Coupling of external electromagnetic fields into the human body has been subject of many investigations in recent years especially with several epidemiological studies linking higher rates of incidence of certain cancers with electromagnetic radiation [1
]. Many investigations have been made to evaluate EM waves coupling into different organs of body and many international guidelines and standards have been set up for exposure limits in order to protect workers against nonionizing radiation in their workplaces.
Regarding the fact that many cancer associations have referred to magnetic radiation and considering the fact that magnetic fields are not shielded by conventional shielding structures, has led to a dominant interest in exploring potential hazards of magnetic induction.
There are many studies in recent years evaluating levels of current densities induced in different body tissues when exposed to low frequency EM waves. The well known scaled FDTD technique has been used widely since proposed by Gandhi [3
] to convert the results of a simulation performed in a higher frequency (in the range of mega hertz) to the results of very low frequency coupling caused by power line radiation in 50 and 60 Hz. Other studies considering the effects of uniform and nonuniform magnetic fields with various polarizations are also performed at 60 Hz using quasi-static impedance method [6
Different combinations of incident waves, including pure magnetic fields with different polarizations and both electric and magnetic fields in the form of a uniform plane wave have been studied in Gandhi's works at power line frequencies. Other studies have explored effects of very low frequency pure electric fields using high resolution models (with cubic voxels of 3.6 mm edges) [6
]. Industrial frequencies in the range of kilo hertz have been also studied due to potential risks imposed on workers near induction heating and melting devices and it has also been shown that for low frequency dosimetric applications, using 1 cm resolution model with realistic shape but relatively lower resolution in discrimination of internal tissues may give good results with acceptable accuracy [7
In this paper a 1 cm resolution anatomically based model with 20 different organs/tissues has been used to evaluate current densities induced in different parts of body when exposed to pure magnetic fields in frequency of 1 KHz. This particular frequency is of interest for two major reasons: first, this is the frequency mostly radiated by industrial heating and melting devices in work places for which many basic restrictions indicating the maximum permissible values of electric and magnetic field inside the human body have already been established. The second, this is the frequency proven to have a remarkable impact on the phenomenon of cell electroporation [8
]. In this phenomenon, tiny pores will be formed on the membrane of cells exposed to electric fields with a particular frequency and magnitude. These pores are formed in several microseconds and may last up to some seconds and the process is irreversible if the voltage induced on the cell membrane exceeds a critical value and cell death will occur. Therefore, studying the magnitude of induced electric fields in different body tissues may potentially help obtaining a better control and insight into potential occurrence of electroporation phenomenon.
The model is manually prepared by converting MRI images of a 46-year old man with the height of 178 cm into suitable matrixes of electrical properties of computational space to be used in FDTD algorithm. MRI images were T1-weighted and obtained with a 1.5T unit and the following parameters: TR = 300–450 ms, TE = 12–15 ms, matrix size = 256 × 256.
20 different tissues and related organs have been identified by an expert physician and a consulting radiologist and have been discriminated due to variations in their conductivities. Pure magnetic radiation is simulated using two plane waves traveling in opposite directions with electric components canceling each other.
It is shown that the orientation of magnetic vector in respect with the body may have a considerable impact on the coupling of external fields into different organs. This may be useful to be considered when seeking for appropriate protective strategies against unwanted effects of external radiation.