Department of Imaging and Interventional Radiology, The Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, New Territories, Hong Kong, China.
J Magn Reson Imaging. 2012 Apr;35(4):916-25. doi: 10.1002/jmri.22885. Epub 2011 Nov 16.
To present a novel heuristic linear mapping method to individually estimate physiological parameters for Tofts model without T(1) measurement and contrast agent concentration.
A linear relationship was used for k(ep) mapping through a heuristic time intensity curve (TIC) shape factor (TSF). K(trans) maps were subsequently estimated using k(ep) maps and another approximate linear model derived from the Tofts model. Twenty-seven patients with head-and-neck squamous cell carcinoma received dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI). Physiological parameters maps were obtained using this heuristic linear mapping method and compared to the maps obtained by the normal nonlinear least-square fitting with T(1) measurement.
High linearity (R(2) >0.95) between k(ep) and TSF was found in all patients for k(ep) <5/min. This linearity is robust for TSF timepoint selection. The k(ep) maps generated by this linear fitting were highly consistent with those by the normal nonlinear approach (P > 0.05). The K(trans) maps were consistent with the normally derived maps in pattern distribution but the absolute value might be scaled due to the assumption of the reference K(trans) value.
This novel method generates reliable and consistent physiological parameter maps with significantly lower computation complexity than the multiparameter nonlinear fitting. The DCE-MRI scan time can be greatly shortened without T(1) mapping.
提出一种新的启发式线性映射方法，无需 T(1)测量和对比剂浓度，即可单独估计 Tofts 模型的生理参数。
通过启发式时间强度曲线（TIC）形状因子（TSF）对 k(ep)进行线性映射。随后使用 k(ep)图和从 Tofts 模型得出的另一个近似线性模型来估计 k(trans)图。27 例头颈部鳞癌患者接受动态对比增强磁共振成像（DCE-MRI）检查。使用这种启发式线性映射方法获得生理参数图，并与使用 T(1)测量的正常非线性最小二乘拟合获得的图进行比较。
在所有患者中，k(ep) <5/min 时，k(ep)与 TSF 之间均表现出高度线性（R(2)>0.95）。这种线性关系对于 TSF 时间点的选择是稳健的。通过这种线性拟合生成的 k(ep)图与通过正常非线性方法生成的 k(ep)图高度一致（P > 0.05）。K(trans)图在分布模式上与正常推导的图一致，但由于参考 K(trans)值的假设，绝对值可能会缩放。
与多参数非线性拟合相比，该新方法生成的生理参数图具有可靠且一致的结果，且计算复杂度显著降低。无需 T(1)映射即可大大缩短 DCE-MRI 扫描时间。
