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Efficacy and Accuracy of Patient Specific Customize Bolus Using a 3-Dimensional Printer for Electron Beam Therapy

전자선 빔 치료 시 삼차원프린터를 이용하여 제작한 환자맞춤형 볼루스의 유용성 및 선량 정확도 평가

  • Choi, Woo Keun (Department of Radiation Oncology, Samsung Medical Center, Sungkyunkwan University School of Medicine) ;
  • Chun, Jun Chul (Department of Medical Physics, Kyonggi University) ;
  • Ju, Sang Gyu (Department of Radiation Oncology, Samsung Medical Center, Sungkyunkwan University School of Medicine) ;
  • Min, Byung Jun (Department of Radiation Oncology, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine) ;
  • Park, Su Yeon (Department of Radiation Oncology, Samsung Medical Center, Sungkyunkwan University School of Medicine) ;
  • Nam, Hee Rim (Department of Radiation Oncology, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine) ;
  • Hong, Chae-Seon (Department of Radiation Oncology, Samsung Medical Center, Sungkyunkwan University School of Medicine) ;
  • Kim, MinKyu (Department of Radiation Oncology, Samsung Medical Center, Sungkyunkwan University School of Medicine) ;
  • Koo, Bum Yong (Department of Radiation Oncology, Samsung Medical Center, Sungkyunkwan University School of Medicine) ;
  • Lim, Do Hoon (Department of Radiation Oncology, Samsung Medical Center, Sungkyunkwan University School of Medicine)
  • 최우근 (성균관대학교 의과대학 삼성서울병원 방사선종양학교실) ;
  • 전준철 (경기대학교 의학물리학과) ;
  • 주상규 (성균관대학교 의과대학 삼성서울병원 방사선종양학교실) ;
  • 민병준 (성균관대학교 의과대학 강북삼성병원 방사선종양학교실) ;
  • 박수연 (성균관대학교 의과대학 삼성서울병원 방사선종양학교실) ;
  • 남희림 (성균관대학교 의과대학 강북삼성병원 방사선종양학교실) ;
  • 홍채선 (성균관대학교 의과대학 삼성서울병원 방사선종양학교실) ;
  • 김민규 (성균관대학교 의과대학 삼성서울병원 방사선종양학교실) ;
  • 구범용 (성균관대학교 의과대학 삼성서울병원 방사선종양학교실) ;
  • 임도훈 (성균관대학교 의과대학 삼성서울병원 방사선종양학교실)
  • Received : 2016.05.23
  • Accepted : 2016.05.26
  • Published : 2016.06.30

Abstract

We develop a manufacture procedure for the production of a patient specific customized bolus (PSCB) using a 3D printer (3DP). The dosimetric accuracy of the 3D-PSCB is evaluated for electron beam therapy. In order to cover the required planning target volume (PTV), we select the proper electron beam energy and the field size through initial dose calculation using a treatment planning system. The PSCB is delineated based on the initial dose distribution. The dose calculation is repeated after applying the PSCB. We iteratively fine-tune the PSCB shape until the plan quality is sufficient to meet the required clinical criteria. Then the contour data of the PSCB is transferred to an in-house conversion software through the DICOMRT protocol. This contour data is converted into the 3DP data format, STereoLithography data format and then printed using a 3DP. Two virtual patients, having concave and convex shapes, were generated with a virtual PTV and an organ at risk (OAR). Then, two corresponding electron treatment plans with and without a PSCB were generated to evaluate the dosimetric effect of the PSCB. The dosimetric characteristics and dose volume histograms for the PTV and OAR are compared in both plans. Film dosimetry is performed to verify the dosimetric accuracy of the 3D-PSCB. The calculated planar dose distribution is compared to that measured using film dosimetry taken from the beam central axis. We compare the percent depth dose curve and gamma analysis (the dose difference is 3%, and the distance to agreement is 3 mm) results. No significant difference in the PTV dose is observed in the plan with the PSCB compared to that without the PSCB. The maximum, minimum, and mean doses of the OAR in the plan with the PSCB were significantly reduced by 9.7%, 36.6%, and 28.3%, respectively, compared to those in the plan without the PSCB. By applying the PSCB, the OAR volumes receiving 90% and 80% of the prescribed dose were reduced from $14.40cm^3$ to $0.1cm^3$ and from $42.6cm^3$ to $3.7cm^3$, respectively, in comparison to that without using the PSCB. The gamma pass rates of the concave and convex plans were 95% and 98%, respectively. A new procedure of the fabrication of a PSCB is developed using a 3DP. We confirm the usefulness and dosimetric accuracy of the 3D-PSCB for the clinical use. Thus, rapidly advancing 3DP technology is able to ease and expand clinical implementation of the PSCB.

삼차원 프린터(3DP)를 이용하여 환자맞춤형 전자선 치료용 볼루스(patient specific customized bolus, PSCB)를 제작하는 절차를 고안하고 제안된 방법으로 제작한 PSCB의 선량 정확도를 평가했다. 치료계획장치에서 치료계획표적용적(PTV)에 적합한 전자선 빔과 조사면 크기를 선택하고 초기 선량계산을 수행했다. 계산된 선량분포를 기반으로 PSCB를 그리고 재계산을 수행했다. 수 차례 반복을 통해 최상의 PSCB를 설계하고 설계된 윤곽자료를 DICOMRT 프로토콜을 이용해 자체 제작한 변환프로그램으로 전송했다. PSCB의 윤곽자료는 자체 변환프로그램을 이용해 3DP에서 인식 가능한 파일(STL 포맷)로 변환한 후 3DP를 이용해 제작했다. PSCB의 유용성을 검증하기 위해 2명의 가상 환자(오목, 볼록 유형)를 생성했고 각각의 환자에 가상의 PTV와 정상장기(OAR)을 생성했다. 3D-PSCB 를 사용했을 때와 사용하지 않았을 때의 선량체적히스토그램(DVH)와 선량 특성을 비교했다. 3D-PSCB 제작의 정확도를 분석하기 위해 필름 선량측정을 통해 선량 정확도를 평가했다. 치료계획 결과와 필름을 이용한 선량분포를 중첩한 후 빔 중심축에서의 심부선량곡선을 구했고 감마분석(3% 선량 오차와 3 mm 거리오차)을 수행 했다. 2명의 가상환자 모두에서 PSCB를 사용한 경우 PTV 선량은 큰 차이를 보이지 않았다. PSCB를 사용할 경우 PSCB를 사용하지 않는 경우에 비해 OAR의 최대 선량, 최소선량, 평균선량은 각각 평균 9.7%, 36.6%, 28.3% 감소했다. 처방선량의 90% 선량($V_{90%}$)을 받는 OAR의 용적은 PSCB를 적용할 경우 약 99% 낮아졌다(14.40 vs $0.1cm^3$). 또한 처방선량의 80% 선량을 받는 OAR 체적도 PSCB를 사용할 경우 약 91% 줄었다(42.6 vs $3.7cm^3$). 감마분석 결과(3%, 3 mm) 오목 및 볼록 볼루스를 적용한 경우 각각 95%, 98% 통과율(pass rate)을 보였다. 3DP를 이용해 PSCB를 제작하는 절차를 정립하고 선량적 정확도를 평가해서 임상적용이 가능한 만족할 만한 결과를 얻었다. 3DP 기술의 빠른 발전에 힘입어 PSCB의 임상적용이 좀 더 쉬워지고 적용대상이 확장될 것으로 생각된다.

Keywords

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