Kang Daehun, Yarach Uten, In Myung-Ho, Gray Erin M, Trzasko Joshua D, Jo Hang Joon, Shu Yunhong, Huston John, Bernstein Matt A
Department of Radiology, Mayo Clinic, Rochester, Minnesota.
Department of Radiologic Technology, Faculty of Associated Medical Sciences, Chiang Mai University, Chiang Mai, Thailand.
Magn Reson Med. 2020 Jul;84(1):192-205. doi: 10.1002/mrm.28110. Epub 2019 Dec 4.
To demonstrate the feasibility of pseudo-continuous arterial-spin-labeled (pCASL) imaging with 3D fast-spin-echo stack-of-spirals on a compact 3T scanner (C3T), to perform trajectory correction for eddy-current-induced deviations in the spiral readout of pCASL imaging, and to assess the correction effect on perfusion-related images with high-performance gradients (80 mT/m, 700T/m/s) of the C3T.
To track eddy-current-induced artifacts with Archimedean spiral readout, the spiral readout in pCASL imaging was performed with 5 different peak gradient slew rate (S ) values ranging from 70 to 500 T/m/s. The trajectory for each S was measured using a dynamic field camera and applied in a density-compensated gridding image reconstruction in addition to the nominal trajectory. The effect of the trajectory correction was assessed with perfusion-weighted (ΔM) images and proton-density-weighted images as well as cerebral blood flow (CBF) maps, obtained from 10 healthy volunteers.
Blurring artifact on ΔM images was mitigated by the trajectory correction. CBF values on the left and right calcarine cortices showed no significant difference after correction. Also, the signal-to-noise ratio of ΔM images improved, on average, by 7.6% after correction (P < .001). The greatest improvement of 12.1% on ΔM images was achieved with a spiral readout using S of 300~400 T/m/s.
Eddy currents can cause spiral trajectory deviation, which leads to deformation of the CBF map even in cases of low value S . The trajectory correction for spiral-readout-based pCASL produces more reliable results for perfusion imaging. These results suggest that pCASL is feasible on C3T with high-performance gradients.
证明在紧凑型3T扫描仪（C3T）上使用三维快速自旋回波螺旋堆叠进行伪连续动脉自旋标记（pCASL）成像的可行性，对pCASL成像螺旋读出中涡流引起的偏差进行轨迹校正，并使用C3T的高性能梯度（80 mT/m，700T/m/s）评估对灌注相关图像的校正效果。
为了用阿基米德螺旋读出跟踪涡流引起的伪影，pCASL成像中的螺旋读出以5个不同的峰值梯度转换率（S）值进行，范围从70到500 T/m/s。使用动态场相机测量每个S的轨迹，并除了标称轨迹之外应用于密度补偿网格化图像重建中。从10名健康志愿者获得的灌注加权（ΔM）图像、质子密度加权图像以及脑血流量（CBF）图评估轨迹校正的效果。
通过轨迹校正减轻了ΔM图像上的模糊伪影。校正后左右距状皮质的CBF值无显著差异。此外，校正后ΔM图像的信噪比平均提高了7.6%（P < .001）。使用300~400 T/m/s的S进行螺旋读出时，ΔM图像的改善最大，为12.1%。
即使在S值较低的情况下，涡流也会导致螺旋轨迹偏差，从而导致CBF图变形。基于螺旋读出的pCASL的轨迹校正为灌注成像产生更可靠的结果。这些结果表明，在具有高性能梯度的C3T上pCASL是可行的。
