目的:时间分辨3D相位对比MRI(4D流MRI)的长时间扫描限制了其在临床实践中的常规使用。基于回波平面成像(EPI)的序列和压缩感测可以减少扫描持续时间。我们的目的是确定EPI对4D流MRI扫描持续时间的影响,图像质量,和定量流量指标。
方法:这是一项对15名健康志愿者(所有男性,平均年龄33±5岁)。传统的灵敏度编码(SENSE),有感觉的EPI(EPI),和压缩的SENSE(CS)(缩减因子:分别为6和12)被扫描。扫描持续时间,图像质量的定性指标,和净流量的定量流量参数,最大流速,壁面剪应力(WSS),评估升主动脉的能量损失(EL)。二维相衬电影MRI(2D-PC)被认为是净流量和最大流速的金标准。
结果:与感觉相比,EPI和CS12将扫描持续时间缩短了71%和73%(EPI,4分39秒;CS6,7分29秒;CS12,4分14秒;和SENSE,15分51秒)。EPI的视觉图像质量明显优于SENSE和CS(P<0.001)。使用SENSE获得的净流量,EPI,CS12和2D-PC获得的CS12和CS12的相关性很好(r分别为0.950、0.871和0.850)。然而,用EPI获得的最大速度被显著低估(P<0.010)。EPI的平均WSS明显高于SENSE,CS6和CS12(分别为P<0.001,P=0.040和P=0.012)。EPI的EL显着低于CS6和CS12(分别为P=0.002和P=0.007)。
结论:EPI减少了扫描持续时间,改善视觉图像质量,与CS相比,与更准确的净流量相关。然而,流速,WSS,用EPI和其他序列获得的EL值可能不是直接可比较的。
OBJECTIVE: Prolonged scanning of time-resolved 3D phase-contrast MRI (4D flow MRI) limits its routine use in clinical practice. An echo-planar imaging (EPI)-based sequence and compressed sensing can reduce the scan duration. We aimed to determine the impact of EPI for 4D flow MRI on the scan duration, image quality, and quantitative flow metrics.
METHODS: This was a prospective study of 15 healthy volunteers (all male, mean age 33 ± 5 years). Conventional sensitivity encoding (SENSE), EPI with SENSE (EPI), and compressed SENSE (CS) (reduction factors: 6 and 12, respectively) were scanned.Scan duration, qualitative indexes of image quality, and quantitative flow parameters of net flow volume, maximum flow velocity, wall shear stress (WSS), and energy loss (EL) in the ascending aorta were assessed. Two-dimensional phase-contrast cine MRI (2D-PC) was considered the gold standard of net flow volume and maximum flow velocity.
RESULTS: Compared to SENSE, EPI and CS12 shortened scan durations by 71% and 73% (EPI, 4 min 39 sec; CS6, 7 min 29 sec; CS12, 4 min 14 sec; and SENSE, 15 min 51 sec). Visual image quality was significantly better for EPI than for SENSE and CS (P < 0.001). The net flow volumes obtained with SENSE, EPI, and CS12 and those obtained with 2D-PC were correlated well (r = 0.950, 0.871, and 0.850, respectively). However, the maximum velocity obtained with EPI was significantly underestimated (P < 0.010). The average WSS was significantly higher with EPI than with SENSE, CS6, and CS12 (P < 0.001, P = 0.040, and P = 0.012, respectively). The EL was significantly lower with EPI than with CS6 and CS12 (P = 0.002 and P = 0.007, respectively).
CONCLUSIONS: EPI reduced the scan duration, improved visual image quality, and was associated with more accurate net flow volume than CS. However, the flow velocity, WSS, and EL values obtained with EPI and other sequences may not be directly comparable.