Progress in Medical Physics (한국의학물리학회지:의학물리)

Korean Society of Medical Physics (한국의학물리학회)
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Dosimetric Evaluation of Amplitude-based Respiratory Gating for Delivery of Volumetric Modulated Arc Therapy

진폭 기반 호흡연동 체적변조회전방사선치료의 선량학적 평가

  • Lee, Chang Yeol (Department of Radiation Oncology, College of Medicine, Inha University) ;
  • Kim, Woo Chul (Department of Radiation Oncology, College of Medicine, Inha University) ;
  • Kim, Hun Jeong (Department of Radiation Oncology, College of Medicine, Inha University) ;
  • Park, Jeong Hoon (Department of Radiation Oncology, College of Medicine, Inha University) ;
  • Min, Chul Kee (Department of Radiation Oncology, College of Medicine, Soonchunhyang University) ;
  • Shin, Dong Oh (Department of Radiation Oncology, College of Medicine, KyungHee University) ;
  • Choi, Sang Hyoun (Research Institute of Radiological and Medical Sciences, Korea Institute of Radiological and Medical Sciences) ;
  • Park, Seungwoo (Research Institute of Radiological and Medical Sciences, Korea Institute of Radiological and Medical Sciences) ;
  • Huh, Hyun Do (Department of Radiation Oncology, College of Medicine, Inha University)
  • 이창열 (인하대학교 의과대학 방사선종양학교실) ;
  • 김우철 (인하대학교 의과대학 방사선종양학교실) ;
  • 김헌정 (인하대학교 의과대학 방사선종양학교실) ;
  • 박정훈 (인하대학교 의과대학 방사선종양학교실) ;
  • 민철기 (순천향대학교 의과대학 방사선종양학교실) ;
  • 신동오 (경희대학교 의과대학 방사선종양학교실) ;
  • 최상현 (한국원자력의학원 방사선의학연구소) ;
  • 박승우 (한국원자력의학원 방사선의학연구소) ;
  • 허현도 (인하대학교 의과대학 방사선종양학교실)
  • Received : 2015.08.13
  • Accepted : 2015.09.08
  • Published : 2015.09.30
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Abstract

The purpose of this study is to perform a dosimetric evaluation of amplitude-based respiratory gating for the delivery of volumetric modulated arc therapy (VMAT). We selected two types of breathing patterns, subjectively among patients with respiratory-gated treatment log files. For patients that showed consistent breathing patterns (CBP) relative to the 4D CT respiration patterns, the variability of the breath-holding position during treatment was observed within the thresholds. However, patients with inconsistent breathing patterns (IBP) show differences relative to those with CBP. The relative isodose distribution was evaluated using an EBT3 film by comparing gated delivery to static delivery, and an absolute dose measurement was performed with a $0.6cm^3$ Farmer-type ion chamber. The passing rate percentages under the 3%/3 mm gamma analysis for Patients 1, 2 and 3 were respectively 93.18%, 91.16%, and 95.46% for CBP, and 66.77%, 48.79%, and 40.36% for IBP. Under the more stringent criteria of 2%/2 mm, passing rates for Patients 1, 2 and 3 were respectively 73.05%, 67.14%, and 86.85% for CBP, and 46.53%, 32.73%, and 36.51% for IBP. The ion chamber measurements were within 3.5%, on average, of those calculated by the TPS and within 2.0%, on average, when compared to the static-point dose measurements for all cases of CBP. Inconsistent breathing patterns between 4D CT simulation and treatment may cause considerable dosimetric differences. Therefore, patient training is important to maintain consistent breathing amplitude during CT scan acquisition and treatment delivery.

