Department of Oncologic Imaging, National Cancer Center, Singapore 169610, Singapore.
Magn Reson Med. 2011 Sep;66(3):886-92. doi: 10.1002/mrm.22868. Epub 2011 Apr 4.
Recent dynamic contrast-enhanced MRI studies using the adiabatic tissue homogeneity model have highlighted potential issues of difficulty in convergence during data-fitting and reduced parameter precision, due to discontinuities in the adiabatic tissue homogeneity model. This study presents two solutions (an analytic approach and a discrete correction method) to such convergence problems and show that these problems can be attributed to an inaccurate approximation of the convolution integral based on the standard trapezoidal quadrature. It is further explained that such issues of discontinuity in the impulse residue function do not pertain only to the adiabatic tissue homogeneity model, but are generic to all tracer kinetic models, if the difference in bolus arrival time between the arterial input and tissue voxels were to be accounted for simultaneously during model-fitting.
最近使用非绝热组织均匀性模型的动态对比增强 MRI 研究强调了在数据拟合过程中可能存在的收敛困难问题，以及由于非绝热组织均匀性模型的不连续性导致参数精度降低的问题。本研究提出了两种解决方案（解析方法和离散校正方法）来解决这些收敛问题，并表明这些问题可以归因于基于标准梯形求积的卷积积分的不准确近似。进一步解释说，脉冲残差函数中的不连续性问题不仅存在于非绝热组织均匀性模型中，如果在模型拟合过程中同时考虑动脉输入和组织体素之间的造影剂到达时间差，那么它也普遍存在于所有示踪剂动力学模型中。
