Accuracy and precision of time-averaged flow as measured by nontriggered 2D phase-contrast MR angiography, a phantom evaluation
Accuracy and precision of time-averaged flow as measured by nontriggered 2D phase-contrast MR angiography, a phantom evaluation
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DOI：
10.1016/0730-725x(95)02005-e
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发表时间：
1995-01-01
影响因子：
2.5
通讯作者：
Mali, WPTM
中科院分区：
文献类型：
--
作者：
Bakker, CJG;Kouwenhoven, M;Mali, WPTM
本研究的目的是评估时间平均流量的准确性和精密度的非触发二维PC测量。单，双，和三相流模式，在人体血管系统中遇到的建模波形，由计算机控制的流量系统产生。时间平均流速测量传统的2D心脏触发电影PC和非触发2D PC的不同设置的激励翻转角和速度灵敏度。通过重复测量（N = 6）并将结果与精确已知的校准值进行比较，确定准确度和精密度。测量结果显示，触发和非触发采集之间的波形特定偏差取决于速度灵敏度，更强烈地说，在非触发实验的翻转角。这证实了理论上预测的振幅效应优于相位效应。系统误差可以通过减小翻转角和速度灵敏度来减小，尽管以信噪比为代价，因此需要额外的信号平均来保持特定的精度。可达到的准确度似乎是可以接受的，只有一个相对较低的脉动指数的波形。该研究证明了弱脉动流的准确和精确的非触发速度测量的可行性，并指出了一条提高高脉动流的可靠性的途径。
The purpose of this study was to assess the accuracy and precision of time-averaged flow as measured by nontriggered 2D PC. Mono-, bi-, and triphasic flow patterns, modelling waveforms encountered in the human vascular system, were generated by a computer-controlled flow system. Time-averaged flow velocity was measured by conventional 2D cardiac-triggered cine PC and by nontriggered 2D PC for different settings of the excitation flip angle and the velocity sensitivity. Accuracy and precision were determined by repeating the measurements (N = 6) and comparing the results against precisely known calibration values. Measurements revealed waveform-specific deviations between triggered and nontriggered acquisitions that depended on the velocity sensitivity and, more strongly, on the flip angle of the nontriggered experiment. This confirmed the theoretically predicted predominance of amplitude over phase effects. Systematic errors could be reduced by decreasing the flip angle and the velocity sensitivity, although at the expense of signal-to-noise, so that additional signal averaging was required to maintain a specified precision. The attainable accuracy appeared to be acceptable only for waveforms with a relatively low pulsatility index. The study demonstrates the feasibility of accurate and precise nontriggered velocity measurements for weakly pulsatile flow and indicates a route towards improving the reliability for highly pulsatile flow.