Purpose To investigate the reliability and accuracy of two pseudo-continuous arterial spin labeling (pCASL) sequences, using 2D gradient-echo echo planar imaging (EPI) and 3D gradient and spin echo (GRASE) as the readout respectively. Materials and Methods Each sequence was performed twice four weeks apart on 6 normal control subjects, 6 elderly subjects with mild cognitive impairment (MCI), and one participant with Alzheimer’s’ disease (AD). Eight of these subjects also underwent H215O positron emission tomography (PET) scans on the same day or proximal to their second MRI scan. The longitudinal repeatability of EPI and GRASE pCASL were evaluated with the intra-class correlation coefficient (ICC) and within-subject coefficient of variation (wsCV). Results The ICCs of global perfusion measurements were 0.697 and 0.413 for GRASE and EPI based pCASL respectively. GRASE pCASL also demonstrated a higher longitudinal repeatability for regional perfusion measurements across 24 regions-of-interests (ICC=0.707, wsCV=10.9%) compared to EPI pCASL (ICC=0.362, wsCV=15.3%). When compared to PET, EPI pCASL showed a higher degree of spatial correlation with PET than GRASE pCASL, although the difference was not statistically significant. Conclusion 3D GRASE pCASL offers better repeatability than 2D EPI pCASL, thereby may provide a reliable imaging marker for the evaluation of disease progression and treatment effects in MCI and early AD subjects.

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Purpose:To present an unenhanced four-dimensional time-resolved dynamic magnetic resonance (MR) angiography technique with true fast imaging with steady-state precession-based spin tagging with alternating radiofrequency (STAR), also called TrueSTAR. Materials and Methods:This study received Institutional Review Board approval and was HIPAA compliant. Informed consent was obtained from all study subjects. In eight healthy volunteers, the spatial and temporal resolution of the TrueSTAR technique were optimized. In another six healthy volunteers, the contrast-to-noise ratio (CNR) and signal-to-noise ratio (SNR) of the TrueSTAR dynamic MR angiography images were compared with those acquired by using a standard Look-Locker echo-planar technique by using the Wilcoxon signed rank test. Finally, one patient with an arteriovenous malformation (AVM) was studied by using this technique. Results:The SNR and CNR of the TrueSTAR dynamic MR angiography images were 29% and 39% higher, respectively, compared with those acquired by using a standard LookLocker echo-planar imaging sequence (both P = .028).In the AVM patient, TrueSTAR dynamic MR angiography delineated the dynamic course of labeled blood fl owing through feeding arteries into the nidus and draining veins. Conclusion:The results suggest that TrueSTAR is a promising unenhanced dynamic MR angiography technique for clinical evaluation of cerebrovascular disorders such as AVM, steno-occlusive disease, and aneurysm.q RSNA, 2010Supplemental material: http://radiology.rsna.org/lookup /suppl