適用於水腦症腦室引流管放置之影像巡航系統

Abstract

背景介紹：水腦症是由於腦脊髓液不正常堆積而導致顱內壓增大的疾病，目前側腦室腹膜腔引流術為治療水腦症病患最常接受的手術，手術中會將腦室針穿刺進入側腦室中並將引流管沿著腦室針穿刺之路徑放入腦室，目的是將過多的腦脊髓液引流至腹膜腔之中。經過幾十年來手術技術以及科技的進步，手術後病患在一年之內發生引流系統故障的機率仍高達40%左右。近年來逐漸有學者開始將影像巡航系統使用於水腦症腦室引流管放置手術，期望減少引流系統因放置位置不理想所引起之併發症。然而，目前臨床用之巡航系統仍有手術時間延長與定位器滅菌消毒過程繁複的缺點與疑慮尚待改善。 研究目的：發展一影像巡航之'定位系統'用於水腦症腦室引流管放置手術，在手術過程中輔助醫師進行腦室穿刺，具有快速且準確地將引流管放置於腦室之中的優勢。本研究設計了一耳戴型定位器，該定位器具有快速操作以及重現性，並可分離感染區與手術區以避免手術感染之優點。本研究之目的在探討該定位器之重現性與準確度。 材料與方法：用耳道灌模技術開發設計具有重現性之耳戴型定位器，本研究將耳戴型定位器配戴在模擬器以及四位受試者的耳朵上，重覆配戴耳戴型定位器八次，利用接觸式量測評估重覆配戴之重現性。影像巡航系統之開發包括三部份，第一部份設計一穿刺導引夾具裝設在方位追蹤器上，輔助腦室針穿刺過程；第二部份使用實驗室自製之影像巡航軟體，搭配耳戴型定位器，透過三珠定位技術，快速完成註冊動作；第三部份製作一模擬器，適用於水腦症腦室引流管放置手術過程模擬，此模擬器包含一有皮膚柔軟度之假人頭，並在假人頭右側裝上一仿真假耳朵，可將耳戴型定位器配戴至假人頭上，並在約為腦室之位置埋入目標物。最後，透過模擬器進行體外精度測試，評估此系統之系統誤差以及操作性誤差。 實驗結果：將耳戴型定位器配戴在模擬器的耳朵上，其重現性約0.3釐米、角度誤差約0.4度。此影像巡航系統，透過模擬器進行影像導引穿刺之過程，其誤差約在2.97 ± 1.14釐米、角度誤差約2.6 ± 1.2度，而該系統之系統誤差約0.9 ± 0.35釐米、角度誤差約0.7 ± 0.6度。四位受試者之耳戴型定位器的重現性測試結果皆相似，耳戴型定位器重現性約0.9 ± 0.25釐米、角度誤差約1 ± 0.48度。 結論： 耳戴型定位器之重現性應可適用於水腦症腦室引流管放置手術；透過模擬器驗證，此影像巡航系統的誤差約在3釐米、角度誤差約2.6度，該精確度應可適用於水腦症腦室引流管放置之手術過程。

Introduction. Hydrocephalus is caused by abnormal accumulation of excessive cerebrospinal fluid (CSF) in ventricle or brain cavity, with the consequence of increased intracranial pressure. The ventriculoperitoneal shunt (VP shunt) is the most frequently used surgery method for the hydrocephalus patient. In order to drain the excessive CSF to peritoneal cavity, a ventricular catheter is placed into lateral ventricle alone the trajectory created by ventricular needle penetration. The standard protocol of placing the catheter is the free-hand maneuver with surgeon’s experience. Despite with the improvement of surgical techniques and technology, shunt failure rate still remain 40% within first year after surgery. The use of image-guided navigation system for hydrocephalus ventricular shunt placement procedure is thus applied to decrease the inappropriate placement of catheter. Nevertheless, extra operation time and the difficulties of sterilization of registration device are two major problems for navigation system. Objective. This study aims to develop a registration device of image-guided navigation system for hydrocephalus ventricular shunt placement procedure. The system can assist surgeons with ventricular needle penetration and provide accurate shunt placement at minimal time. Material and method. In this study, an ear-based registration device (EBR) was developed using ear-mold impression technique. The patient wears EBR during CT scanning and operation procedures, hence the wearing repeatability is critical for the accuracy of subsequent imaged-guided shunt placement. Therefore, the repeatability test of EBR wearing was conducted to evaluate the proposed registration device. A Microscribe measurement system along with five individual EBRs manufactured for one phantom subject and four human subjects was used for the test. To evaluate the accuracy performance of EBR, including system and operation errors, used in hydrocephalus ventricular shunt placement, a head phantom with human-like soft ear and skin was developed. An in-house navigation system with three-point registration procedure was used for the accuracy tests. The system accuracy test was conducted to evaluate the inherent error of the navigation system with EBR in placed; while the operation accuracy test was performed to explore the overall error of navigated shunt placement procedure ex vivo. Result. The repeatability of the EBR device was 0.3 mm in distance and 0.4 degree in angle for the phantom subject. The repeatability of the EBR device for the four human subjects was 0.9 ± 0.25 mm and 1 ± 0.48 degree in average. The system error was 0.9 ± 0.35 mm and 0.7 ± 0.6 degree, and the operation error was 2.97 ± 1.14 mm and 2.6 ± 1.2 degree. Conclusion. The ear-based registration device may be an ideal candidate for hydrocephalus shunt placement procedure. The errors of this image-guided navigation system are approximately 3 mm in distance and 3 degree in angle. The accuracy of developed system is sufficient for hydrocephalus shunt placement procedure.