Department of Imaging Physics, The University of Texas M. D. Anderson Cancer Center, 1400 Pressler St., Houston, TX 77030, USA.
NMR Biomed. 2011 Dec;24(10):1414-21. doi: 10.1002/nbm.1707. Epub 2011 Jul 1.
In order to investigate simultaneous MR temperature imaging and direct validation of tissue damage during thermal therapy, temperature-dependent signal changes in proton resonance frequency (PRF) shifts, R(2)* values, and T1-weighted amplitudes are measured from one technique in ex vivo tissue. Using a multigradient echo acquisition and the Stieglitz-McBride algorithm, the temperature sensitivity coefficients of these parameters are measured in each tissue at high spatiotemporal resolutions (1.6 x 1.6 x 4 mm 3,≤ 5sec) at the range of 25-61 °C. Non-linear changes in MR parameters are examined and correlated with an Arrhenius rate dose model of thermal damage. Using logistic regression, the probability of changes in these parameters is calculated as a function of thermal dose to determine if changes correspond to thermal damage. Temperature sensitivity of R(2)* and, in some cases, T1-weighted amplitudes are statistically different before and after thermal damage occurred. Significant changes in the slopes of R(2)* as a function of temperature are observed. Logistic regression analysis shows that these changes could be accurately predicted using the Arrhenius rate dose model (Ω = 1.01 ± 0.03), thereby showing that the changes in R(2)* could be direct markers of protein denaturation. Overall, by using a chemical shift imaging technique with simultaneous temperature estimation, R(2)* mapping and T1-W imaging, it is shown that changes in the sensitivity of R(2)* and, to a lesser degree, T1-W amplitudes are measured in ex vivo tissue when thermal damage is expected to occur. These changes could possibly be used for direct validation of thermal damage in contrast to model-based predictions.
为了研究磁共振（MR）温度成像与热疗过程中组织损伤的直接验证，本研究在离体组织中采用一种技术测量质子共振频率（PRF）偏移、R2* 值和 T1 加权幅度的与温度相关的信号变化，以获得这些参数的温度灵敏度系数。使用多梯度回波采集和斯蒂格勒-麦克布莱德算法，在 25-61°C 的范围内，以高时空分辨率（1.6×1.6×4mm3，≤5s）测量这些参数在每种组织中的温度灵敏度系数。研究了 MR 参数的非线性变化，并将其与热损伤的阿伦尼乌斯剂量模型相关联。使用逻辑回归，计算这些参数变化的概率作为热剂量的函数，以确定变化是否对应于热损伤。在热损伤发生前后，R2和在某些情况下 T1 加权幅度的 MR 参数的温度灵敏度具有统计学差异。观察到 R2随温度变化的斜率发生显著变化。逻辑回归分析表明，这些变化可以使用阿伦尼乌斯剂量模型准确预测（Ω=1.01±0.03），从而表明 R2的变化可能是蛋白质变性的直接标志物。总的来说，通过使用具有同时温度估计的化学位移成像技术、R2映射和 T1-W 成像，表明在离体组织中当预计发生热损伤时，可以测量 R2*和在较小程度上 T1-W 幅度的灵敏度变化。这些变化可能可用于直接验证热损伤，而不是基于模型的预测。
