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1 Original Article PROGRESS in MEDICAL PHYSICS Vol. 25, No. 2, June, Comparison of the Dose Distributions with Beam Arrangements in the Stereotactic Body Radiotherapy (SBRT) for Primary Lung Cancer Ji Woon Yea Department of Radiation Oncology, Yeungnam University College of Medicine, Daegu, Korea To compare 2 beam arrangements, circumferential equally angles (EA) beams or partially angles (PA) beams for stereotactic body radiation therapy (SBRT) of primary lung cancer for intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT) delivery techniques with respect to target, ipsilateral lung, contralateral lung, and organs-at-risk (OAR) dose-volume metrics, as well as treatment delivery efficiency. Data from 12 patients, four treatment plans were generated per data sets (IMRT EA,, VMAT EA, VMAT PA). The prescribed dose (PD) was 60 Gy in 4 fractions to 95% of the planning target volume (PTV) for a 6-MV photon beam. When compared with the IMRT and VMAT treatment plan for 2 beams, conformity index, homogeneity index, high dose spillage, D2 cm (Dmax at a distance 2 cm beyond the PTV), R50 (ratio of volume circumscribed by the 50% isodose line and the PTV), resulted in similar. But Dmax of the Organ at risk (OAR), spinal cord, trachea, resulted in differ between four treatment plans. Especially HDS location showed big difference in 21.63% vs %. Key Words: Dose distribution, Equal angle, Partial angle, Stereotatic body radiotherapy (SBRT) 서 초기폐암의원칙적인치료는수술적제거이나의학적으로수술불가능한경우과거에는고식적방사선치료 (conventional radiotherapy) 를시행하여왔었다. 최근에는정위적체부방사선치료를통해종양에대한고정밀 4차원전산화단층촬영술과컴퓨터시스템하의영상유도위치검증으로 3 차원단층촬영기반의입체조형방사선치료보다환자의표적체적정확도와개별성이향상되었다. 1) 이런기술의급진적발전으로 2-4) 분할선량을높일수있으며치료기간의단축, 방사선부작용감소, 국소제어율증가의결과를가져왔다. 5,6) 한편정위적체부방사선치료의치료계획과치료방법은개인또는치료기관에따라조금씩다르게시행되어왔으나, 최근미국방사선치료암연구단체 (Radiation Therapy Oncology Group; RTOG) 와유럽암치료연구단체 (European Received 30 April 2014, Revised 26 May 2014, Accepted 2 June 2014 Correspondence: Ji Woon Yea (yjw1160@ynu.ac.kr) Tel: , Fax: cc This is an Open-Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License ( which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. 론 Organisation for Research and Treatment of Cancer; EORTC) 에서초기원발성폐암의정위적체부방사선치료권고안을제시하였다. 7,8) 이들권고안중에는환자대상, 방사선량, 전산화단층촬영술 (computed tomography; CT) 및계산방법 (Calculation algorithms) 등전반적인가이드라인을제시하고있지만, 치료전달방법에서최적의빔배열을제시하고있지는않다. 따라서본연구는 360 o 회전각도 (Equally angles, EA) 와부분각도 (partially angles; PA) 의빔배열 (Beam arrangements) 에따른세기조절방사선치료 (Intensity-modulated radiation therapy, IMRT) 와체적변조회전치료 (Volumetric-modulated arc therapy, VMAT) 에서종양의선량, 주요장기의선량, 선량일치지수 (conformity index; CI), 균질성지수 (homogeneity index; HI), 모니터단위 (monitor unit; MU) 등의차이를비교분석하였다. 재료및방법 1. 환자특성 2012년 8월부터 2013년 12월까지본원에서폐정위적체부방사선치료시행한환자 12명의영상을이용하였다. 환자군의나이는 42세에서 86세사이였으며중간값은 72세이

PROGRESS in MEDICAL PHYSICS Vol. 25, No. 2, June, 2014 고성별은남자 10명, 여자 2명으로남자환자가많았다. 육안적종양체적은최저 0.4 cc에서최고 44.3 cc로다양하였으며평균 9.8 cc였고계획용표적체적은최저 7.6 cc에서최고 137.3 cc로평균 39.7 cc였다.

