Petiet Alexandra, Hedlund Laurence, Johnson G Allan
Center for In Vivo Microscopy, Duke University Medical Center, Durham, NC 27710, USA.
J Magn Reson Imaging. 2007 Jun;25(6):1192-8. doi: 10.1002/jmri.20932.
To develop a magnetic resonance histology (MRH) staining and fixation method by immersion to enhance the signal-to-noise ratio (SNR) with a paramagnetic contrast agent permitting microscopic acquisition within a 3-hour scan time.
Methods were optimized for embryonic day 18.5 (E18.5) rat fetuses and imaging at 9.4T with an RF refocused spin-echo pulse sequence (TR/TE = 75 msec/5.2 msec). Fixation/staining was performed by immersion in Bouin's fixative containing varied concentrations of ProHance (from 10:1 to 500:1 Bouin's:ProHance) and for varied immersion durations (up to 24 hours).
The results showed a significant change in T1 and T2 relaxation times as a function of concentration of contrast agent and immersion duration. As the contrast agent penetrated the tissues, T1 was reduced as desired (typically by 10x), but at the same time T2 was profoundly reduced (typically by 3x) due to both protein cross-linking from the fixative and the high concentration of contrast agent. A systematic assessment of this staining protocol showed an increased SNR (by 5x) over that in unstained specimens.
This staining protocol reduced scan time for very-high-resolution images (19.5 microm) to only 3 hours, making MRH a routine tool for evaluating fetal development.
开发一种通过浸泡进行磁共振组织学（MRH）染色和固定的方法，以利用顺磁性造影剂提高信噪比（SNR），从而在3小时扫描时间内实现微观采集。
针对胚胎第18.5天（E18.5）的大鼠胎儿进行方法优化，并使用射频重聚焦自旋回波脉冲序列（TR/TE = 75毫秒/5.2毫秒）在9.4T下成像。通过浸泡在含有不同浓度ProHance（Bouin固定液与ProHance的比例从10:1到500:1）的Bouin固定液中并浸泡不同时间（长达24小时）来进行固定/染色。
结果显示，T1和T2弛豫时间随造影剂浓度和浸泡时间的变化有显著改变。随着造影剂渗透到组织中，T1按预期降低（通常降低10倍），但与此同时，由于固定液中的蛋白质交联和造影剂的高浓度，T2大幅降低（通常降低3倍）。对该染色方案进行的系统评估表明，与未染色的标本相比，SNR提高了5倍。
该染色方案将超高分辨率图像（19.5微米）的扫描时间缩短至仅3小时，使MRH成为评估胎儿发育的常规工具。
