IHU Liryc, Electrophysiology and Heart Modeling Institute, Fondation Bordeaux Université, Pessac-Bordeaux, France.
Centre de recherche Cardio-Thoracique de Bordeaux, U1045, Univ. Bordeaux, Bordeaux, France.
PLoS One. 2021 May 13;16(5):e0250636. doi: 10.1371/journal.pone.0250636. eCollection 2021.
To propose a MR-thermometry method and associated data processing technique to predict the maximal RF-induced temperature increase near an implanted wire for any other MRI sequence.
A dynamic single shot echo planar imaging sequence was implemented that interleaves acquisition of several slices every second and an energy deposition module with adjustable parameters. Temperature images were processed in real time and compared to invasive fiber-optic measurements to assess accuracy of the method. The standard deviation of temperature was measured in gel and in vivo in the human brain of a volunteer. Temperature increases were measured for different RF exposure levels in a phantom containing an inserted wire and then a MR-conditional pacemaker lead. These calibration data set were fitted to a semi-empirical model allowing estimation of temperature increase of other acquisition sequences.
The precision of the measurement obtained after filtering with a 1.6x1.6 mm2 in plane resolution was 0.2°C in gel, as well as in the human brain. A high correspondence was observed with invasive temperature measurements during RF-induced heating (0.5°C RMSE for a 11.5°C temperature increase). Temperature rises of 32.4°C and 6.5°C were reached at the tip of a wire and of a pacemaker lead, respectively. After successful fitting of temperature curves of the calibration data set, temperature rise predicted by the model was in good agreement (around 5% difference) with measured temperature by a fiber optic probe, for three other MRI sequences.
This method proposes a rapid and reliable quantification of the temperature rise near an implanted wire. Calibration data set and resulting fitting coefficients can be used to estimate temperature increase for any MRI sequence as function of its power and duration.
提出一种磁共振测温方法和相关的数据处理技术，以预测任何其他 MRI 序列下植入导线附近的射频诱导的最大温度升高。
实现了一种动态单次回波平面成像序列，该序列每秒对多个切片进行采集，并具有可调节参数的能量沉积模块。实时处理温度图像，并与侵入性光纤测量进行比较，以评估该方法的准确性。在凝胶中和志愿者的人脑内进行了体内测量，以测量标准偏差。在包含插入导线的体模中测量了不同射频暴露水平下的温度升高，然后是磁共振条件下的起搏器导线。这些校准数据集拟合到一个半经验模型中，允许估计其他采集序列的温度升高。
使用 1.6x1.6mm2 平面分辨率进行滤波后的测量精度在凝胶中以及人脑内均为 0.2°C。在射频加热期间，与侵入性温度测量具有高度一致性（11.5°C 温度升高时的 RMSE 为 0.5°C）。在导线尖端和起搏器导线上分别达到了 32.4°C 和 6.5°C 的温度升高。成功拟合校准数据集的温度曲线后，模型预测的温升与光纤探头测量的温度非常吻合（相差约 5%），适用于另外三种 MRI 序列。
该方法提出了一种快速可靠的方法来量化植入导线附近的温升。校准数据集和由此产生的拟合系数可用于根据其功率和持续时间估计任何 MRI 序列的温升。
