Hybrid referenceless and multibaseline subtraction MR thermometry for monitoring thermal therapies in moving organs
Hybrid referenceless and multibaseline subtraction MR thermometry for monitoring thermal therapies in moving organs
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DOI：
10.1118/1.3475943
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发表时间：
2010-09-01
期刊：
影响因子：
3.8
通讯作者：
Pauly, Kim Butts
中科院分区：
文献类型：
--
作者：
Grissom, William A.;Rieke, Viola;Pauly, Kim Butts
目的：使用质子共振频率（PRF）偏移的磁共振测温法是一种很有前途的指导热消融的技术。对于运动器官（如肝脏和心脏）的温度监测，必须解决运动问题。已经提出了多基线减影技术，其使用覆盖呼吸和心动周期的基线图像库。然而，由于肺和横膈膜运动引起的主要场移位可在多基线减影中引起大的不准确性。基于多项式相位回归的无参考温度测量方法不受运动和磁化率变化的影响。虽然无参考方法可以准确地估计器官内的温度，但一般来说，器官/组织界面处的背景相位需要大的多项式阶数来拟合，从而导致加热区域本身将由多项式拟合并且热剂量将被低估的危险增加。在本文中，一种混合的方法在运动器官的PRF测温相结合的优势referenceless和多基线thermometry.Methods：混合图像模型假设三个源有助于图像相位在热处理：背景解剖相，空间平滑的相位偏差，和焦点，热引起的相移。新的模型和温度估计算法在正常志愿者的心脏和肝脏中进行了测试，在移动体模HIFU加热实验中，以及在热消融的数值模拟中。结果进行了比较，多基线和referenceless方法单独。结果：混合方法允许在体内温度估计在肝脏和心脏的温度不确定性较低的多基线和referenceless方法相比。运动体模HIFU实验表明，该方法准确地估计温度在运动过程中存在的平滑的主要领域的转变。数值模拟说明了该方法的算法参数和热点features.Conclusions的敏感性：这种新的混合方法MR测温在运动的器官结合了多基线减法和无参考测温的优势，克服了他们的根本弱点。(C)2010年美国医学物理学家协会。[DOI：10.1118/1.3475943]
Purpose: Magnetic resonance thermometry using the proton resonance frequency (PRF) shift is a promising technique for guiding thermal ablation. For temperature monitoring in moving organs, such as the liver and the heart, problems with motion must be addressed. Multi-baseline subtraction techniques have been proposed, which use a library of baseline images covering the respiratory and cardiac cycle. However, main field shifts due to lung and diaphragm motion can cause large inaccuracies in multi-baseline subtraction. Referenceless thermometry methods based on polynomial phase regression are immune to motion and susceptibility shifts. While referenceless methods can accurately estimate temperature within the organ, in general, the background phase at organ/tissue interfaces requires large polynomial orders to fit, leading to increased danger that the heated region itself will be fitted by the polynomial and thermal dose will be underestimated. In this paper, a hybrid method for PRF thermometry in moving organs is presented that combines the strengths of referenceless and multi-baseline thermometry.Methods: The hybrid image model assumes that three sources contribute to image phase during thermal treatment: Background anatomical phase, spatially smooth phase deviations, and focal, heat-induced phase shifts. The new model and temperature estimation algorithm were tested in the heart and liver of normal volunteers, in a moving phantom HIFU heating experiment, and in numerical simulations of thermal ablation. The results were compared to multi-baseline and referenceless methods alone.Results: The hybrid method allows for in vivo temperature estimation in the liver and the heart with lower temperature uncertainty compared to multi-baseline and referenceless methods. The moving phantom HIFU experiment showed that the method accurately estimates temperature during motion in the presence of smooth main field shifts. Numerical simulations illustrated the method's sensitivity to algorithm parameters and hot spot features.Conclusions: This new hybrid method for MR thermometry in moving organs combines the strengths of both multi-baseline subtraction and referenceless thermometry and overcomes their fundamental weaknesses. (C) 2010 American Association of Physicists in Medicine. [DOI: 10.1118/1.3475943]