2 PROGRESS in MEDICAL PHYSICS Vol. 25, No. 2, June, 2014 고성별은남자 10명, 여자 2명으로남자환자가많았다. 육안적종양체적은최저 0.4 cc에서최고 44.3 cc로다양하였으며평균 9.8 cc였고계획용표적체적은최저 7.6 cc에서최고 cc로평균 39.7 cc였다. 병소의위치는우하엽 6 명으로가장많았고우상엽 1명, 우중엽 1명, 좌상엽 3명, 좌하엽 1명이었고환자의특성은아래와같다 (Table 1). 2. 빔배치와선량처방최적화 세기조절방사선치료기법에서 360 o 회전각도 (IMRT EA) 는 0 o / Table 1. 환자특성. 나이 ( 중간값 =72) 성별 남자 10 여자 02 종양크기 육안적종양체적 0.4 cc 44.3 cc 평균 9.8 cc 계획용표적체적 7.6 cc cc 평균 39.7 cc 종양위치 우상엽 1 우중엽 1 우하엽 6 좌상엽 3 좌하엽 1 총수 o /80 o /120 o /160 o /200 o /240 o /280 o /320 o 로 40 o 등간격으로 9개의조사면을이용하였고, 종양의위치가왼쪽에있는경우에부분각도 () 는 335 o /0 o /25 o /50 o /75 o /100 o /125 o /150 o /175 o / 200 o /225 o 로종양을중심으로 11개의조사면을이용하였다. 종양이오른쪽에있는경우는왼쪽폐의선량이적게들어가도록 320 o /345 o /10 o /35 o /60 o /85 o /110 o /135 o /160 o /185 o /210 o 의부분각도로배열하였다. 또한, 체적변조회전치료기법에서 360 o 회전각도 (VMAT EA) 는 181 o 179 o 의시계방향 1ARC와 179 o 181 o 의반시계방향의 1ARC로구성된총 2ARC로치료계획을하였고, 부분각도 (VMAT PA) 에서는종양의위치가왼쪽폐에있는경우에는 320 o 179 o 의시계방향 1ARC와 179 o 320 o 의반시계방향의 1ARC로구성된총 2ARC로치료계획을하였고, 오른쪽폐에있는경우에는 200 o 50 o 의시계방향 1ARC와 50 o 200 o 의반시계방향의 1ARC로구성된총 2ARC로치료계획을하여반대측폐의조사선량이최소가되게하였다. 이들의빔배열에대한구성은 Fig. 1에표시하였다. IMRT와 VMAT은동일한제약조건 (constraint) 을사용하였으며, 이들제약조건은 RTOG-0813, 9) RTOG-0915, 10) AAPM TG ) 등의선량부피그림표한계 (dose volume histogram limits; DVH limits) 조건을만족시키기위하여, 최적화 (optimizations) 과정을 200회로고정하여실시하였다. 선량계산은비균질영역에서비교적정확하다고보고된 Aniso- Fig. 1. Comparisons of the IMRT and VMAT with equally ((a); (c)) or partially ((b); (d)) beam arrangements. (a) IMRT EA; (b) ; (c) VMAT EA; (d) VMAT PA

3 Ji Woon Yea:Comparison of the Dose Distributions with Beam Arrangements in the Stereotactic Body Radiotherapy (SBRT) for Primary Lung Cancer tropic Analytical Algorithm (AAA, Varian Medical Systems) 알고리즘을사용하여 12) 치료계획을수행하였다. 3. 치료계획평가기준 계획용표적체제 (planning target volume; PTV) 의최대, 최소및평균방사선량 (Gy) 을분석하였다. 또한 RTOG-0817/ 0915에서제안한 high dose spillage (HDS location, HDS volume) 와 low dose spillage (D 2cm, R 50) 을분석하였다. HDS location 와 HDS volume 은식 (1) 와 (2) 으로표현할수있다. HDS location= cumulative volume of all tissue outside the PTV receiving a dose>105% of prescription dose (1) volume of the PTV HDS volume= volume of the prescription isodose (2) volume of the PTV Low dose spillage의 2항목 (D 2cm, R 50) 은계획용표적체제밖에서의방사선량이급격히줄어들어주위주요장기에선량이최소화할수있도록평가하는항목이다. D 2cm 은계획용표적체제로부터모든방향으로 2cm을확장하여, 계획용표적체제를뺀용적의최대선량값으로정의된다. R 50 은다음과같이표현될수있다. R 50= volume of the 50% of the prescription isodose (3) volume of the PTV RTOG에서는 HDS location 의값을 15% 이하로권고하고있으며, HDS volume, D 2cm, R 50 의값은 Table 2에서계획용표적체제에따라서각각권고되고있다. 