Clinical usefulness of the mDIXON Quant the method for estimation of the salivary gland fat fraction: Comparison with MR spectroscopy

Objective: To estimate the fat fraction (FF) in the salivary glands (SGs) by the mDIXON method and the 1H-MR spectroscopy (MRS) method, and to compare the results. Methods: 16 healthy volunteers were enrolled. mDIXON Quant and MRS (point-resolved spectroscopy: PRESS) with a single TE were employed to measure the FF in the parotid gland (PG) and submandibular gland (SMG). Multiple TEs were applied in 10 volunteers to correct for T2 decay. In addition, we assumed that the 1.3 ppm peak accounted for 60% of the total fat peak and estimated the FF (MRS all) as a gold standard. On mDIXON Quant images, volumes of interest were set on the bilateral SGs and we obtained the FF (mDIXON) of each volume of interest. Results: There was a strong correlation between the results of the mDIXON Quant method and the MRS (single TE) method (R2 = 0.960, slope = 0.900). Using PRESS with multiple TEs, there was also a strong correlation between FF (mDIXON) and FF (MRS all) (R2 = 0.963, slope = 1.18). FF (MRS all) was 24.9±12.7% in the PG and 4.5±3.0% in the SMG, while FF (mDIXON) was 29.4±16.2% in the PG and 6.4±4.7% in the SMG. There were no significant differences between the two methods, but the Bland-Altman plot showed that FF (mDIXON) was slightly larger than FF (MRS all) for small FF areas. Conclusion: The mDIXON Quant method could be clinically useful for evaluating the FF of SGs, but the absolute values need careful interpretation. Advance in knowledge: This study suggested the potential clinical usefulness of the mDIXON Quant method for the SGs.