Lo William Chun Yip, Redmond Keith, Luu Jason, Chow Paul, Rose Jonathan, Lilge Lothar
University of Toronto, Department of Medical Biophysics, Rm. 8-324,610 University Avenue, Toronto, Ontario M5G 2M9 Canada.
J Biomed Opt. 2009 Jan-Feb;14(1):014019. doi: 10.1117/1.3080134.
Monte Carlo (MC) simulations are being used extensively in the field of medical biophysics, particularly for modeling light propagation in tissues. The high computation time for MC limits its use to solving only the forward solutions for a given source geometry, emission profile, and optical interaction coefficients of the tissue. However, applications such as photodynamic therapy treatment planning or image reconstruction in diffuse optical tomography require solving the inverse problem given a desired dose distribution or absorber distribution, respectively. A faster means for performing MC simulations would enable the use of MC-based models for accomplishing such tasks. To explore this possibility, a digital hardware implementation of a MC simulation based on the Monte Carlo for Multi-Layered media (MCML) software was implemented on a development platform with multiple field-programmable gate arrays (FPGAs). The hardware performed the MC simulation on average 80 times faster and was 45 times more energy efficient than the MCML software executed on a 3-GHz Intel Xeon processor. The resulting isofluence lines closely matched those produced by MCML in software, diverging by only less than 0.1 mm for fluence levels as low as 0.00001 cm(-2) in a skin model.
蒙特卡罗（MC）模拟在医学生物物理学领域得到了广泛应用，特别是用于模拟光在组织中的传播。MC的高计算时间限制了其仅用于求解给定源几何形状、发射轮廓和组织光学相互作用系数的正向解。然而，诸如光动力疗法治疗计划或扩散光学断层扫描中的图像重建等应用分别需要在给定所需剂量分布或吸收体分布的情况下求解逆问题。一种更快的执行MC模拟的方法将使基于MC的模型能够用于完成此类任务。为了探索这种可能性，在具有多个现场可编程门阵列（FPGA）的开发平台上实现了基于多层介质蒙特卡罗（MCML）软件的MC模拟的数字硬件实现。该硬件执行MC模拟的速度平均比在3 GHz英特尔至强处理器上执行的MCML软件快80倍，且能源效率高45倍。在皮肤模型中，对于低至0.00001 cm(-2)的通量水平，所得的等通量线与软件中MCML生成的等通量线紧密匹配，偏差仅小于0.1 mm。
