Exploiting multicompartment effects in triple-echo steady-state T2mapping for fat fraction quantification.
OBJECTIVE
To investigate and exploit the effect of intravoxel off-resonance compartments in the triple-echo steady-state (TESS) sequence without fat suppression for T2mapping and to leverage the results for fat fraction quantification.


METHODS
In multicompartment tissue, where at least one compartment is excited off-resonance, the total signal exhibits periodic modulations as a function of echo time (TE). Simulated multicompartment TESS signals were synthesized at various TEs. Fat emulsion phantoms were prepared and scanned at the same TE combinations using TESS. In vivo knee data were obtained with TESS to validate the simulations. The multicompartment effect was exploited for fat fraction quantification in the stomach by acquiring TESS signals at two TE combinations.


RESULTS
Simulated and measured multicompartment signal intensities were in good agreement. Multicompartment effects caused erroneous T2offsets, even at low water-fat ratios. The choice of TE caused T2variations of as much as 28% in cartilage. The feasibility of fat fraction quantification to monitor the decrease of fat content in the stomach during digestion is demonstrated.


CONCLUSIONS
Intravoxel off-resonance compartments are a confounding factor for T2quantification using TESS, causing errors that are dependent on the TE. At the same time, off-resonance effects may allow for efficient fat fraction mapping using steady-state imaging. Magn Reson Med 79:423-429, 2018. © 2017 International Society for Magnetic Resonance in Medicine.
Institute for Biomedical Engineering, University and ETH Zurich, Switzerland.
Dian
D
Liu
Institute for Biomedical Engineering, University and ETH Zurich, Switzerland.|Division of Gastroenterology and Hepatology, University Hospital Zurich, Switzerland.
Andreas
A
Steingoetter
Institute for Biomedical Engineering, University and ETH Zurich, Switzerland.|Division of Gastroenterology and Hepatology, University Hospital Zurich, Switzerland.
Jelena
J
Curcic
Institute for Biomedical Engineering, University and ETH Zurich, Switzerland.
Sebastian
S
Kozerke
D000465:Algorithms; D002356:Cartilage / Q000000981:diagnostic imaging; D003198:Computer Simulation; D005223:Fats; D006801:Humans; D007089:Image Enhancement; D007091:Image Processing, Computer-Assisted; D007717:Knee / Q000000981:diagnostic imaging*; D007719:Knee Joint / Q000000981:diagnostic imaging; D008279:Magnetic Resonance Imaging; D019047:Phantoms, Imaging; D015203:Reproducibility of Results; D013270:Stomach / Q000000981:diagnostic imaging
D005223:Fats
T2 quantification; chemical shift; fat quantification; multicompartment; triple-echo steady state