Objective To evaluate the capacity of SWI and DWI in detecting metal ion with MRI in vitro.Methods Solution of Fe3+ , Fe2+ , Cu2+ , Ca2+ with gradient concentration were put into plastic tubes.MR scans, including T2W, T1W,SWI, DWI were performed, and the signal changes of images were analyzed.Results Compared with the signal of pure water, there was no difference of signal in low concentration (0.4 mmol/L) ion solution with SWI and DWI.With higher concentration (40 mmol/L), Fe3+ manifested as significantly low signal and Ca2+ as slight low signal with SWl, while Fe2+and Cu2+ manifested as slight high signal with SWI.DWI was more sensitive in detecting iron than other sequences, presented as signal loss on DWI images.With the gradient concentrations between 0.3125-10 mmol/L, Fe3+ manifested as gradual hypointensity with the increasing concentrations on T2WI, T1WI and SWI images, while Fe2+ and Cu2+ manifested as gradual hyperintensity with the increasing concentrations on SWI.DWI was sensitive to Fe3+ , but had no gradient MR signal changes.Conclusion SWI has no higher sensitivity in detecting free Fe3+ than conventional MRI.Free Fe2+ and Cu2+ show slight hyperintensity on SWI in vitro.DWI is quite sensitive in detecting free iron especially Fe3+.%目的 采用体外实验方法对比SWI和DWI对金属离子的成像特性及敏感性.方法 将等量不同浓度梯度Fe3+、Fe2+、Cu2+、Ca2+溶液装入小塑料管中,分别行常规T2W、T1W、SWI、DWI序列成像,观察信号变化规律,并进行对比.结果与水信号相比较,浓度较低时(0.4 mmol/L),SWI和DWI上各种离子溶液信号无明显差别;当浓度较高时(40 mmol/L),SWI显示Fe3+呈明显低信号,Ca2+呈稍低信号,而Fe2+和Cu2+呈稍高信号;DWI对Fe3+和Fe2+都很敏感,超过T2WI和SWI的敏感性,基本表现为信号缺失.当浓度为0.3125～10 mmol/L时,Fe3+在T2WI、T1WI及SWI图像上的信号随浓度增加而呈梯度减低,T2WI对其敏感性略高于SWI,DWI对Fe3+敏感性相对更高,但梯度性不明显,SWI显示Fe2+和Cu2+信号随浓度增高而呈增高趋势.结论 SWI显示游离Fe3+的敏感性并不高于常规T1WI和T2WI;SWI上Fe2+和Cu2+信号随浓度增加而增强;DWI检测铁离子、特别是Fe3+非常敏感,超过其他序列.
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