Center of Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, 55455, USA.
Contrast Media Mol Imaging. 2014 Mar-Apr;9(2):169-76. doi: 10.1002/cmmi.1568.
In vitro T(1) and T(2) () relaxivities (r(1) and r(2) () ) of Gd-DTPA (GaD) in oxygenated human venous blood (OVB) and aqueous solution (AS) at 3 and 7 T were calculated. GaD concentrations ([GaD]) in OVB and AS were prepared in the range 0-5 mM. All measurements were acquired at 37 ± 2 °C. At both 3 and 7 T, a linear relationship was observed between [GaD] and R(1) in both AS and OVB. At 7 T, r(1) in AS decreased by 7.5% (p = 0.045) while there was a negligible change in OVB. With respect to R(2) () , a linear relationship with [GaD] was only observed in AS, while a more complex relationship was observed in OVB; quadratic below and linear above 2 mM at both field strengths. There was a significant increase of over 4-fold in r(2) () with GaD in OVB at 7 T (for [GaD] above 2 mM, p <<0.01) as compared with 3 T. Furthermore, in comparison to r1 , r2 () in AS was less than 2-fold higher at both field strengths while in OVB it was ~20-fold and ~90-fold higher at 3 and 7 T, respectively. This observation emphasizes the importance of r(2) () knowledge at high magnetic fields, ≥3 T. The comparison between r(1) and r(2) () presented in this work is crucial in the design and optimization of high-field MRI studies making use of paramagnetic contrast agents. This is especially true in multiple compartment systems such as blood, where r(2) () dramatically increases while r1 remains relatively constant with increasing magnetic field strength.
在 3 和 7 T 下，测量了含氧人静脉血（OVB）和水溶液（AS）中 Gd-DTPA（GaD）的体外 T1 和 T2弛豫率（r1 和 r2）。在 OVB 和 AS 中制备 GaD 浓度（[GaD]）范围为 0-5 mM。所有测量均在 37°C±2°C 下进行。在 3 和 7 T 下，在 AS 和 OVB 中均观察到[GaD]与 R1 之间存在线性关系。在 7 T 时，AS 中的 r1 降低了 7.5%（p=0.045），而 OVB 中几乎没有变化。关于 R2（），仅在 AS 中观察到与[GaD]的线性关系，而在 OVB 中观察到更复杂的关系；在两种场强下，低于 2 mM 时为二次关系，高于 2 mM 时为线性关系。与 3 T 相比，在 7 T 时，GaD 在 OVB 中的 r2（）增加了 4 倍以上（对于[GaD]高于 2 mM，p<<0.01）。此外，与 r1 相比，在两种场强下，AS 中的 r2（）都不到 2 倍，而在 OVB 中分别为20 倍和90 倍。这一观察结果强调了在高磁场（≥3 T）下了解 r2（）的重要性。本工作中 r1 和 r2（）的比较对于利用顺磁对比剂进行高场 MRI 研究的设计和优化至关重要。在血液等多腔系统中，情况更是如此，随着磁场强度的增加，r2（）急剧增加，而 r1 相对保持不变。
