• 대한방사선기술학회지:방사선기술과학
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• 제43권5호
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• pp.375-382
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• 2020

PET/CT is a medical equipment that detects 0.511 MeV of gamma rays. The radiation workers are inevitably exposed to ionizing radiation in the process of handling the isotope. Accordingly, PET/CT workers use syringe shields made of lead and tungsten to protect their hands. However, lead and tungsten are known to generate very high scattering particles by interacting with gamma rays. Therefore, in this study, we tried to find out the effect on the scattering particles emitted from the syringe shield. In the experiment, first, the exposure dose to the hand (Rod phantom) was evaluated according to the metal material (lead, tungsten, iron, stainless steel) using Monte Carlo simulation. The exposure dose was compared according to whether or not plastic is attached. Second, the exposure dose of scattering particles was measured using a dosimeter and lead. As a result of the experiment, the shielding rate of plastics using the Monte Carlo simulation showed the largest difference in dose of about 40 % in lead, and the lowest in iron, about 15 %. As a result of the dosimeter test, when the plastic tape was wound on lead, it was found that the reduction rate was about 15 %, 28 %, and 39 % depending on the thickness. Based on the above results, it was found that 0.511 MeV of gamma ray interacts with the shielding tool to emit scattered rays and has a very large effect on radiation exposure. However, it was considered that the scattering particles could be sufficiently removed with plastics with a low atomic number. From now on, when using high-energy radiation, the shielding tool and the skin should not be in direct contact, and should be covered with a material with a low atomic number.

• Journal of Radiation Protection and Research
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• 제47권3호
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• pp.158-166
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• 2022

Background: The effects of radiation on the health of radiation workers who are constantly susceptible to occupational exposure must be assessed based on an accurate and reliable reconstruction of organ-absorbed doses that can be calculated using personal dosimeter readings measured as H_p(10) and dose conversion coefficients. However, the data used in the dose reconstruction contain significant biases arising from the lack of reality and could result in an inaccurate measure of organ-absorbed doses. Therefore, this study quantified the biases involved in organ dose reconstruction and calculated the bias-corrected H_p(10)-to-organ-absorbed dose coefficients for the use in epidemiological studies of Korean radiation workers. Materials and Methods: Two major biases were considered: (a) the bias in H_p(10) arising from the difference between the dosimeter calibration geometry and the actual exposure geometry, and (b) the bias in air kerma-to-H_p(10) conversion coefficients resulting from geometric differences between the human body and slab phantom. The biases were quantified by implementing personal dosimeters on the slab and human phantoms coupled with a Monte Carlo method and considered to calculate the bias-corrected H_p(10)-to-organ-absorbed dose conversion coefficients. Results and Discussion: The bias in H_p(10) was significant for large incident angles and low energies (e.g., 0.32 for right lateral at 218 keV), whereas the bias in dose coefficients was significant for the posteroanterior (PA) geometry only (e.g., 0.79 at 218 keV). The bias-corrected H_p(10)-to-organ-absorbed dose conversion coefficients derived in this study were up to 3.09- fold greater than those from the International Commission on Radiological Protection publications without considering the biases. Conclusion: The obtained results will aid future studies in assessing the health effects of occupational exposure of Korean radiation workers. The bias-corrected dose coefficients of this study can be used to calculate organ doses for Korean radiation workers based on personal dose records.

• 대한방사선치료학회지
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• 제31권1호
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• pp.33-41
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• 2019

