A theoretical study on magnetic induction frequency dependence of phase shift in oedema and haematoma.

The spectroscopic distribution of induction phase shift as a function of the relative volume of oedema and haematoma in the brain, lung and muscle in the bulk of tissue was produced from the available tissue data and a simple mathematical model of electromagnetic induction in tissue. The results show that the phase shift is sensitive to the relative volume of oedema/haematoma at frequencies higher than approximately 10 MHz. The effect of oedema/haematoma on brain, lung and muscle tissues is tissue-type specific. Increasing the volume of tissue has the effect of lowering the frequency at which the phase shift becomes sensitive to the volume of oedema/haematoma. The results indicate that bulk induction measurement of the phase shift has the potential for becoming a simple means for non-contact detection of formation of oedema and haematoma in brain, lung and muscle tissues.