因此,TR主要决定图像的T1对比,TR越大,T1权重越小,反之,TR越小,T1权重越大。TR越大,图像的信噪比越高,扫描时间越长。(问题:TR主要决定了谁?) 2、回波时间(TE):是指RF激励脉冲的中心点到回波信号中心点的时间间隔。TE主要决定了图像的T2对比,TE时间越短质子...
如果保持TR不变,增加TE=145ms,数值计算显示,脂肪和水的回波信号幅值完全相等,对应到图像上将出现油水等亮的效果,图4所示。 图4 TR=300ms,TE=145ms时,脂肪和水信号幅值相同,图像上等亮 同理,如果保持TR不变,增加TE=200ms,数值计算显示,脂肪和水的回波信号幅值...
T1加权像短TR、短TE——T1加权像，T1像特点：组织的T1越短，恢复越快，信号就越强；组织的T1越长，恢复越慢，信号就越弱。T2加权像 长TR、长TE——T2加权像， T2像特点：组织的T2越长，恢复越慢，信号就越强；组织的T2越短，恢复越快，信号就越弱。质子密度加权像长TR、短TE——质子密度加权像，图像特...
在SE序列中TR即指相邻两个90。脉冲中点间的时间间隔；在梯度回波TR是指相邻两个小角度脉冲中点之间的时间间隔；在反转恢复序列和快速反转恢复序列中，TR是指相邻两个180。反转脉冲中点间的时间间隔；在单次激发序列中，只有一个90。脉冲激发，TR等于无穷大。2）回波时间(echo time，TE) 是指产生宏观横向磁化矢...
We also examined the time course of the relative BOLD signal change in the activated barrel field during whisker stimulation. The type of anesthesia and the size of the activated barrel field influenced the relative amplitudes of the BOLD activations (Supplementary Fig. S10) while the pretreatments...
This hints that the observed signal change might not solely originate from the hydroxyl exchange of glucose, but as discussed above, also from glucose metabolic products3,6, and glutamate and glutamine3. Moreover, the relaxivity of the DGE effect potentially differs between the in vivo and in ...
As such, care should be taken in the interpretation of RBF measurements, or when comparing longitudinal RBF measurements, in conditions where the haematocrit is likely to change (e.g. anemia). The efficiency of labelling may also vary across subjects and time, especially if there are large ...
values to 0.55 T, our values (mean ± std. dev. over region of interestT1: 491 ms ± 188 ms;T2: 77 ms ± 97 ms) show longer T1 andT2 values as compared to 0.55 T (T1: 359.9 ms,T2: 45.2 ms) [49]. While a prolongation ofT1 with increasing field strength is ...
24 All values reported in this work are the median, for each metric, of all usable voxels in the liver within the image slice. T1 relaxation time reflects extracellular fluid and is characteristic of fibrosis and inflammation. The presence of iron, which can be determined from T2∗ maps, ...
This process required iterative optimizations between scanners, since available values of parameters are often limited across multiple, diverse systems provided by vendors. For example, the echo time value of the functional MRI (TE = 34.4 ms) was the only option that was allowed to be set in ...