摘要Objective:This study aimed to noninvasively characterize the metabolic alterations in ischemic brain tissues using Z-spectrum-fitted multiparametric chemical exchange saturation transfer-weighted magnetic resonance imaging(CEST-MRI).Methods:Three sets of Z-spectrum data with saturation power(B1)values of 1.5,2.5,and 3.5 μT,respectively,were acquired from 17 patients with ischemic stroke.Multiple contrasts contributing to the Z-spectrum,including fitted amide proton transfer(APTfitted),+2 ppm peak(CEST@2ppm),concomitantly fitted APTfitted and CEST@2ppm(APT&CEST@2ppm),semisolid magnetization transfer contrast(MT),aliphatic nuclear Overhauser effect(NOE),and direct saturation of water(DSW),were fitted with 4 and 5 Lorentzian functions,respectively.The CEST metrics were compared between ischemic lesions and contralateral normal white matter(CNWM),and the correlation between the CEST metrics and the apparent diffusion coefficient(ADC)was assessed.The differences in the Z-spectrum metrics under varied B,values were also investigated.Results:Ischemic lesions showed increased APTfitted,CEST@2ppm,APT&CEST@2ppm,NOE,and DSW as well as decreased MT.APT&CEST@2ppm,MT,and DSW showed a significant correlation with ADC[APT&CEST@2ppm at the 3 B1 values:R=0.584/0.467/0.551;MT at the 3 B1 values:R=-0.717/-0.695/-0.762(4-parameter fitting),R=-0.734/-0.711/-0.785(5-parameter fitting);DSW of 4-/5-parameter fitting:R=0.794/0.811(2.5μT),R=0.800/0.790(3.5 μT)].However,the asymmetric analysis of amide proton transfer(APTasym)could not differentiate the lesions from CNWM and showed no correlation with ADC.Furthermore,the Z-spectrum contrasts varied with B1.Conclusion:The Z-spectrum-fitted multiparametric CEST-MRI can comprehensively detect metabolic alterations in ischemic brain tissues.