An investigation of statistical power for continuous arterial spin labeling imaging at 1.5 T

• Published in: NeuroImage (Orlando, Fla.) Vol. 39; no. 3; pp. 1246 - 1256
• Main Authors: Asllani, Iris, Borogovac, Ajna, Wright, Clinton, Sacco, Ralph, Brown, Truman R., Zarahn, Eric
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.02.2008; Elsevier Limited
• Subjects: Acquisitions & mergers; Aged; Algorithms; Analysis of Variance; ASL; Brain; CBF; Cerebral Arteries - anatomy & histology; Cerebrovascular Circulation - physiology; Cohort Studies; Echo-Planar Imaging - statistics & numerical data; fMRI; Humans; Image Processing, Computer-Assisted - statistics & numerical data; Intersubject variance; Intrasubject variance; Medical imaging; Reproducibility of Results; Sample variance; Spin Labels; Statistical power; Studies; fMRI; ASL; Intrasubject variance; Statistical power; CBF; Intersubject variance
• ISSN: 1053-8119; 1095-9572
• DOI: 10.1016/j.neuroimage.2007.10.015

Variance estimates can be used in conjunction with scientifically meaningful effect sizes to design experiments with type II error control. Here we present estimates of intra- and inter-subject variances for region of interest (ROI) from resting cerebral blood flow (CBF) maps obtained using whole brain, spin echo echoplanar (SE-EPI) continuous arterial spin labeling (CASL) imaging on 52 elderly subjects (age=70.5±7.9 years, 29 males). There was substantial intrasubject systematic variability in CBF of gray matter ROIs corresponding to a range of standard deviations=[39–168] (ml/(100 g min)). This variability was mainly due to two factors: (1) an expected inverse relationship between ROI volume and intrasubject variance and (2) an increased effective post-labeling delay for more superior slices acquired later in the sequence. For example, intrasubject variance in Brodmann area 4 (BA 4) was ∼8 times larger than in hippocampus, despite their similar gray matter volumes. Estimated ROI-wise power was computed for various numbers of acquired CBF images, numbers of subjects, and CBF effect sizes for two experimental designs: independent sample t-test and paired t-test. The theoretical effects of pulse sequence and field strength on general applicability of these results are discussed.