Browsing by Author "Toivonen, Tommi"
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- ItemGSM mobile phone radiation suppresses brain glucose metabolism.(2011-12-01) Kwon, Myoung Soo; Vorobyev, Victor; Kännälä, Sami; Laine, Matti; Rinne, Juha O; Toivonen, Tommi; Johansson, Jarkko; Teräs, Mika; Lindholm, Harri; Alanko, Tommi; Hämäläinen, HeikkiWe investigated the effects of mobile phone radiation on cerebral glucose metabolism using high resolution positron emission tomography PET with the 18 F deoxyglucose FDG tracer A long half life 109 minutes of the 18 F isotope allowed a long natural exposure condition outside the PET scanner Thirteen young right handed male subjects were exposed to a pulse modulated 902 4 MHz Global System for Mobile Communications signal for 33 minutes while performing a simple visual vigilance task Temperature was also measured in the head region forehead eyes cheeks ear canals during exposure 18 F deoxyglucose PET images acquired after the exposure showed that relative cerebral metabolic rate of glucose was significantly reduced in the temporoparietal junction and anterior temporal lobe of the right hemisphere ipsilateral to the exposure Temperature rise was also observed on the exposed side of the head but the magnitude was very small The exposure did not affect task performance reaction time error rate Our results show that short term mobile phone exposure can locally suppress brain energy metabolism in humans
- ItemNo effects of short-term GSM mobile phone radiation on cerebral blood flow measured using positron emission tomography.(2012-03-05) Kwon, Myoung Soo; Vorobyev, Victor; Kännälä, Sami; Laine, Matti; Rinne, Juha O; Toivonen, Tommi; Johansson, Jarkko; Teräs, Mika; Joutsa, Juho; Tuominen, Lauri; Lindholm, Harri; Alanko, Tommi; Hämäläinen, HeikkiThe present study investigated the effects of 902 4 MHz global system for mobile communications GSM mobile phone radiation on cerebral blood flow using positron emission tomography PET with the 15 O water tracer Fifteen young healthy right handed male subjects were exposed to phone radiation from three different locations left ear right ear forehead and to sham exposure to test for possible exposure effects on brain regions close to the exposure source Whole brain O H O PET images were acquired 12 times 3 for each condition in a counterbalanced order Subjects were exposed for 5 min in each scan while performing a simple visual vigilance task Temperature was also measured in the head region forehead eyes cheeks ear canals during exposure The exposure induced a slight temperature rise in the ear canals but did not affect brain hemodynamics and task performance The results provided no evidence for acute effects of short term mobile phone radiation on cerebral blood flow
- ItemSpecific absorption rate and electric field measurements in the near field of six mobile phone base station antennas.(2009-04-08) Toivonen, Tommi; Toivo, Tim; Puranen, Lauri; Jokela, KariIn this article the exposure to radio frequency electromagnetic fields was studied in close proximity distances of 10 100 300 and 600 mm to six base station antennas The specific absorption rate SAR in 800 mm x 500 mm x 200 mm box phantom as well as unperturbed electric field E in air was measured The results were used to determine whether the measurement of local maximum of unperturbed electric field can be used as a compliance check for local exposure Also the conservativeness of this assessment method compared to the ICNIRP basic restriction was studied Moreover the assessment of whole body exposure was discussed and the distance ranges presented in which the ICNIRP limit for local exposure could be exceeded before the limit for whole body SAR These results show that the electric field measurement alone can be used for easy compliance check for the local exposure at all distances and for all antenna types studied However in some cases when the local peak value of E was compared directly to the ICNIRP reference level for unperturbed E the exposure was overestimated only very slightly by factor 1 1 compared to the basic restriction for localized SAR in a human and hence these results can not be generalized to all antenna types Moreover it was shown that the limit for localized exposure could be exceeded before the limit for the whole body average SAR if the distance to the antenna was less than 240 mm
- ItemThermal effects of mobile phone RF fields on children: a provocation study.(2011-11-29) Lindholm, Harri; Alanko, Tommi; Rintamäki, Hannu; Kännälä, Sami; Toivonen, Tommi; Sistonen, Heli; Tiikkaja, Maria; Halonen, Janne; Mäkinen, Tero; Hietanen, MailaThe aim of this study was to examine thermal and local blood flow responses in the head area of the preadolescent boys during exposure to radiofrequency RF electromagnetic fields produced by a GSM mobile phone The design was a double blinded sham controlled study of 26 boys aged 14 15 years The SAR distribution was calculated and modelled in detail The duration of the sham periods and exposures with GSM 900 phone was 15 min each and the tests were carried out in a climatic chamber in controlled thermoneutral conditions The ear canal temperatures were registered from both ear canals and the skin temperatures at several sites of the head trunk and extremities The local cerebral blood flow was monitored by a near infrared spectroscopy NIRS and the autonomic nervous system function by recordings of ECG and continuous blood pressure During the short term RF exposure local cerebral blood flow did not change the ear canal temperature did not increase significantly and autonomic nervous system was not interfered The strengths of this study were the age of the population multifactorial physiological monitoring and strictly controlled thermal environment The limitations of the study were large inter individual variation in the physiological responses and short duration of the exposure Longer provocation protocols however might cause in children distress related confounding physiological responses