근치적 유방절제술을 시행받은 환자의 Chest wall 치료시 step bolus사용에 대한 유용성 고찰

백태성,방동완,이상훈,박재일 대한방사선치료학회 1999 大韓放射線治療技術學會誌 Vol.11 No.1

고선량률(HDR) 근접치료의 동위원소 Ir-192에 대한 측정방법에 관한 고찰

백태성,이승욱,나수경,Baek, Tae-Seong,Lee, Seung-Wook,Na, Soo-Kyong 대한방사선치료학회 2007 대한방사선치료학회지 Vol.19 No.1

Purpose: To compare of the accuracy among various measurement procedures of HDR Brachytherapy, and to evaluate the clinical suitability and usefulness of alternative PMMA (polymethylmethacrylateplastics: $C_5H_8O_2$) plate phantom without any additional cost due to the purchase of measuring apparatus. Materials and Methods: We made a comparative study on three types of measuring systems: well type chamber, source calibration jig, and PMMA plate phantom. Farmer type chamber was used for source calibration jig method and PMMA plate phantom method. Measurement was done 5 times each in comparison with the measurement values from manufacturer. Measurement results from experiment were compared with that from the manufacturer which is offered with the source whenever a source is substituted by a new one and evaluate the accuracy of source activity. Results: As a consequence of Ir-192 source measurement using well type chamber, source calibration jig and PMMA plate phantom, RMS (Root Mean Square) values for the relative error are 0.6%, 1.57%, 2.1%, respectively, compared with the data from manufacturer. And the mean errors with standard deviation are given $-0.2{\pm}0.5%$, $0.97{\pm}1.23%$, $-0.89{\pm}1.87%$ respectively. Conclusion: From the results shown by the three types of measurement system (well type chamber, source calibration jig, and PMMA plate phantom), the measurement with well type chamber produced the best accuracy. It turns out that we can also use the alternative system of PMMA plate phantom clinically without purchasing any additional particular apparatus since the system does not exceed the recommendation of AAPM (American Association of Physicists in Medicine), which requires the error range of within ${\pm}5%$.

Detection of IMRT Delivery Errors Based on a Simple Constancy Check of Transit Dose by using an EPID

백태성,정은지,손재만,윤명근 한국물리학회 2015 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.67 No.10

Beam delivery errors during intensity modulated radiotherapy (IMRT) were detected based on a simple constancy check of the transit dose by using an electronic portal imaging device (EPID). Twenty-one IMRT plans were selected from various treatment sites, and the transit doses during treatment were measured by using an EPID. Transit doses were measured 11 times for each course of treatment, and the constancy check was based on gamma index (3%/3 mm) comparisons between a reference dose map (the first measured transit dose) and test dose maps (the following ten measured dose maps). In a simulation using an anthropomorphic phantom, the average passing rate of the tested transit dose was 100% for three representative treatment sites (head & neck, chest, and pelvis), indicating that IMRT was highly constant for normal beam delivery. The average passing rate of the transit dose for 1224 IMRT fields from 21 actual patients was 97.6% ± 2.5%, with the lower rate possibly being due to inaccuracies of patient positioning or anatomic changes. An EPIDbased simple constancy check may provide information about IMRT beam delivery errors during treatment.

유중 용존수소 감지를 위한 Pd/Pt Gate MISFET 센서의 제조와 그 특성

백태성,이재곤,최시영 ( Tae Sung baek,Jae Gon Lee,Sie Yong Choi ) 한국센서학회 1996 센서학회지 Vol.5 No.4

The Pd/Pt gate MISFET type hydrogen sensors, for detecting dissolved hydrogen gas in the transformer oil, were fabricated and their characteristics were investigated. These sensors including diffused resistor heater and temperature monitoring diode were fabricated on the same chip by a conventional silicon process technique. The differential pair plays a role in minimizing the intrinsic voltage drift of the MISFET. To avoid the drift of the sensors induced by the hydrogen, the gate insulators of both FETs were constructed with double layers of silicon dioxide and silicon nitride. In order to eliminate the blister formation on the surface of the hydrogen sensing gate metal, Pt and Pd double metal layers were deposited on the gate insulator. The hydrogen response of the Pd/Pt gate MISFET suggests that the proposed sensor can detect the dissolved hydrogen in transformer oil with 40mV/10ppm of sensitivity and 0.14mV/day of stability.

