Analysis of the Dose Distribution of Moving Organ using a Moving Phantom System

김연래,박병문,배용기,강민영,이귀원,방동완,Kim, Yon-Lae,Park, Byung-Moon,Bae, Yong-Ki,Kang, Min-Young,Lee, Gui-Won,Bang, Dong-Wan Korean Society for Radiation Therapy 2006 대한방사선치료학회지 Vol.18 No.2

Purpose: Few researches have been peformed on the dose distribution of the moving organ for radiotherapy so far. In order to simulate the organ motion caused by respiratory function, multipurpose phantom and moving device was used and dosimetric measurements for dose distribution of the moving organs were conducted in this study. The purpose of our study was to evaluate how dose distributions are changed due to respiratory motion. Materials and Methods: A multipurpose phantom and a moving device were developed for the measurement of the dose distribution of the moving organ due to respiratory function. Acryl chosen design of the phantom was considered the most obvious choice for phantom material. For construction of the phantom, we used acryl and cork with density of $1.14g/cm^3,\;0.32g/cm^3$ respectively. Acryl and cork slab in the phantom were used to simulate the normal organ and lung respectively. The moving phantom system was composed of moving device, moving control system, and acryl and cork phantom. Gafchromic film and EDR2 film were used to measure dose ditrbutions. The moving device system may be driven by two directional step motors and able to perform 2 dimensional movements (x, z axis), but only 1 dimensional movement(z axis) was used for this study. Results: Larger penumbra was shown in the cork phantom than in the acryl phantom. The dose profile and isodose curve of Gafchromic EBT film were not uniform since the film has small optical density responding to the dose. As the organ motion was increased, the blurrings in penumbra, flatness, and symmetry were increased. Most of measurements of dose distrbutions, Gafchromic EBT film has poor flatness and symmetry than EDR2 film, but both penumbra distributions were more or less comparable. Conclusion: The Gafchromic EBT film is more useful as it does not need development and more radiation dose could be exposed than EDR2 film without losing film characteristics. But as response of the optical density of Gafchromic EBT film to dose is low, beam profiles have more fluctuation at Gafchromic EBT. If the multipurpose phantom and moving device are used for treatment Q.A, and its corrections are made, treatment quality should be improved for the moving organs.

Dosimetric Comparison of a 6-MV Flattening-filter and a Flattening-filter-free Beam for Lung Stereotactic Ablative Radiotherapy Treatment

김연래,정진범,김재성,이정우,김진영,강상원,서태석 한국물리학회 2015 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.67 No.9

The purpose of this study was to test the feasibility of clinical usage of a flattening-filter-free (FFF) beam for treatment with lung stereotactic ablative radiotherapy (SABR). Ten patients were treated with SABR and a 6-MV FFF beam for this study. All plans using volumetric modulated arc therapy (VMAT) were optimized in the Eclipse treatment planning system (TPS) by using the Acuros XB (AXB) dose calculation algorithm and were delivered by using a Varian TrueBeamTM linear accelerator equipped with a high-definition (HD) multi-leaf collimator. The prescription dose used was 48 Gy in 4 fractions. In order to compare the plan using a conventional 6-MV flattening-filter (FF) beam, the SABR plan was recalculated under the condition of the same beam settings used in the plan employing the 6-MV FFF beam. All dose distributions were calculated by using Acuros XB (AXB, version 11) and a 2.5-mm isotropic dose grid. The cumulative dosevolume histograms (DVH) for the planning target volume (PTV) and all organs at risk (OARs) were analyzed. Technical parameters, such as total monitor units (MUs) and the delivery time, were also recorded and assessed. All plans for target volumes met the planning objectives for the PTV (i.e., V95% > 95%) and the maximum dose (i.e., Dmax < 110%) revealing adequate target coverage for the 6-MV FF and FFF beams. Differences in DVH for target volumes (PTV and clinical target volume (CTV)) and OARs on the lung SABR plans from the interchange of the treatment beams were small, but showed a marked reduction (52.97%) in the treatment delivery time. The SABR plan with a FFF beam required a larger number of MUs than the plan with the FF beam, and the mean difference in MUs was 4.65%. This study demonstrated that the use of the FFF beam for lung SABR plan provided better treatment efficiency relative to 6-MV FF beam. This strategy should be particularly beneficial for high dose conformity to the lung and decreased intra-fraction movements because of the shorter treatment delivery time. Future studies are necessary to assess the clinical outcome and the toxicity.

