A method of inverse calculation for regions of small susceptibility variations

Author

Eastham, J.F. ; Hill-Cottingham, R.J. ; Young, I.R. ; Hajnal, J.V.

Author_Institution

Bath Univ., UK

Volume

33

Issue

2

fYear

1997

fDate

3/1/1997 12:00:00 AM

Firstpage

1212

Lastpage

1215

Abstract

The paper considers the determination, from a knowledge of the perturbation of a constant incident field, the susceptibility of regions where the susceptibility is 0.01 to 10 ppm different from the majority of the space of interest. This is pertinent to magnetic resonance imaging (MRI), and is an inverse problem. Two forward methods of calculating the B field are considered. First, the normal finite element method and secondly, the method of considering the induced polarity in the region of enhanced susceptibility, and calculating the difference field. The accuracies of the methods are explored and the induced polarity method is chosen for the inverse calculation. An iterative technique for inverse calculation is described utilising knowledge of the geometry of the problem, which is available from an MR plot. The numerical work is validated using experimental data from an MR imaging machine

Keywords

biomedical NMR; finite element analysis; inverse problems; iterative methods; magnetic fields; magnetic susceptibility; medical image processing; B field; MR imaging machine; MRI; accuracies; constant incident field perturbation; difference field; experimental data; finite element method; induced polarity; induced polarity method; inverse calculation method; inverse problem; iterative technique; magnetic resonance imaging; small susceptibility variations; Accuracy; Arithmetic; Boundary conditions; Context modeling; Demagnetization; Dynamic range; Magnetic resonance imaging; Permeability; Quantization; Testing;

fLanguage

English

Journal_Title

Magnetics, IEEE Transactions on

Publisher

ieee

ISSN

0018-9464

Type

jour

DOI

10.1109/20.582471

Filename

582471