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

利用10对有腹水和无腹水的CT扫描数据，分析腹水对放射治疗剂量-体积直方图的影响。在肝脏、腹主动脉旁淋巴结、髂骨淋巴结、子宫和前列腺(直径2~4 cm)设置假靶点，采用四箱野方法对每个靶点进行放射治疗计划。所有病例距CTV边缘均为1 cm。结果为每个假手术靶点制定了40对放射治疗计划(肝脏、腹主动脉旁淋巴结、髂动脉淋巴结、子宫或前列腺)，并用放射计算机对这些计划的DVH进行了比较和分析。上腹部肿瘤的危险器官定义为肠和腹壁或隔膜。对于盆腔肿瘤，危险器官定义为直肠和膀胱。在所有患者中，腹水的存在和体积对剂量或肠道、直肠、膀胱没有显著影响。然而，在肝表面肿瘤放射治疗的情况下，腹水炎显著减少了横隔部和腹壁的剂量。对于邻近肠道(部分肝表面下)的肝肿瘤的放射治疗，腹水也有望减少肠道的照射剂量。结论：体表肝肿瘤放射治疗前向腹膜腔内注射液体似乎可以减少毒性。然而，患者的日常CT检查和定位是必不可少的。用于患者固定的分床和专用担架将患者从CT床运送到直线加速器床是非常有用的。

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.