호흡에 의해 내부 움직임을 갖는 장기에 전달되는 선량에서 Time Gating Threshold (TGT)의 효과

김연래,정진범,정원균,홍세미,서태석,Kim Yon Lae,Chung Jin Bum,Chung Won Kyun,Hong Semie,Suh Tae Suk 한국의학물리학회 2005 의학물리 Vol.16 No.2

본 연구는 호흡에 따라 내부 장기가 움직일 때, 내부 장기가 가장 안정적인 구간의 문턱 값(threshold)을 시간으로 설정한 후 선량분포에 대한 연구를 수행하였다. 일반적으로 정상적인 호흡주기 중에서 시간대비 내부 장기 움직임이 호기 상태에서 적게 나타난다. 그러므로 시간동기 문턱 값(time gating threshold, TGT)은 내부 장기 움직임이 가장 적은 호기 시 1 초 동안 움직일 때의 선량분포를 평가하였다. TGT를 설정했을 때 선량분포를 비교하기 위해 다음 조건으로 방사선을 조사하였다. 내부 장기가 1) 고정된 상태, 2) 문책 값 범위 내에서 움직일 때, 3) 문턱 값 범위 밖에서 움직일 때, 각각의 내부 장기 움직임 조건을 구동팬톰시스템으로 모사하였다. 그리고 필름 선량 측정법(film dosimetry)을 이용하여 비교 평가하였다. TGT를 1초로 설정하고 내부적 움직임을 고려하여 선량분포를 획득했을 때 치료시간은 증가하였다. 그러나 TGT를 1초로 설정한 것은 내부적 움직임을 고려하지 않은 선량분포 즉, 치료 조사면 내에 장기의 움직임이 없을 때와 비슷한 선량분포를 얻을 수 있었다. 그리고 문턱 詰없이 내부 장기가 움직일 때와 비교해서 반음영 영역에 불필요한 선량을 줄일 수 있었다. 또한 치료시간을 줄이기 위해서 문턱 값을 1.4초로 설정했을 때가 1초로 설정했을 때보다 시간 비에 따른 선량분포에 대해 효과적인 결과를 얻지 못했다. 즉, 시간은 줄었지만 치료영역 밖에 많은 선량이 분포하였다. 임상적으로 TGT를 설정해서 방사선 치료를 하기 위해서는 수학적인 계산 방법에 의한 내부 장기의 움직임을 표현하는 것이 아니라 실측에 의해서 모든 환자의 외부 움직임과 내부 움직임을 측정해야 한다. 또한 내부와 외부 움직임의 상관관계를 분석해서 환자의 호흡주기에 따른 내부 장기의 움직임 중에 이상적인 위치에서 문책 값을 설정 후 방사선치료를 시행하면 정상조직은 낮은 선량이 분포하면서 치료성적이 향상될 것이라 예상된다. In this study, we investigated the effect of time gating threshold on the delivered dose at a organ with internal motion by respiration. Generally, the internal organs have minimum motion at exhalation during normal breathing. Therefore to compare the dose distribution time gating threshold, in this paper, was determined as the moving region of target during 1 sec at the initial position of exhalation. The irradiated fields were then delivered under three conditions; 1) non-moving target 2) existence of the moving target in the region of threshold (1sec), 3) existence of the moving target region out of threshold (1.4 sec, 2 sec). And each of conditions was described by the moving phantom system. It was compared with the dose distributions of three conditions using film dosimetry. Although the treatment time increased when the dose distributions was obtained by the internal motion to consider the TGT, it could be obtained more exact dose distribution than in the treatment field that didn't consider the internal motion. And it could be reduced the unnecessary dose at the penumbra region. When we set up 1.4 sec of threshold, to reduce the treatment time, it could not be obtained less effective dose distribution than 1 sec of threshold. Namely, although the treatment time reduce, the much dose was distributed out of the treatment region. Actually when it is treated the moving organ, it would rather measure internal motion and external motion of the moving organ than mathematical method. If it could be analyzed the correlation of the internal and external motion, the treatment scores would be improved.

