ESWAN序列参数对不同浓度FeSO4溶液成像效果的研究

目的采用体外实验方法研究增强梯度回波T2*加权血管成像(enhanced gradient echo T2star weighted angiography,ESWAN)序列不同参数设置对不同浓度顺磁性离子(Fe2+)的成像效果的影响。方法建立1个不同浓度FeSO4溶液模型,在ESWAN序列上使用不同的回波数、翻转角(flip angle,FA)、带宽(bandwidth,BW)、视野(field of view,FOV)对样本进行重复扫描,观察信号的变化。通过测量样本各层面图像感兴趣区的相位值,分析成像结果与不同参数之间的关系。结果 ESWAN显示Fe2+呈稍高信号。当Fe2+浓度≤0.01 mmol/L时,相位值随浓度增高而增高。当浓度为0.1 mmol/L时,伪影增多,相位值降低。在不同的回波数、FA、BW与FOV参数条件下,相位值的变化缺乏特异性。当浓度≥0.001 mmol/L时,回波数越小,对比度信噪比(contrast to noise ratio,CNR)越大(P<0.05);当Fe2+浓度≤0.01 mmol/L时,CNR随FA的变化差异没有统计学意义(P>0.05);当浓度≥0.001 mmol/L时,宽BW时,CNR值较大(P<0.05),而CNR随FOV的变化差异没有统计学意义(P>0.05)。结论 ESWAN序列不同参数对成像特点的影响各不相同,回波数、BW对图像质量影响较大。

Imaging of FeSO4 solution at different concentrations by ESWAN sequence with different parameters

Objective To determine the effect of different parameter setting in enhanced gradient echo T2 star weighted angiography(ESWAN) sequence on paramagnetic ion(Fe2+)’s imaging at different concentrations in vitro.Methods A model of FeSO4 solution at different concentrations was established.The samples were scanned repeatedly using different numbers of echo time,flip angle(FA),bandwidth(BW) and field of view(FOV) on the ESWAN sequence for signal changes.Relationship between imaging results and different parameters was analyzed by measuring phase values of interested areas in the images at different layers.Results ESWAN displayed slightly high signal of Fe2+.When Fe2+ ’s concentration was no more than 0.01 mmol/L,phase value was increased with the increase of concentrations.When Fe2+ ’s concentration was 0.1 mmol/L,artifacts were increased while phase value was decreased.There was no a certain rule in change of phase values under different conditions of number of echo time,FA,BW,and FOV.When Fe2+ ’s concentration was higher than 0.001 mmol/L,the number of echo time was smaller,and the contrast to noise ratio(CNR) was greater(P<0.05).When Fe2+ ’s concentration was lesser than 0.01 mmol/L,CNR had no statistically significant difference at different FAs(P>0.05).When Fe2+ ’s concentration was higher than 0.001 mmol/L,the CNR value was greater with wider BW(P<0.05),while the CNR difference between different FOVs was not statistically significant(P>0.05).Conclusion The imaging features are various from different ESWAN sequence parameters,and the number of echo time and bandwidth impact most on the image quality.