McDannold N, Hynynen K, Jolesz F
Department of Radiology, Division of MRI, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA.
J Magn Reson Imaging. 2001 Mar;13(3):421-7. doi: 10.1002/jmri.1061.
MRI-derived thermometry based on the temperature-dependence of the proton resonant frequency (PRF) is extremely sensitive to changes in tissue unrelated to temperature changes, including tissue swelling. This study investigated the maximum amount of time that this phase-subtraction-based method can be used to accurately monitor temperature changes in vivo. Long-duration focused ultrasound sonications were delivered in rabbit thigh muscle with a phased-array transducer, and the time that tissue swelling began was monitored. Tissue swelling began to occur at about one minute. The temperature correlated well with an implanted thermocouple up to this time. After this time, severe artifacts in the phase-difference maps were observed. The thermal dose model predicted the extent of tissue damage well for subsequent one minute sonications. These results will have implications for MRI guidance of thermal therapies with long exposure times.
基于质子共振频率（PRF）对温度的依赖性的MRI测温对与温度变化无关的组织变化（包括组织肿胀）极为敏感。本研究调查了这种基于相位减法的方法可用于准确监测体内温度变化的最长时间。使用相控阵换能器在兔大腿肌肉中进行长时间聚焦超声照射，并监测组织肿胀开始的时间。组织肿胀在大约一分钟时开始出现。在此之前，温度与植入的热电偶相关性良好。在此之后，在相位差图中观察到严重伪影。热剂量模型对随后一分钟的超声照射所造成的组织损伤程度预测良好。这些结果将对长时间暴露的热疗的MRI引导产生影响。
