MRI检查中骨科金属植入材料的致热效应

Thermal effect of orthopedics metal implants in magnetic resonance imaging examination

目的MRI中磁场的激发作用会引起骨科金属植入材料的致热效应,可能存在潜在的安全风险,故需进一步研究以确定金属植入材料在MRI检查中的安全性。方法选择不锈钢(S,型号00Cr17Ni14Mo3)、钛合金(TC20,型号Ti-6Al-7Nb),钛合金(TC4,型号Ti-6Al-4V)和纯钛(Ti)4种骨科金属植入材料。使用组织补偿液模拟人体组织环境,搭建测温平台,使用标定过的热敏电阻作为温度传感器,测试其在磁场强度为1.5T和3.0TMRI检查环境下的温度变化,将环境温度变化作为对照组。使用数据采集系统和LabVIEW软件采集记录数据,利用MATLAB处理数据,绘制不同金属植入材料,不同磁场强度下金属植入材料温度与环境温度的时间温度变化曲线,进行数据分析。结果热敏电阻的标定结果显示其阻值和温度有高度的线性负相关性。相对环境温度,在1.5T MRI的同一扫描序列下,不锈钢(S)、钛合金(TC20)、钛合金(TC4)和纯钛(Ti)分别升温0.94℃、1.81℃、2.10℃和1.22℃;3.0T MRI设备扫描下,4种材料分别升温0.99℃、3.03℃、2.27℃和1.96℃。结论MRI设备的致热效应与金属植入材料种类密切相关,相同的MRI扫描条件下,钛合金植入材料的致热效应最明显,纯钛材料次之,不锈钢材料最弱;另外,MRI设备的场强越大,金属植入材料的致热效应越明显。

Objective To study the safety of metal implants in magnetic resonance imaging(MRI) examination, because magnetic field excitation in MRI causes thermal effect of orthopedic metal implants, which may be the potential safety risk.Methods Four kinds of orthopedics metal implants, stainless steel(S, 00Cr17Ni14Mo3), titanium alloy-1(TC20, Ti-6Al-7Nb),titanium alloy-2(TC4, Ti-6Al-4V) and pure titanium(Ti) were selected. Human tissue environment was simulate using tissue compensation fluid, and temperature measurement platform were built, and calibrated thermal resistors were used as temperature sensors. The temperature curves of metal implant plates under magnetic field intensity of 1.5 T and 3.0 T MRI scanning were detected respectively, and environment temperature was tested as control group data. The temperature data was collected and recorded by data acquisition system and LabVIEW software. MATLAB was used to process data to draw time temperature curve of material and environment temperature for different materials at two magnetic field intensity, and the data was analyzed. Results The calibration results of thermal resistors showed that there was high negative linear correlation between resistance and temperature. As compared with the background, temperature of metal implant plates of S, TC20, TC4and Ti increased by 0.94 ℃, 1.81 ℃, 2.10 ℃ and 1.22 ℃ under 1.5 T MRI, and increased by 0.99 ℃, 3.03 ℃, 2.27 ℃ and1.96 ℃ under 3.0 T MRI, respectively. Conclusion It is demonstrated that thermal effect is closely related to material type of the implant. Under the same MRI scanning condition, the temperature effect of titanium implant material is the most obvious,followed by pure titanium, and that of stainless steel is the weakest. Meanwhile, the greater the field intensity of MRI equipment, the more obvious the thermal effect of implants.