본 연구의 목적은 진폭 기반 호흡연동 체적변조회전방사선치료의 선량학적인 평가를 하고자 한다. 이 치료를 받은 환자의 호흡 Log 파일을 획득하여 분석하였으며, 4D CT 호흡 형태의 40%~60% 위상 영상 구간 진폭을 기준으로 치료 Log 파일 호흡 진폭의 구간이 4D CT의 진폭 구간과 일치하는 호흡 형태(CBP)와 일치하지 않는 호흡 형태(IBP)로 구분하였다. 상대적인 등선량 분포는 EBT3 필름을 사용하여 측정하였으며, 절대 선량 측정은 PTW $0.6cm^3$ 이온전리함을 이용하여 측정하였다. 감마 인덱스 3%/3 mm을 적용한 환자 1, 2, 3의 CBP 호흡인 경우 각각 93.18%, 91.16%, 95.46%이며, 환자 1, 2, 3의 IBP 호흡인 경우 각각 66.77%, 48.79%, 40.36%으로 분석되었다. 또한 감마 인덱스 2%/2 mm을 적용한 환자 1, 2, 3의 CBP 호흡인 경우 각각 73.05%, 67.14%, 86.85%이며, IBP 호흡인 경우 각각 46.53%, 32.73%, 36.51%으로 분석되었다. 모든 CBP호흡인 경우의 이온전리함 측정값은 치료계획 시스템에서 계산된 값과 평균 3.5% 이내로 일치하였으며, 정적인 팬톰 조사와의 차이는 평균 2.0% 이내로 일치하였다. 환자 3의 IBP 호흡인 경우 이온전리함 측정값과 계산된 값과의 차이가 평균 56%로 큰 차이를 보였다. 이는 4D CT의 진폭 구간과 치료시의 진폭 구간의 차이가 크기 때문인 것으로 사료되며, 4D CT 모의 치료시와 환자 치료시의 진폭의 크기를 일정하게 유지하는 것이 중요하다고 판단된다.

Keywords

References

  1. M Teoh, C H Clark, K Wood, et al: Volumetric modulated arc therapy: a review of current literature and clinical use in practice. Br J Radiol. 84:967-996 (2011). https://doi.org/10.1259/bjr/22373346
  2. Li R, Mok E, Han B, et al: Evaluation of the geometric accuracy of surrogate-based gated VMAT using intrafraction kilovoltage x-ray images. Med Phys. 39:2686-2693 (2012). https://doi.org/10.1118/1.4704729
  3. Choi K, Xing L, Koong A, et al: First study of on-treatment volumetric imaging during respiratory gated VMAT. Medical physics. United States: American Association of Physicists in Medicine. 40 (2013).
  4. Jiwon Sung, Myonggeun Yoon, Weon Kuu Chung, et al: Evaluation of the Accuracy for Respiratory-gated RapidArc. PROGRESS in MEDICAL PHYSICS. 24, No. 2 (2013).
  5. G. Nicolini, E. Vanetti, A. Clivio, et al: Preclinical evaluation of respiratory-gated delivery of volumetric modulated arc therapy with RapidArc. Phys. Med. Biol. 55:347-357 (2010). https://doi.org/10.1088/0031-9155/55/12/N01
  6. J. Qian, L. Xing,W. Liu, et al: Dose verification for respiratory gated volumetric modulated arc therapy. Phys. Med. Biol. 56:4827-838 (2011). https://doi.org/10.1088/0031-9155/56/15/013
  7. Craig Riley, Yong Yang, Tianfang Li, et al: Dosimetric evaluation of the interplay effect in respiratory-gated RapidArc radiation therapy. Med. Phys. 41:011715 (2014). https://doi.org/10.1118/1.4855956
  8. Otto K. Volumetric modulated arc therapy: IMRT in a single gantry arc. Med. Phys. 35(1):310-17 (2008). https://doi.org/10.1118/1.2818738
  9. D. A. Low, W. B. Harms, S. Mutic, et al: A technique for the quantitative evaluation of dose distributions. Med. Phys. 25: 656-661 (1998). https://doi.org/10.1118/1.598248
  10. N. Agazaryan, T. D. Solberg, J. J. DeMarco: Patient specific quality assurance for the delivery of intensity modulated radiotherapy. J. Appl. Clin. Med. Phys. 4:40-50 (2003). https://doi.org/10.1120/1.1525243
  11. Valeria Casanova Borca, Massimo Pasquino, Giuliana Russo, et al: Dosimetric characterization and use of GAFCHROMIC EBT3 film for IMRT dose verification. J. of Appl. Clin. Med. Phys. 14: No. 2 (2013).
  12. Kan MWK, Cheung JYC, Leung LHT, et al: The accuracy of dose calculations by anisotropic analytical algorithms for stereotactic radiotherapy in nasopharyngeal carcinoma. Phys. Med. Biol. 56:397 (2011). https://doi.org/10.1088/0031-9155/56/2/008