Supplementary Material for: Phantom Safety Assessment of 3 Tesla Magnetic Resonance Imaging in Directional and Sensing Deep Brain Stimulation Devices

INTRODUCTION
MRI is both a crucial clinical and research tool for patients with deep brain stimulation (DBS) devices. However, safety concerns predominantly related to device heating have limited such imaging. Rigorous safety testing has demonstrated that scanning outside of vendor guidelines may be both safe and feasible, unlocking unique opportunities for advanced imaging in this patient population. Currently, however, 3T MRI safety data including advanced MRI sequences in novel directional and sensing DBS devices is lacking.

METHODS
An anthropomorphic phantom replicating bilateral DBS system was used to assess the temperature rise at the electrode tips, implantable pulse generator, and cranial loop during acquisition of routine clinical sequences (3D T1, GRE T2*, T2 FSE) and advanced imaging sequences including functional MRI (fMRI), arterial spin labelling (ASL) and diffusion weighted imaging (DWI). Measures of radiofrequency exposure specific absorption rate (SAR) and root-mean-square value of the MRI effective component of the RF transmission field (B1+rms) were also recorded as an indirect measure of heating. Testing involved both a new directional and sensing DBS device (Medtronic: B30015 leads and Percept PC neurostimulator) and a previous-generation DBS device (Medtronic: 3387 leads and Percept PC neurostimulator) in combination with a state-of-the-art (Siemens MAGNETOM Prisma) and a previous-generation (GE Signa HDxt) 3T MRI scanner.

RESULTS
On the state-of-the-art 3T MRI scanner, the new DBS device produced safe temperature rises with clinically used sequences and fMRI but not with other advanced sequences such as DWI and ASL, which also exceeded B1+rms vendor guidelines (i.e.≤2μT). When scanned on the previous MRI scanner, the recent DBS device produced overall lower and slower temperature rises compared to the previous DBS model. Among the sequences performed on this scanner, several (3D T1, DWI, T2 FSE, and ASL) exceeded the approved SAR vendor limit (

引言
核磁共振成像（MRI）既是深部脑刺激（DBS）装置患者的关键临床和研究工具，亦然。然而，与设备加热相关的主要安全担忧限制了此类成像的应用。严格的安
全测试表明，在厂商指南之外进行扫描既安全又可行，为该患者群体的高级成像提供了独特的机遇。然而，目前缺乏3T MRI安全数据，包括新型方向和传感DBS装置中的高级MRI序列。

方法
本研究采用拟人化的人体模型，模拟双边DBS系统，以评估在采集常规临床序列（3D T1、GRE T2*、T2 FSE）和高级成像序列（包括功能磁共振成像（fMRI）、动脉自旋标记（ASL）和弥散加权成像（DWI））时，电极尖端、植入式脉冲发生器和颅骨环的温度升高情况。同时，还记录了射频暴露的测量值（特定吸收率（SAR）和MRI射频传输场有效成分的均方根值（B1+rms）），作为加热的间接指标。测试涉及新型方向和传感DBS装置（Medtronic：B30015电极和Percept PC神经刺激器）和上一代DBS装置（Medtronic：3387电极和Percept PC神经刺激器），并结合最先进的（Siemens MAGNETOM Prisma）和上一代的（GE Signa HDxt）3T MRI扫描仪进行。

结果
在最先进的3T MRI扫描仪上，新型DBS装置在使用临床序列和fMRI时产生了安全的温度升高，但在其他高级序列（如DWI和ASL）中并未产生，这些序列的B1+rms值也超过了厂商指南（即≤2μT）。当在之前的MRI扫描仪上进行扫描时，与上一代DBS模型相比，新型DBS装置产生的总体温度升高较低且较慢。在此扫描仪上进行的序列中，有几个（3D T1、DWI、T2 FSE和ASL）超过了批准的SAR厂商限制（