Phillip Zhe Sun1,2,3. 1. Athinoula A Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA. 2. Yerkes Imaging Center, Yerkes National Primate Research Center, Emory University, Atlanta, Georgia, USA. 3. Department of Radiology and Imaging Sciences, Emory University School of Medicine, Atlanta, Georgia, USA.
Abstract
PURPOSE: Amide proton transfer-weighted (APTw) MRI provides a non-invasive pH-sensitive image, complementing perfusion and diffusion imaging for refined stratification of ischemic tissue. Although the commonly used magnetization transfer (MT) asymmetry (MTRasym ) calculation reasonably corrects the direct RF saturation effect, it is susceptible to the concomitant semisolid macromolecular MT contribution. Therefore, this study aimed to compare the performance of MTRasym and magnetization transfer and relaxation-normalized APT (MRAPT) analyses under 2 representative experimental conditions. METHODS: Multiparametric MRI scans were performed in a rodent model of acute stroke, including relaxation, diffusion, and Z spectral images under 2 representative RF levels of 0.75 and 1.5 µT. Both MTRasym and MRAPT values in the ischemic diffusion lesion and the contralateral normal areas were compared using correlation and Bland-Altman tests. In addition, the acidic lesion volumes were compared. RESULTS: MRAPT measurements from the diffusion lesion under the 2 conditions were highly correlated (R2 = 0.97) versus MTRasym measures (R2 = 0.58). The pH lesion sizes determined from MRAPT analysis were in good agreement (178 ± 43 mm3 vs. 186 ± 55 mm3 for B1 of 0.75 and 1.5 µT, respectively). CONCLUSIONS: The study demonstrated that MRAPT analysis could be generalized to moderately different RF amplitudes, providing a more consistent depiction of acidic lesions than the MTRasym analysis.
PURPOSE: Amide proton transfer-weighted (APTw) MRI provides a non-invasive pH-sensitive image, complementing perfusion and diffusion imaging for refined stratification of ischemic tissue. Although the commonly used magnetization transfer (MT) asymmetry (MTRasym ) calculation reasonably corrects the direct RF saturation effect, it is susceptible to the concomitant semisolid macromolecular MT contribution. Therefore, this study aimed to compare the performance of MTRasym and magnetization transfer and relaxation-normalized APT (MRAPT) analyses under 2 representative experimental conditions. METHODS: Multiparametric MRI scans were performed in a rodent model of acute stroke, including relaxation, diffusion, and Z spectral images under 2 representative RF levels of 0.75 and 1.5 µT. Both MTRasym and MRAPT values in the ischemic diffusion lesion and the contralateral normal areas were compared using correlation and Bland-Altman tests. In addition, the acidic lesion volumes were compared. RESULTS: MRAPT measurements from the diffusion lesion under the 2 conditions were highly correlated (R2 = 0.97) versus MTRasym measures (R2 = 0.58). The pH lesion sizes determined from MRAPT analysis were in good agreement (178 ± 43 mm3 vs. 186 ± 55 mm3 for B1 of 0.75 and 1.5 µT, respectively). CONCLUSIONS: The study demonstrated that MRAPT analysis could be generalized to moderately different RF amplitudes, providing a more consistent depiction of acidic lesions than the MTRasym analysis.
Authors: W Taylor Kimberly; Bruna Garbugio Dutra; Anna M M Boers; Heitor C B R Alves; Olvert A Berkhemer; Lucie van den Berg; Kevin N Sheth; Yvo B W E M Roos; Aad van der Lugt; Ludo F M Beenen; Diederik W J Dippel; Wim H van Zwam; Robert J van Oostenbrugge; Hester F Lingsma; Henk Marquering; Charles B L M Majoie Journal: JAMA Neurol Date: 2018-04-01 Impact factor: 18.302