Visualizing artery‐specific blood flow patterns above the circle of Willis with vessel‐encoded arterial spin labeling

Abstract

Purpose To establish the feasibility of using vessel‐encoded pseudocontinuous arterial spin labeling (VEPCASL) for noninvasive vascular territory imaging (VTI) and artery‐specific dynamic angiography of a large number of arterial branches above the circle of Willis within a clinically feasible scan time. Methods 3D time‐of‐flight angiography was used to select a labeling plane and establish 7 pairs of encoding cycles. These were used for VEPCASL VTI and dynamic 2D angiography (8 min and 3 min acquisition times, respectively) in healthy volunteers, allowing the separation of signals arising from 13 arterial branches (including extracranial arteries) in postprocessing. To demonstrate the clinical potential of this approach, VEPCASL angiography was also applied in 5 patients with brain arteriovenous malformation (AVM). Results In healthy volunteers, the artery‐specific filling of the vascular tree and resulting perfusion territories were well depicted. SNRs were approximately 5 times higher than those achievable with single‐artery selective methods. Blood supply to the AVMs was well visualized in all cases, showing the main feeding arteries and venous drainage. Conclusions VEPCASL is a highly efficient method for both VTI and dynamic angiography of a large number of arterial branches, providing a comprehensive picture of vascular flow patterns and the effect on downstream tissue perfusion within an acceptable scan time. Automation of labeling plane and vessel‐encoding selection would improve robustness and efficiency, and further refinement could allow quantitative blood flow measurements to be obtained. This technique shows promise for visualizing the blood supply to lesions and collateral flow patterns.

Measurement of collateral perfusion in acute stroke: a vessel-encoded arterial spin labeling study

“…from the right anterior cerebral artery to the right MCA) could not be observed. Labeling a larger number of arterial branches more distally has been demonstrated 46,47 , but this may not be practical in acute patients because of planning time and restricted brain coverage.…”

Intracranial 3D and 4D MR Angiography Using Arterial Spin Labeling: Technical Considerations

“…Another option is balanced steady-state free precession (bSSFP) sequence, 22,32,33 in which the transverse magnetization is recycled for the next TR without being spoiled, Fig. 3 The behavior of the longitudinal magnetization (M z ) was simulated by means of Bloch equation simulations, by assuming the labeled blood (in labeling image) and nonlabeled blood (in control image) enter the imaging volume and receive excitation RF-pulses over 1400 ms.…”

“…However, when compared with the traditional one-by-one acquisition, ve-pCASL still results in a scan-time reduction and SNR efficiency. 33 The minimum number of Hadamard-encodings required to separate the three arterial trees of RICA, LICA and VAs is four as shown in Equation [1]. For successful application of ve-pCASL for ASL-MRA, it is essential to have (i) a sharp spatial transition between the labeling and control conditions to accurately separate the targeted artery from other nontargeted arteries (−1 versus 1 in Equation [1]), and (ii) a broad and flat control condition to provide the same control condition for all non-targeted arteries (1 for all non-targeted arteries in Equation [1]) even though they are located separately.…”

The Study of Cerebral Blood Flow Variations Following Radiation Dose Gradients for Brain Metastasis Patients During Radiotherapy

“…However, the clinical application of DCE is limited due to its prolonged imaging time and high degree of trauma [17]. In contrast, 3D arterial spin labeling (ASL) perfusion imaging allows for the evaluation of CBF without a contrast agent, and it is an entirely noninvasive technique that can obtain repeated measures [18,19].…”