21/01/2015
Human Exposure from Pulsed Magnetic Field Therapy Mats: A Numerical Case Study with Three Commercial Products
Valerio De Santis, Mark Douglas, Jagadish Nadakuduti, Stefan Benkler, Xi Lin Chen, and Niels Kuster, Bioelectromagnetics, Volume 36, Issue 2, pp. 149–161, February 2015, online January 16, 2015
Due to the popularity of pulsed magnetic field therapy (PMFT) mats for private therapeutic use, regulators need to evaluate whether the products are compliant with the basic restrictions and how overexposure can be determined. In a previous study, it was found that incident magnetic field exposure from PMFT mats can exceed ICNIRP 1998 reference levels.
Electromagnetic exposure from three different commercially available PMFT products was assessed. Experimentally validated numerical models of these mats were developed, and the induced fields, evaluated in high-resolution adult, child, and pregnant anatomical models of the IT’IS Virtual Population, were compared to the safety guidelines. As expected, PMFT design, anatomy, lying position, and body orientation were found to significantly influence exposure. The maximum exposure of one PMFT exceeds 3.1 times the basic restrictions of ICNIRP 1998 for the central nervous system tissues and 1.36 times the limit of ICNIRP 2010 for the peripheral tissues. Body loops can significantly increase the electric fields close to the skin, e.g., when the hand and thigh are in contact during mat use. PMFT products are therefore not intrinsically compliant with ICNIRP 1998 and ICNIRP 2010 basic restrictions and require special considerations.
The scientific and technical impact of the study can be summarized as:
- An approach for determining the level of compliance of PMFT mats with the basic restrictions of safety guidelines is described.
- The induced fields from exposure to the PMFT mats at 50 Hz were numerically assessed with the Magneto Quasi-Static solver of SEMCAD X in highly detailed adult, child, and pregnant anatomical models.
- The influence on induced fields of body posture, position on the mat, body orientation, and body loops was investigated.
- For some PMFT mats, worst-case exposures can significantly exceed the basic restrictions.