목 적: 식도암 방사선치료 시 세기조절방사선치료(Intensity Modulated Radiation Therapy, IMRT) 및 용적세기조절회전치료(Volumetric Modulated Arc Therapy, VMAT)에서 Jaw-Tracking 기법 유 무에 따라 저선량 영역에 대한 주변 정상장기의 용적선량을 분석하여 그 유용성을 평가하고자 한다. 대상 및 방법: 본 원에서 사용하고 있는 선형가속기 VitalBeamTM(Varian Medical System, U.S.A)으로 식도암 방사선치료를 받은 27명을 대상으로 하였으며, 치료계획은 Eclipse(Ver. 13.6 Varian, U.S.A)를 이용하여 Jaw-Tracking(JT)을 사용한 치료계획과 Non Jaw-Tracking(NJT) 치료계획을 수립하였으며, 치료계획용적(Planning Target Volume, PTV)에 빗장위림프절(Supraclavicular Lymph Nodes, SCL)이 포함되어 있는 T자형 PTV를 가진 환자를 대상으로 하였다. 조사범위에 대한 영향을 확인하기 위해 복강(Celiac) 포함 여부로 비교군을 나누었다. 수립된 치료계획의 비교를 위해 손상위험장기는 양측 폐, 심장, 척수를 비교하였으며 Conformity Index(CI), Homogeneity Index(HI)를 비교하였다. 임상적용 검증을 위해 전자포탈영상장치(Electronic Portal Imaging Device, EPID)를 이용하여 Portal Dosimetry를 실시하였고, 선량 영역의 임계치(Threshold)를 10 %, 5 %, 0 %로 매개변수로 설정하여 감마분석을 실시하였다. 결 과: 모든 치료계획은 3 mm / 3 %, 감마통과율 95 % 기준에 대해 Threshold 10 %의 경우 95 % 이상으로 JT, NJT 모두 통과하였으며, IMRT는 Threshold가 5 %, 0 %로 줄어들수록 JT보다 NJT의 값이 1 % 이상 줄어 들었다. IMRT에서 양측 폐의 $V_5$와 $V_{10}$은 JT에서 Celiac을 포함하지 않을 때 최대 14.7 %, 평균 8.5 %, 5.3 % 만큼 감소했고, $D_{mean}$은 $72.3{\pm}51cGy$ 감소하였으며, Celiac을 포함할 때 JT에서 선량감소가 증가하였다. 심장의 $D_{mean}$은 $68.9{\pm}38.5cGy$, 척수의 $D_{max}$는 $39.7{\pm]30.1cGy$만큼 감소하였다. VMAT은 JT기법 사용 시 폐에서 $V_5$ 평균 2.5 % 감소하였고, 심장 및 척수에서 소량 감소하였으며, Celiac 포함 시 JT의 선량감소가 증가하였다. 결 론: 식도암 치료계획에서 IMRT가 JT 사용 시 양측 폐의 $V_5$, $V_{10}$에서 유의미한 감소가 나타났고, 저 선량영역에서 조사범위가 클수록 선량감소가 크게 나타났다. 따라서 식도암 방사선치료에는 IMRT가 VMAT보다 JT 적용 시 더 효과적이며, 저 선량영역에서의 MLC 누설 및 투과선량으로부터 정상장기를 보호할 수 있다.

• Asian Pacific Journal of Cancer Prevention
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• 제16권8호
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• pp.3257-3265
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• 2015

Background: Radiotherapy is an important treatment of choice for breast cancer patients after breast-conserving surgery, and we compare the feasibility of using dual arc volumetric modulated arc therapy (VMAT2), single arc volumetric modulated arc therapy (VMAT1) and Multi-beam Intensity Modulated Radiotherapy (M-IMRT) on patients after breast-conserving surgery. Materials and Methods: Thirty patients with breast cancer (half right-sided and half left-sided) treated by conservative lumpectomy and requiring whole breast radiotherapy with tumor bed boost were planned with three different radiotherapy techniques: 1) VMAT1; 2) VMAT2; 3) M-IMRT. The distributions for the planning target volume (PTV) and organs at risk (OARs) were compared. Dosimetries for all the techniques were compared. Results: All three techniques satisfied the dose constraint well. VMAT2 showed no obvious difference in the homogeneity index (HI) and conformity index (CI) of the PTV with respect to M-IMRT and VMAT1. VMAT2 clearly improved the treatment efficiency and can also decrease the mean dose and V5Gy of the contralateral lung. The mean dose and maximum dose of the spinal cord and contralateral breast were lower for VMAT2 than the other two techniques. The very low dose distribution (V1Gy) of the contralateral breast also showed great reduction in VMAT2 compared with the other two techniques. For the ipsilateral lung of right-sided breast cancer, the mean dose was decreased significantly in VMAT2 compared with VMAT1 and M-IMRT. The V20Gy and V30Gy of the ipsilateral lung of the left-sided breast cancer for VMAT2 showed obvious reduction compared with the other two techniques. The heart statistics of VMAT2 also decreased considerably compared to VMAT1 and M-IMRT. Conclusions: Compared to the other two techniques, the dual arc volumetric modulated arc therapy technique reduced radiation dose exposure to the organs at risk and maintained a reasonable target dose distribution.

