Baron Paul, Deckers Roel, de Greef Martijn, Merckel Laura G, Bakker Chris J G, Bouwman Job G, Bleys Ronald L A W, van den Bosch Maurice A A J, Bartels Lambertus W
Image Sciences Institute, University Medical Center Utrecht, Utrecht, The Netherlands.
Magn Reson Med. 2014 Dec;72(6):1580-9. doi: 10.1002/mrm.25063. Epub 2013 Dec 17.
In this study, we aim to demonstrate the sensitivity of proton resonance frequency shift (PRFS) -based thermometry to heat-induced magnetic susceptibility changes and to present and evaluate a model-based correction procedure.
To demonstrate the expected temperature effect, field disturbances during high intensity focused ultrasound sonications were monitored in breast fat samples with a three-dimensional (3D) gradient echo sequence. To evaluate the correction procedure, the interface of tissue-mimicking ethylene glycol gel and fat was sonicated. During sonication, the temperature was monitored with a 2D dual flip angle multi-echo gradient echo sequence, allowing for PRFS-based relative and referenced temperature measurements in the gel and T1 -based temperature measurements in fat. The PRFS-based measurement in the gel was corrected by minimizing the discrepancy between the observed 2D temperature profile and the profile predicted by a 3D thermal model.
The HIFU sonications of breast fat resulted in a magnetic field disturbance which completely disappeared after cooling. For the correction method, the 5th to 95th percentile interval of the PRFS-thermometry error in the gel decreased from 3.8°C before correction to 2.0-2.3°C after correction.
This study has shown the effects of magnetic susceptibility changes induced by heating of breast fatty tissue samples. The resultant errors can be reduced by the use of a model-based correction procedure.
在本研究中，我们旨在证明基于质子共振频率偏移（PRFS）的温度测量对热诱导磁化率变化的敏感性，并提出和评估一种基于模型的校正程序。
为了证明预期的温度效应，使用三维（3D）梯度回波序列监测乳腺脂肪样本在高强度聚焦超声超声处理过程中的场干扰。为了评估校正程序，对仿组织乙二醇凝胶和脂肪的界面进行超声处理。在超声处理过程中，使用二维双翻转角多回波梯度回波序列监测温度，从而在凝胶中进行基于PRFS的相对和参考温度测量，在脂肪中进行基于T1的温度测量。通过最小化观察到的二维温度分布与三维热模型预测的分布之间的差异，对凝胶中基于PRFS的测量进行校正。
乳腺脂肪的高强度聚焦超声超声处理导致磁场干扰，冷却后完全消失。对于校正方法，凝胶中PRFS温度测量误差的第5至95百分位数区间从校正前的3.8°C降至校正后的2.0 - 2.3°C。
本研究显示了乳腺脂肪组织样本加热引起的磁化率变化的影响。通过使用基于模型的校正程序，可以减少由此产生的误差。
