CEST imaging benefits from longer saturation duration and a higher saturation duty cycle. Dielectric shading effects occur when the RF wavelength approaches the object size. Here, we proposed a parallel-transmission-based CEST (pTx-CEST) sequence to extend the maximum saturation duration at 100% duty-cycle and mitigate shading effects. The maximum saturation duration in pTx-CEST was lengthened to 2170, 3150, and 4130ms compared to 1050ms in non-pTx-CEST at TR of 3s, 4s, and 5s, respectively, leading to a significant sensitivity enhancement. Besides, the optimal amplitude ratio and phase difference between RF channels, manifesting circular or elliptical polarization, help reduce the dielectric shading effects.