• Radiation Oncology Journal
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• 제7권2호
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• pp.171-183
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• 1989

Roesch의 생존 방정식속에 세포증식으로 일어나는 생존증가를 가장 일반적 형식으로 포함시킨 식을 유도하고 이 식으로부터 저선량률 방사선에만 적용되는 동결과선량식 (Isoeffect formula)을 유도하였다. 이 저선량률식이 파라메터 하나로 결정해주는 총선량은 Paterson과 Green에 의하여 얻어진 실험 임상결과와 일치한다. 이 파라메터와 선량률 효과 사이의 관계의 의의를 논하였다. 또한 고선량률 분절(fractionation) 치료와 동저선량률 계속치료를 연락하는 동결과 선량식을 유도 사용하여, Ellis가 잰 실험결과와 비교하였다. 그 결과, Ellis와 Paterson이 쓴 'tolerance'의 표준이 $\alpha/\beta$의 비 4Gy에 해당하는 것임이 밝혀졌다. 그러므로 이들의 'tolerance'의 표준은 'early effect'에만 두고 본 것이 아님을 알 수 있다. 개념적인 면에서도, 아래와 같은 새로운 견해가 나올 수 있다. KHT sarcoma의 생존선도 (survival curve)에 선량률 효과가 보이지 않는 이유로 $\alpha/\beta$의 비가 큰 점을 들을 수 있다. 이것은 이 survival curve에 어께 (shoulder)가 보이지 않는 것으로도 증명이 된다. Pierquin이 선량률에 무관하게 head and neck tumor치료에 같은 총선량을 쓴 것을 정당화시킬 수 있다.

• Radiation Oncology Journal
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• 제14권2호
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• pp.123-128
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• 1996

목적 : 악성 종양으로 인해 기도 폐쇄가 온 환자들을 저선량 및 고선량으로 내기관지 근접 치료하였을 경우의 대중치료 효과, 생존율 및 병발증을 비교 검토한다. 대상 및 방법 : 1988년 10월부터 1992년 6월까지 저선량 방법으로 21명, 1992년 8월부터 1994년 4월까지 고선량 방법으로 22명, 총 43명의 환자들에게 내기관지 근접치료를 시행하였다. 총 91회의 치료시, 모두 Fluorocopy하에서 굴절성 Fiberoptlc 내시경을 이용하였으며, 저선량 방법의 21회는 15-30 Gy를 0.75 cm 원경에, 고선량 방법의 64회는 5-7.5 Gy를 Ir-192 선원으로부터 1 Cm 원경에 각각 투사하였다. 결과 : 주관적 및 객관적 치료효과의 분석은 임상재진시 나타난 환자의 증상, 흥부 방사선 사진 및 흥부 단층촬영의 결과로 이루어졌다. 저산량으로 치료한 21명 중 15명의 환자와 고선량으로 치료한 22명 중 19명의 환자들이 주관적 치료효과가 있었음을 보였고, 8명의 저선량 환자와 10명의 고선량 환자가 흥부 방사선 사진과 단층 촬영상에서 객관적 효과가 있었음을 나타냈다. 결론 : 저선량 및 고선량 방사선에 의해 근접치료의 기술은 비교적 간단하며 환자가 별다른 후유증 없이 치료를 잘 받아 드리는 편이다. 이 치료 방법은 여생이 얼마 남지 않은 말기 폐암환자에게 내기관지 협착 내지는 폐쇄가 왔을 때 기관지의 공기소통을 원활히 증진시켜주는 대증치료 방법 이다.

