Pseudo-continuous arterial spin labelling (pCASL) is the MRI method of choice for non-invasive perfusion measurement in research and clinical practice. Knowledge of the labelling efficiency, α, is essential for accurate quantification of cerebral blood flow (CBF). Typically, a theoretical α value is used, based on an idealistic model and an assumption of spins flowing perpendicularly to the labelling plane. The aim of this work was to investigate the effect of violating this assumption, and to characterize the influence of labelling plane angulation with respect to the vessel direction on labelling efficiency and measured CBF. The effect of labelling plane angulation on labelling efficiency was demonstrated using a numerical simulation of spins at different velocities. Acquisitions from healthy volunteers were used to test the effect of a range of angulation offsets. Additional sub-optimal positions of the labelling plane with respect to the vertebral arteries, at locations where the direction of flow changes significantly from the head-foot direction, were also considered. No significant change in the measured CBF was seen when the labelling plane was angled up to 60° to the labelled vessel or when it was placed in sub-optimal positions. This study shows that in adult subjects, the efficiency of pCASL is robust to the angulation and positioning of the labelling plane beyond the range of potential operator error.

中文翻译：

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标记平面角度和位置对伪连续动脉自旋标记中标记效率和脑血流定量的影响。

伪连续动脉自旋标记 (pCASL) 是研究和临床实践中非侵入性灌注测量的首选 MRI 方法。标记效率 α 的知识对于准确量化脑血流量 (CBF) 至关重要。通常，使用理论 α 值，基于理想模型和自旋垂直于标记平面流动的假设。这项工作的目的是研究违反这一假设的影响，并描述标记平面角度相对于血管方向对标记效率和测量的 CBF 的影响。使用不同速度下的自旋的数值模拟证明了标记平面角度对标记效率的影响。来自健康志愿者的采集被用来测试一系列角度偏移的影响。还考虑了标记平面相对于椎动脉的其他次优位置，在流动方向从头足方向发生显着变化的位置。当标记平面与标记的血管成 60° 角或放置在次优位置时，测量的 CBF 没有显着变化。该研究表明，在成人受试者中，pCASL 的效率对于标记平面的角度和定位超出了潜在的操作员错误范围是稳健的。还考虑了在流动方向从头脚方向发生显着变化的位置。当标记平面与标记的血管成 60° 角或放置在次优位置时，测量的 CBF 没有显着变化。该研究表明，在成人受试者中，pCASL 的效率对于标记平面的角度和定位超出了潜在的操作员错误范围是稳健的。还考虑了在流动方向从头脚方向发生显着变化的位置。当标记平面与标记的血管成 60° 角或放置在次优位置时，测量的 CBF 没有显着变化。该研究表明，在成人受试者中，pCASL 的效率对于标记平面的角度和定位超出了潜在的操作员错误范围是稳健的。