Measuring the labeling efficiency of pseudocontinuous arterial spin labeling

Abstract

The optimized labeling efficiency sequence provides robust artery-specific labeling efficiency measurement within a short acquisition time (∼30 s), thereby enabling improved accuracy of pCASL CBF quantification. Magn Reson Med 77:1841-1852, 2017. © 2016 International Society for Magnetic Resonance in Medicine Magn Reson Med 77:1841-1852, 2017. © 2016 International Society for Magnetic Resonance in Medicine.

Cerebral hemodynamics and pseudo‐continuous arterial spin labeling considerations in adults with sickle cell anemia

“…caffeine consumption) have also been reported to affect the pCASL labeling efficiency during the time of the scan . In very recent work, experimental measurements of labeling efficiency have been made in healthy adults using a fast single slice Look‐Locker echo planar imaging readout . Thus, the relevance of subject‐specific labeling efficiency calculation is becoming increasingly realized, and in this study we extend this line of reasoning to a pressing clinical need in SCA.…”

“…First, as is the case in nearly all pCASL application studies, cardiac gating was not utilized during the phase contrast MRA scans; therefore, the resulting flow velocities are averaged over the entire cardiac cycle and cannot be mapped to individual phases, resulting in flow velocities that appear lower than the values reported using transcranial Doppler ultrasound, which is typically conducted at peak systole. Recently, pCASL approaches for deriving vessel‐specific labeling efficiencies using cardiac gating have been proposed . Cardiac gated phase contrast data can provide information on the effect of varying flow velocities over the cardiac cycle on labeling efficiency…”

“…A typical labeling efficiency in healthy vessels for routinely used parameters is 85–95%, while blood flowing at higher velocities, as expected in adults with SCA, will have reduced labeling efficiency unless labeling parameters are adjusted. While recent work has elucidated variations in labeling efficiencies in healthy subjects and commented on flow velocity effects in children with SCA, the effect of variations in cervical flow velocity secondary to SCA on pCASL‐measured CBF has yet to be elucidated in adults with SCA. This issue is fundamental, as when pCASL is used for assessment of stroke risk or transfusion response in adults with SCA it may underestimate CBF if inappropriate labeling efficiencies are assumed.…”

Comparison of multi-delay FAIR and pCASL labeling approaches for renal perfusion quantification at 3T MRI

“…Optimization of pCASL labeling parameters for renal application has been shown to improve robustness to off-resonance effects and aortic flow pulsatility [41]. To improve repeatability of perfusion quantification and to detect failed measurements on a subject level, we think that it is recommended to measure the labeling efficiency at the labeling location, similar as has been proposed for the brain [42,43]. This will permit to judge the technical validity of the ASL measurement and to correct for the labeling efficiency in the quantification.…”

Temporal and Spatial Variances in Arterial Spin-Labeling Are Inversely Related to Large-Artery Blood Velocity

“…Recently, a sequence that measures artery-specific label efficiency, thereby improving ASL-CBF accuracy, has been proposed and validated. 35 Comparison of PC-CBF with ASL-CBF using this calibration method may facilitate investigation into the impact of age-and disease-related increases in hemodynamic pulsatility on ASL after controlling for effects on label efficiency.…”