Hybrid multiband excitation multiecho acquisition for hyperpolarized (13) C spectroscopic imaging.
OBJECTIVE
Fast dynamic imaging of hyperpolarized (13) C-labeled pyruvate and its downstream metabolites shows great potential for probing metabolic changes in the heart. Sequences that allow for fast encoding of the spectral and spatial information of the myocardial metabolism and optimal signal excitation are usually limited by gradient performance, especially at high magnetic fields. Here we propose a combination of a spectral-spatial multiband excitation and multiecho readout to overcome these limitations.


METHODS
By using a low-bandwidth, two-pulse excitation, a thinner slice compared with conventional spectral-spatial excitation is achieved, while at the same time allowing for low flip angle excitation on pyruvate and high flip angle excitation on bicarbonate and lactate, which optimizes signal-to-noise ratio (SNR) in cardiac metabolic imaging. The implementation was evaluated in 13 healthy female Sprague-Dawley rats at 9.4T.


RESULTS
Using a slice thickness of 4 mm, a mean (± standard deviation) peak SNR of 18.3 (±8.4), 15.2 (±6.6), and 8.6 (±2.0) was observed for pyruvate, lactate, and bicarbonate, respectively.


CONCLUSIONS
This approach provides high SNR in metabolic images while at the same time allowing for a thin slice selection even at high magnetic fields. This is crucial in metabolic imaging in small animal models.
Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland.
Andreas
A
Sigfridsson
Kilian
K
Weiss
Lukas
L
Wissmann
Julia
J
Busch
Marcin
M
Krajewski
Michael
M
Batel
Georgios
G
Batsios
Matthias
M
Ernst
Sebastian
S
Kozerke
D000465:Algorithms; D000818:Animals; D066241:Carbon-13 Magnetic Resonance Spectroscopy / Q000379:methods*; D017352:Echo-Planar Imaging / Q000379:methods*; D004734:Energy Metabolism / Q000502:physiology*; D005260:Female; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D009206:Myocardium / Q000378:metabolism* / Q000473:pathology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012680:Sensitivity and Specificity
cardiac metabolic imaging; hyperpolarized 13C; multiecho; spectral-spatial