title: Correction for artifacts induced by B(0) and B(1) field inhomogeneities in pH-sensitive chemical exchange saturation transfer (CEST) imaging.
abstract: Chemical exchange saturation transfer (CEST) imaging provides an indirect detection mechanism that allows quantification of certain labile groups unobservable using conventional MRI. Recently, amide proton transfer (APT) imaging, a variant form of CEST imaging, has been shown capable of detecting lactic acidosis during acute ischemia, providing information complementary to that of perfusion and diffusion MRI. However, CEST contrast is usually small, and therefore, it is important to optimize experimental conditions for reliable and quantitative CEST imaging. In particular, CEST imaging is sensitive to B(0) and B(1) field, while on the other hand; field inhomogeneities persist despite recent advances in magnet technologies, especially for in vivo imaging at high fields. Consequently, correction algorithms that can compensate for field inhomogeneity-induced measurement errors in CEST imaging might be very useful. In this study, the dependence of CEST contrast on field distribution was solved and a correction algorithm was developed to compensate for field inhomogeneity-induced CEST imaging artifacts. In addition, the proposed algorithm was verified with both numerical simulation and experimental measurements, and showed nearly complete correction of CEST imaging measurement errors caused by moderate field inhomogeneity.
authors.affiliation: Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts, USA. pzhesun@nmr.mgh.harvard.edu
authors.forename: Phillip Zhe
authors.initials: PZ
authors.lastname: Sun
authors.forename: Christian T
authors.initials: CT
authors.lastname: Farrar
authors.forename: A Gregory
authors.initials: AG
authors.lastname: Sorensen
mesh_terms: D000465:Algorithms; D016477:Artifacts; D006863:Hydrogen-Ion Concentration; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D019047:Phantoms, Imaging; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity