Radiological Center, University of Fukui Hospital, Eiheiji, Fukui, Japan.
Department of Radiology, Faculty of Medical Sciences, University of Fukui, Eiheiji, Fukui, Japan.
NMR Biomed. 2020 Aug;33(8):e4319. doi: 10.1002/nbm.4319. Epub 2020 May 19.
Arterial transit time (ATT) prolongation causes an error of cerebral blood flow (CBF) measurement during arterial spin labeling (ASL). To improve the accuracy of ATT and CBF in patients with prolonged ATT, we propose a robust ATT and CBF estimation method for clinical practice. The proposed method consists of a three-delay Hadamard-encoded pseudo-continuous ASL (H-pCASL) with an additional-encoding and single-delay with long-labeled long-delay (1dLLLD) acquisition. The additional-encoding allows for the reconstruction of a single-delay image with long-labeled short-delay (1dLLSD) in addition to the normal Hadamard sub-bolus images. Five different images (normal Hadamard 3 delay, 1dLLSD, 1dLLLD) were reconstructed to calculate ATT and CBF. A Monte Carlo simulation and an in vivo study were performed to access the accuracy of the proposed method in comparison to normal 7-delay (7d) H-pCASL with equally divided sub-bolus labeling duration (LD). The simulation showed that the accuracy of CBF is strongly affected by ATT. It was also demonstrated that underestimation of ATT and CBF by 7d H-pCASL was higher with longer ATT than with the proposed method. Consistent with the simulation, the 7d H-pCASL significantly underestimated the ATT compared to that of the proposed method. This underestimation was evident in the distal anterior cerebral artery (ACA; P = 0.0394) and the distal posterior cerebral artery (PCA; 2 P = 0.0255). Similar to the ATT, the CBF was underestimated with 7d H-pCASL in the distal ACA (P = 0.0099), distal middle cerebral artery (P = 0.0109), and distal PCA (P = 0.0319) compared to the proposed method. Improving the SNR of each delay image (even though the number of delays is small) is crucial for ATT estimation. This is opposed to acquiring many delays with short LD. The proposed method confers accurate ATT and CBF estimation within a practical acquisition time in a clinical setting.
动脉渡越时间（ATT）延长会导致动脉自旋标记（ASL）期间脑血流（CBF）测量出现误差。为了提高延长 ATT 患者的 ATT 和 CBF 测量精度，我们提出了一种用于临床实践的稳健 ATT 和 CBF 估计方法。该方法由具有附加编码的三延迟 Hadamard 编码伪连续 ASL（H-pCASL）和单延迟长标记长延迟（1dLLLD）采集组成。附加编码允许重建除正常 Hadamard 亚脉冲图像之外的具有长标记短延迟（1dLLSD）的单延迟图像。重建了 5 种不同的图像（正常 Hadamard 3 延迟、1dLLSD、1dLLLD）来计算 ATT 和 CBF。进行了蒙特卡罗模拟和体内研究，以比较正常 7 延迟（7d）H-pCASL 与具有相等亚脉冲标记持续时间（LD）划分的 7d H-pCASL 方法，评估所提出方法的准确性。模拟结果表明，CBF 的准确性受到 ATT 的强烈影响。还表明，与所提出的方法相比，7d H-pCASL 对 ATT 和 CBF 的低估在 ATT 较长时更高。与模拟结果一致，与所提出的方法相比，7d H-pCASL 显著低估了 ATT。这种低估在远侧大脑前动脉（ACA；P = 0.0394）和远侧大脑后动脉（PCA；2 P = 0.0255）中很明显。与 ATT 一样，与所提出的方法相比，7d H-pCASL 在远侧大脑中动脉（P = 0.0099）、远侧大脑中动脉（P = 0.0109）和远侧 PCA（P = 0.0319）中也低估了 CBF。提高每个延迟图像的 SNR（即使延迟数量较少）对于 ATT 估计至关重要。这与使用短 LD 采集多个延迟相反。在临床环境中，该方法在实际采集时间内提供了准确的 ATT 和 CBF 估计。
