Effects of changing from non-accelerated to accelerated MRI for follow-up in brain atrophy measurement
Effects of changing from non-accelerated to accelerated MRI for follow-up in brain atrophy measurement
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DOI：
10.1016/j.neuroimage.2014.11.049
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发表时间：
2015-02-15
期刊：
影响因子：
5.7
通讯作者：
Fox, Nick C.
中科院分区：
文献类型：
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作者：
Leung, Kelvin K.;Malone, Ian M.;Fox, Nick C.
在纵向研究中，稳定的MR采集对于脑萎缩的可靠测量至关重要。最近MRI的一个有吸引力的进展是使用并行成像加速采集（例如，将体积T1加权采集扫描时间从约9分钟减少到5分钟）。在某些研究中，可能故意决定更改为加速采集，而在其他研究中，可能偶尔会意外使用加速采集进行重复扫描。在ADNI中，在每个个体的同一扫描会话中获得非加速和加速扫描。我们使用来自ADNI的422名受试者的扫描，研究了在12个月的时间间隔内从非加速MRI采集变为加速MRI采集时，通过k均值标准化边界位移积分（KN-BSI）和基于变形的形态测量法测量对脑萎缩的影响。使用非加速基线扫描和非加速12个月扫描（即一致采集）以及非加速基线扫描和加速12个月扫描（即变更采集）计算KN-BSI。还对这些扫描进行了基于流体的非刚性配准，以估计脑萎缩率。我们发现对KN-BSI和基于流体的非刚性配准的影响取决于扫描仪制造商。对于KN-BSI，在Philips和Siemens扫描仪中，变更对测量的萎缩率影响很小（从一致采集到变更采集，Philips增加0.051%，Siemens增加-0.035%），而在GE中，变更导致脑萎缩率平均降低0.65%。这可能是由于GE使用IR-FSPGR而不是MP-MRS的非加速和加速扫描中灰质和脑脊液之间的组织对比度存在差异。对于基于液体的非刚性配准，与Philips中的一致性采集相比，变更导致变更采集中的脑萎缩率平均增加0.29%，而在GE和Siemens中，变更对平均萎缩率的影响较小（GE增加0.18%，Siemens增加0.049%）。从非加速基线扫描转移到加速扫描进行随访，可能对计算的萎缩率几乎没有影响，这取决于确切的序列细节和扫描仪制造商;即使是这种性质的意外不一致扫描也可能仍然有用。(C)2014 Elsevier Inc. All rights reserved.
Stable MR acquisition is essential for reliable measurement of brain atrophy in longitudinal studies. One attractive recent advance in MRI is to speed up acquisition using parallel imaging (e.g. reducing volumetric T1-weighted acquisition scan times from around 9 to 5 min). In some studies, a decision to change to an accelerated acquisition may have been deliberately taken, while in others repeat scans may occasionally be accidentally acquired with an accelerated acquisition. In ADNI, non-accelerated and accelerated scans were acquired in the same scanning session on each individual. We investigated the impact on brain atrophy as measured by k-means normalized boundary shift integral (KN-BSI) and deformation-based morphometry when changing from non-accelerated to accelerated MRI acquisitions over a 12-month interval using scans of 422 subjects from ADNI. KN-BSIs were calculated using both a non-accelerated baseline scan and non-accelerated 12-month scans (i.e. consistent acquisition), and a non-accelerated baseline scan and an accelerated 12-month scan (i.e. changed acquisition). Fluidbased non-rigid registration was also performed on those scans to estimate the brain atrophy rate. We found that the effect on KN-BSI and fluid-based non-rigid registration depended on the scanner manufacturer. For KN-BSI, in Philips and Siemens scanners, the change had very little impact on the measured atrophy rate (increase of 0.051% in Philips and -0.035% in Siemens from consistent acquisition to changed acquisition), whereas, in GE, the change caused a mean reduction of 0.65% in the brain atrophy rate. This is likely due to the difference in tissue contrast between gray matter and cerebrospinal fluid in the non-accelerated and accelerated scans in GE, which uses IR-FSPGR instead of MP-RAGE. For fluid-based non-rigid registration, the change caused a mean increase of 0.29% in the brain atrophy rate in the changed acquisition compared with consistent acquisition in Philips, whereas in GE and Siemens, the change had less impact on the mean atrophy rate (increase of 0.18% in GE and 0.049% in Siemens). Moving from non-accelerated baseline scans to accelerated scans for follow-up may have surprisingly little effect on computed atrophy rates depending on the exact sequence details and the scanner manufacturer; even accidentally inconsistent scans of this nature may still be useful. (C) 2014 Elsevier Inc. All rights reserved.