Department of Radiation Oncology, National Cancer Center Hospital, 5-1-1 Tsukiji, Chuo-ku, Tokyo 104-0045, Japan.
Radiation Safety and Quality Assurance Division, Common Department, National Cancer Center Hospital, 5-1-1 Tsukiji, Chuo-ku, Tokyo 104-0045, Japan.
J Radiat Res. 2023 Nov 21;64(6):967-972. doi: 10.1093/jrr/rrad072.
The uterus is known as one of the moving organs. We evaluated the movement of the uterus during irradiation and the effects of changes in the surrounding organs using a magnetic resonance (MR)-guided radiotherapy system. Seven patients with cervical cancer underwent pre- and posttreatment MR imaging to assess changes in the positioning of the uterus and cervix as well as the alterations in bladder and rectal volume. The study revealed that the movements of the uterus were greater than that of the cervix and showed a tendency to correlate with the bladder rather than the rectum. We also examined whether intrafractional motion could lead to insufficient dose coverage of the clinical target volume (CTV), specifically focusing on the D98% of the CTV in the uterine body and cervix. The impact of intrafractional motion on the D98% varied among patients, with one out of the seven patients experiencing an average dosimetric change of -2.6 Gy in the uterus, although larger planning target volume margins of 1.5 cm were applied, therefore, indicating the need for individualized optimal margins in each case. Online adaptive radiotherapy offers the advantage of modifying the treatment plan when irradiating moving organs, such as the uterus. However, it should be noted that this approach may result in longer overall treatment times compared with the traditional methods. Therefore, we must carefully consider the influence of intrafractional organ motions when opting for such a treatment.
子宫是一种运动器官。我们使用磁共振（MR）引导放射治疗系统评估了照射过程中子宫的运动以及周围器官变化的影响。七例宫颈癌患者在治疗前后进行了 MR 成像，以评估子宫和宫颈的定位变化以及膀胱和直肠体积的变化。研究表明，子宫的运动大于宫颈的运动，并且与膀胱而不是直肠有相关性。我们还检查了子宫内运动是否会导致临床靶体积（CTV）的剂量覆盖不足，特别是关注子宫体和宫颈的 CTV 的 D98%。子宫内运动对 D98%的影响因患者而异，七例患者中有一例在子宫中平均剂量变化为-2.6Gy，尽管应用了更大的计划靶体积边界 1.5cm，但这表明需要为每个病例个体化优化边界。在线自适应放疗在照射运动器官（如子宫）时具有修改治疗计划的优势。然而，应该注意的是，与传统方法相比，这种方法可能会导致整体治疗时间延长。因此，我们在选择这种治疗方法时必须仔细考虑子宫内器官运动的影响。
