Effect of and correction for in-plane myocardial motion on estimates of coronary-volume flow rates.
Effect of and correction for in-plane myocardial motion on estimates of coronary-volume flow rates.
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平面内心肌运动对冠状动脉体积流量估计的影响和校正。
DOI：
10.1002/jmri.1880070508
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发表时间：
1997
期刊：
影响因子：
--
通讯作者：
Mistretta,CA
中科院分区：
文献类型：
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作者：
Frayne,R;Polzin,JA;Mazaheri,Y;Grist,TM;Mistretta,CA
从理论和实验上研究了相位差（PD）和复差分（CD）处理策略对平面内运动的敏感性。速度和容积流速（VFR）估计的误差归因于（a）不同速度编码之间的运动，以及（B）分段k空间采集策略中的运动。发现PD估计对速度编码之间的平面内运动不敏感，而CD VFR估计对该运动敏感。然而，PD估计值受到部分容积效应的影响。开发了一种校正CD（CD '）方案，可最大限度地减少部分容积和平面内运动效应。研究了采用顺序偏移和顺序交错偏移（或中心）相位编码方案的分段k空间采集。发现使用这些技术获得的图像包括模糊和复制伪影。伪影的数量通常随着每段视图数（vps）和平面内速度的增加而增加。发现PD、CD和CD' VFR估计值被这些伪影降低。当在心肌运动的生理范围（>12 cm/s）内取平均值时，顺序偏移相位编码方案通常具有可接受的VFR误差（在4 vps时，CD' VFR误差为7.0%）;然而，在此范围外观察到较大的误差。使用顺序交错相位编码方案在4 vps下获得的VFR估计值不可接受。更准确的VFR测量获得使用修改后的分段PC策略，颠倒了速度和相位编码交错的顺序。使用修正策略获得的加权平均CD' VFR误差为24.5%（对于4 vps）。使用从两个速度编码图像获得的位移信息，获得面内速度的估计值，并用于校正采集的数据。这降低了VFR误差（4 vps时的加权平均CD'误差从24.5%降低到−6.3%）;然而，实施的校正算法可能会在图像中引入其他伪影。
The sensitivities of phase‐difference (PD) and complex‐difference (CD) processing strategies to in‐plane motion were examined theoretically and experimentally. Errors in velocity and volume flow rate (VFR) estimates were attributed to (a) motion between different velocity encodings and, in the case of segmented k‐space acquisition strategies, (b) motion over the segment duration. PD estimates were found to be insensitive to in‐plane motion between velocity encodings, whereas CD VFR estimates were found to be sensitive to this motion. PD estimates, however, were affected by partial volume effects. A corrected CD (CD') scheme was developed that minimizes both partial‐volume and in‐plane motion effects. Segmented k‐space acquisitions with sequential offset and sequential interleaved offset (or centric) phase‐encoding schemes were studied. Images obtained using these techniques were found to include both blurring and replication artifacts. The amount of artifact generally increased with the number of views per segment (vps) and the in‐plane velocity. PD, CD, and CD' VFR estimates were found to be degraded by these artifacts. The sequential offset phase‐encoding scheme generally had acceptable VFR errors (at 4 vps, a CD' VFR error of 7.0%) when averaged over the physiologic range of myocardial motion (>12 cm second−1); however, larger errors were observed outside this range. VFR estimates obtained using the sequential interleaved phase‐encoding scheme at 4 vps were unacceptable. More accurate VFR measurements were obtained using a revised segmented PC strategy, which reversed the order in which the velocity and phase encodings were interleaved. The weighted average CD' VFR error obtained using the revised strategy was 24.5% (for 4 vps). Using displacement information obtained from the two velocity‐encoded images, an estimate of the in‐plane velocity was obtained and used to correct the acquired data. This decreased the VFR error (weighted average CD' error at 4 vps decreased from 24.5% to −6.3%); however, the implemented correction algorithm could potentially introduced other artifacts in the images.