8) 유방절제술 후 환자의 Chest Wall 치료시 Step Bolus 사용에 대한 유용성 고찰

백태성,박동완,이상훈,박재일 대한방사선사협회 1999 대한방사선사협회지 Vol.25 No.1

Estimate of the Shielding Effect on Secondary Cancer Risk due to Cone-beam CT in Image-guided Radiotherapy

성지원,백태성,윤명근,김동욱,김동현 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.65 No.5

This study evaluated the effect of a simple shielding method using a thin lead sheet on the imagingdose caused by cone-beam computed tomography (CBCT) in image-guided radiation therapy(IGRT). Reduction of secondary doses from CBCT was measured using a radio-photoluminescenceglass dosimeter (RPLGD) placed inside an anthropomorphic phantom. The entire body, except forthe region scanned by using CBCT, was shielded by wrapping it with a 2-mm lead sheet. Changes insecondary cancer risk due to shielding were calculated using BEIR VII models. Doses to out-of-fieldorgans for head-and-neck, chest, and pelvis scans were decreased 15 100%, 23 90%, and 23 98%, respectively, and the average reductions in lifetime secondary cancer risk due to the 2-mmlead shielding were 1.6, 11.5, and 12.7 persons per 100,000, respectively. These findings suggestthat a simple, thin-lead-sheet-based shielding method can effectively decrease secondary doses toout-of-field regions for CBCT, which reduces the lifetime cancer risk on average by 9 per 100,000patients.

방사선치료에서 투과선량을 이용한 체내선량 검증프로그램 개발

황의중,백태성,윤명근,Hwang, Ui-Jung,Baek, Tae Seong,Yoon, Myonggeun 한국의학물리학회 2014 의학물리 Vol.25 No.1

방사선치료에서는 환자 체내에 전달된 선량이 원래 의도한 데로 분포되는 지 확인하기 위하여 균질한 팬텀을 이용한 정도 관리를 치료 전에 주로 시행하고 있다. 하지만 균질한 팬텀을 이용한 정도 관리는 표면이 불규칙적이고 불균질한 인체에 대한 선량분포를 완전히 보증해 주지는 못하고 있다. 본 연구에서는 환자를 투과하는 선량의 분포를 측정하여 역으로 환자체내 선량 분포를 계산하는 투과선량 기반 체내선량 검증프로그램을 개발하였다. 투과선량은 주방사선과 산란방사선으로 이루어져 있는데, 본 연구에서는 전자포탈영상장치로 측정한 선량분포로부터 주방사선만을 이용한 간단한 식으로 환자체내선량분포를 계산하는 프로그램과 감마값 분포를 평가하여 두 선량분포를 서로 비교할 수 있는 프로그램을 개발하였다. 개발된 프로그램을 이용하여 계산한 팬텀의 등중심점을 지나는 관상면의 체내선량 분포는 치료계획시스템에서 제공하는 동일 평면의 선량분포와의 비교결과 균질팬텀에서 평균 95%, 비균질팬텀에서 81.8%의 감마통과율을 보였다. The purpose of this study is to evaluate the developed dose verification program for in vivo dosimetry based on transit dose in radiotherapy. Five intensity modulated radiotherapy (IMRT) plans of lung cancer patients were used in the irradiation of a homogeneous solid water phantom and anthropomorphic phantom. Transit dose distribution was measured using electronic portal imaging device (EPID) and used for the calculation of in vivo dose in patient. The average passing rate compared with treatment planning system based on a gamma index with a 3% dose and a 3 mm distance-to-dose agreement tolerance limit was 95% for the in vivo dose with the homogeneous phantom, but was reduced to 81.8% for the in vivo dose with the anthropomorphic phantom. This feasibility study suggested that transit dose-based in vivo dosimetry can provide information about the actual dose delivery to patients in the treatment room.