쐐기필터 사용 시 레디오크로믹 필름을 이용한 조직에 따른 선량분포 연구

김연래(Yon-Lae Kim),이정우(Jeong-Woo Lee),박병문(Byung-Moon Park),정재용(Jae-Yong Jung),박지연(Ji-Yeon Park),서태석(Tae-Suk Suh) 대한방사선과학회(구 대한방사선기술학회) 2012 방사선기술과학 Vol.35 No.2

본 논문의 목적은 쐐기필터를 사용한 방사선조사면에서 다양한 조직전자밀도가 선량분포에 미치는 영향을 분석하고자 함이다. 구성된 물질에 따라 밀도가 다른 고체 팬텀, 코르크팬텀, 그리고 공기층에서 동적쐐기필터와 금속쐐기필터를 이용하여 선량분포의 변형정도를 평가하였다. 본 실험에서는 매질 내 삽입이 용이하고 우수한 선량특성을 가지고 있는 레디오크로믹 필름(Gafchromic EBT2, International Speciality Products, NJ)을 사용하였다. 선형가속기 6 ㎹ 광자선을 이용해서 10×10 ㎠ 조사면에 400 MU를 조사하였다. 필름의 선량분포는 선량 분석프로그램을 이용하여 조사면 내 영역과 반음영 영역을 분석하였다. 조직의 밀도가 같을 때 동적쐐기필터와 금속 쐐기필터의 선량분포는 금속 쐐기필터 선량이 동적쐐기필터 선량보다 높게 나타났다. 조직전자밀도가 다른 부위에 쐐기필터의 종류에 따른 선량분포는 고체팬텀과 코르크팬텀에서 2% 이내 차이를 나타내고 있었다. 그러나 공기층에서 선량분포는 고체팬텀이나 코르크 팬텀의 선량분포와 큰 차이를 보이고 있다. 공기층에서 쐐기필터의 선량분포는 쐐기 사용 효과가 나타나지 않고 있다. 쐐기필터의 두꺼운 부분과 얇은 부분 밖에서 반음영의 크기는 1 ㎝에서 2 ㎝ 정도 크게 두꺼운 부분에서 크게 나타났다. 그리고 금속 쐐기필터에서 반음영이 동적쐐기필터 보다 평균 6.4%정도 높게 반음영이 나타났다 본 실험을 통해 공기층과 같이 조직전자밀도 현저히 작은 매질에서는 쐐기필터의 효과가 크게 떨어지는 것과 불균질 물질에 따라 흡수되는 선량분포가 크게 변형되는 것을 알 수 있었다. 따라서 조직전자밀도의 차이가 큰 부위의 방사선치료계획 시 쐐기필터의 적용에 따른 적절한 보정이 이루어져야 한다. The purpose of this study is to analyze the dose distribution when wedge filter is used in the various tissue electron density materials. The dose distribution was assessed that the enhanced dynamic wedge filter and physical wedge filter were used in the solid water phantom, cork phantom, and air cavity. The film dosimetry was suitable simple to measure 2D dose distribution. Therefore, the radiochromic films (Gafchromic EBT2, ISP, NJ, USA) were selected to measure and to analyze the dose distributions. A linear accelerator using 6 ㎹ photon were irradiated to field size of 10×10 ㎠ with 400 MUs. The dose distributions of EBT2 films were analyzed the in-field area and penumbra regions by using dose analysis program. In the dose distributions of wedge field, the dose from a physical wedge was higher than that from a dynamic wedge at the same electron density materials. A dose distributions of wedge type in the solid water phantom and the cork phantom were in agreements with 2%. However, the dose distribution in air cavity showed the large difference with those in the solid water phantom or cork p hantom dose distributions. Dose distribution of wedge field in air cavity was not shown the wedge effect. The penumbra width, out of the field of thick and thin, was observed larger from 1 ㎝ to 2 ㎝ at the thick end. The penumbra of physical wedge filter was much larger average 6 % than the dynamic wedge filter. If the physical wedge filter is used, the dose was increased to effect the scatter that interacted with photon and physical wedge. In the case of difference in electron like the soft tissue, lung, and air, the transmission, absorption, and scattering were changed in the medium at high energy photon. Therefore, the treatment at the difference electron density should be inhomogeneity correction in treatment planning system.

