$GafChromic^{(R)}$ EBT2 Film Dosimetry를 위한 품질 관리용 초기 프로그램 개발 Development of Preliminary Quality Assurance Software for $GafChromic^{(R)}$ EBT2 Film Dosimetry원문보기
GafChromic EBT2 필름 dosimetry에 필요한 품질 관리용 소프트웨어를 개발하였다. 개발한 프로그램에서는 EBT2 필름특성에 맞게 붉은색, 초록색, 파란색 및 회색 채널에 따른 필름 교정이 가능하도록 하였다. 또한 평판형 스캐너의 빛의 산란 효과나 필름 내 방사선에 반응하는 물질(active layer)의 두께 차이가 선량 검증에 미치는 영향을 평가할 수 있도록 하였다. EBT2 필름을 이용한 측정 결과는 방사선 치료계획 시스템, ECLIPSE 또는 2차원 이온 전리함 배열의 선량 값과 비교할 수 있다. 개발한 소프트웨어를 이용한 GafChromic EBT2 필름의 선량 검증은 파일 입력, 잡음 제거, 배경 보정(background) 및 반응 물질 보정(active layer correction), 선량 계산 및 평가 단계를 통해서 이루어진다. 절대적 또는 상대적 배경 보정 방법을 선택적으로 적용할 수 있으며 필름 교정 결과 및 교정 곡선에 대한 적합식(fittingequation)은 결과 파일로 출력할 수 있다. 선량 행렬의 화소 크기 조정을 위한 보간법, 대화식 영상 이동 및 회전 기능을 이용하여 선량 행렬 간 구조적 위치를 일치시킨 후, 빔 측면도(beam profile) 및 등선량곡선(isodose curve)을 비교할 수 있다. 또한 거리 및 선량 차이에 대한 허용값을 적용하여 gammaindex 및 gamma histogram을 이용한 선량 분석이 가능하다. 60도 동적 쐐기 조사면과 전립선 세기조절방사선치료의 조사면을 이용하여 개발한 소프트웨어의 기초 성능 평가를 수행하였을 때, 동적 쐐기 조사면에서 ECLIPSE와 EBT2 필름 간 절대적 빔 측면도는 3% 오차 범위 내에서 일치하였다. EBT2 필름을 이용한 두 종류의 선량 검증 모두, 99% 이상의 영역이 3 mm, 3%의 gamma index의 평가 기준을 만족하였다. 개발한 선량 검증용 소프트웨어를 이용하여 주기적으로 수행되는 일반적인 품질관리뿐만 아니라 빔의 세기가 조절된 복잡한 조사면의 품질관리에도 활용할 수 있으며, Radiochromic 필름을 이용한 선량 평가에 필요한 유용한 분석 툴을 제공할 수 있다.
GafChromic EBT2 필름 dosimetry에 필요한 품질 관리용 소프트웨어를 개발하였다. 개발한 프로그램에서는 EBT2 필름특성에 맞게 붉은색, 초록색, 파란색 및 회색 채널에 따른 필름 교정이 가능하도록 하였다. 또한 평판형 스캐너의 빛의 산란 효과나 필름 내 방사선에 반응하는 물질(active layer)의 두께 차이가 선량 검증에 미치는 영향을 평가할 수 있도록 하였다. EBT2 필름을 이용한 측정 결과는 방사선 치료계획 시스템, ECLIPSE 또는 2차원 이온 전리함 배열의 선량 값과 비교할 수 있다. 개발한 소프트웨어를 이용한 GafChromic EBT2 필름의 선량 검증은 파일 입력, 잡음 제거, 배경 보정(background) 및 반응 물질 보정(active layer correction), 선량 계산 및 평가 단계를 통해서 이루어진다. 절대적 또는 상대적 배경 보정 방법을 선택적으로 적용할 수 있으며 필름 교정 결과 및 교정 곡선에 대한 적합식(fitting equation)은 결과 파일로 출력할 수 있다. 선량 행렬의 화소 크기 조정을 위한 보간법, 대화식 영상 이동 및 회전 기능을 이용하여 선량 행렬 간 구조적 위치를 일치시킨 후, 빔 측면도(beam profile) 및 등선량곡선(isodose curve)을 비교할 수 있다. 또한 거리 및 선량 차이에 대한 허용값을 적용하여 gamma index 및 gamma histogram을 이용한 선량 분석이 가능하다. 60도 동적 쐐기 조사면과 전립선 세기조절방사선치료의 조사면을 이용하여 개발한 소프트웨어의 기초 성능 평가를 수행하였을 때, 동적 쐐기 조사면에서 ECLIPSE와 EBT2 필름 간 절대적 빔 측면도는 3% 오차 범위 내에서 일치하였다. EBT2 필름을 이용한 두 종류의 선량 검증 모두, 99% 이상의 영역이 3 mm, 3%의 gamma index의 평가 기준을 만족하였다. 개발한 선량 검증용 소프트웨어를 이용하여 주기적으로 수행되는 일반적인 품질관리뿐만 아니라 빔의 세기가 조절된 복잡한 조사면의 품질관리에도 활용할 수 있으며, Radiochromic 필름을 이용한 선량 평가에 필요한 유용한 분석 툴을 제공할 수 있다.
