Room: AAPM ePoster Library
Purpose: To determine if differences exist between apparent transverse relaxation (T2) times of ?-3 and non-?-3 fat methyl protons that could affect their relative quantification with magnetic resonance spectroscopy (MRS) at 9.4 T. Omega-3 fat content is relevant to the study of disease, including obesity, bone disease, and breast cancer.
Methods: All experiments were performed with a 21 cm diameter 9.4 T animal MRI scanner using a volume radiofrequency (RF) coil and a Point RESolved Spectroscopy (PRESS) pulse sequence. Quantum mechanical product operator calculations were used to estimate two echo times (TE) where the ?-3 methyl peak and non-?-3 methyl peak are resolved from each other (by minimizing area of the side multiplets of each resonance). PRESS spectra were acquired from four oils of varying ?-3 fat content using the two determined echo times, namely, 109 ms (TE1 = 15 ms, TE2 = 94 ms) and 399 ms (TE1= 15 ms, TE2 = 384 ms). Gated PRESS spectra were also acquired from abdominal adipose tissue of two mice fed a high ?-3 fat diet for 6 months. Peak areas of the ?-3 and non-?-3 resonances were fit to a mono-exponentially decaying function in MATLAB to estimate an apparent (includes J-coupling effects) T2 relaxation time for the ?-3 and non-?-3 methyl protons for the oils and for the mice.
Results: In oils, average apparent T2 relaxation rates were 906 ms and 414ms for ?-3 and non-?-3 methyl protons, respectively. Apparent T2 relaxation times were on average 436 ms and 252 ms for ?-3 and non-?-3 methyl protons in mice, respectively.
Conclusion: The ?-3 methyl proton T2 relaxation time is higher than that of the non-?-3 methyl protons at 9.4 T and should be accounted for when estimating their relative amounts from long TE spectra.