Chen F S
Department of Radiation Oncology, Saint John Regional Hospital, New Brunswick, Canada.
Med Phys. 1990 May-Jun;17(3):464-9. doi: 10.1118/1.596485.
The polynomial formula proposed by Chen [Med. Phys. 15, 348 (1988)] in calculating the electron beam output from a Therac 20 linear accelerator has been applied to generating the output factor of various machines with photon energies ranging from 100 kVp to 18 MeV. The calculated outputs are within 1% of the measured values. This formula can be very useful to the physicist in preparing an output table of photon beams or electron beams for a therapeutic unit. An equation is derived from this formula to calculate the equivalent square. The derivation shows that only under special circumstances is the equivalent square field equivalent to 2ab/(a + b); otherwise the equivalent square field depends on the formula's parameters as well as the sides of the rectangular field. These parameters, in turn, are dependent on the photon energy, the medium irradiated, and the collimator design.
陈[《医学物理》15, 348 (1988)]提出的用于计算Therac 20直线加速器电子束输出的多项式公式，已被应用于生成各种光子能量范围从100 kVp到18 MeV的机器的输出因子。计算得到的输出值在测量值的1%以内。该公式对于物理学家为治疗单元准备光子束或电子束的输出表非常有用。从该公式推导出一个用于计算等效方的方程。推导表明，只有在特殊情况下等效方场才等于2ab/(a + b)；否则等效方场取决于公式的参数以及矩形野的边长。反过来，这些参数又取决于光子能量、被辐照介质和准直器设计。
