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Apparent Transverse Relaxation Times of Omega-3 and Non-Omega-3 Fat Methyl Protons in Mouse Adipose Tissue at 9.4 T

CJ Fallone1*, AG Tessier1,2, CJ Field3, A Yahya1,2, (1) Department of Oncology, University of Alberta, Edmonton, AB, CA, (2) Department of Medical Physics, Cross Cancer Institute, Edmonton, AB, CA, (3)Department of Agricultural, Food, and Nutritional Science, University of Alberta, Edmonton, AB, CA


(Sunday, 7/12/2020)   [Eastern Time (GMT-4)]

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.

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IM- MRI : Spectroscopy

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