Erwin L. Hahn Institute for Magnetic Resonance Imaging, University Duisburg-Essen, Essen, North Rhine Westphalia, Germany.
Department of Neurosurgery, University Hospital Essen, University Duisburg-Essen, Essen, North Rhine Westphalia, Germany.
PLoS One. 2023 Oct 11;18(10):e0292666. doi: 10.1371/journal.pone.0292666. eCollection 2023.
The quantity of ultra-high field MRI neuroimaging studies has rapidly increased. This study tests function, safety, and image artifacts of two frequently implanted programmable ventriculo-peritoneal (VP) shunt valves in a 7T MRI system.
All tests were performed using a whole-body 7T MRI system. Three proGAV 2.0 and 3 CODMAN CERTAS® Plus programmable VP-shunt valves were tested in three steps. 1) Deflection angle tests close to the bore opening at the location of a static magnetic field gradient of 3-5 T/m. 2) Valves were fixed on a spherical phantom in 3 positions (a. lateral, b. cranial, c. cranial with 22.5° tilt anteriorly) and assessed for keeping the programmed pressure setting and reprogrammability. 3) Valves were fixed on the phantom and positioned lateral in a radiofrequency head coil. MRI scans were performed for both models, including MPRAGE, GRE and SE sequences.
Deflection angles were moderate (13°, 14°, 13°) for the proGAV valves and close to critical (43°, 43°, 41°) for the CODMAN valves at the test location. Taking a scaling factor of 2-3 for the maximum spatial magnetic field gradient accessible to a patient within the magnet bore into account renders both valves MR unsafe regarding ferromagnetic attraction. The proGAV valves kept the pressure settings in all positions and were reprogrammable in positions a. and b. In position c., reprogrammability was lost. The CODMAN valves changed their pressure setting and reprogrammability was lost in all positions. MR image signal homogeneity was unaltered in the phantom center, artifacts limit the assessability of structures in close vicinity to the valves.
Both tested programmable VP-shunt valves are MR unsafe for 7T systems. Novel programming mechanisms using permanent magnets with sufficient magnetic coercivity or magnet-free mechanisms may allow the development of programmable VP-shunt valves that are conditional for 7T MR systems.
超高场 MRI 神经影像学研究的数量迅速增加。本研究在 7T MRI 系统中测试了两种经常植入的可编程脑室-腹腔（VP）分流阀的功能、安全性和图像伪影。
所有测试均在全身 7T MRI 系统上进行。在三个步骤中测试了三个 proGAV 2.0 和 3 CODMAN CERTAS® Plus 可编程 VP 分流阀。1）在磁场梯度为 3-5 T/m 的接近磁体孔开口的位置进行偏转角测试。2）将阀门固定在球形体模上的 3 个位置（a. 外侧，b. 颅侧，c. 颅侧，前倾角为 22.5°），评估保持程控压力设定值和可重新编程性。3）将阀门固定在体模上并置于射频头线圈的外侧。对两种型号均进行 MRI 扫描，包括 MPRAGE、GRE 和 SE 序列。
在测试位置，proGAV 阀的偏转角适中（13°、14°、13°），而 CODMAN 阀接近临界值（43°、43°、41°）。考虑到患者在磁体孔内可达到的最大空间磁场梯度的缩放系数为 2-3，这两种阀门都存在因铁磁性吸引而导致的磁共振不安全的问题。proGAV 阀在所有位置均保持压力设定值，并且在位置 a 和 b 可重新编程。在位置 c，可重新编程性丧失。CODMAN 阀改变了其压力设定值，并且在所有位置都失去了可重新编程性。在体模中心，磁共振图像信号均匀性未改变，但是伪影限制了对靠近阀门的结构的评估。
在 7T 系统中，两种测试的可编程 VP 分流阀都存在磁共振不安全的问题。使用具有足够磁矫顽力的永磁体或无磁体机制的新型编程机制可能允许开发适用于 7T MR 系统的可编程 VP 分流阀。
