의학물리학

본문글자크기
  • [J Appl Clin Med Phys .] Comparative study of SRS end-to-end QA processes of a diode array device and an anthropomorphic phantom loaded with GafChromic XD film

    Memorial Sloan Kettering Cancer Center / 임승보*

  • 출처
    J Appl Clin Med Phys .
  • 등재일
    2022 Sep
  • 저널이슈번호
    23(9):e13747. doi: 10.1002/acm2.13747. Epub 2022 Aug 10.
  • 내용

    바로가기  >

    Abstract
    Purpose: End-to-end testing (E2E) is a necessary process for assessing the readiness of the stereotactic radiosurgery (SRS) program and annual QA of an SRS system according to the AAPM MPPG 9a. This study investigates the differences between using a new SRS MapCHECK (SRSMC) system and an anthropomorphic phantom film-based system in a large network with different SRS delivery techniques.

    Methods and materials: Three SRS capable Linacs (Varian Medical Systems, Palo Alto, CA) at three different regional sites were chosen to represent a hospital network, a Trilogy with an M120 multi-leaf collimator (MLC), a TrueBeam with an M120 MLC, and a TrueBeam Stx with an HD120 MLC. An anthropomorphic STEEV phantom (CIRS, Norfolk, VA) and a phantom/diode array: StereoPHAN/SRSMC (Sun Nuclear, Melbourne, FL) were CT scanned at each site. The new STV-PHANTOM EBT-XD films (Ashland, Bridgewater, NJ) were used. Six plans with various complexities were measured with both films and SRSMC in the StereoPHAN to establish their dosimetric correlations. Three SRS cranial plans with a total of sixteen fields using dynamic conformal arc and volumetric-modulated arc therapy, with 1-4 targets, were planned with Eclipse v15.5 treatment planning system (TPS) using a custom SRS beam model for each machine. The dosimetric and localization accuracy were compared. The time of analysis for the two systems by three teams of physicists was also compared to assess the throughput efficiency.

    Results: The correlations between films and SRSMC were found to be 0.84 (p = 0.03) and 0.16 (p = 0.76) for γ (3%, 1 mm) and γ (3%, 2 mm), respectively. With film, the local dose differences (ΔD) relative to the average dose within the 50% isodose line from the three sites were found to be -3.2%-3.7%. The maximum localization errors (Elocal ) were found to be within 0.5 ± 0.2 mm. With SRSMC, the ΔD was found to be within 5% of the TPS calculation. Elocal were found to be within 0.7 to 1.1 ± 0.4 mm for TrueBeam and Trilogy, respectively. Comparing with film, an additional uncertainty of 0.7 mm was found with SRSMC. The delivery and analysis times were found to be 6 and 2 h for film and SRSMC, respectively.

    Conclusions: The SRS MapCHECK agrees dosimetrically with the films within measurement uncertainties. However, film dosimetry shows superior sub-millimeter localization resolving power for the MPPG 9a implementation.

     

     

    Affiliation

    Seng Boh Lim 1, LiCheng Kuo 1, Tianfang Li 1, Xiang Li 1, Ase M Ballangrud 1, Michael Lovelock 1, Maria F Chan 1
    1Department of Medical Physics, Memorial Sloan Kettering Cancer Center, New York, New York, USA.

  • 키워드
    SBRT; SRS; end-to-end test; quality assurance; radiochromic film dosimetry.
  • 편집위원

    정위방사선수술(SRS) 등 고정밀 방사선치료는 양날의 검과 같아 사용전 준비나 시스템 전체의 적합성 여부를 확인하기 위해서는 매년 처음부터 끝까지 치료 전 절차를 평가하는 프로세스인 전면계통(end-to-end) 검사 수행을 권고하고 있다. 본 연구에서는 필름 기반 SRS E2E 검사나 연간 품질관리는 상당한 시간과 노력, 자원이 필요한 만큼 다이오드 배열 측정인 SRS MapCHECK(SRSMC)은 선량측정이나 병변 위치 정확성의 측면에서 측정 불확도 범위 내에서 필름 기반 측정 결과와 잘 일치하고 있어 환자별 SRS E2E QA나 연간 품질관리(QA)에 인체모형 필름측정법의 대안 솔루션으로 활용할 것으로 기대된다.

    2022-11-01 16:00:24

  • 덧글달기
    덧글달기
       IP : 35.173.233.176

    등록