Department of Medical Physics, Greater Poland Cancer Centre, Poznań, Poland.
Department of Medical Physics, Greater Poland Cancer Centre, Poznań, Poland; Department of Electroradiology, Poznań University of Medical Sciences, Poznań, Poland.
Phys Med. 2019 Jan;57:183-190. doi: 10.1016/j.ejmp.2019.01.008. Epub 2019 Jan 11.
In this study, relations between dose cumulated in organs at risk and treatment based on different image guidance strategies (IG) of cervical cancer were analyzed.
MATERIAL/METHODS: Thirty patients with cervical cancer were subjected to analysis. The first phase of the study involved analysis of shifts resulting from the registration process and calculations of margins based on shifts data. The margin was calculated for two imaging scenarios - based on the analysis of bones and soft tissues. The margins thus obtained were used in the second phase of the study where the VMAT and IMRT treatment plans were prepared and, in consequence, analyzed in the light of the dose distribution.
Using different IG implicates different margins for specified parts of the CTV. IG based on bones allows to establish margins for lymph nodes (CTV2) that are smaller than margins for the vagina/paravaginal tissues (CTV1). The opposite applies to the IG based on soft tissues, for which margins for CTV1 are smaller than for CTV2. While decreasing the margins for CTV1 reduces the doses in the bladder and rectum, doses cumulated in the bone marrow are independent of the size of the margin resulting from the type of IG used. Nevertheless, the average doses and the values of normal tissue complication probability in the bone marrow were smaller for VMAT than for IMRT.
The VMAT plan and image guidance based on soft tissue registration for the vagina/paravaginal tissues are recommended for radiotherapy of cervical cancer patients.
本研究分析了宫颈癌不同图像引导策略（IG）下靶区剂量累积与治疗之间的关系。
材料/方法：对 30 例宫颈癌患者进行分析。第一阶段的研究包括分析配准过程中的移位并根据移位数据计算边界。基于骨骼和软组织分析计算了两种成像情况下的边界。获得的边界用于研究的第二阶段，在该阶段中制备了 VMAT 和 IMRT 治疗计划，并根据剂量分布对其进行了分析。
使用不同的 IG 会导致CTV 指定部位的边界不同。基于骨骼的 IG 可以为淋巴结（CTV2）建立比阴道/旁阴道组织（CTV1）更小的边界。相反，基于软组织的 IG 则相反，对于 CTV1 的边界小于 CTV2。虽然减少 CTV1 的边界会降低膀胱和直肠的剂量，但骨髓中累积的剂量与所使用 IG 类型产生的边界大小无关。然而，对于 VMAT，骨髓中的平均剂量和正常组织并发症概率值均小于 IMRT。
推荐对宫颈癌患者进行放疗时使用 VMAT 计划和基于阴道/旁阴道软组织的 IG。
