A generalized QUCESOP method for amide and NOE quantification in rat brain tumor

Motivation: Current CEST quantification methods only calculated the fractional concentration fb and the exchange rate kb for each solute pool, but consider R2b as a constant. Goal(s): To quantify the change of b, kb and R2b corresponding to the amide and NOE pool in brain tumor imaging of rats. Approach: Partial Z-spectra around the target frequency offsets were acquired using several saturation amplitudes, and the QUCESOP method was employed to fit the parameters of the amide solute and the “NOE solute” respectively. Results: Tumor exhibited higher R2b and lower fb for “NOE solute”, with a slightly-elevated amide pool size, compared with the normal tissue. Impact: Tumor displayed an increase of R2b and a decrease of fb for the “NOE solute”, that originated from the aliphatic protons on the macromolecular pool. The larger R2b may reflect the increased cell density in the tumor region.