Knollmann F D, Böck J C, Rautenberg K, Beier J, Ebert W, Felix R
Strahlenklinik und Poliklinik Charité, Virchow-Klinikum, Medizinische Fakultät der Humboldt, Universität zu Berlin, Germany.
Invest Radiol. 1998 Sep;33(9):637-43. doi: 10.1097/00004424-199809000-00019.
To determine the effect of particle size of superparamagnetic iron oxide (SPIO) contrast agents on magnetic resonance angiography of the portal venous system.
We studied eight beagle dogs by a T1-weighted 3D turbo-gradient echo magnetic resonance (MR) angiography sequence (TE 4 milliseconds, TR 11 milliseconds, flip angle 25 degrees, coronal imaging plane) before and after administration of either Resovist (SHU555A), a superparamagnetic iron oxide contrast agent with a mean particle size of 60 nm and a relaxivity ratio R2/R1 of approximately 7, or a new ultrasmall superparamagnetic iron oxide (USPIO) contrast agent with a mean particle size of approximately 20 nm and a R2/R1 ratio of approximately 2. Images were acquired on a 1.5-T MR body scanner. Both agents were injected as a peripheral bolus of 40 mumol Fe/kg body weight. Repeated scans were acquired before, immediately after, and 10, 20, 30, and 40 minutes after administration of the agent.
After administration of Resovist, portal venous signal increased to 237% of control immediately after injection, while hepatic parenchymal signal intensity decreased to 86% of control. The maximal CNR increase to 177% was achieved immediately after injection of the agent. After USPIO, portal venous signal increased to 401% of the precontrast value immediately after injection, while hepatic parenchymal signal intensity also increased to 131% of control at this time. Hepatic signal then decreased progressively to 49% of control after 40 minutes. The maximal CNR increase to 326% was achieved 10 minutes after injection of the agent.
It is concluded that superparamagnetic iron oxide particles of different sizes have different R2/R1 ratios and, consequently, different mechanisms of contrast improvement in T1-weighted portal MR angiograms.
确定超顺磁性氧化铁（SPIO）造影剂的粒径对门静脉系统磁共振血管造影的影响。
我们使用T1加权三维快速梯度回波磁共振（MR）血管造影序列（回波时间4毫秒，重复时间11毫秒，翻转角25度，冠状成像平面）对8只比格犬进行研究，在注射Resovist（SHU555A）（一种平均粒径为60纳米、弛豫率R2/R1约为7的超顺磁性氧化铁造影剂）或一种平均粒径约为20纳米、R2/R1比约为2的新型超小超顺磁性氧化铁（USPIO）造影剂之前和之后进行扫描。图像在1.5-T MR体部扫描仪上采集。两种造影剂均以40微摩尔铁/千克体重的外周团注方式注射。在注射造影剂之前、之后立即以及注射后10、20、30和40分钟进行重复扫描。
注射Resovist后，门静脉信号在注射后立即增加至对照值的237%，而肝实质信号强度降至对照值的86%。注射造影剂后立即实现最大对比噪声比（CNR）增加至177%。注射USPIO后，门静脉信号在注射后立即增加至造影前值的401%，而此时肝实质信号强度也增加至对照值的131%。肝信号随后在40分钟后逐渐降至对照值的49%。注射造影剂10分钟后实现最大CNR增加至326%。
得出结论，不同大小的超顺磁性氧化铁颗粒具有不同的R2/R1比，因此在T1加权门静脉MR血管造影中具有不同的对比增强机制。
