Radio frequencies and microwave radiations

Suitable measures to reduce risks arising from the employment of such radiations are basically linked to the control of the source which must comply with the homologation rules and which must be supplied with safety instructions. Furthermore, the source must be appropriately shielded and the surrounding area delimited. The shielding depends on the type of employed metal and on its thickness; such shields must be without fissures and must avoid the conveying of the field aloof through the emission cables. Furthermore, an important measure is the reduction of the time of exposure of the workers.
As far as the installation of a MRI equipment is concerned, this is provided for by the Italian law 29/11/1985. The recommended limits of exposure to a static magnetic field should not exceed values of 2 Tesla (the Tesla is the unit of measure of magnetic induction and it is equal to 1 weber/square metre; the weber is the unit of measure of magnetic flux and is equal to 1 volt per second).
When choosing an appropriate site for the installation, it is necessary to take into consideration a number of devices in order to assure an appropriate shielding of the source and realize safety distances both from big metallic objects (air conditioners, generators, etc.) and from moving metallic masses (lifts, cars, etc.).
In the case of MRI systems employing superconductor magnets which need cryogenic liquids (He, N₂), it is necessary to have a series of installations:
- appropriate ventilation system;
- emergency system with acoustic alarm in the case of a fortuitous emission of the gases;
- self-locking system for the ducts of adduction of helium and nitrogen;
- emergency duct to guarantee a complete air exchange.
No legislation exists as far as health surveillance is concerned, both before appointment and during the job. The frequency of the periodical checks is left to the competent doctor who must take into account the source characteristics and the exposure modality. The medical and paramedical personnel must be appropriately trained with specific courses in order to acquire a sound competence and be made aware of safety related to MRI systems employment.

	Ambulatories
	Diagnostic services
	Laboratories
	Operating theatres

	Ambulatories
	Diagnostic services
	Physical laboratories
	Operating theatres

Radio frequencies and microwave radiations