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目的探讨应用MRI快速电影相位对比序列研究时流速编码大小和方向的正确选择。方法将内径为3 mm塑料管固定在水模中,用高压注射器以平均流速42.46 cm/s向管腔内注射0.9%氯化钠溶液,应用3.0 T高场强MRI扫描仪快速电影相位对比序列进行扫描。分别设置不同的流速编码值(40、60、80、100、120、140、160、180、200、220、240、260、280、300、350、400、500 cm/s)和流速编码方向[S→I;Slice;ALL(oblique S/I Flow);ALLs(oblique R/L Flow、oblique A/P Flow和oblique S/I Flow)]对模型进行扫描,测量实际平均流速及峰值流速。分析流速编码大小和方向的选择对液体实际流速大小和方向的影响。结果当流速编码=40 cm/s及60 cm/s时,管腔内出现混淆伪影;当流速编码=80 cm/s时,混淆伪影消失。当流速编码≥80 cm/s时,测量流速与实际流速间差异有统计学意义(t=2.52,P<0.05)。测量流速与流速编码之间无相关性(P>0.05)。当流速编码=100 cm/s时,所测得的流速与真实值最接近。当流速编码方向分别选择为S→I、Slice、ALL(obligue S/I Flow)、ALLs(obligue R/L Flow,obligue A/P Flow和obligue S/I Flow)时相位图均能正确显示液体流动方向,各方向时所测流速与实际流速间差异无统计学意义(t=0.29,P>0.05)。结论临床血流测量中要根据峰值流速大小选取适当的流速编码值才能确保测量的准确性,不能过大也不能过小;流速编码方向选择Slice,能够满足大多数血流动力学测量的需要。
Objective To explore the correct choice of the size and direction of velocity-velocity codes when using MRI contrast sequences. Methods A plastic tube with an inner diameter of 3 mm was fixed in a water phantom. A 0.9% sodium chloride solution was injected into the lumen through a high pressure syringe at an average flow rate of 42.46 cm / s. A 3.0 T high field strength MRI scanner Scan. Respectively set the different flow rate code values (40,60,80,100,120,140,160,180,200,220,240,260,280,300,350,400,500 cm / s) and the flow rate encoding direction [ ALL (oblique R / L Flow, oblique A / P Flow and oblique S / I Flow)] were used to scan the model and the actual mean flow rate and peak flow rate were measured. Analyze the effect of the choice of flow rate code size and direction on the actual flow rate and direction of the liquid. Results Confusion artifacts appeared in the lumen when the flow velocity codes were 40 cm / s and 60 cm / s, and the aliasing artifacts disappeared when the flow velocity was 80 cm / s. When the flow rate was ≥80 cm / s, the difference between the measured flow velocity and the actual flow velocity was statistically significant (t = 2.52, P <0.05). There was no correlation between measured flow rate and flow rate coding (P> 0.05). When the flow rate code = 100 cm / s, the measured flow rate is closest to the true value. The phase diagram correctly displays the liquid when the flow rate encoding direction is S → I, Slice, ALL (obligue S / I Flow), ALLs (obligue R / L Flow, obligue A / P Flow and obligatory S / I Flow) Flow direction, the measured velocity in all directions and the actual flow rate was no significant difference (t = 0.29, P> 0.05). Conclusion In clinical blood flow measurement, it is necessary to select the appropriate value of the flow rate according to the peak flow rate to ensure the accuracy of the measurement, which can not be too large or too small. Select Slice in the direction of flow coding to meet the needs of most hemodynamic measurements.