무릎 체중부하 촬영 보조장치 개발

김연래(Yon-Lae Kim),윤영우(Young-Woo Yoon) 대한방사선과학회(구 대한방사선기술학회) 2023 방사선기술과학 Vol.46 No.5

체적조절호형방사선치료 시 갠트리 회전과 다엽콜리메이터의 이동 속도에 따른 선량분포 평가

김연래(Kim Yon-Lae),정진범(Chung Jin-Beom),이정우(Lee Jeong-woo),신영주(Shin Young-Joo),강동진(Kang Dong-Jin),정재용(Jung Jae-Yong) 대한방사선과학회(구 대한방사선기술학회) 2019 방사선기술과학 Vol.42 No.3

The purpose of this study is to evaluate the dose distribution by gantry rotation and MLC moving speed on treatment planning system(TPS) and linear accelerator. The dose analyzer phantom(Delta 4) was scanned by CT simulator for treatment planning. The planning target volumes(PTVs) of prostate and pancreas was prescribed 6,500 cGy, 5,000 cGy on VMAT(Volumetric Modulated Arc Therapy) by TPS while MLC speed changed. The analyzer phantom was irradiated linear accelerator using by planned parameters. Dose distribution of PTVs were evaluated by the homogeneity index, conformity index, dose volume histogram of organ at risk(rectum, bladder, spinal cord, kidney). And irradiated dose analysis were evaluated dose distribution and conformity by gamma index. The PTV dose of pancreas was 4,993 cGy during 0.1㎝/deg leaf and gantry that was the most closest prescribed dose(5,000 cGy). The dose of spinal cord, left kidney, and right kidney were accessed the lowest during 0.1 ㎝/deg, 1.5 ㎝/deg, 0.3 ㎝/deg. The PTV dose of prostate was 6,466 cGy during 0.1 ㎝/deg leaf and gantry that was the most closest prescribed dose(6,500 cGy). The dose of bladder and rectum were accessed the lowest during 0.3 ㎝/deg, 2.0 ㎝/deg. For gamma index, pancreas and prostate were analyzed the lowest error 100% at 0.8, 1.0 ㎝/deg and 99.6% at 0.3, 0.5 ㎝/deg. We should used the optimal leaf speed according to the gantry rotation if the treatment cases are performed VMAT.

동일 기종 선형가속기간 8 MV 광자선에 대한 빔 매칭 정확도 평가

김연래(Yon-Lae Kim),정진범(Jin-Beom Chung),강성희(Seong-Hee Kang) 대한방사선과학회(구 대한방사선기술학회) 2020 방사선기술과학 Vol.43 No.2

