gms | German Medical Science

Question: Well-known, that non-invasive electric (BSPM) or magnetic (MCG) methods, giving images of heart fields, are promising from medical viewpoint. As a rule, real maps are non-dipole and include few sources and some noise. Quantitive map analyses, based on electrodynamical approach, has no correct solution within multipole expansion (MPE) because Legendre polinoms are non-orthogonal by low index. Aim of work is to develop new method of image analysis.

Method used: Approach is based on Modified Furie Transform (MFT), determining both planar projections and co-ordinates of each harmonic. For map, created by 36 leads arranged into 6X6 grid, only low 36 MFT harmonics were introduced into consideration. Physical spectrum (21 components) is interpreted according to Helmholtz theorem and MPE. Firstly map is decomposed onto vortex and flow part, after each of them is divided onto dipole, quadru-, octu-, and hexadecapole.

Results: Forward model include ideal map (dipole directed to left-down and located into center), and quasi- and non-dipole maps formed by 7 harmonics. Analysis consists in MFT spectral analysis and decomposition of model maps. Average error between model and parameters estimated from MFT is near 1%.

Conclusion: New methods for pattern recognition and orthogonal decompo-sition of images were developed. Quantity MFT analysis is correct and unique compare to inverse problem solution (IPS) methods. Firstly, it is method to improve SNR by smoothing (interpolation and spatial filtration at the same time). Secondly, each decomposed map may be processed by IPS procedures, and current source, interested from medical viewpoint (dipole or non-dipole (non-homogeneous), vortex or laminar (homogeneous), up to 14 sources), can be revealed in such a way. Method is promising for analysis of BSPM or MCG maps.