Reconstruction algorithm for Pigeon Hole Imaging (PHI)

Pigeon Hole Imaging (PHI) is a non-ionizing imaging modality that maps spatial distribution of electrical conductivity within a volume conductor. In PHI, electrical impedance is measured placing an electrode array on the surface of a volume conductor and the conductivity distribution in a plane parallel to the electrode array is obtained. This paper describes an image reconstruction algorithm for PHI based on 4-electrode Focused Impedance Measurements (FIM). The impedance measurements were simulated in a finite element based simulation software COMSOL Multiphysics for 5×5 and 6×6 PHI matrices. The measured impedance on the volume conductor surface just above an object of different conductivity compared to the volume conductor was found to be different than that in the neighbouring regions which is the basis of the image reconstruction algorithm. The developed algorithm was tested by modelling volume conductors containing multiple objects of different conductivities at different depths. It was found that PHI has 3D sensitivity and the developed algorithm can fairly detect objects with diameter at least of the order of half the electrode separation with depth equal to or less than electrode separation. Being a low cost and non-ionizing method, there is a potential of using PHI in the imaging of organs, tumors and blood vessels in human body although the image resolution is low.