Ultrafast in vivo diffusion imaging of stroke at 21.1 T by spatiotemporal encoding.
OBJECTIVE
This study quantifies in vivo ischemic stroke brain injuries in rats using ultrahigh-field single-scan MRI methods to assess variations in apparent diffusion coefficients (ADCs).


METHODS
Magnitude and diffusion-weighted spatiotemporally encoded imaging sequences were implemented on a 21.1 T imaging system, and compared with spin-echo and echo-planar imaging diffusion-weighted imaging strategies. ADC maps were calculated and used to evaluate the sequences according to the statistical comparisons of the ipsilateral and contralateral ADC measurements at 24, 48, and 72 h poststroke.


RESULTS
Susceptibility artifacts resulting from normative anatomy and pathological stroke conditions were particularly intense at 21.1 T. These artifacts strongly distorted single-shot diffusion-weighted echo-planar imaging experiments, but were reduced in four-segment interleaved echo-planar imaging acquisitions. By contrast, nonsegmented diffusion-weighted spatiotemporally encoded images were largely immune to field-dependent artifacts. Effects of stroke were apparent in both magnitude images and ADC maps of all sequences. When stroke recovery was followed by ADC variations, spatiotemporally encoded, echo-planar imaging, and spin-echo acquisitions revealed statistically significant increase in ADCs.


CONCLUSIONS
Consideration of experiment duration, image quality, and mapped ADC values provided by spatiotemporally encoded demonstrates that this single-shot acquisition is a method of choice for high-throughput, ultrahigh-field in vivo stroke quantification.
Department of Chemical Physics, Weizmann Institute of Science, Rehovot, Israel.
Avigdor
A
Leftin
Jens T
JT
Rosenberg
Eddy
E
Solomon
Fabian
F
Calixto Bejarano
Samuel C
SC
Grant
Lucio
L
Frydman
D000465:Algorithms; D000818:Animals; D001921:Brain / Q000473:pathology*; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted; D062211:Spatio-Temporal Analysis; D020521:Stroke / Q000473:pathology*
diffusion-weighted imaging; magnetic resonance imaging; stroke; ultrafast imaging; ultrahigh-field MRI