan for 8:8, 8:10(8mm slice thickness, 10mm/sec movement velocity of the table), 10:10, 10:12(10mm slice thickness, 12mm/sec movement velocity of the table) and 10:15(10mm slice thickness, 15mm/sec movement velocity of the table) methods, 8:8 method of the absorption doses of exposure area was the most highest and 10:15 method was the most lowest. The absorption doses of 8:10 method was relatively lower than those of the other methods. In conclusion, the 8:10 method is the most suitable to give a low radiation burden to patient without distorting image quality.