Software for GafChromic EBT2 film dosimetry was developed in this study. The software provides film calibration functions based on color channels, which are categorized depending on the colors red, green, blue, and gray. Evaluations of the correction effects for light scattering of a flat-bed scanne...
Software for GafChromic EBT2 film dosimetry was developed in this study. The software provides film calibration functions based on color channels, which are categorized depending on the colors red, green, blue, and gray. Evaluations of the correction effects for light scattering of a flat-bed scanner and thickness differences of the active layer are available. Dosimetric results from EBT2 films can be compared with those from the treatment planning system ECLIPSE or the two-dimensional ionization chamber array MatriXX. Dose verification using EBT2 films is implemented by carrying out the following procedures: file import, noise filtering, background correction and active layer correction, dose calculation, and evaluation. The relative and absolute background corrections are selectively applied. The calibration results and fitting equation for the sensitometric curve are exported to files. After two different types of dose matrixes are aligned through the interpolation of spatial pixel spacing, interactive translation, and rotation, profiles and isodose curves are compared. In addition, the gamma index and gamma histogram are analyzed according to the determined criteria of distance-to-agreement and dose difference. The performance evaluations were achieved by dose verification in the $60^{\circ}$-enhanced dynamic wedged field and intensity-modulated (IM) beams for prostate cancer. All pass ratios for the two types of tests showed more than 99% in the evaluation, and a gamma histogram with 3 mm and 3% criteria was used. The software was developed for use in routine periodic quality assurance and complex IM beam verification. It can also be used as a dedicated radiochromic film software tool for analyzing dose distribution.
Software for GafChromic EBT2 film dosimetry was developed in this study. The software provides film calibration functions based on color channels, which are categorized depending on the colors red, green, blue, and gray. Evaluations of the correction effects for light scattering of a flat-bed scanner and thickness differences of the active layer are available. Dosimetric results from EBT2 films can be compared with those from the treatment planning system ECLIPSE or the two-dimensional ionization chamber array MatriXX. Dose verification using EBT2 films is implemented by carrying out the following procedures: file import, noise filtering, background correction and active layer correction, dose calculation, and evaluation. The relative and absolute background corrections are selectively applied. The calibration results and fitting equation for the sensitometric curve are exported to files. After two different types of dose matrixes are aligned through the interpolation of spatial pixel spacing, interactive translation, and rotation, profiles and isodose curves are compared. In addition, the gamma index and gamma histogram are analyzed according to the determined criteria of distance-to-agreement and dose difference. The performance evaluations were achieved by dose verification in the $60^{\circ}$-enhanced dynamic wedged field and intensity-modulated (IM) beams for prostate cancer. All pass ratios for the two types of tests showed more than 99% in the evaluation, and a gamma histogram with 3 mm and 3% criteria was used. The software was developed for use in routine periodic quality assurance and complex IM beam verification. It can also be used as a dedicated radiochromic film software tool for analyzing dose distribution.
