一种基于笔形束核的快速剂量计算方法

Pencil beam kernel-based method for fast dose calculation

针对传统笔形束核剂量算法计算过程复杂、速度较慢的问题,提出一种基于笔形束核的快速剂量计算方法。该方法在球壳坐标系下,利用射束与不同球壳层碰撞后轴线与体素相交情况的相似性,通过对每条射束只计算初始球壳层碰撞点处轴线与体素的相交情况,并将初始球壳层深度与其它球壳层深度的比值作为校正因子得到其他层碰撞点处轴线与体素的相交情况。避免射线追踪法的重复使用,在不影响算法精度的情况下节省大量时间。实验结果表明:在不同射野大小[(3×3)、(5×5)、(10×10)cm^2]的水模体中计算深度剂量分布,两种算法的计算精度基本一致,改进算法的计算速度提升约2.7倍。同时当射野面积为(10×10)cm^2时,在肺阻块模体和骨阻块模体不同深度的剖面剂量计算中,改进算法与传统算法的计算精度也基本一致,但计算速度提升约2.6倍。

Considering the complicated calculation process and slow speed of the traditional pencil beam kernel dose algorithm,a fast dose calculation method based on pencil beam kernel is proposed.In the spherical shell coordinate system,the similarity of the intersection between the axis and the voxel after the beam collision with different spherical shells is analyzed,and only the intersection of the axis and the voxel at the initial spherical shell collision point is calculated for each beam.Moreover,the ratio of the initial spherical shell depth to the other spherical shell depths is taken as a correction factor to obtain the intersection of the axis and the voxel at the collision point of the other layer.The method can be used to save a lot of time without affecting the algorithm accuracy by avoiding the repeated use of ray tracing method.The experimental results show that when the depth dose distribution is calculated at the different field sizes of(3×3),(5×5)and(10×10)cm^2of water phantoms,the calculation accuracies of two algorithms are basically the same,but the calculation speed of the improved algorithm is improved by about 2.7 times.Meanwhile,when the field size is(10×10)cm^2,the calculation accuracies of the improved algorithm and the traditional algorithm are basically similar in the calculation of the profile dose of lung block phantom and bone block phantom,but the calculation speed of the proposed method is improved by about 2.6 times.