Aberdeen Biomedical Imaging Centre, University of Aberdeen, Aberdeen, Scotland, United Kingdom.
Magn Reson Med. 2012 Feb;67(2):531-40. doi: 10.1002/mrm.23021. Epub 2011 Jun 7.
The variation of the native T(1) (T(10)) of different tissues and B(1) transmission-field inhomogeneity at 3 T are major contributors of errors in the quantification of breast dynamic contrast-enhanced MRI. To address these issues, we have introduced new enhancement indices derived from saturation-recovery snapshot-FLASH (SRSF) images. The stability of the new indices, i.e., the SRSF enhancement factor (EF(SRSF)) and its simplified version (EF'(SRSF)) with respect to differences in T(10) and B(1) inhomogeneity was compared against a typical index used in breast dynamic contrast-enhanced MRI, i.e., the enhancement ratio (ER), by using computer simulations. Imaging experiments with Gd-DTPA-doped gel phantoms and a female volunteer were also performed. A lower error was observed in the new indices compared to enhancement ratio in the presence of typical T(10) variation and B(1) inhomogeneity. At changes of relaxation rate (ΔR(1)) of 8 s(-1), the differences between a T(10) of 1266 and 566 ms are <1, 12, and 58%, respectively, for EF(SRSF), EF'(SRSF), and ER, whereas differences of 20, 8, and 51%, respectively, result from a 50% B(1) field reduction at the same ΔR(1). These quantification techniques may be a solution to minimize the effect of T(10) variation and B(1) inhomogeneity on dynamic contrast-enhanced MRI of the breast at 3 T.
在 3T 下，不同组织的固有 T1（T10）变化和 B1 传输场不均匀性是导致乳腺动态对比增强 MRI 定量误差的主要因素。为了解决这些问题，我们引入了新的增强指数，这些指数来自饱和恢复快照 FLASH（SRSF）图像。通过计算机模拟，比较了新指数（即 SRSF 增强因子 EF(SRSF)及其简化版 EF'(SRSF)）与乳腺动态对比增强 MRI 中常用的典型指数——增强比（ER），比较了它们对 T10 和 B1 不均匀性差异的稳定性。还进行了 Gd-DTPA 掺杂凝胶体模和女性志愿者的成像实验。与增强比相比，在存在典型 T10 变化和 B1 不均匀性的情况下，新指数的误差更小。在弛豫率（ΔR1）变化为 8 s-1 的情况下，对于 EF(SRSF)、EF'(SRSF)和 ER，当 T10 分别为 1266ms 和 566ms 时，其差异分别小于 1%、12%和 58%，而当 B1 场减少 50%时，其差异分别为 20%、8%和 51%。在相同的ΔR1 下。这些定量技术可能是一种解决方案，可以最大限度地减少 T10 变化和 B1 不均匀性对 3T 下乳腺动态对比增强 MRI 的影响。
