Mô phỏng máy gia tốc tuyến tính bằng phương pháp Monte Carlo dùng chương trình EGSnr

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Tác giả: Thanh Tài Dương, Đức Tuân Hoàng, Thị Oanh Lương, Đông Sơn Nguyễn, Thị Hồng Loan Trương

Ngôn ngữ: vie

Ký hiệu phân loại: 511.8 Mathematical models (Mathematical simulation)

Thông tin xuất bản: Tạp chí Phát triển Khoa học & Công nghệ: Chuyên san Khoa học Tự nhiên, 2018

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Bộ sưu tập: Metadata

ID: 493200

Thêm vào giỏ

Phương pháp Monte Carlo được xem là một phương pháp tính liều chính xác nhất trong xạ trị. Mô phỏng máy gia tốc chính xác là một yêu cầu cần thiết trong tính liều bằng phương pháp này. Trong nghiên cứu này, máy gia tốc Primus M5497 của hãng Siemens tại Bệnh viện Đa khoa Đồng Nai được mô phỏng bằng chương trình EGSnrc cho mức năng lượng photon 6 MV. BEAMnrc và DOSXYZnrc là hai chương trình được sử dụng trong việc mô phỏng và tính toán phân bố liều trong phantom nước. Phần trăm liều theo độ sâu (Percentage depth dose, PDD) và phân bố liều theo phương ngang (Beam profiles, OCR) có được từ mô phỏng được so sánh với dữ liệu thực nghiệm để đánh giá độ chính xác trong mô phỏng. Kết quả thu được có sự phù hợp tốt giữa mô phỏng và thực nghiệm với sự khác biệt của PDD là 1,26 % và OCR nhỏ hơn 2 %. Bên cạnh đó, chúng tôi sử dụng phương pháp đánh giá bằng chỉ số Gamma chạy trên Matlab. Phần trăm liều theo độ sâu có phần trăm chỉ số Gamma đạt 100% và phân bố liều theo phương ngang có phần trăm chỉ số gamma đạt 98,5 % với yêu cầu sai biệt về liều là 3 % và độ lệch về khoảng cách là 3 mm. Kết quả trên cho thấy đã mô phỏng thành công máy gia tốc tuyến tính với độ chính xác cao.The Monte Carlo method is considered to be the most accurate algorithm for dose calculation in radiotherapy. Linear accelerator accurate simulation is required as a prior condition for Monte Carlo dose calculation algorithm. In this study, the 6 MV photon beams from a Siemens Primus Linear Accelerator (LINAC) M5497 at the Dong Nai General Hospital was modelled by using EGSnrc. The BEAMnrc và DOSXYZnrc user code were used for simulation the head of LINAC and the dose distribution in water phantom. The percentage depth dose (PDD) and beam profiles (OCR) were calculated and then compared with the measured ones in order to evaluate the simulation accuracy. Excellent agreement was found between simulations and measurements with an average difference of 1.26 % for PDD, less than 2 % for OCR. In addition, the gamma evaluation method for simulation was also performed using an in-house Matlab code. The percentage gamma passing rate was 100% for PDD and 98.5 % for OCR with 3 % dose difference and 3 mm distance to agreement as acceptance criteria. The result showed that we had successfully simulated LINAC with excellent agreement.

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