Measurement of brain perfusion in newborns: pulsed arterial spin labeling (PASL) versus pseudo-continuous arterial spin labeling (pCASL).
BACKGROUND
Arterial spin labeling (ASL) perfusion-weighted imaging (PWI) by magnetic resonance imaging (MRI) has been shown to be useful for identifying asphyxiated newborns at risk of developing brain injury, whether or not therapeutic hypothermia was administered. However, this technique has been only rarely used in newborns until now, because of the challenges to obtain sufficient signal-to-noise ratio (SNR) and spatial resolution in newborns.


OBJECTIVE
To compare two methods of ASL-PWI (i.e., single inversion-time pulsed arterial spin labeling [single TI PASL], and pseudo-continuous arterial spin labeling [pCASL]) to assess brain perfusion in asphyxiated newborns treated with therapeutic hypothermia and in healthy newborns.


METHODS
We conducted a prospective cohort study of term asphyxiated newborns meeting the criteria for therapeutic hypothermia; four additional healthy term newborns were also included as controls. Each of the enrolled newborns was scanned at least once during the first month of life. Each MRI scan included conventional anatomical imaging, as well as PASL and pCASL PWI-MRI. Control and labeled images were registered separately to reduce the effect of motion artifacts. For each scan, the axial slice at the level of the basal ganglia was used for comparisons. Each scan was scored for its image quality. Quantification of whole-slice cerebral blood flow (CBF) was done afterwards using previously described formulas.


RESULTS
A total number of 61 concomitant PASL and pCASL scans were obtained in nineteen asphyxiated newborns treated with therapeutic hypothermia and four healthy newborns. After discarding the scans with very poor image quality, 75% (46/61) remained for comparison between the two ASL methods. pCASL images presented a significantly superior image quality score compared to PASL images (p < 0.0001). Strong correlation was found between the CBF measured by PASL and pCASL (r = 0.61, p < 0.0001).


CONCLUSIONS
This study demonstrates that both ASL methods are feasible to assess brain perfusion in healthy and sick newborns. However, pCASL might be a better choice over PASL in newborns, as pCASL perfusion maps had a superior image quality that allowed a more detailed identification of the different brain structures.
Division of Newborn Medicine, Department of Pediatrics, Montreal Children's Hospital, McGill University, Montreal, Canada.
Elodie
E
Boudes
MR Clinical Science, Philips Healthcare, Montreal, Quebec, Canada.
Guillaume
G
Gilbert
Montreal Neurological Institute, McGill University, Canada.
Ilana Ruth
IR
Leppert
Center for Innovative Medicine, Research Institute, McGill University Health Centre, Montreal, Canada.
Xianming
X
Tan
Hotchkiss Brain Institute, University of Calgary, Calgary, Canada ; Department of Radiology, University of Calgary, Calgary, Canada.
G Bruce
GB
Pike
Department of Radiology, Montreal Children's Hospital, McGill University, Montreal, Canada.
Christine
C
Saint-Martin
Division of Newborn Medicine, Department of Pediatrics, Montreal Children's Hospital, McGill University, Montreal, Canada.
Pia
P
Wintermark
D001238:Asphyxia Neonatorum / Q000175:diagnosis / Q000503:physiopathology; D001783:Blood Flow Velocity / Q000502:physiology; D001921:Brain / Q000098:blood supply / Q000503:physiopathology*; D002560:Cerebrovascular Circulation / Q000502:physiology*; D015331:Cohort Studies; D005260:Female; D006801:Humans; D020925:Hypoxia-Ischemia, Brain / Q000175:diagnosis* / Q000503:physiopathology*; D007231:Infant, Newborn; D018810:Magnetic Resonance Angiography / Q000379:methods*; D011446:Prospective Studies; D013113:Spin Labels
D013113:Spin Labels
Brain; Hypoxic–ischemic encephalopathy; MRI, magnetic resonance imaging; Magnetic resonance imaging; Newborn; PASL, pulsed arterial spin labeling; PWI, perfusion-weighted imaging; Perfusion; SNR, signal-to-noise ratio; pCASL, pseudo-continuous arterial spin labeling