Saw C B, Korb L J, Ayyangar K M, Krishna K V
Division of Radiation Oncology, Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown, 26506, USA.
Int J Radiat Oncol Biol Phys. 1996 Mar 15;34(5):1147-52. doi: 10.1016/0360-3016(95)02203-1.
An expression that relates the wedge isodose angle to the gradient of the percent depth-dose curves for photon beams has been formulated and verified experimentally.
The expression that relates a wedge angle to another via the gradient of their corresponding percent depth-dose curves was derived. Because the field size affects the percent depth-dose curves, measurement of wedged isodose distributions were carried out for different field sizes to validate the expression. The 6 MV and 23 MV photon beams and a range of field sizes from 5 x 5 cm to 20 x 20 cm were used. For each field size, the wedge angle and percent depth-dose curve slope were measured at the depth of 10 cm. Measured and calculated wedge angles were compared.
The variation of the wedge angle caused by the change in field size is about 6 degrees. For field sizes larger than 10 x 10 cm, the variation of wedge angle is less than 3 degrees. The calculated wedge angles agree with the measured wedge angles to within 1 degree. The knowledge of the extent of wedge angle variation due to the change in field size and the availability of an expression to determine an accurate wedge angle would be helpful in the use of the universal wedge equation.
已推导出一个将楔形等剂量角与光子束百分深度剂量曲线的梯度相关联的表达式，并通过实验进行了验证。
通过相应百分深度剂量曲线的梯度推导出将一个楔形角与另一个楔形角相关联的表达式。由于射野大小会影响百分深度剂量曲线，因此针对不同射野大小进行了楔形等剂量分布测量，以验证该表达式。使用了6MV和23MV的光子束以及从5×5cm到20×20cm的一系列射野大小。对于每个射野大小，在10cm深度处测量楔形角和百分深度剂量曲线斜率。比较测量的和计算的楔形角。
射野大小变化引起的楔形角变化约为6度。对于大于10×10cm的射野大小，楔形角变化小于3度。计算的楔形角与测量的楔形角在1度范围内相符。了解由于射野大小变化导致的楔形角变化程度以及有一个确定准确楔形角的表达式，将有助于通用楔形方程的使用。
