NMR, MRI, and spectroscopic MRI in inhomogeneous fields

US8614575B2 · kind B2 · utility

Assignee

• The Regents of the University of California · US

Inventors

• Vasiliki Demas · San Jose, US
• Alexander Pines · Berkeley, US
• Rachel W. Martin · Irvine, US
• John Franck · Berkeley, US
• Jeffrey A. Reimer · Corona, US

Key dates

• Filing date: Jun 16, 2006
• Grant date: Dec 24, 2013
• Expiry date: Jun 23, 2029

Classification

• Technology area (CPC G): Physics
• CPC primary: G01R33/445
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

A method for locally creating effectively homogeneous or “clean” magnetic field gradients (of high uniformity) for imaging (with NMR, MRI, or spectroscopic MRI) both in in-situ and ex-situ systems with high degrees of inhomogeneous field strength. The method of imaging comprises: a) providing a functional approximation of an inhomogeneous static magnetic field strength B0({right arrow over (r)}) at a spatial position {right arrow over (r)}; b) providing a temporal functional approximation of {right arrow over (G)}shim(t) with i basis functions and j variables for each basis function, resulting in vij variables; c) providing a measured value Ω, which is an temporally accumulated dephasing due to the inhomogeneities of B0({right arrow over (r)}); and d) minimizing a difference in the local dephasing angle φ({right arrow over (r)},t)=γ∫0t√{square root over (|{right arrow over (B)}1({right arrow over (r)},t′)|2+({right arrow over (r)}·{right arrow over (G)}shimGshim(t′)+∥{right arrow over (B)}0({right arrow over (r)})∥Δω({right arrow over (r)},t′)/γ)2)}dt′−Ω by varying the vij variables to form a set of minimized vij variables. The method requires calibration of the static fields prior…