Ahmad Rozilawati, Hoogeman Mischa S, Quint Sandra, Mens Jan Willem, de Pree Ilse, Heijmen Ben J M
Department of Radiation Oncology, Erasmus MC - Daniel den Hoed Cancer Center, Rotterdam, The Netherlands.
Radiother Oncol. 2008 Nov;89(2):172-9. doi: 10.1016/j.radonc.2008.07.005. Epub 2008 Aug 12.
For cervical cancer patients, bladder filling variations may result in inadequate EBRT target coverage, unless large safety margins are used. For a group of patients who received full bladder instructions, inter-fraction variations and time trends in bladder volume were quantified, and a 3D ultrasound (US) scanner was tested for on-line bladder volume measurements.
For 24 patients, the bladder volume was measured with US at the time of the planning CT scan, and twice weekly during the course of RT. Comparisons of US with planning CT were used to assess the bladder scanner accuracy. Patients were treated in prone on a belly board, EPID images were acquired to correlate set-up errors with bladder filling variations.
Measured US and CT bladder volumes were strongly correlated (R = 0.97, slope 1.1 +/- 0.1). The population mean bladder volume at planning of 378 +/- 209 ml (1 SD) reduced to 109 +/- 88 ml (1 SD) in week 6, a reduction by 71% (average reduction 46 ml/week), revealing a large inter-fraction time trend. Intra-patient variation in bladder volume during RT was 168 ml (1 SD) (range 70-266 ml). Rotation around the LR axis was significantly correlated with bladder volume changes.
Despite a full bladder instruction, bladder volumes reduced dramatically during treatment, implying large time trends in target position of these patients. The portable US scanner provides a quick and reliable measurement of the bladder volume, which might assist future online treatment adaptation.
对于宫颈癌患者，膀胱充盈变化可能导致外照射放疗（EBRT）靶区覆盖不足，除非采用较大的安全边界。对于一组接受膀胱充盈指导的患者，对膀胱体积的分次间变化和时间趋势进行了量化，并对一台三维超声（US）扫描仪进行了在线膀胱体积测量测试。
对24例患者，在计划CT扫描时用超声测量膀胱体积，并在放疗过程中每周测量两次。通过超声与计划CT的比较来评估膀胱扫描仪的准确性。患者俯卧于腹托板上接受治疗，采集电子射野影像装置（EPID）图像以将摆位误差与膀胱充盈变化相关联。
测量的超声和CT膀胱体积高度相关（R = 0.97，斜率1.1±0.1）。计划时膀胱体积的总体平均值为378±209 ml（标准差1），在第6周降至109±88 ml（标准差1），减少了71%（平均每周减少46 ml），显示出较大的分次间时间趋势。放疗期间患者膀胱体积的个体内变化为168 ml（标准差1）（范围70 - 266 ml）。绕左右轴的旋转与膀胱体积变化显著相关。
尽管有膀胱充盈指导，但治疗期间膀胱体积仍显著减小，这意味着这些患者的靶区位置存在较大的时间趋势。便携式超声扫描仪可快速可靠地测量膀胱体积，这可能有助于未来的在线治疗调整。
