Artificial spacing of risk organs from radiation target by liquid injection into peritoneal cavity

利用10对CT扫描数据集，一对有腹水，另一对无腹水，研究了腹水对放射治疗剂量体积直方图的影响。在肝脏、主动脉旁淋巴结、髂淋巴结、子宫和前列腺（直径2-4cm）中设置假靶，并使用四箱野方法对每个靶点进行放射治疗计划。CTV边缘均为1cm。对每个假靶点分别制作40对放射治疗计划（肝脏、腹主动脉旁淋巴结、髂淋巴结、子宫或前列腺），用放射治疗计算机对这些计划的DVH进行比较分析。上腹部肿瘤的危险器官定义为肠和腹壁或膈肌。盆腔肿瘤的危险器官为直肠和膀胱，所有患者中，腹水的存在和体积对肠、直肠、膀胱的剂量无显著影响。然而，在肝脏表面肿瘤放射治疗的情况下，腹水显著减少了横膈膜和腹壁的剂量。在邻近肠的肝肿瘤的放射治疗的情况下（在肝表面的一部分下），腹水也预计会减少肠辐射剂量。总之，液体，在表面肝肿瘤放射治疗前注入腹膜空间似乎可以减少毒性。然而，每天对患者进行CT检查和定位是必不可少的。用于患者固定的子床和用于将患者从CT床运送到直线加速器床的专用担架在这方面非常有用。

Using 10 pair of CT scan data set, one with ascitis and another without ascitis, the influence of ascitis on dose volume histogram of radiation therapy. Sham targets were set in liver, para-aortic lymph nodes, iliac lymph nodes, uterus, and prostate (2-4cm in diameter) and radiotherapy planning was done for each target using four box-field method. The margin from CTV was 1cm in all cases. As a result, 40 pair of radiotherapy plan (liver, para-aortic lymph node, iliac lymph node, and uterus or prostate) was made for each sham target and DVH of these plans were compared and analyzed with radiotherapy computer. Risk organ was defined as intestine and abdominal wall or diaphragm for upper abdominal tumor. For pelvic tumor, risk organs was defined as rectum and urinary bladder.In all patients, the existence and volume of ascitis did not significantly influence dose or intestine, rectum, urinary bladder. However, in case of liver surface tumor radiation therapy, ascitis significantly reduce the dose for diaphragm and abdominal wall. In case of radiation therapy of liver tumor that is adjacent to intestine (under part of liver surface), ascitis was also expected to reduce the intestinal radiation dose.In conclusion, liquid, injection into peritoneal space before radiation therapy for surface liver tumor seems to reduce toxicity. However, daily CT checking and positioning of patients is essential. Subtable for patients fixation and special stretcher to transport patients from CT table to linac table is very useful for this pourpose.