Efthymios Karabetsos

Occupational Electromagnetic Fields exposure in Magnetic Resonance Imaging systems - Preliminary results for the RF harmonic content.

PURPOSE European legislation concerning the protection of workers from exposure to Electromagnetic Fields (EMF) was recently (26.6.2013) completed by Directive 2013/35/ΕU. This Directive is a specific one of the framework Directive 89/391/EEC and part of the overall legislation for Occupational Health and Safety (OHS). Magnetic Resonance Imaging (MRI) systems have played a key role, both in the postponement of the former 2004/40 EMF Directive and in the formation of the latest limits adopted by the new Directive. On the other hand, MRI systems are associated with the exposure of personnel to EMF of various frequencies and modulations, arousing peculiar safety issues. Therefore, we will try to acquire the highly important knowledge of the exact occupational exposure levels, in all working scenarios and practices. METHODS Different MRI systems (1.5 and 3 T) have been chosen for a variety of measurements in order to assess occupational exposure compared to the limits (ALs) of the Directive and to the main OHS principles. Gradient function of MRI systems results in low frequency exposure, while high frequency exposure comes from the application of the RF excitation frequency. RESULTS In most of the cases the RMS and peak value measurements do not exceed the corresponding ALs, apart from a few specific hot spots, manageable through OHS principles. DISCUSSION Complete occupational exposure results can form the basis for dealing with multiple exposures present in MRI systems. Peculiar RF harmonic components, of no safety concern, were detected. Their origin is under examination.

Non‐Ionizing Radiation: Evaluation of General Public’s Exposures in Greece and Albania

With the growth of electric power generation and transmission, the development of new telecommunication systems and advances in medical and industrial applications, humans are increasingly exposed to electromagnetic fields (EMF). The need to understand the potentially harmful effects of EMF on human health has been met by several decades of research, but the development of exposure standards is more recent and a variety of national standards now exist. A number of organizations have formulated guidelines establishing limits for occupational and residential EMF exposure. The exposure limits for EMF developed by the ICNIRP were based in large reviews of scientific literature, including thermal and non‐thermal effects.

Evaluation of occupational exposure to ELF magnetic fields at power plants in Greece in the context of European directives.

The scope of this paper is to comparatively present the extremely low-frequency (ELF) measurements performed at four power plants in Greece, focusing on: (a) the worst-case exposure conditions, (b) the existence of magnetic field harmonic components, (c) the technical similarities among the power plants and (d) comparison of the measured percentages of reference levels at typical working areas in the power plants. A detailed measurement methodology is proposed, including broadband on-site inspection of the working areas, weighted averaged root-mean-square and peak values of magnetic flux density, percentage of reference levels, according to 1998 ICNIRP guidelines and harmonic analysis of the multi-frequency magnetic fields. During the analysis of the occupational exposure in all power plants, the new Directive 2013/35/EU has been taken into account. The study concludes by proposing a mapping procedure of working areas into certain zones, in order to take measures for workers safety.

The electromagnetic environment of Magnetic Resonance Imaging systems. Occupational exposure assessment reveals RF harmonics

Magnetic Resonance Imaging (MRI) systems played a crucial role in the postponement of the former occupational electromagnetic fields (EMF) European Directive (2004/40/EC) and in the formation of the latest exposure limits adopted in the new one (2013/35/EU). Moreover, the complex MRI environment will be finally excluded from the implementation of the new occupational limits, leading to an increased demand for Occupational Health and Safety (OHS) surveillance. The gradient function of MRI systems and the application of the RF excitation frequency result in low and high frequency exposures, respectively. This electromagnetic field exposure, in combination with the increased static magnetic field exposure, makes the MRI environment a unique case of combined EMF exposure. The electromagnetic field levels in close proximity of different MRI systems have been assessed at various frequencies. Quality Assurance (QA) & safety issues were also faced. Preliminary results show initial compliance with the forthcoming limits in each different frequency band, but also revealed peculiar RF harmonic components, of no safety concern, to the whole range detected (20-1000MHz). Further work is needed in order to clarify their origin and characteristics.

