Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA.
Int J Radiat Oncol Biol Phys. 2012 Jan 1;82(1):256-62. doi: 10.1016/j.ijrobp.2010.08.024. Epub 2010 Nov 17.
To evaluate variations in bladder and rectal volume and the position of the vaginal vault during a 5-week course of pelvic intensity-modulated radiation therapy (IMRT) after hysterectomy.
Twenty-four patients were instructed how to fill their bladders before simulation and treatment. These patients underwent computed tomography simulations with full and empty bladders and then underwent rescanning twice weekly during IMRT; patients were asked to have full bladder for treatment. Bladder and rectal volumes and the positions of vaginal fiducial markers were determined, and changes in volume and position were calculated.
The mean full and empty bladder volumes at simulation were 480 cc (range, 122-1,052) and 155 cc (range, 49-371), respectively. Bladder volumes varied widely during IMRT: the median difference between the maximum and minimum volumes was 247 cc (range, 96-585). Variations in rectal volume during IMRT were less pronounced. For the 16 patients with vaginal fiducial markers in place throughout IMRT, the median maximum movement of the markers during IMRT was 0.59 cm in the right-left direction (range, 0-0.9), 1.46 cm in the anterior-posterior direction (range, 0.8-2.79), and 1.2 cm in the superior-inferior direction (range, 0.6-2.1). Large variations in rectal or bladder volume frequently correlated with significant displacement of the vaginal apex.
Although treatment with a full bladder is usually preferred because of greater sparing of small bowel, our data demonstrate that even with detailed instruction, patients are unable to maintain consistent bladder filling. Variations in organ position during IMRT can result in marked changes in the position of the target volume and the volume of small bowel exposed to high doses of radiation.
评估子宫切除术后接受盆腔强度调节放射治疗（IMRT）的 5 周过程中膀胱和直肠容积以及阴道穹窿位置的变化。
24 名患者在模拟和治疗前接受了充盈膀胱的指导。这些患者接受了全膀胱和空膀胱的计算机断层扫描模拟，然后在 IMRT 期间每周进行两次重新扫描；患者被要求在治疗时保持膀胱充盈。确定了膀胱和直肠的容积以及阴道基准标记的位置，并计算了容积和位置的变化。
模拟时平均全膀胱和空膀胱容积分别为 480cc（范围，122-1052）和 155cc（范围，49-371）。在 IMRT 过程中，膀胱容积变化很大：最大和最小容积之间的中位数差异为 247cc（范围，96-585）。在 IMRT 期间直肠容积的变化不那么明显。对于在整个 IMRT 期间都有阴道基准标记的 16 名患者，标记物在 IMRT 期间的最大移动中位数为 0.59cm（范围，0-0.9）在左右方向，1.46cm（范围，0.8-2.79）在前后方向，1.2cm（范围，0.6-2.1）在上下方向。直肠或膀胱容积的较大变化经常与阴道顶点的明显移位相关。
尽管由于小肠的保护更好，通常首选全膀胱治疗，但我们的数据表明，即使有详细的指导，患者也无法保持一致的膀胱充盈。在 IMRT 过程中器官位置的变化会导致靶体积位置和暴露于高剂量辐射的小肠体积发生明显变化。
