Wlodarczyk W, Hentschel M, Wust P, Noeske R, Hosten N, Rinneberg H, Felix R
Clinic for Radiation Medicine, Charité Medical School-Campus Virchow-Klinikum, Berlin, Germany.
Phys Med Biol. 1999 Feb;44(2):607-24. doi: 10.1088/0031-9155/44/2/022.
Non-invasive detection of small temperature changes (< 1 degree C) is pivotal to the further advance of regional hyperthermia as a treatment modality for deep-seated tumours. Magnetic resonance (MR) thermography methods are considered to be a promising approach. Four methods exploiting temperature-dependent parameters were evaluated in phantom experiments. The investigated temperature indicators were spin-lattice relaxation time T1, diffusion coefficient D, shift of water proton resonance frequency (water PRF) and resonance frequency shift of the methoxy group of the praseodymium complex (Pr probe). The respective pulse sequences employed to detect temperature-dependent signal changes were the multiple readout single inversion recovery (T One by Multiple Read Out Pulses; TOMROP), the pulsed gradient spin echo (PGSE), the fast low-angle shot (FLASH) with phase difference reconstruction, and the classical chemical shift imaging (CSI). Applying these sequences, experiments were performed in two separate and consecutive steps. In the first step, calibration curves were recorded for all four methods. In the second step, applying these calibration data, maps of temperature changes were generated and verified. With the equal total acquisition time of approximately 4 min for all four methods, the uncertainties of temperature changes derived from the calibration curves were less than 1 degree C (Pr probe 0.11 degrees C, water PRF 0.22 degrees C, D 0.48 degrees C and T1 0.93 degrees C). The corresponding maps of temperature changes exhibited slightly higher errors but still in the range or less than 1 degree C (0.97 degrees C, 0.41 degrees C, 0.70 degrees C, 1.06 degrees C respectively). The calibration results indicate the Pr probe method to be most sensitive and accurate. However, this advantage could only be partially transferred to the thermographic maps because of the coarse 16 x 16 matrix of the classical CSI sequence. Therefore, at present the water PRF method appears to be most suitable for MR monitoring of small temperature changes during hyperthermia treatment.
对小温度变化（<1摄氏度）进行无创检测对于将区域热疗作为深部肿瘤的一种治疗方式的进一步发展至关重要。磁共振（MR）热成像方法被认为是一种很有前景的方法。在体模实验中评估了四种利用温度相关参数的方法。所研究的温度指标是自旋晶格弛豫时间T1、扩散系数D、水质子共振频率（水PRF）的偏移以及镨配合物甲氧基的共振频率偏移（Pr探针）。用于检测温度相关信号变化的各自脉冲序列分别是多次读出单次反转恢复序列（TOMROP）、脉冲梯度自旋回波序列（PGSE）、具有相位差重建的快速低角度激发序列（FLASH）以及经典化学位移成像序列（CSI）。应用这些序列，实验分两个独立且连续的步骤进行。第一步，记录所有四种方法的校准曲线。第二步，应用这些校准数据生成并验证温度变化图。对于所有四种方法，总采集时间均约为4分钟，从校准曲线得出的温度变化不确定度小于1摄氏度（Pr探针为0.11摄氏度，水PRF为0.22摄氏度，D为0.48摄氏度，T1为0.93摄氏度）。相应的温度变化图显示的误差略高，但仍在1摄氏度范围内或小于1摄氏度（分别为0.97摄氏度、0.41摄氏度、0.70摄氏度、1.06摄氏度）。校准结果表明Pr探针方法最灵敏且准确。然而，由于经典CSI序列的16×16粗糙矩阵，这一优势只能部分地转移到热成像图上。因此，目前水PRF方法似乎最适合在热疗过程中对小温度变化进行MR监测。
