Dynamic Magnetic Resonance Imaging of Cerebral Blood Flow Using Arterial Spin Labeling

Abstract

Modern functional neuroimaging techniques, including functional MRI, positron emission tomography and optical imaging of intrinsic signals, rely on a tight coupling between neural activity and cerebral blood flow (CBF) to visualize brain activity using CBF as a surrogate marker. Because the spatial and temporal resolution of neuroimaging modalities is ultimately determined by the spatial and temporal specificity of the underlying hemodynamic signals, characterization of the spatial and temporal profiles of the hemodynamic response to focal brain stimulation is of paramount importance for the correct interpretation and quantification of functional data. The ability to properly measure and quantify CBF with MRI is a major determinant of progress into our understanding of brain function. This chapter reviews the dynamic arterial spin labeling (DASL) method to measure CBF and the CBF functional response with high temporal resolution.

Spatiotemporal Evolution of the Functional Magnetic Resonance Imaging Response to Ultrashort Stimuli

“…CBF had the lowest detectability, while BOLD had the highest (Table S1). While most rats showed robust BOLD response to all stimulus durations, not all rats presented a detectable CBF response, due to the inherently low SNR of ASL (Detre and Wang, 2002), which is further compromised under the conditions of short TR and thus low labeling efficiency of the DASL sequence utilized here (Silva and Paiva, 2009). For the dosage of iron-oxide particles used (5mg/kg), detectability of the CBV response was between that of the CBF and of the BOLD.…”

“…For simultaneous BOLD-CBF acquisition, a dynamic ASL (DASL) sequence (Barbier et al, 2001; Silva and Paiva, 2009) was employed in which an ASL period of 199.7ms was used and cycles of 120 label images and 120 control images were alternately acquired every 60s. For CBV measurements, 5mg/kg of 30nm ultra-small super-paramagnetic iron oxide (USPIO) particles (Molday ION, Biophysics Assay Laboratory, Inc., Worcester, MA) were injected intravenously to the animal after completion of the BOLD-CBF experiments.…”

“…[13.10] in (Silva and Paiva, 2009). This modeling yields pixel-by-pixel maps of resting CBF, the transit-time between the labeling plane and the imaging slice, and the tissue T 1 (Barbier et al, 2001; Silva and Paiva, 2009).…”

“…[13.10] in (Silva and Paiva, 2009). This modeling yields pixel-by-pixel maps of resting CBF, the transit-time between the labeling plane and the imaging slice, and the tissue T 1 (Barbier et al, 2001; Silva and Paiva, 2009). Then, functional CBF values were determined by deconvolution of the DASL curve with the T 1 -decay curve (Silva et al, 2000).…”

Intrinsic connectivity network mapping in young children during natural sleep

“…For many years, these physiological variables could only be measured using radiotracers, i.e., with exposure to ionizing radiation. More recently, advances in fMRI methods allow several hemodynamic and metabolic variables to be quantified without radiation exposure, thereby making them acceptable for routine use in children (Silva & Paiva, 2009). Of these fMRI techniques, CBF as measured by arterial spin labeling (ASL) is the most well validated and widely available.…”