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Oxygen extraction fraction mapping with multi-parametric quantitative BOLD MRI: reduced transverse relaxation bias using 3D-GraSE imaging
NeuroImage ( IF 5.7 ) Pub Date : 2020-10-01 , DOI: 10.1016/j.neuroimage.2020.117095
Stephan Kaczmarz 1 , Fahmeed Hyder 2 , Christine Preibisch 3
Affiliation  

Magnetic resonance imaging (MRI)-based quantification of the blood-oxygenation-level-dependent (BOLD) effect allows oxygen extraction fraction (OEF) mapping. The multi-parametric quantitative BOLD (mq-BOLD) technique facilitates relative OEF (rOEF) measurements with whole brain coverage in clinically applicable scan times. Mq-BOLD requires three separate scans of cerebral blood volume and transverse relaxation rates measured by gradient-echo (1/T2*) and spin-echo (1/T2). Although the current method is of clinical merit in patients with stroke, glioma and internal carotid artery stenosis (ICAS), there are relaxation measurement artefacts that impede the sensitivity of mq-BOLD and artificially elevate reported rOEF values. We posited that T2-related biases caused by slice refocusing imperfections during rapid 2D-GraSE (Gradient and Spin Echo) imaging can be reduced by applying 3D-GraSE imaging sequences, because the latter requires no slice selective pulses. The removal of T2-related biases would decrease overestimated rOEF values measured by mq-BOLD. We characterized effects of T2-related bias in mq-BOLD by comparing the initially employed 2D-GraSE and two proposed 3D-GraSE sequences to multiple single spin-echo reference measurements, both in vitro and in vivo. A phantom and 25 participants, including young and elderly healthy controls as well as ICAS-patients, were scanned. We additionally proposed a procedure to reliably identify and exclude artefact affected voxels. In the phantom, 3D-GraSE derived T2 values had 57% lower deviation from the reference. For in vivo scans, the formerly overestimated rOEF was reduced by −27% (p < 0.001). We obtained rOEF = 0.51, which is much closer to literature values from positron emission tomography (PET) measurements. Furthermore, increased sensitivity to a focal rOEF elevation in an ICAS-patient was demonstrated. In summary, the application of 3D-GraSE improves the mq-BOLD-based rOEF quantification while maintaining clinically feasible scan times. Thus, mq-BOLD with non-slice selective T2 imaging is highly promising to improve clinical diagnostics of cerebrovascular diseases such as ICAS.

中文翻译:

使用多参数定量 BOLD MRI 绘制氧气提取分数图:使用 3D-GraSE 成像减少横向弛豫偏差

基于磁共振成像 (MRI) 的血氧水平依赖性 (BOLD) 效应量化允许氧提取分数 (OEF) 映射。多参数定量 BOLD (mq-BOLD) 技术有助于相对 OEF (rOEF) 测量,并在临床适用的扫描时间内覆盖全脑。Mq-BOLD 需要通过梯度回波 (1/T2*) 和自旋回波 (1/T2) 测量脑血容量和横向弛豫率的三个单独扫描。尽管目前的方法在中风、神经胶质瘤和颈内动脉狭窄 (ICAS) 患者中具有临床价值,但存在松弛测量伪影,阻碍了 mq-BOLD 的灵敏度并人为地提高了报告的 rOEF 值。我们假设在快速 2D-GraSE(梯度和自旋回波)成像期间由切片重新聚焦缺陷引起的 T2 相关偏差可以通过应用 3D-GraSE 成像序列来减少,因为后者不需要切片选择脉冲。消除 T2 相关偏差将降低由 mq-BOLD 测量的高估 rOEF 值。我们通过将最初采用的 2D-GraSE 和两个提议的 3D-GraSE 序列与体外和体内的多个单自旋回波参考测量值进行比较来表征 mq-BOLD 中 T2 相关偏差的影响。扫描了一个幻影和 25 名参与者,包括年轻和年长的健康对照以及 ICAS 患者。我们还提出了一种可靠地识别和排除受人为影响的体素的程序。在体模中,3D-GraSE 得出的 T2 值与参考值的偏差低 57%。对于体内扫描,之前高估的 rOEF 降低了 -27% (p < 0.001)。我们获得了 rOEF = 0.51,这更接近于正电子发射断层扫描 (PET) 测量的文献值。此外,证明了 ICAS 患者对局灶性 rOEF 升高的敏感性增加。总之,3D-GraSE 的应用改进了基于 mq-BOLD 的 rOEF 量化,同时保持了临床可行的扫描时间。因此,具有非切片选择性 T2 成像的 mq-BOLD 非常有希望改善 ICAS 等脑血管疾病的临床诊断。证明了 ICAS 患者对局灶性 rOEF 升高的敏感性增加。总之,3D-GraSE 的应用改进了基于 mq-BOLD 的 rOEF 量化,同时保持了临床可行的扫描时间。因此,具有非切片选择性 T2 成像的 mq-BOLD 非常有希望改善 ICAS 等脑血管疾病的临床诊断。证明了 ICAS 患者对局灶性 rOEF 升高的敏感性增加。总之,3D-GraSE 的应用改进了基于 mq-BOLD 的 rOEF 量化,同时保持了临床可行的扫描时间。因此,具有非切片选择性 T2 成像的 mq-BOLD 非常有希望改善 ICAS 等脑血管疾病的临床诊断。
更新日期:2020-10-01
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