臨床上神經外科取樣手術過程中，腦組織會因開顱或手術器械穿刺使得腦脊髓液流失，導致目標點位置與術前規劃的位置有偏差，由於無法即時監測手術器械在腦組織的位置，進而導致定位失準，因此發展術中磁振導引即時監控腦組織與目標點，是目前神經外科手術重要研究之一。本研究欲發展幾何形狀仿真假體，其腦質假體與豬腦之機械性質相近，且能在磁振造影中使腫瘤假體與腦質假體呈現不同顯像，以應用於磁振造影相容手術機器人檢驗與醫師手術訓練之用。
首先由病患頭部磁振影像應用軟體3D Slicer、Solidworks與Meshmixer設計模具，以3D列印製作模具，並由半球形假體試件與豬腦進行鬆弛試驗，測試腦質假體與豬腦之黏彈性質，另外進行腫瘤假體標準試件準靜態試驗，測試其彈性性質，最後以臨床活檢針穿刺幾何形狀仿真假體與豬腦，測量穿刺過程力量之變化。藉由添加不同濃度的硫酸銅於腦質假體與腫瘤假體，改變其磁振造影的T1鬆弛時間。結果顯示0.6%洋菜濃度最適合作為腦質假體材料，由果凍蠟與0.4%洋菜濃度組合的腫瘤假體與膠質母細胞瘤彈性性質相近，組織內部的剛性為豬腦大於無腫瘤的幾何形狀仿真假體，但其差異對於人體感受甚小。將病患與幾何形狀仿真的假體的磁振造影像，以豪斯多夫距離與Dice係數比較發現兩者幾何相似度很高。總之，本研究發展的幾何形狀仿真假體，可能應用於磁振造影相容立體定位手術機器人檢驗以及神經外科手術術前規畫與教學。

During the clinical neurosurgery operation, patient’s brain will lose cerebrospinal fluid due to craniotomy or surgical instrument puncture, and the target may be displaced away from the pre-surgical planned position. Lacking information of intra-operative position of the needle tip in brain tissue will reduce the positioning accuracy. The development of intraoperative MRI method to monitor the needle and target points in real time is an important field of neurosurgery nowadays. The main goals of this study were two-fold, first, to develop geometry mimicking phantoms of human brain which can be used in neurosurgery. The mechanical properties imitate those of the patient’s brain, and the material is MRI visible and healthy tissue is distinguishable from the pathological tissue, so as to be applied to validate the accuracy and precision of the MRI compatible robot and surgeon training. Secondly, phantoms are characterized for application in validating the performance of a MRI-compatible surgical robot.
The MRI image of a patient from the literature were utilized to build the phantom. Software such as 3D Slicer, Solidworks and Meshmixer were employed to design the molds for the geometry mimicking phantom. The molds were fabricated by a 3D printer. Agar solution with concentration of 0.6% was chosen as the phantom cerebrum and 0.4% for the phantom tumor for glioblastoma. For MR visibility the phantom cerebrum and phantom tumor were doped with 3.2mM of copper sulfate and 1mM of copper sulfate respectively. Relaxation test of the phantom cerebrum material were performed on a material testing machine to characterize its viscoelasticity using the quasi-viscoelasticity theory. In addition, the quasi static compression tests of the phantom tumor were also conducted to characterize its elasticity. A clinical biopsy needle was utilized to perform insertion procedure on the brain-and-tumor phantom to characterize the biomechanics of the operation using the material testing machine and compared with the surgeon’s subjective feeling. T1 MRI of the phantom of the patient was acquired by a 3T-MR machine. The geometric accuracy of the phantom images was compared with those of the original images. The results show that the phantom material made of 0.6% agar has apparent Young’s modulus close to that of the swine brain. The phantom material made of 0.4% agar solution has Young’s modulus close to that of the swine brain glioblastoma.
Although the rigidity derived from the insertion force-displacement curve of the cerebrum phantom is greater than that of the swine, the surgeon detects no difference between the insertion forces of the human brain and the brain phantom. MR images analysis of the brain phantom of the patient shows that the jelly wax coated on tumor phantom surface can effectively block the diffusion of copper anion from cerebrum phantom. Hausdorff distance and Dice similarity analyses show the brain phantom has a high degree of similarity to original MR images and geometry of the patient brain when its MRI was acquired. In conclusion, a method for fabricating MRI and mechanical mimicking brain phantom of patient was developed and the insertion mechanics of the phantoms was evaluated. The phantoms may be applicable for preoperative planning, training of neurology surgeons and validating of MRI-guided surgical robots.

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