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【medical-news】钙离子对比可以提高磁共振分子影
12/6/2006
By: Shalmali Pal
http://www.auntminnie.com/index.asp?Sec=sup&Sub=mri&Pag=dis&ItemId=73881
A calcium-sensitive contrast agent, married with superparamagnetic iron oxide particles (SPIO), could make MR studies of the brain on a molecular level feasible, according to researchers from the Massachusetts Institute of Technology in Cambridge.
Functional MRI (fMRI) techniques can capture blood flow in the brain, but these hemodynamic changes occur seconds after the neuron has fired. As a result, current techniques are not equipped to measure precise neuronal activity. Optical imaging, which is sophisticated enough to capture this activity, still suffers from a restricted field-of-view.
"MRI studies of calcium dynamics could, in principle, complement optical approaches by offering both greatly expanded coverage and depth penetration in vivo," wrote Tatjana Atanasijevic, a graduate student in the departments of nuclear science and engineering at MIT. Her co-authors included Alan Jasanoff, Ph.D., an associate member of the McGovern Institute for Brain Research at MIT (Proceedings of the National Academy of Sciences, October 3, 2006, Vol. 103:50, 1407-1412).
For this study, the group used a 4.7-tesla research scanner (Avance, Bruker BioSpin, Billerica, MA) and SPIO nanoparticles coated with a streptavidin protein. To construct the MR calcium sensors, two molecular binding agents, biotin-CaM and biotin-M13, were produced and attached to the SPIOs.
The imaging protocol for the mica samples consisted of a spin-echo pulse sequence with multiecho acquisition to collect images at several parallel echo times, the authors explained.
According to the results, "the images indicate that the MRI signal ... is significantly greater when calcium is present, and that the effect is mot pronounced at longer echo time while still maintaining excellent signal-to-noise ratio," they stated. "MRI measurements collectively show that calcium-induced clustering of our sensors corresponds to decreases in T2 relaxivity (producing greater T2-weighted MRI signal), in contrast to results obtained with smaller mononuclear iron oxides."
Jasanoff's group is currently working on noninvasive ways to deliver this calcium sensor to brain cells in vivo in small animal studies.
By Shalmali Pal
AuntMinnie.com staff writer
December 6, 2006 本人已认领该文编译，48小时后若未提交译文，请其他战友自由认领。 Calcium contrast boosts T2-weighted signal in molecular MRI
12/6/2006
By: Shalmali Pal
http://www.auntminnie.com/index.asp?Sec=sup&Sub=mri&Pag=dis&ItemId=73881
钙离子对比可以提高磁共振分子影像学的T2信号
A calcium-sensitive contrast agent, married with superparamagnetic iron oxide particles (SPIO), could make MR studies of the brain on a molecular level feasible, according to researchers from the Massachusetts Institute of Technology in Cambridge.
剑桥麻省理工学院的一项研究表明，一种钙离子敏感造影剂与超顺磁性氧化铁分子(SPIO)相结合，使得在分子水平上对大脑进行磁共振研究成为可能。
Functional MRI (fMRI) techniques can capture blood flow in the brain, but these hemodynamic changes occur seconds after the neuron has fired. As a result, current techniques are not equipped to measure precise neuronal activity. Optical imaging, which is sophisticated enough to capture this activity, still suffers from a restricted field-of-view.
机能磁共振成像技术能够捕捉大脑血流情况，但神经元一经激活，血流就会在瞬息之间发生动态改变。目前的成像技术还没有成熟到能够精确测定神经元的活性。光学成像技术能够成功捕捉神经元的活性状况，但视野范围还很局限。
"MRI studies of calcium dynamics could, in principle, complement optical approaches by offering both greatly expanded coverage and depth penetration in vivo," wrote Tatjana Atanasijevic, a graduate student in the departments of nuclear science and engineering at MIT. Her co-authors included Alan Jasanoff, Ph.D., an associate member of the McGovern Institute for Brain Research at MIT (Proceedings of the National Academy of Sciences, October 3, 2006, Vol. 103:50, 1407-1412).
“基本上，针对钙离子动态学的MRI研究通过非常广泛的体内扫描范围和深度窥悉，弥补了光学成像技术的不足。”麻省理工学院原子工程系的研究生Tatjana Atanasijevic对此写道。该研究报告的合著者还包括Alan Jasanoff博士，一位麻省理工学院McGovern大脑研究所的准会员。（国家科学院学报， 2006 年 10月 3日，第 103卷：50, 1407-1412）
For this study, the group used a 4.7-tesla research scanner (Avance, Bruker BioSpin, Billerica, MA) and SPIO nanoparticles coated with a streptavidin protein. To construct the MR calcium sensors, two molecular binding agents, biotin-CaM and biotin-M13, were produced and attached to the SPIOs.
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