Radiotherapy, Imaging Division, University Medical Center Utrecht, Utrecht, The Netherlands.
NMR Biomed. 2024 Jan;37(1):e5044. doi: 10.1002/nbm.5044. Epub 2023 Sep 29.
In quantitative measurement of the value of tissues, the diffusion of water molecules has been recognized as a confounder. This is most notably so for transient-state quantitative mapping techniques, which allow simultaneous estimation of and . In prior work, apparently conflicting conclusions are presented on the level of diffusion-induced bias on the T estimate. So far there is a lack of studies on the effect of the RF pulse angle sequence on the level of diffusion-induced bias. In this work, we show that the specific transient-state RF pulse sequence has a large effect on this level of bias. In particular, the bias level is strongly influenced by the mean value of the RF pulse angles. Also, for realistic values of the spoiling gradient area, we infer that the diffusion-induced bias is negligible for non-liquid human tissues; yet, for phantoms, the effect can be substantial (15% of the true value) for some RF pulse sequences. This should be taken into account in validation procedures.
在组织定量测量中，水分子的扩散已被认为是一个混杂因素。对于瞬态定量映射技术来说，情况更是如此，因为这种技术可以同时估计 和 。在之前的工作中，关于扩散引起的 T 估计偏差水平，出现了明显相互矛盾的结论。到目前为止，还缺乏关于射频脉冲序列角度对扩散引起的偏差水平影响的研究。在这项工作中，我们表明，特定的瞬态射频脉冲序列对这种偏差水平有很大的影响。特别是，偏差水平受到射频脉冲角度平均值的强烈影响。此外，对于实际的失活梯度区域，我们推断扩散引起的偏差对于非液体人体组织可以忽略不计；然而，对于体模，对于某些射频脉冲序列，这种影响可能很大（真实 值的 15%）。在验证过程中应考虑到这一点。
