One-dimensional image-selected in vivo spectroscopy localized phosphorus saturation transfer at 7T.
OBJECTIVE
To evaluate the feasibility of a one-dimensional image-selected in vivo spectroscopy (1D-ISIS) saturation transfer (ST) sequence at 7T for localized in vivo measurements of energy metabolism in different tissues in clinically reasonable examination times.


METHODS
The performance of a gradient offset independent adiabacity-based 1D-ISIS localization was tested on phantom and the localized ST sequence was compared with the nonlocalized version in vivo. We performed localized measurements of basal metabolism of human liver and different muscle groups of the calf. Localized ST experiments took 15-25 minutes.


RESULTS
The selectivity of the 1D-ISIS sequence was 81.63% and the outer volume suppression was 97.57%. The ST parameters acquired with the 1D-ISIS sequence and with the nonlocalized acquisition in the muscle were not statistically different. The forward rate constants for phosphocreatine (PCr)-adenosine triphosphate (ATP) and inorganic phosphate (Pi)-ATP exchange reactions were measured in the soleus (kCK  = 0.30 ± 0.06 s(-1) and kATP  = 0.11 ± 0.02 s(-1) , respectively) and in the medial gastrocnemius (kCK  = 0.27 ± 0.06 s(-1) and kATP  = 0.09 ± 0.03s(-1) , respectively) in 15 minutes per muscle group. The corresponding fluxes were FCK  = 6.26 ± 1.28 μmol/g/s, FATP  = 0.22 ± 0.05 μmol/g/s and FCK  = 6.29 ± 1.66 μmol/g/s, FATP  = 0.21 ± 0.07 μmol/g/s, for soleus and gastrocnemius, respectively. The hepatic ATP synthesis measurement was feasible in 24 minutes.


CONCLUSIONS
The fast assessment of PCr-ATP and Pi-ATP exchange rates at 7T makes the 1D-ISIS ST sequence a promising tool for examining local resting-state metabolism in clinically acceptable measurement times.
High Field MR Centre, Department of Biomedical Imaging and Image-guided Therapy, Medical University Vienna, Vienna, Austria; Department of Imaging Methods, Institute of Measurement Science, Slovak Academy of Sciences, Bratislava, Slovakia.
Ladislav
L
Valkovič
Wolfgang
W
Bogner
Martin
M
Gajdošík
Michal
M
Považan
Ivica Just
IJ
Kukurová
Martin
M
Krššák
Stephan
S
Gruber
Ivan
I
Frollo
Siegfried
S
Trattnig
Marek
M
Chmelík
D000255:Adenosine Triphosphate / Q000378:metabolism*; D000328:Adult; D000465:Algorithms; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D007866:Leg; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism*; D010725:Phosphocreatine / Q000378:metabolism*; D010759:Phosphorus Isotopes / Q000493:pharmacokinetics; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014018:Tissue Distribution
D010759:Phosphorus Isotopes; D019275:Radiopharmaceuticals; D010725:Phosphocreatine; D000255:Adenosine Triphosphate
31P-MRS; 7T; energy metabolism; saturation transfer