Feasibility Study of a Simple Approximation Algorithm for In-vivo Dose Reconstruction by Using the Transit Dose Measured Using an EPID

황의중,송미희,백태성,정은지,윤명근 한국물리학회 2015 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.66 No.4

The purpose of this study is to verify the accuracy of the dose delivered to the patient duringintensity-modulated radiation therapy (IMRT) by using in-vivo dosimetry and to avoid accidentalexposure to healthy tissues and organs close to tumors. The in-vivo dose was reconstructed byback projection of the transit dose with a simple approximation that considered only the percentdepth dose and inverse square law. While the average gamma index for comparisons of dose distributionsbetween the calculated dose map and the film measurement was less than the one for96.3% of all pixels with the homogeneous phantom, the passing rate was reduced to 92.8% with theinhomogeneous phantom, suggesting that the reduction was apparently due to the inaccuracy of thereconstruction algorithm for inhomogeneity. The proposed method of calculating the dose insidea phantom was of comparable or better accuracy than the treatment planning system, suggestingthat it can be used to verify the accuracy of the dose delivered to the patient during treatment.

Estimate of the Risk of Radiation-induced Cancers after Linear-accelerator-based Breast-cancer Radiotherapy

고의관,서정주,백태성,정은지,윤명근,이현호 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.63 No.1

The aim of this study is to assess and compare the excess absolute risks (EARs) of radiationinduced cancers following conformal (3D-CRT), fixed-field intensity-modulated (IMRT) and volumetric modulated arc (RapidArc) radiation therapy in patients with breast cancer. 3D-CRT, IMRT and RapidArc were planned for 10 breast cancer patients. The organ-specific EAR for cancer induction was estimated using the organ equivalent dose (OED) based on computed dose volume histograms (DVHs) and the secondary doses measured at various points from the field edge. The average secondary dose per Gy treatment dose from 3D-CRT, measured 10 to 50 cm from the field edge, ranged from 8.27 to 1.04 mGy. The secondary doses per Gy from IMRT and RapidArc, however,ranged between 5.86 and 0.54 mGy, indicating that IMRT and RapidArc are associated with smaller doses of secondary radiation than 3D-CRT. The organ specific EARs for out-of-field organs,such as the thyroid, liver and colon, were higher with 3D-CRT than with IMRT or RapidArc. In contrast, EARs for in-field organs were much lower with 3D-CRT than with IMRT or RapidArc. The overall estimate of EAR indicated that the radiation-induced cancer risk was 1.8 - 2.0 times lower with 3D-CRT than with IMRT or RapidArc. Comparisons of EARs during breast irradiation suggested that the predicted risk of secondary cancers was lower with 3D-CRT than with IMRT or RapidArc.

자궁경부암 근접치료 시 선량 검증 프로그램을 통한 임상적 위험성 평가

강동진,신영주,강진규,정재용,이우진,백태성,이보람 대한방사선과학회 2022 방사선기술과학 Vol.45 No.6

The purpose of this study is to evaluate the clinical risk according to the applicator heterogeneity, mislocation, and tissue heterogeneity correction through a dose verification program during brachytherapy of cervical cancer. We performed image processing with MATLAB on images acquired with CT simulator. The source was modeled and stochiometric calibration and Monte-Carlo algorithm were applied based on dwell time and location to calculate the dose, and the secondary cancer risk was evaluated in the dose verification program. The result calculated by correcting for applicator and tissue heterogeneity showed a maximum dose of about 25% higher. In the bladder, the difference in excess absolute risk according to the heterogeneity correction was not significant. In the rectum, the difference in excess absolute risk was lower than that calculated by correcting applicator and tissue heterogeneity compared to the water-based calculation. In the femur, the water-based calculation result was the lowest, and the result calculated by correcting the applicator and tissue heterogeneity was 10% higher. A maximum of 14% dose difference occurred when the applicator mislocation was 20 mm in the Z-axis. In a future study, it is expected that a system that can independently verify the treatment plan can be developed by automating the interface between the treatment planning system and the dose verification program.