This study aimed to assess of beam-matching accuracy for an 8 MV beam between the same model linear accelerators(Linac) commissioned over two years. Two models were got the customer acceptance procedure(CAP) criteria. For commissioning data for beam-matched linacs, the percentage depth doses(PDDs), beam profiles, output factors, multi-leaf collimator(MLC) leaf transmission factors, and the dosimetric leaf gap(DLG) were compared. In addition, the accuracy of beam matching was verified at phantom and patient levels. At phantom level, the point doses specified in TG-53 and TG-119 were compared to evaluate the accuracy of beam modelling. At patient level, the dose volume histogram(DVH) parameters and the delivery accuracy are evaluated on volumetric modulated arc therapy(VMAT) plan for 40 patients that included 20 lung and 20 brain cases. Ionization depth curve and dose profiles obtained in CAP showed a good level for beam matching between both Linacs. The variations in commissioning beam data, such as PDDs, beam profiles, output factors, TF, and DLG were all less than 1%. For the treatment plans of brain tumor and lung cancer, the average and maximum differences in evaluated DVH parameters for the planning target volume(PTV) and the organs at risk(OARs) were within 0.30% and 1.30%. Furthermore, all gamma passing rates for both beam-matched Linacs were higher than 98% for the 2%/2 ㎜ criteria and 99% for the 2%/3 ㎜ criteria. The overall variations in the beam data, as well as tests at phantom and patient levels remains all within the tolerance (1% difference) of clinical acceptability between beam-matched Linacs. Thus, we found an excellent dosimetric agreement to 8 MV beam characteristics for the same model Linacs.

전산화단층 모의치료장치의 정도관리 항목 제안

김연래(Yon-Lae Kim),윤영우(Young-Woo Yoon),정재용(Jae-Yong Jung),이정우(Jeong-Woo Lee),정진범(Jin-Beom Chung) 대한방사선과학회(구 대한방사선기술학회) 2021 방사선기술과학 Vol.44 No.4

A quality assurance of computed tomography(CT) have done seven items that were water attenuation coefficient, noise, homogeneity, spatial resolution, contrast resolution, slice thickness, artifact using by standard phantom. But there is no quality assurance items and methods for CT simulator at domestic institutions yet. Therefore the study aimed to access the CT dose index(CTDI), table tilting, image distortion, laser accuracy, table movement accuracy and CT seven items for CT simulator quality assurance. The CTDI at the center of the head phantom was 0.81 for 80 kVp, 1.55 for 100 kVp, 2.50 for 120 ㎜, 0.22 for 80 kVp at the center of the body phantom, 0.469 for 100 kVp, and 0.81 for 120 kVp. The table tilting was within the tolerance range of ±1.0° or less. Image distortion had 1 ㎜ distortion in the left and right images based on the center, and the laser accuracy was measured within ±2 ㎜ tolerance. The purpose of this study is to improve the quality assurance items suitable for the current situation in Korea in order to protect the normal tissues during the radiation treatment process and manage the CT simulator that is implemented to find the location of the tumor more clearly. In order to improve the accuracy of the CT simulator when looking at the results, the error range of each item should be small. It is hoped that the quality assurance items of the CT simulator will be improved by suggesting the quality assurance direction of the CT simulator in this study, and the results of radiation therapy will also improve.

VitalBeam 선형가속기의 심부선량백분율과 측방선량분포 측정을 위한 새로운 기준 전리함으로서 스텔스 전리함의 성능 평가

김연래(Yon-Lae Kim),정진범(Jin-Beom Chung),강성희(Seong-Hee Kang),강상원(Sang-Won Kang),김경현(Kyeong-Hyeon Kim),정재용(Jae-Yong Jung)신영주(Young-Joo Shin),서태석(Tae-Suk Suh),이정우(Jeong-Woo Lee) 대한방사선과학회(구 대한방사선기술학회) 2018 방사선기술과학 Vol.41 No.3

Abstract The purpose of this study is to evaluate the performance of a “stealth chamber” as a novel reference chamber for measuring percentage depth dose (PDD) and profile of 6, 8 and 10 MV photon energies. The PDD curves and dose profiles with fields ranging from 3 × 3 to 25 × 25 cm 2 were acquired from measurements by using the stealth chamber and CC 13 chamber as reference chamber. All measurements were performed with Varian VitalBeam linear accelerator. In order to assess the performance of stealth chamber, PDD curves and profiles measured with stealth chamber were compared with measurement data using CC13 chamber. For PPDs measured with both chambers, the dosimetric parameters such as d max (depth of maximum dose), D 50 (PDD at 50 ㎜ depth), and D 100 (PDD at 100 ㎜ depth) were analyzed. Moreover, root mean square error (RMSE) values for profiles at d max and 100 ㎜ depth were evaluated. The measured PDDs and profiles between the stealth chamber and CC13 chamber as reference detector had almost comparable. For PDDs, the evaluated dosimetric parameters were observed small difference (<1%) for all energies and field sizes, except for d max less than 2 ㎜. In addition, the difference of RMSEs for profiles at d max and 100 ㎜ depth was similar for both chambers. This study confirmed that the use of stealth chamber for measuring commission beam data is a feasible as reference chamber for fields ranging from 3 × 3 to 20 × 20 cm 2 . Furthermore, it has an advantage with respect to measurement of the small fields (less than 3 × 3 cm 2 field) although not performed in this study.

