title: Quantification of susceptibility change at high-concentrated SPIO-labeled target by characteristic phase gradient recognition.
abstract: Phase map cross-correlation detection and quantification may produce highlighted signal at superparamagnetic iron oxide nanoparticles, and distinguish them from other hypointensities. The method may quantify susceptibility change by performing least squares analysis between a theoretically generated magnetic field template and an experimentally scanned phase image. Because characteristic phase recognition requires the removal of phase wrap and phase background, additional steps of phase unwrapping and filtering may increase the chance of computing error and enlarge the inconsistence among algorithms. To solve problem, phase gradient cross-correlation and quantification method is developed by recognizing characteristic phase gradient pattern instead of phase image because phase gradient operation inherently includes unwrapping and filtering functions. However, few studies have mentioned the detectable limit of currently used phase gradient calculation algorithms. The limit may lead to an underestimation of large magnetic susceptibility change caused by high-concentrated iron accumulation. In this study, mathematical derivation points out the value of maximum detectable phase gradient calculated by differential chain algorithm in both spatial and Fourier domain. To break through the limit, a modified quantification method is proposed by using unwrapped forward differentiation for phase gradient generation. The method enlarges the detectable range of phase gradient measurement and avoids the underestimation of magnetic susceptibility. Simulation and phantom experiments were used to quantitatively compare different methods. In vivo application performs MRI scanning on nude mice implanted by iron-labeled human cancer cells. Results validate the limit of detectable phase gradient and the consequent susceptibility underestimation. Results also demonstrate the advantage of unwrapped forward differentiation compared with differential chain algorithms for susceptibility quantification at high-concentrated iron accumulation.
authors.affiliation: Division of Nuclear Technology and Applications, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China; Beijing Engineering Research Center of Radiographic Techniques and Equipment, Beijing 100049, China.
authors.forename: Haitao
authors.initials: H
authors.lastname: Zhu
authors.affiliation: Division of Nuclear Technology and Applications, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China; Beijing Engineering Research Center of Radiographic Techniques and Equipment, Beijing 100049, China.
authors.forename: Binbin
authors.initials: B
authors.lastname: Nie
authors.affiliation: Division of Nuclear Technology and Applications, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China; Beijing Engineering Research Center of Radiographic Techniques and Equipment, Beijing 100049, China.
authors.forename: Hua
authors.initials: H
authors.lastname: Liu
authors.affiliation: Center for Biomedical Imaging Research, Department of Biomedical Engineering, Tsinghua University, Beijing 100084, China.
authors.forename: Hua
authors.initials: H
authors.lastname: Guo
authors.affiliation: Department of Nuclear Engineering and Management, the University of Tokyo, Tokyo 113-8586, Japan.
authors.forename: Kazuyuki
authors.initials: K
authors.lastname: Demachi
authors.affiliation: Department of Electrical Engineering and Information Systems, the University of Tokyo, Tokyo 113-8656, Japan.
authors.forename: Masaki
authors.initials: M
authors.lastname: Sekino
authors.affiliation: Division of Nuclear Technology and Applications, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China; Beijing Engineering Research Center of Radiographic Techniques and Equipment, Beijing 100049, China. Electronic address: shanbc@ihep.ac.cn.
authors.forename: Baoci
authors.initials: B
authors.lastname: Shan
mesh_terms: D000465:Algorithms; D000818:Animals; D045744:Cell Line, Tumor; D003287:Contrast Media / Q000737:chemistry*; D003911:Dextrans / Q000737:chemistry*; D006801:Humans; D008279:Magnetic Resonance Imaging; D058185:Magnetite Nanoparticles / Q000737:chemistry*; D008819:Mice, Nude; D009368:Neoplasm Transplantation; D019047:Phantoms, Imaging
chemical_list: D003287:Contrast Media; D003911:Dextrans; D058185:Magnetite Nanoparticles; C065507:ferumoxides
keywords: Least squares; Phase gradient; Positive contrast imaging; Superparamagnetic iron oxide nanoparticle; Unwrapping