각치료계획의계획용표적체제의방사선량의품질을평가하기위하여선량일치지수 (conformity index; CI) 는 Van t Riet et al. 13) 이제시한아래수식을사용하였다. CI= TVRI TVRI (4) TV V RI 여기서 TV RI=target volume covered by 95% isodose, V RI= volume of 95 % isodose, TV=target volume 로각각정의된다. 균질성지수 (homogeneity index; HI) 는 rdhi (radical dose homogeneity index) 와 mdhi (moderate homogeneity index) 로구분하여분석하였다. 이지수들은이전연구 2) 에서정의되었다. 결 총 200회의치료계획최적화과정을수행하였고, 계획용표적체적은최소 7.6 (cc) 에서최대 (cc) 이며평균 39.7 (cc) 였다. 치료계획평가변수비교에서 IMRT EA VMAT EA VMAT PA 에서표적체적선량의분포는 65.37, 65.29, 64.94, 64.90를나타내었으며, 선량일치지수는 0.74, 0.70, 0.68, 0.67를나타내었으며, 균질성지수는 0.92, 0.86, 0.81, 0.87를나타내었으며, 고선량유출은 HDS location 에서 1.61, 2.05, 3.63, 4.93의큰차이를나타내었으며, R 50 은 0.74, 0.70, 0.68, 0.67를나타내었으며, 모니터단위는 5287, 4493, 3565, 303의큰차이를나타내었다 (Table 3). 과 Table 2. Plan evaluation table for HDS volume, D 2cm, R 50 in the RTOG 9). PTV volume (cc) Ratio of prescription isodose volume to the PTV volume Ratio of 50% prescription isodose volume to the PTV volume, R 50% Maximum dose (in % of dose Percent of lung receiving 20 2 cm from PTV Gy total or more, V 20 (%) in any direction, D 2cm (Gy) Deviation Deviation Deviation Deviation None Minor None Minor None Minor None Minor 1.8 <1.2 <1.5 <5.9 <7.5 <50.0 <57.0 <10 < <1.2 <1.5 <5.5 <6.5 <50.0 <57.0 <10 < <1.2 <1.5 <5.1 <6.0 <50.0 <58.0 <10 < <1.2 <1.5 <4.7 <5.8 <50.0 <58.0 <10 < <1.2 <1.5 <4.5 <5.5 <54.0 <63.0 <10 < <1.2 <1.5 <4.3 <5.3 <58.0 <68.0 <10 < <1.2 <1.5 <4.0 <5.0 <62.0 <77.0 <10 < <1.2 <1.5 <3.5 <4.8 <66.0 <86.0 <10 < <1.2 <1.5 <3.3 <4.4 <70.0 <89.0 <10 < <1.2 <1.5 <3.1 <4.0 <73.0 <91.0 <10 < <1.2 <1.5 <2.9 <3.7 <77.0 <94.0 <10 <

4 PROGRESS in MEDICAL PHYSICS Vol. 25, No. 2, June, 2014 또한치료계획조사선량평가비교에서 IMRT EA VMAT EA VMAT PA 에서양쪽폐를고려한경우에서 V 20 (%) 은 6.40, 6.20, 7.18, 7.05를나타내었으며, V 5 (%) 은 20.35, 17.21, 19.62, 16.57를나타내었으며, 종양이있는부위의폐에대해서는 V 20 (%) 은 12.63, 12.48, 14.51, 14.25를나타내었으며, V 5 (%) 은 30.12, 29.77, 31.61, 31.54를나타내었으 Table 3. Comparisons of PTV, HI, CI, RTOG plan evaluation s parameter and MU between the equally angles and the partially angles for the beam arrangements. IMRT EA Difference (%) VMAT EA VMAT PA Mean diff (%) PTV D max (Gy) 71.57± ± ± ± D mean (Gy) 65.37± ± ± ± D min (Gy) 52.09± ± ± ± HI & CI rdhi 0.73± ± ± ± mdhi 0.92± ± ± ± CI 0.74± ± ± ± RTOG HDS location 1.61± ± ± ± HDS volume 1.09± ± ± ± D 2cm 0.74± ± ± ± R ± ± ± ± MU 5287± ± ± ± IMRT EA: Intensity-modulated radiotherapy arranged by equally beam angles, : Intensity-modulated radiotherapy arranged by partially beam angles, VMAT EA: Volumetric-modulated arc therapy arranged by equally beam angles, VMAT PA: Intensity-modulated radiotherapy arranged by partially beam angles, SD: standard deviation, rdhi: radical dose homogeneity index, mdhi: moderate dose homogeneity index, CI: conformity index, HDS location: location of the high dose spillage described by the RTOG, HDS volume: volume of the high dose spillage described by the RTOG, D 2cm: location of the low dose spillage described by the RTOG, R 50: volume of the low dose spillage described by the RTOG, and MU: monitor units. Table 4. Dose difference analysis according to the equally angles and the partially angles for the beam arrangements. Structure Parameter IMRT EA Difference (%) VMAT EA VMAT PA Difference (%) Both MLD (Gy) 4.61± ± ± ± lung V 5 (%) 20.35± ± ± ± V 12.5 (cc) ± ± ± ± V 13.5 (cc) ± ± ± ± V 20 (%) 6.40± ± ± ± V 25 (%) 4.39± ± ± ± Ipsilateral MLD (Gy) 7.40± ± ± ± lung V 5 (%) 30.12± ± ± ± V 10 (%) 23.18± ± ± ± V 20 (%) 12.63± ± ± ± V 30 (%) 7.24± ± ± ± Contralateral MLD (Gy) 1.75± ± ± ± lung V 5 (%) 10.28± ± ± ± V 10 (%) 5.40± ± ± ± PRV Spinal cord D max (Gy) 13.36± ± ± ± OAR Trachea D max (Gy) 11.78± ± ± ± OAR Heart D max (Gy) 23.53± ± ± ± V 5/10/20/25/30 (%): percentage volumes that received 5, 10, 20, 25 and 30 Gy, respectively, V 12.5/13.5 (cc): absolute volumes that received 12.5 and 13.5 Gy, respectively, MLD: Mean Lung Dose

5 Ji Woon Yea:Comparison of the Dose Distributions with Beam Arrangements in the Stereotactic Body Radiotherapy (SBRT) for Primary Lung Cancer 며, 조양이없는반대편폐에대해서는 V 5 (%) 은 10.28, 4.30, 7.50, 3.93를나타내었으며, 중요장기척추에조사되는최대선량의평균선량에대해서는 Gy, Gy, Gy, 9.59 Gy를나타내었다 (Table 4). 고찰및결론이중양측폐나동측폐, 척수, 기도, 심장에분포하는선량지표는큰차이가없었으며반대측폐의 V 10 (%) 이부분각배열에서 5배이상의큰차이를보여방사선수술이후만성합병증인방사선폐렴과드물게발생하는섬유화로인한폐기능저하발생빈도를감소시킨다. 최근폐암의정위적체부방사선치료 (SBRT) 는 RTOG와 EORTC 권고안에따라여러가지빔배열방법이사용되고있다. SBRT에서적합한빔방향은표적체적에는적절한선량분포를얻고손상위험장기는최대한피하며단거리빔경로를이용하고치료기의기계적인제한점없이선택하게된다. 7) 따라서충분한개수의빔을여러방향에서입사되도록하는것이좋으며이전연구에서빔갯수가방향보다더중요성을가진다. 10) 그러나실제환자치료에서는여러가지제약이있고 SBRT에서적절한빔배치에대한근거도부족하며다만반대측폐를통과하는빔배치는되도록제한하는정도이다. 14,15) 따라서본연구는방사선치료를시행한환자의영상을이용하여종양주위에빔배열을균등하게한 360 o 회전각도와부분각도로배열한치료계획의선량차이를알아보기위해세기조절방사선치료 (Intensity-modulated radiation therapy, IMRT) 와체적변조회전치료 (Volumetric-modulated arc therapy, VMAT) 으로분류하고각각선량분포를비교하였다. 치료계획평가변수중선량일치지수, 균질성지수, 고선량유출, D 2cm, R 50 은빔배열에따라크게차이가나지않았다. 또한손상위험장기인척수, 기관지, 식도의최고선량은각각의방법에따라차이가있었으나빔배열에의한차이보다는표적체적의위치차이에의한것으로생각된다. HDS location 에서는 360 o 회전각도의빔균등배열에비해부분각도빔배열이빔의집중성때문에 21.63% 와 26.46% 의큰차이를나타낸것으로생각된다. 모니터단위는부분각빔배열에서작았으며반대측폐의 V 10 (%) 도동일한결과를보였고특히세기조절방사선치료에서 5배이상의큰차이를보였다. 본연구에서원발성폐암의정위적체부방사선치료시빔배열에따른선량분포의차이를분석하였고결론적으로 부분각빔배열에따른치료계획이적은모니터단위로환자의치료에는효율적이고반대측폐의방사선량은감소시켜부작용의위험을줄일수있다. 본연구의제한점은환자수가적고후향적연구로좀더많은환자를대상으로전향적연구를시행하여수치를분석하는것이통계적인의의를나타낼수있을것으로생각된다. References 1. Robert D, Timmerman MD, Brain D, et al: Stereotactic Body Radiation Therapy in Multiple Organ Sites. Journal of Clinical Oncology 25: (2007) 2. Oh SA, Kang MK, Kim SK, Yea JW: Comparison of IMRT and VMAT techniques in spine stereotactic radiosurgery with international spine radiosurgery consortium consensus guidelines. Prog Med Phys 24(3): (2013) 3. Lim DH, YI BY, Mirmiran A, et al: Optimal beam arrangement for stereotactic body radiation therapy delivery in lung tumors. Acta Oncologica 49: (2010) 4. Mara WR, Catherine MK, Kelly MPC, et al: Circumferential or sectored beam arrangements for stereotactic body radiation therapy (SBRT) of primary lung tumors: Effect on target and normal-structure dose-volume metrics. Med Dos 38: (2013) 5. Robert T, Rebecca P, James G, et al: Stereotactic Body Radiation Therapy for Inoperable Early Stage Lung Cancer, JAMA 303(11): (201) 6. Nagata Y, Takayama K, Matsuo Y, et al: Clinical outcomes of a phase I/II study of 48 Gy of stereotactic body radiotherapy in 4 fractions for primary lung cancer using a stereotactic body frame. Int J Radiat Oncol Biol Phys 63(5): (2005) 7. Timmerman R, Galvin J, Michalski J, et al: Accreditation and quality assurance for Radiation Therapy Oncology Group: multicenter clinical trials using stereotactic body radiation therapy in lung cancer. Acta Oncol 45(7): (2006) 8. Dirk De R, Corinne FF, Ursula N, et al: European Organization for Research and Treatment of Cancer Recommendations for Planning and Delivery of High-Dose, High-Precision Radiotherapy for Lung Cancer. 