Medical Physics in Radiation Oncology, German Cancer Research Center (DKFZ), Heidelberg, Germany. National Center for Radiation Research in Oncology, Heidelberg Institute for Radiooncology, Heidelberg, Germany. Department of Physics and Astronomy, Heidelberg University, Heidelberg, Germany. Author to whom any correspondence should be addressed.
Phys Med Biol. 2019 Feb 11;64(4):04NT05. doi: 10.1088/1361-6560/aafd5f.
Applicability and accuracy of the rapidly developing tools and workflows for image-guided radiotherapy need to be validated under realistic treatment-like conditions. We present the construction of the ADAM-pelvis phantom, an anthropomorphic, deformable and multimodal (CT and MRI) phantom of the male pelvis. The phantom covers patient-like uncertainties in image-guided radiotherapy workflows including imaging artifacts for the special case of the human anatomy as well as organ motion. Principles and methods were further improved from previous work. The phantom includes surrogates for muscle tissue, adipose, inner and outer bone, as well as deformable silicone organs. Anthropomorphic shapes are realized with 3D-printing techniques for the bone and the construction of the hollow silicone organ shells. Organs are constructed from patient image segmentation and further guided by reported deformation models. Imaging markers and pockets for dosimeters are included in the organ shells. The improved phantom surrogates match imaging characteristics in MRI (T1 and T2 relaxation time) and CT (Hounsfield units) of human tissues. The surrogates are suited for long term use (several months) of the phantom. Previously reported artifacts of the muscle surrogate were avoided by improved composition of the used agarose gel. Interfractional organ motion is successfully realized for the water filled bladder and the air filled rectum and showed to be reproducible with deviation below 1 mm. Volume variations of both induce displacement, rotation and deformation of the prostate. We present solutions for the construction of an anthropomorphic phantom suitable for MRI and CT imaging including deformable organs. The developed concepts of phantom surrogates and construction techniques were successfully applied in building the ADAM-pelvis phantom and can as well be adopted for other anthropomorphic phantoms. The presented phantom allows for the systematic and controlled investigation of image-guided radiotherapy workflows in presence of organ motion.
快速发展的图像引导放射治疗工具和工作流程的适用性和准确性需要在类似于治疗的真实条件下进行验证。我们提出了 ADAM-骨盆模型的构建，这是一种男性骨盆的拟人化、可变形和多模态（CT 和 MRI）模型。该模型涵盖了图像引导放射治疗工作流程中类似患者的不确定性，包括特殊人体解剖结构的成像伪影以及器官运动。该模型的原理和方法是在之前工作的基础上进一步改进的。该模型包括肌肉组织、脂肪、内外骨骼以及可变形硅酮器官的替代品。骨骼和空心硅酮器官壳的构建采用 3D 打印技术实现了拟人化形状。器官是根据患者的图像分割，并进一步由报告的变形模型引导构建的。器官壳中包含成像标记物和剂量计口袋。改进后的模型替代品在 MRI（T1 和 T2 弛豫时间）和 CT（亨氏单位）中与人体组织的成像特征匹配。这些替代品适合于模型的长期使用（几个月）。通过改进琼脂糖凝胶的组成，避免了之前报道的肌肉替代品的伪影。填充水的膀胱和充气的直肠的分次间器官运动成功实现，并且显示出具有低于 1 毫米的偏差的可重复性。这两个器官的体积变化会导致前列腺的位移、旋转和变形。我们提出了一种适合 MRI 和 CT 成像的拟人化模型构建方案，包括可变形器官。所开发的模型替代品和构建技术的概念已成功应用于 ADAM-骨盆模型的构建，并可应用于其他拟人化模型。所提出的模型允许在存在器官运动的情况下系统地和受控地研究图像引导放射治疗工作流程。
