Rapid methods for the calculation of the magnetic fields associated with the human thorax

Rapid calculation of magnetic fields close to a magnetized human thorax is investigated. The work has relevance to the potential use of SQUID (superconducting quantum interference device) magnetometry as a clinical diagnostic tool. The calculational method is based on a model of the human thorax which consists of 26 planes of 33*35 1-cm cubes, each of which has a magnetic susceptibility assigned on the basis of its biological content. The use of a reciprocity technique to calculate fields close to a thorax using this model has led to simplification of the computational problem to one of a series of multiplicative manipulations using a set of lookup tables. It is established that the reciprocity method is inherently more accurate and computationally faster than direct integral methods and shows relatively greater sensitivity to the internal structure of the thorax.