Testing Hybrid Technology Cars: Static and Extremely Low-Frequency Magnetic Field Measurements

Static and extremely low-frequency (ELF) magnetic fields are encountered in hybrid technology cars. These fields are mainly due to the currents flowing through the circuits, the motor, and the battery. To determine the magnetic field levels in the passenger compartment, measurements were made in all four seats at three heights (feet, chest, and head) in various types (full or mild hybrid) and models of hybrid cars. Because the magnetic flux density ^Bh changes constantly as the car travels, following the functioning sequence of the combustion engine and the electric motor, measurements were performed in four different driving conditions: stationary (idling) and traveling at 20-40 km/h, 80-120 km/h (during high-speed cruising), and over 120 km/h. The static and ELF magnetic field values were measured in the frequency range 0-32 kHz. The corresponding percentages of the 1998 International Commission on Nonionizing Radiation Protection (ICNIRP) reference values for the exposure of the general public were derived for all driving conditions. The results showed that the higher values- which instantaneously reached 78.8% of the ICNIRPs 1998 reference values for the general public-were measured in the foot area of the passengers seats and during braking and accelerating.

Two interlaboratory comparison programs on EMF measurements performed in Greece

This paper presents two interlaboratory comparison schemes on electromagnetic field measurements. The first scheme involves measurements of the electric field produced by a scale transmission line and of the magnetic field produced by a medium voltage cable, whereas the second scheme involves measurements of the high frequency electromagnetic fields level and calculation of the total exposure ratio in the vicinity of mobile phone base stations and antennas transmitting in the radio and TV frequency bands. The measurements procedure and the calculation of the performance statistics z scores are analyzed for both schemes. Emphasis is given to the evaluation of the results, in order to investigate possible improvements on the overall implementation of the schemes and error factors related to the equipment and the measurement procedures of the participants.

An interlaboratory comparison programme on radio frequency electromagnetic field measurements: the second round of the scheme

The second round of an interlaboratory comparison scheme on radio frequency electromagnetic field measurements has been conducted in order to evaluate the overall performance of laboratories that perform measurements in the vicinity of mobile phone base stations and broadcast antenna facilities. The participants recorded the electric field strength produced by two high frequency signal generators inside an anechoic chamber in three measurement scenarios with the antennas transmitting each time different signals at the FM, VHF, UHF and GSM frequency bands. In each measurement scenario, the participants also used their measurements in order to calculate the relative exposure ratios. The results were evaluated in each test level calculating performance statistics (z-scores and En numbers). Subsequently, possible sources of errors for each participating laboratory were discussed, and the overall evaluation of their performances was determined by using an aggregated performance statistic. A comparison between the two rounds proves the necessity of the scheme.

An interlaboratory comparison program on ELF electric and magnetic fields measurements performed in Greece: Second round of the scheme.

The second round of an interlaboratory comparison program for extremely low frequency electric and magnetic fields measurements was performed at the High Voltage Laboratory of the National Technical University of Athens (Greece). The 16 participating laboratories measured the following: (i) electric field produced by a scale transmission line; (ii) magnetic field produced by a medium voltage cable; and (iii) magnetic field and frequency at the center of a standard square coil and their delivered results were evaluated in all measurement scenarios with use of performance statistics z-scores. Deviations between z-scores based on usual estimators (mean value, standard deviation) and robust estimators (derived with the robust algorithm described by the International Organization for Standardization [ISO, 2005]) highlight improved performance of the robust algorithm. An overall comparison to measurement procedure and performance results of the first round proves effectiveness and necessity of the scheme. Improper instrumentation or calibration, instability of the field source and measurement position uncertainty are factors that may cause unsatisfactory performance of the participants.