• Radiation Oncology Journal
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• 제33권3호
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• pp.242-249
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• 2015

Purpose: The purpose of this study is to compare the dosimetry of electron beam (EB) plans and three-dimensional helical tomotherapy (3DHT) plans for the patients with left-sided breast cancer, who underwent breast conserving surgery. Materials and Methods: We selected total of 15 patients based on the location of tumor, as following subsite: subareolar, upper outer, upper inner, lower lateral, and lower medial quadrants. The clinical target volume (CTV) was defined as the area of architectural distortion surrounded by surgical clip plus 1 cm margin. The conformity index (CI), homogeneity index (HI), quality of coverage (QC) and dose-volume parameters for the CTV, and organ at risk (OAR) were calculated. The following treatment techniques were assessed: single conformal EB plans; 3DHT plans with directional block of left anterior descending artery (LAD); and 3DHT plans with complete block of LAD. Results: 3DHT plans, regardless of type of LAD block, showed significantly better CI, HI, and QC for the CTVs, compared with the EB plans. However, 3DHT plans showed increase in the $V_{1Gy}$ at skin, left lung, and left breast. In terms of LAD, 3DHT plans with complete block of LAD showed extremely low dose, while dose increase in other OARs were observed, when compared with other plans. EB plans showed the worst conformity at upper outer quadrants of tumor bed site. Conclusion: 3DHT plans offer more favorable dose distributions to LAD, as well as improved target coverage in comparison with EB plans.

• Nuclear Engineering and Technology
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• 제54권2호
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• pp.674-680
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• 2022

In the present study, radiation shielding and protection ability of prepared Flyash-lime-Gypsum (FaLG) bricks has been studied in terms of energy exposure build up factors and dose parameters. The energy exposure build up factors of Flyash-lime-Gypsum (FaLG) bricks have been calculated for the energy range of 0.015 MeV-15 MeV and for penetration depth upto 40 mfp directly using a new and simplified Piecewise Linear Spline Interpolation Method (PLSIM). In this new method, the calculations of G.P fitting parameters are not required. The verification and accuracy of this new method has been checked by comparing the results of exposure build up factor for NBS concrete calculated using present method with the results obtained by using G.P fitting method. Further, the relative dose distribution and reduced exposure dose rate for various radioactive isotopes without any shielding material and with Flyash-lime-Gypsum (FaLG) bricks have been calculated in the energy range of 59.59-1332 keV. On the basis of the obtained results, it has been reported that the prepared Flyash-lime-Gypsum (FaLG) bricks possess satisfactory radiation shielding properties and can be used as environmentally safe storage facilities for low level nuclear waste.

• Asian Pacific Journal of Cancer Prevention
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• 제15권18호
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• pp.7811-7816
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• 2014

Background: Despite advances in radiotherapy, overall survival of glioblastoma multiforme (GBM) patients is still poor. Moreover dosimetrical analyses with these newer treatment methods are insufficient. The current study is aimed to compare intensity modulated radiation therapy (IMRT) linear accelerator (linac) and helical tomotherapy (HT) treatment plans for patients with prognostic aggressive brain tumors. Material and Methods: A total of 20 GBM patient plans were prospectively evaluated in both linac and HT planning systems. Plans are compared with respect to homogenity index, conformity index and organs at risk (OAR) sparing effects of the treatments. Results: Both treatment plans provided good results that can be applied to GBM patients but it was concluded that if the critical organs with relatively lower dose constraints are closer to the target region, HT for radiotherapeutical application could be preferred. Conclusion: Tomotherapy plans were superior to linear accelerator plans from the aspect of OAR sparing with slightly broader low dose ranges over the healthy tissues. In case a clinic has both of these IMRT systems, employment of HT is recommended based on the observed results and future re-irradiation strategies must be considered.

• 대한안전경영과학회지
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• 제17권4호
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• pp.193-198
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• 2015

This study analyzed the total number of 19,636 patients and radiation technologists, 11,433 of male and 8,203 of female by examined body parts, age, types of detectors, the using contrast enhancement and working condition of the technologists, regular staffs or rotation-duty staffs, based on the K-DOS program distributed by FDA with the DLP value of diagnostic evaluation. The result shows that the effective radiation dose was 0.7mSv~41.7mSv for each region and male patients had more radiation exposure than females. And the amount of exposure was also affected by the types and the method of detectors. Furthermore, the regular staffs took the role of helping the patient to get reduced amount of radiation exposure than rotation duty-staffs. Computed tomography (CT) use has increased dramatically over the past several decades. In this reason, to support the patients and the workers' health in the field, the hospitals should apply specialized regular working radiation technologist system and manufacturing companies of those CTs should develop low medical radiation exposure devices.