28(36): (2010) 9. RTOG 0813: Seamless Phase I/II Study of Stereotactic Lung Radiotherapy (SBRT) for Early Stage, Centrally Located, Non-Small Cell Lung Cancer (NSCLC) in Medically Inoperable Patients. aspx?study= RTOG 0915: A randomized phase II study comparing 2 stereotactic body radiation therapy (SBRT) schedules for medically inoperable patients with stage I peripheral non-small cell lung cancer. aspx?study= Benedict SH, Yenice KM, Followill D, et al: Stereotactic body radiation therapy: The report of AAPM task group

6 PROGRESS in MEDICAL PHYSICS Vol. 25, No. 2, June, 2014 Med Phys 37: (2010) 12. Oh SA, Kang MK, Yea JW, Kim SH, Kim KH, Kim SK: Comparison of intensity modulated radiation therapy dose calculations with a PBC and AAA algorithms in the lung cancer. Korea J Med Phys 23:48-53 (2012) 13. Feuvret L, Noel G, Mazeron JJ, Bey P: Conformity index: a review. Int J Radiat Oncol Biol Phys 64: (2006) 14. Ong CL, Verbakel WF, Cuijpers JP, et al: Stereotactic radiotherapy for peripheral lung tumors: A comparison of volumetric modulated arc therapy with 3 other delivery techniques Radiother Oncol 97: (2010) 15. Holt A, van Vliet-Vroegindeweij C, Mans A, et al: Volumetric-Modulated Arc Therapy for Stereotactic body radiotherapy of lung tumors: A comparison with intensity-modulated radiotherapy techniques. Int J Radiat Oncol Biol Phys 81: (2011) 원발성폐암에서정위적체부방사선치료의빔배열에따른선량분포의비교 영남대학교의과대학방사선종양학교실 예지원 원발성폐암의정위적체부방사선치료 (Stereotatic Body Radiation Therapy; SBRT) 시에, 종양주위의빔배열을균등하게한 360 o 회전각도 (Equally angles; EA) 와종양주위의빔배열을부분각도 (Partially angles; PA) 로배열한치료계획의선량차이를확인하기위하여, 세기조절방사선치료 (Intensity-modulated radiation therapy, IMRT) 와체적변조회전치료 (Volumetric-modulated arc therapy, VMAT) 의종양의선량, 동측폐의선량, 반대측폐의선량, 손상위험장기 (Organ at risk, OAR) 의선량, 치료효율등을비교분석하였다. 12명의환자에서각각 4종류 (IMRT EA,, VMAT EA, VMAT PA) 의치료계획을생성하였으며, 처방선량은총선량 60 Gy, 4회분할치료로표적체적 95% 에대해 100% 선량이포함되게하였다. IMRT와 VMAT의치료계획평가에서 360 o 회전각도의빔균등배열과부분각도빔배열에서변수중선량일치지수, 균질성지수, 고선량유출, D 2cm, R 50 은빔배열에따라크게차이가나지않았다. 또한손상위험장기인척수, 기관지, 식도의최고선량은각각의방법에따라차이를나타내었다. 특히 HDS location 에서 21.63% 와 26.46% 의큰차이를나타내었다. 중심단어 : 선량분포, 전체각, 부분각, 정위적체부방사선치료

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( )Jkstro011.hwp 비인강암의방사선치료결과및생존율에관한예후인자분석 2005 2 1 2005 3 28. :, Tel: 053)250-7665, Fax: 053)250-7984 E-mail: jhkim@dsmc.or.kr 정영연외 2 인 : 비인강암의예후인자분석 정영연외 2 인 : 비인강암의예후인자분석 Carcinoma of the nasopharynx treated by radiotherapy