Volatility analysis for asymmetry-based CEST/NOE evaluation methods in the presence of multi-pool background systems with MT – Application to creatine CEST

Here, we aim to demonstrate the effects of complex multi-pool background systems with magnetization transfer (MT) on asymmetry and ratio-based analyses for CEST/NOE experiments. By using creatine in cross-linked BSA as a model, we show effects of background variations on such analyses for creatine CEST (CrCEST) based on experimentally obtained spin system parameters. For changes of up to 50% in background pool fractions, the CrCEST peak was found to change by up to 35% in asymmetry analysis. The necessity of model-based fitting with inclusion of complex background systems in contrast to conventional lineshape-based analysis is outlined.