Brooks Chris, Cheung Rex Min, Kudchadker Rajat J
Department of Radiation Oncology, The University of Texas M. D. Anderson Cancer Center, Houston, 77030, USA.
Med Dosim. 2010 Summer;35(2):87-91. doi: 10.1016/j.meddos.2009.03.005. Epub 2009 Apr 18.
Megavoltage photon intensity-modulated radiation therapy (IMRT) is typically used in the treatment of prostate cancer at our institution. Approximately 1% to 2% of patients with prostate cancer have hip prostheses. The presence of the prosthesis usually complicates the planning process because of dose perturbation around the prosthesis, radiation attenuation through the prosthesis, and the introduction of computed tomography artifacts in the planning volume. In addition, hip prostheses are typically made of materials of high atomic number, which add uncertainty to the dosimetry of the prostate and critical organs in the planning volume. When the prosthesis is bilateral, treatment planning is further complicated because only a limited number of beam angles can be used to avoid the prostheses. In this case study, we will report the observed advantages of using noncoplanar beams in the delivery of IMRT to a prostate cancer patient with bilateral hip prostheses. The treatment was planned for 75.6 Gy using a 7-field coplanar approach and a noncoplanar arrangement, with all fields avoiding entrance though the prostheses. Our results indicate that, compared with the coplanar plan, the noncoplanar plan delivers the prescribed dose to the target with a slightly better conformality and sparing of rectal tissue versus the coplanar plan.
在我们机构，兆伏级光子调强放射治疗（IMRT）通常用于前列腺癌的治疗。大约1%至2%的前列腺癌患者有髋关节假体。假体的存在通常会使治疗计划过程变得复杂，这是因为假体周围存在剂量扰动、射线通过假体时发生衰减以及在计划靶区内引入了计算机断层扫描伪影。此外，髋关节假体通常由高原子序数材料制成，这给前列腺及计划靶区内关键器官的剂量测定增加了不确定性。当双侧都有假体时，治疗计划会更加复杂，因为只能使用有限数量的射野角度来避开假体。在本病例研究中，我们将报告在对一名双侧髋关节假体的前列腺癌患者进行IMRT治疗时使用非共面射野所观察到的优势。采用7野共面和非共面布局将治疗计划设定为75.6 Gy，所有射野均避免从假体进入。我们的结果表明，与共面计划相比，非共面计划在向靶区递送规定剂量时，与共面计划相比，具有稍好的适形性和对直肠组织的保护。
