An image-based method to quantify biomechanical properties of the rectum in radiotherapy of prostate cancer
An image-based method to quantify biomechanical properties of the rectum in radiotherapy of prostate cancer
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DOI：
10.3109/0284186x.2015.1066933
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发表时间：
2015-10-21
期刊：
影响因子：
3.1
通讯作者：
Muren, Ludvig P.
中科院分区：
文献类型：
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作者：
Casares-Magaz, Oscar;Thor, Maria;Muren, Ludvig P.
背景。前列腺癌放射治疗（RT）后胃肠道发病率可能与直肠的生物力学特性有关。在这项研究中，我们提出了一种基于磁共振成像（MRI）的方法来量化前列腺癌患者接受rt治疗时直肠壁的厚度和弹性。四名先前接受过前列腺癌RT治疗的患者接受了一次逐步放气直肠袋的MRI检查（从最大可耐受容积到0毫升，每50毫升），并将探针插入袋内以监测直肠内压。在每个放气步骤使用Dixon序列（4 mm轴向切片厚度）获得mri。直肠壁从直肠-乙状结肠交界处至肛管上方3cm处定义为内、外壁表面之间的空间。确定肠壁厚度，并根据压力测量和mri分段直肠壁计算生物力学特性（应变和应力）。不同患者的直肠积分压在最大可耐受容积（150-250 ml）范围内变化，范围为1.3 - 4.0 kPa （SD = 1.2 kPa）。肠壁厚度在不同患者之间以及不同直肠节段之间存在差异，在50ml膨胀体积下不同节段的平均（SD）厚度为1.8 ~ 4.0 (0.6)mm。应力比应变变化更大，不同节段的平均（SD）值在1.5 ~ 7.0 (1.5)kpa之间。我们已经开发了一种量化直肠壁生物力学特性的方法。所得到的直肠壁厚度、应变和应力在患者之间以及不同直肠壁截面之间存在差异。这些发现可以为未来的预测结果建模提供指导，以便更好地了解直肠剂量-体积反应关系。
Background. Gastrointestinal morbidity after radiotherapy (RT) for prostate cancer may be related to the biomechanical properties of the rectum. In this study we present a magnetic resonance imaging (MRI)-based method to quantitate the thickness and elasticity of the rectal wall in prostate cancer patients treated with RT.Material and methods. Four patients previously treated with RT for prostate cancer underwent an MRI session with stepwise rectal bag deflation (from a maximum tolerable volume to 0 ml, in 50 ml steps), with a probe inserted inside the bag to monitor the internal rectal pressure. MRIs were acquired using Dixon sequences (4 mm axial slice thickness) at each deflation step. Rectal walls were defined from the recto-sigmoid junction to 3 cm above the anal canal as the space between the inner and outer wall surfaces. The wall thickness was determined and biomechanical properties (strain and stress) were calculated from the pressure measurements and the MRI-segmented rectal walls.Results. The integral rectal pressure varied for the maximum tolerable volume (range 150-250 ml) across patients and ranged from 1.3 to 4.0 kPa (SD = 1.2 kPa). Wall thickness was found to vary between patients and also across different rectum segments, with a mean (SD) thickness for the different segments at the 50 ml distension volume of 1.8-4.0 (0.6) mm. Stress showed larger variation than strain, with mean (SD) values for the different segments ranging between 1.5 and 7.0 (1.5) kPa.Conclusion. We have developed a method to quantify biomechanical properties of the rectal wall. The resulting rectal wall thickness, strain and stress differed between patients, as well as across different rectal wall sections. These findings could provide guidance in future predictive outcome modelling in order to better understand the rectal dose-volume response relationship.