쐐기필터 사용에 따른 선량증가 영역에서 선량평가

김연래(Yon-Lae Kim),문성공(Seong-Kong Moon),서태석(Tae-Suk Suh),정진범(Jin-Beom Chung),김진영(Jin-Young Kim),이정우(Jeong-Woo Lee) 대한방사선과학회(구 대한방사선기술학회) 2014 방사선기술과학 Vol.37 No.4

쐐기필터는 고선량 부분의 선량분포를 균등하게하기 위해서 사용된다. 금속쐐기필터와 기능강화 동적쐐기 필터가 광자선과 상호 작용으로 표면과 선량강화영역 조사면내, 외에 선량변화를 평가하였다. 본 논문에서는 2차원적 조직등가물질로 공간 선량분포가 우수하고, 흡수선량에 따라 현상 없이 실시간으로 광학농도가 변하는 가프크로믹 EBT3 필름을 사용하여 선량평가를 실시하였다. 선형가속기 광자선 에너지는 6MV, SSD 100 cm, 조사면 10×10 cm 으로 고정하고 최대선량점에 400 cGy로 조사하였다. 선량분포는 열린 조 사면과 15°, 30°, 그리고 45° 금속쐐기필터와 기능강화 동적쐐기필터를 사용 하였을 때 비교 평가 하였다. 15° 금속쐐기필터를 사용하면 조사면내 표면선량과 선량증가영역 선량은 기능강화 동적쐐기필터보다 증가 하였다. 30° 금속쐐기필터를 사용하면 조사면내 표면선량과 선량증가영역 선량은 기능강화 동적쐐기필터 보다 감소하였다. 45° 금속쐐기필터를 사용하면 조사면내 표면선량과 선량증가영역 선량은 많은 차이로 감소하였다. 조사면 주변 반음영 영역에서는 두꺼운 방향은 증가하고 얇은 방향은 감소하였다. 선량분포를 변화하고자 하는 치료 부위에 금속쐐기필터를 적절히 사용하고 유방암 치료와 같이 표면과의 거리가 가까워지지 않으면 표면 및 선량증가영역 선량이 감소하리라 사료된다. Wedge filter could use to increase the dose distribution at the hot dose regions. We evaluated dose discrepancy at surface and build region in the infield and outfield that Metal Wedge (MW) and Enhance Dynamic Wedge (EDW) were interact with photon. In this paper, we used Gafchromic EBT3 film that had excellent spatial resolution, composed the water equivalent materials and changed the optical density without development. The set up conditions of linear accelerator were fixed 6 MV photon, 100 cm SSD, 10×10 cm 2 field size and were irradiated 400 cGy at Dmax. The dose distribution and absorbed dose were evaluated when we compared the open field with 15°, 30°, 45° metal wedge and enhanced dynamic wedge. A 15° metal wedge could increase the surface and build up region dose than using a 15° enhanced dy-namic wedge. A 30° metal wedge could decrease the surface and build up region dose than using a 30° enhanced dynamic wedge. A 45° metal wedge could decrease by large deviation the surface and build up region dose than using a 15° enhanced dynamic wedge. The dose of penumbra region at outfield were increased on the thick side but were decreased on the thin side. It could be decrease the surface dose and build up region dose, if the metal wedge filters were prop-erly used to make a good dose distribution and not closed the distance of surface.