Biggs P J, Russell M D
Department of Radiation Medicine, Massachusetts General Hospital, Boston 02114.
Int J Radiat Oncol Biol Phys. 1988 Mar;14(3):581-6. doi: 10.1016/0360-3016(88)90279-9.
A few patients undergoing pelvic irradiation present with a prosthetic hip. The presence of this metal object often interferes with the lateral treatment fields if a four-field box irradiation technique is used. Measurements of the effect such a prosthesis may have on the dose delivered to the pelvis for beams of 60Co gamma rays and 10 MV and 25 MV X-rays, as a function of field size and depth have been made. The results show a strong variation in the dose behind the prosthesis depending on the position of the measurement, with little or no increase through the center of the head or ball, but a sharp drop either around its circumference or along the stem of the prosthesis. Measurements made with ionization chambers through the head of the prosthesis indicate an average dose decrease of approximately 2% for 25 MV X rays and average increases of approximately 2% for 10 MV X rays and 5% for 60Co. There is little variation with field size and depth except close to the prosthesis, at 25 MV. Measurements also indicate an increase in dose close to the upstream surface of the prosthesis at all energies, but in the downstream direction, only the data at 25 MV shows an increase.
一些接受盆腔照射的患者体内有髋关节假体。如果采用四野盒式照射技术，这种金属物体的存在常常会干扰侧方治疗野。已经针对60Co伽马射线束以及10MV和25MV X射线束，测量了这种假体对盆腔剂量的影响，该影响是作为野大小和深度的函数。结果表明，假体后方的剂量根据测量位置有很大变化，通过假体头部或球部中心时剂量几乎没有增加或根本没有增加，但在其圆周周围或沿假体柄部会有急剧下降。通过电离室对假体头部进行测量表明，对于25MV X射线，平均剂量降低约2%；对于10MV X射线，平均剂量增加约2%；对于60Co，平均剂量增加5%。除了在25MV且靠近假体处，剂量随野大小和深度变化不大。测量还表明，在所有能量下，靠近假体上游表面处剂量增加，但在下游方向，只有25MV的数据显示剂量增加。
