OBJECTIVE Percutaneously-placed cannulated screws are the implant of choice for treatment of skeletal deformity associated with growing children that have spastic cerebral palsy (CP). These patients often require MRI examinations throughout their childhood to evaluate associated comorbidities and frequently for research protocols. There are concerns related to the use of MRI when metallic implants are present. Therefore, this study characterized MRI safety and imaging artifacts for a cannulated screw commonly used for guided growth. METHODS Standardized and well-accepted in vitro techniques were used to evaluate a cannulated screw (4.5 mm diameter x 50 mm length, 316 L stainless steel) for MRI issues. Static magnetic field interactions (i.e., translational attraction and torque) and artifacts were tested at 3-Tesla. Radiofrequency-related heating was assessed at 1.5-Tesla/64-MHz and 3-Tesla/128-MHz using relatively high levels of RF energy (whole-body averaged specific absorption rates of 2.7 W/kg and 2.9-W/kg, respectively). Artifacts were determined using T1-weighted, spin echo and gradient echo pulse sequences. RESULTS The cannulated screw exhibited minor magnetic field interactions (14° deflection angle, no torque). The highest temperature changes at 1.5-Tesla/64-MHz and 3-Tesla/128-MHz MRI were 2.1 °C and 2.4 °C, respectively. The maximum artifact size on a gradient echo sequence extended 20 mm relative to the dimensions of the implant. CONCLUSIONS The in vitro tests performed on the cannulated screw indicated that there were no substantial concerns with respect to the use of 1.5- and 3-Tesla MRI. Therefore, a patient with this cannulated screw can safely undergo MRI by following specific conditions to ensure safety.

中文翻译：

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评估了用于引导生长手术的空心螺钉的MRI安全性和成像伪影。

目的经皮置入空心螺钉是治疗与成长性痉挛性脑瘫儿童相关的骨骼畸形的首选植入物。这些患者在整个童年时期通常都需要进行MRI检查，以评估相关的合并症，并经常进行研究。当存在金属植入物时，与MRI的使用有关。因此，本研究对通常用于引导生长的空心螺钉的MRI安全性和成像伪像进行了表征。方法采用标准化且广为接受的体外技术评估MRI问题的空心螺钉（直径4.5 mm x长度50 mm，316 L不锈钢）。在3-Tesla上测试了静磁场相互作用（即，平移吸引力和扭矩）和伪影。使用相对较高水平的RF能量（分别为2.7 W / kg和2.9 W / kg的全身平均比吸收率）在1.5-Tesla / 64-MHz和3-Tesla / 128-MHz下评估与射频相关的加热）。使用T1加权，自旋回波和梯度回波脉冲序列确定伪像。结果空心螺钉显示出较小的磁场相互作用（偏转角为14°，无扭矩）。1.5-Tesla / 64-MHz和3-Tesla / 128-MHz MRI的最高温度变化分别为2.1°C和2.4°C。梯度回波序列上的最大伪影尺寸相对于植入物的尺寸扩展了20 mm。结论在空心螺钉上进行的体外测试表明，使用1.5特斯拉和3特斯拉MRI并没有实质性的担忧。所以，