Department of Radiation Oncology, Vanderbilt University School of Medicine, Vanderbilt-Ingram Cancer Center, Nashville, Tennessee 37232-5671, USA.
Int J Radiat Oncol Biol Phys. 2010 Mar 1;76(3):924-34. doi: 10.1016/j.ijrobp.2009.06.068. Epub 2009 Dec 11.
To determine whether image guidance can improve the dose delivered to target organs and organs at risk (OARs) for prostate cancer patients treated with intensity-modulated radiotherapy (IMRT).
Eight prostate cancer patients were treated with IMRT to 76 Gy at 2 Gy per fraction. Daily target localization was performed via alignment of three intraprostatic fiducials and weekly kV-cone beam computed tomography (CBCT) scans. The prostate and OARs were manually contoured on each CBCT by a single physician. Daily patient setup shifts were obtained by comparing alignment of skin tattoos with the treatment position based on fiducials. Treatment fields were retrospectively applied to CBCT scans. The dose distributions were calculated using actual treatment plans (an 8-mm PTV margin everywhere except for 6-mm posteriorly) with and without image guidance shifts. Furthermore, the feasibility of margin reduction was evaluated by reducing planning margins to 4 mm everywhere except for 3 mm posteriorly.
For the eight treatment plans on the 56 CBCT scans, the average doses to 98% of the prostate (D98) were 102% (range, 99-104%) and 99% (range, 45-104%) with and without image guidance, respectively. Using margin reduction, the average D98s were 100% (range, 84-104%) and 92% (range, 40-104%) with and without image guidance, respectively.
Currently, margins used in IMRT plans are adequate to deliver a dose to the prostate with conventional patient positioning using skin tattoos or bony anatomy. The use of image guidance may facilitate significant reduction of planning margins. Future studies to assess the efficacy of decreasing margins and improvement of treatment-related toxicities are warranted.
确定在接受调强放疗（IMRT）的前列腺癌患者中，图像引导是否能改善靶器官和危及器官（OARs）的剂量分布。
8 名前列腺癌患者接受了 76 Gy 的 IMRT，每次 2 Gy。每天通过三个前列腺内基准点的对齐和每周的千伏锥形束计算机断层扫描（CBCT）来进行靶区定位。由一位医生在每次 CBCT 上手动勾画前列腺和 OAR。通过比较基于基准点的皮肤纹身与治疗位置的对齐，获得每日患者摆位偏差。将治疗野回顾性地应用于 CBCT 扫描。使用实际治疗计划（除了后部 6mm 外，所有部位都有 8mm 的 PTV 边界）计算剂量分布，包括和不包括图像引导偏差。此外，通过将计划边界减少到除后部 3mm 外所有部位 4mm，评估减少边界的可行性。
在 56 次 CBCT 扫描的 8 个治疗计划中，前列腺的 98%（D98）的平均剂量分别为 102%（范围，99-104%）和 99%（范围，45-104%），分别有和没有图像引导。使用边界减少，D98 的平均剂量分别为 100%（范围，84-104%）和 92%（范围，40-104%），分别有和没有图像引导。
目前，在使用皮肤纹身或骨性解剖进行常规患者定位的情况下，IMRT 计划中使用的边界足以给予前列腺足够的剂量。图像引导的使用可能有助于显著减少计划边界。需要进一步研究以评估减少边界的效果和改善与治疗相关的毒性。
