Wong T, Wallace S, Fernando W, Schumer W, Quong G
Radiation Oncology Centre, Austin and Repatriation Medical Centre, West Heidelberg, Victoria, Australia.
Phys Med Biol. 1999 Feb;44(2):357-63. doi: 10.1088/0031-9155/44/2/005.
The dose rate at point P at 0.25 cm in water from the transverse bisector of a straight catheter with an active stepping source (Nucletron microSelectron HDR source) with a dwell length of 2 cm was calculated using Monte Carlo code MCNP 4.A. The source step sizes were 1 cm and 0.25 cm. The Monte Carlo (MC) results were used for comparison with the results calculated with the Nucletron brachytherapy planning system (BPS) formalism, first with BPS variants and then with its respective MC calculated radial dose function and anisotropy function. The dose differences at point P calculated using the BPS formalism and variants are +15.4% and +3.1% for the source step size of 1 cm and 0.25 cm respectively. This reduction in dose difference is caused by the increased importance of errors in the anisotropy function with the smaller step size, which counter the errors in the radial dose function. Using the MC calculated radial dose function and anisotropy function with the BPS formalism. 1% dose calculation accuracy can be achieved, even in the near field, with negligible extra demand on computation time.
使用蒙特卡罗代码MCNP 4.A计算了在水中距带有2厘米驻留长度的有源步进源（Nucletron microSelectron HDR源）的直形导管横向平分线0.25厘米处的点P的剂量率。源步长为1厘米和0.25厘米。将蒙特卡罗（MC）结果与使用Nucletron近距离治疗计划系统（BPS）形式主义计算的结果进行比较，首先是BPS变体，然后是其各自的MC计算的径向剂量函数和各向异性函数。对于1厘米和0.25厘米的源步长，使用BPS形式主义和变体计算的点P处的剂量差异分别为+15.4%和+3.1%。剂量差异的这种减小是由于步长较小时各向异性函数中误差的重要性增加，这抵消了径向剂量函数中的误差。使用MC计算的径向剂量函数和各向异性函数与BPS形式主义。即使在近场，也可以实现1%的剂量计算精度，对计算时间的额外要求可以忽略不计。
