Saturation-recovery metabolic-exchange rate imaging with hyperpolarized [1-13C] pyruvate using spectral-spatial excitation.
Within the last decade hyperpolarized [1-13C] pyruvate chemical-shift imaging has demonstrated impressive potential for metabolic MR imaging for a wide range of applications in oncology, cardiology, and neurology. In this work, a highly efficient pulse sequence is described for time-resolved, multislice chemical shift imaging of the injected substrate and obtained downstream metabolites. Using spectral-spatial excitation in combination with single-shot spiral data acquisition, the overall encoding is evenly distributed between excitation and signal reception, allowing the encoding of one full two-dimensional metabolite image per excitation. The signal-to-noise ratio can be flexibly adjusted and optimized using lower flip angles for the pyruvate substrate and larger ones for the downstream metabolites. Selectively adjusting the excitation of the down-stream metabolites to 90° leads to a so-called "saturation-recovery" scheme with the detected signal content being determined by forward conversion of the available pyruvate. In case of repetitive excitations, the polarization is preserved using smaller flip angles for pyruvate. Metabolic exchange rates are determined spatially resolved from the metabolite images using a simplified two-site exchange model. This novel contrast is an important step toward more quantitative metabolic imaging. Goal of this work was to derive, analyze, and implement this "saturation-recovery metabolic exchange rate imaging" and demonstrate its capabilities in four rats bearing subcutaneous tumors.
GE Global Research, Munich, Germany. Rolf.Schulte@research.ge.com
Rolf F
RF
Schulte
Jonathan I
JI
Sperl
Eliane
E
Weidl
Marion I
MI
Menzel
Martin A
MA
Janich
Oleksandr
O
Khegai
Markus
M
Durst
Jan Henrik
JH
Ardenkjaer-Larsen
Steffen J
SJ
Glaser
Axel
A
Haase
Markus
M
Schwaiger
Florian
F
Wiesinger
D000409:Alanine / Q000378:metabolism*; D000818:Animals; D001639:Bicarbonates / Q000378:metabolism*; D002247:Carbon Isotopes / Q000493:pharmacokinetics; D045744:Cell Line, Tumor; D005260:Female; D019344:Lactic Acid / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008657:Metabolic Clearance Rate; D009374:Neoplasms, Experimental / Q000175:diagnosis / Q000378:metabolism*; D011522:Protons; D019289:Pyruvic Acid / Q000493:pharmacokinetics*; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D051381:Rats; D011916:Rats, Inbred F344
D001639:Bicarbonates; D002247:Carbon Isotopes; D011522:Protons; D019275:Radiopharmaceuticals; D019344:Lactic Acid; D019289:Pyruvic Acid; D000409:Alanine