Patent ID: 7616984

Claim:
A method for obtaining a time series of tomographic images of a target medium from an imaging apparatus, wherein source-detector pairs are positioned about a boundary of the target medium, and, in each source-detector pair, for different points in the time series, the source emits energy into the target medium and the detector measures the energy emerging from the target medium after passage therethrough, comprising: selecting a reference medium; providing a weight matrix describing an influence that volume elements of the reference medium have on energy traveling from sources to detectors in source-detector pairs of the reference medium, wherein said detectors measure an intensity of scattered energy; transforming said weight matrix to reduce a dimension of said weight matrix employing a weight transformation technique, wherein an M×N matrix is transformed to an M×M matrix by said transforming, wherein N is a number of nodes comprising a finite element mesh and wherein M is the number of said source-detector pairs; and for the different points in the time series, solving a system equation for the target medium to determine properties of volume elements of the target medium that correspond to the volume elements of the reference medium based on the weight matrix and the energy emerging at the detectors of the target medium, wherein one or more of the properties of volume elements is employed at least for providing a time series of tomographic images of a target medium.