Huq M S, Yu Y, Chen Z P, Suntharalingam N
Department of Radiation Oncology, Bodine Center for Cancer Treatment, Thomas Jefferson University, Philadelphia, Pennsylvania 19107-5097, USA.
Med Phys. 1995 Feb;22(2):241-7. doi: 10.1118/1.597461.
The dosimetric characteristics of a multileaf collimator (MLC) retrofitted to a SL25 linear accelerator have been investigated. Central-axis depth dose, surface dose, penumbra, beam flatness and symmetry, field size factors, beam transmission through leaves and/or diaphragms, and leakage between the leaves were measured. Quantitative measurements of all beam parameters show good agreement with the design specifications of the manufacturer. No changes were observed in flatness, symmetry, penumbra, and penetration for both 6- and 25-MV photon beams when compared to the values for the standard collimator. No significant differences were observed in the penumbra as a function of leaf position. Transmission measurements in areas shielded by either X diaphragms or leaves plus diaphragms are less than 1% of dose within open field. The average leakage between leaves is about 2.5% for 6-MV and 3.5% for 25-MV photon beams. The peak value of the leakage at any point between leaves is less than 5%. The dosimetric features of shaped fields using the MLC are comparable to those of alloy shaped fields with the standard SL25 collimator.
已对改装到SL25直线加速器上的多叶准直器（MLC）的剂量学特性进行了研究。测量了中心轴深度剂量、表面剂量、半值层、射野平坦度和对称性、射野大小因子、射线通过叶片和/或准直器的透射率以及叶片间的泄漏。所有射束参数的定量测量结果与制造商的设计规格吻合良好。与标准准直器的值相比，6兆伏和25兆伏光子束的平坦度、对称性、半值层和穿透率均未观察到变化。半值层作为叶片位置的函数未观察到显著差异。在由X准直器或叶片加准直器屏蔽的区域中的透射测量结果小于开放射野内剂量的1%。对于6兆伏光子束，叶片间的平均泄漏约为2.5%，对于25兆伏光子束为3.5%。叶片间任意点的泄漏峰值小于5%。使用MLC的成形射野的剂量学特征与使用标准SL25准直器的合金成形射野的剂量学特征相当。
