Shmatukha Andriy V, Bakker Chris J G
Image Sciences Institute, University Medical Center Utrecht, Utrecht, The Netherlands.
Phys Med Biol. 2006 Sep 21;51(18):4689-705. doi: 10.1088/0031-9155/51/18/015. Epub 2006 Sep 4.
Respiratory induced resonance offset (RIRO) is a periodic disturbance of a magnetic field due to breathing. Such disturbance handicaps the accuracy of the proton resonance frequency shift (PRFS) method of MRI temperature mapping in anatomies situated nearby the lungs and chest wall. In this work, we propose a method capable of minimizing errors caused by RIRO in PRFS temperature maps. In this method, a set of baseline images characterizing RIRO at a variety of respiratory cycle instants is acquired before the thermal treatment starts. During the treatment, the temperature evolution is found from two successive images. Then, the calculated temperature changes are corrected for the additional contribution caused by RIRO using the pre-treatment baseline images acquired at the identical instances of the respiratory cycle. Our method is shown to improve the accuracy and stability of PRFS temperature maps in the presence of RIRO and inter-scan motion in phantom and volunteers' breathing experiments. Our method is also shown to be applicable to anatomies moving during breathing if a proper registration procedure is applied.
呼吸诱导共振偏移（RIRO）是由呼吸引起的磁场周期性干扰。这种干扰会影响位于肺部和胸壁附近解剖结构的MRI温度映射中质子共振频率偏移（PRFS）方法的准确性。在这项工作中，我们提出了一种能够最小化PRFS温度图中由RIRO引起的误差的方法。在该方法中，在热处理开始之前获取一组表征不同呼吸周期时刻RIRO的基线图像。在治疗过程中，从两幅连续图像中发现温度变化。然后，使用在呼吸周期相同时刻获取的预处理基线图像，对由RIRO引起的额外影响进行校正，从而得到计算出的温度变化。在体模和志愿者呼吸实验中，我们的方法在存在RIRO和扫描间运动的情况下，提高了PRFS温度图的准确性和稳定性。如果应用适当的配准程序，我们的方法也适用于呼吸过程中移动的解剖结构。
