Saharkhiz Hodaiseh, Gharehaghaji Nahideh, Nazarpoor Mahmood, Mesbahi Asghar, Pourissa Masoud
Department of Medical Physics, Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran ; Student Research Committee, School of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran.
Department of Radiology, School of Paramedicine, Tabriz University of Medical Sciences, Tabriz, Iran.
Iran J Radiol. 2014 May;11(2):e12667. doi: 10.5812/iranjradiol.12667. Epub 2014 May 15.
Magnetic nanoparticles have been widely applied in recent years for biomedical applications. Signal intensity (SI) of magnetic resonance (MR) images depends on the concentration of nanoparticles. It is important to find the minimum concentration of iron oxide nanoparticles that produces maximum SI and determines the minimum injection dose for clinical studies.
This study was performed to determine the relationship between the iron oxide nanoparticle concentration and SI using inversion recovery (IR) sequence in T1-weighted MR images.
Different concentrations of carboxydextran-coated iron oxide nanoparticles 20 nm in size were prepared. In vitro MR imaging was performed with inversion times (TI) of 100-400 ms (interval of 20 ms) and IR Turbo-FLASH (Turbo fast low angle shot) pulse sequence using a 1.5 T MRI system. Then the SI produced by each concentration of nanoparticles was measured and the minimum nanoparticle concentration that led to the maximum SI was determined. Coil non-uniformity was also considered for measuring the accurate SI of each image.
The results indicate that SI depended on the concentration of nanoparticles and TI. In addition, SI increased by increasing the TIs ranging from 200 to 400 ms for all studied concentrations. The linear relationship between the nanoparticle concentrations and SI that gave a square correlation coefficient (R(2)) equal to 0.99 was seen up to 76.83 µmol Fe/L in 400 ms for long TI and 239.16 µmol Fe/L in 200 ms for short TI.
TI is an important parameter to consider in the relationship between SI and nanoparticle concentrations. An increase in TI leads to a decrease in the range of linearity.
近年来，磁性纳米颗粒已广泛应用于生物医学领域。磁共振（MR）图像的信号强度（SI）取决于纳米颗粒的浓度。找到能产生最大SI的氧化铁纳米颗粒的最低浓度，并确定临床研究的最低注射剂量非常重要。
本研究旨在利用T1加权MR图像中的反转恢复（IR）序列确定氧化铁纳米颗粒浓度与SI之间的关系。
制备了不同浓度、尺寸为20nm的羧基葡聚糖包被的氧化铁纳米颗粒。使用1.5T MRI系统，采用反转时间（TI）为100 - 400ms（间隔20ms）的IR Turbo-FLASH（快速低角度激发）脉冲序列进行体外MR成像。然后测量每种浓度纳米颗粒产生的SI，并确定导致最大SI的最低纳米颗粒浓度。在测量每个图像的准确SI时也考虑了线圈不均匀性。
结果表明，SI取决于纳米颗粒的浓度和TI。此外，对于所有研究浓度，SI在TI从200ms增加到400ms时会增加。在400ms长TI时，纳米颗粒浓度与SI之间的线性关系在铁浓度高达76.83µmol Fe/L时呈现出平方相关系数（R²）等于0.99；在200ms短TI时，铁浓度高达239.16µmol Fe/L时呈现出该线性关系。
TI是在SI与纳米颗粒浓度关系中需要考虑的一个重要参数。TI的增加会导致线性范围的减小。
