Department of Physics, Boston College, Chestnut Hill, MA, USA.
MAGMA. 2012 Feb;25(1):5-14. doi: 10.1007/s10334-011-0272-9. Epub 2011 Jul 29.
To develop an ultrafast MRI-based temperature monitoring method for application during rapid ultrasound exposures in moving organs.
A slice selective 90° - 180° pair of RF pulses was used to solicit an echo from a column, which was then sampled with a train of gradient echoes. In a gel phantom, phase changes of each echo were compared to standard gradient-echo thermometry, and temperature monitoring was tested during focused ultrasound sonications. Signal-to-noise ratio (SNR) performance was evaluated in vivo in a rabbit brain, and feasibility was tested in a human heart.
The correlation between each echo in the acquisition and MRI-based temperature measurements was good (R = 0.98 ± 0.03). A temperature sampling rate of 19 Hz was achieved at 3T in the gel phantom. It was possible to acquire the water frequency in the beating heart muscle with 5-Hz sampling rate during a breath hold.
Ultrafast thermometry via phase or frequency monitoring along single columns was demonstrated. With a temporal resolution around 50 ms, it may be possible to monitor focal heating produced by short ultrasound pulses.
开发一种基于超快 MRI 的温度监测方法，应用于移动器官中快速超声辐射期间。
采用片选 90°-180°一对 RF 脉冲从一列中获取回波，然后用梯度回波序列对其进行采样。在凝胶模型中，比较每个回波的相位变化与标准梯度回波测温法，并在聚焦超声声辐射期间进行温度监测。在兔脑进行了体内信噪比 (SNR) 性能评估，在人心进行了可行性测试。
采集到的每个回波与基于 MRI 的温度测量之间的相关性良好（R = 0.98 ± 0.03）。在凝胶模型中，在 3T 时实现了 19 Hz 的温度采样率。在屏气期间，可以以 5-Hz 的采样率采集到跳动心肌中的水频率。
通过单柱相位或频率监测证明了超快测温法的可行性。该方法的时间分辨率约为 50ms，可能能够监测短超声脉冲产生的焦点加热。