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가설 설정
(a) Calculation of average pixel values in the calibration film. (b) Calibration data of the EBT2 film based on the red channel. (c) Fitting equation of the sensitometric curve.
(a) Absolute x-axis profile in the horizontal direction at the center of the field. (b) Gamma index distribution applied using a distance-to-agreement of 3 mm and a dose difference of 3%. (c) Comparison of isodose curves for dose levels with the box for EBT2 films and without the box for a planning system.
제안 방법
A hybrid plan, which was configured by the composition for seven IM beams at the same gantry angles of the 0° position, was created to evaluate the performance of the developed software.
Dose comparison between measured values using GafChromicⓇ EBT2 films and ECLIPSE data in a 60º -enhanced dynamic wedged field.
In the experiments, a SP33 phantom was scanned by computed tomography (CT), and the calculated dose distribution was then applied for a source-to-axis distance of 100 cm with a field size of 10×10 cm.
Thus, the evaluation of EBT film dosimetry using existing software is difficult. In this study, customized and modifiable software was developed that can facilitate dose verification using EBT2 films. Moreover, the software provides proper functions for dose comparison between EBT2 films and other dosimeters.
In this study, we developed QA software for the initial stage featuring calibrations based on each RGB channel and several approaches to background corrections for GafChromicⓇ EBT2 film dosimetry. The functions of the software were tested by implementing application examples for dose comparison between the measured and calculated values obtained from EBT2 films and a treatment planning system (TPS).
EBT2 film dosimetry. The functions of the software were tested by implementing application examples for dose comparison between the measured and calculated values obtained from EBT2 films and a treatment planning system (TPS).
, Long Beach, CA, USA) in landscape orientation. To take the grid size in TPS into account for dose calculation, scanned film images were acquired for a resolution of 72 dpi (dots per inch), and a relative background correction was applied.
To test the validity of the software, a 60° -enhanced dynamic wedged (EDW) field and IM beams were applied for dose verification using the developed software.
대상 데이터
The film pieces are placed on the slab phantom (SP33, Scanditronix-Wellhofer, Schwarzenbruck, Germany) for a source-to-surface distance of 100 cm with a field size of 10×10 cm.
The software was developed using MATLAB (version R2008a, Mathworks, Natick, MA, USA) and is composed of two frames (Fig. 1), which display the imported and resultant images obtained at each processing step. Dose verification using EBT2 films are carried out in the following sequence on each tab panel: file import, noise filtering, background and active layer corrections, dose calculation, comparison, and evaluation.
성능/효과
As the doses were calculated using eq. (4) at the applied ODs of 0.569 and 0.785, which correspond to 450 and 700 cGy, the dose differences were approximately 2.1% and 3.9%, respectively, when compared to the delivered doses.
참고문헌 (7)
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Fuss M, Sturtewagen E, De Wagter C, Georg D: Dosimetric characterization of GafChromic EBT film and its implication on film dosimetry quality assurance. Phys Med Biol 21:4211-4225 (2007)
Fiandra C, Ricardi U, Ragona R, et al: Clinical use of EBT model Gafchromic film in radiotherapy. Med Phys 33:4314-4319 (2006)
Wilcox EE, Daskalov GM, Pavlonnis G 3rd, Shumway R, Kaplan B, VanRooy E: Dosimetric verification of intensity modulated radiation therapy of 172 patients treated for various disease sites: comparison of EBT film dosimetry, ionc hamber measurements, and independent MU calculations. Med Dosim 33:303-309 (2008)
Devic S, Seuntjens J, Abdel-Rahman W, et al: Accurate skin dose measurements using radiochromic film in clinical applications. Med Phys 33:1116-1124 (2006)
$GAFCHROMIC^{\circledR}$ EBT2 SELF-DEVOPING FILM FOR FARIOTHERAPY DOSIMETRY. INTERNATIONAL SPECIALTY PRODUCTS, Alps Road Wayne, NJ (2009)
Sankar A, Ayyangar KM, Nehru RM, et al: Comparison of Kodak EDR2 and Gafchromic EBT film for intensity-modulated radiation therapy dose distribution verification. Med Dosim 31: 273-282 (2006)
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